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3D-Printed Brain Clear the Way to Find Cancer Treatments
Reported by: Irina Robu, PhD
Glioblastomas are aggressive and malignant grade IV brain tumors and can located wherever in the brain and do not regularly spread outside of the brain. Common symptoms patients with glioblastoma experience include headaches, seizures, confusion, memory loss, muscle weakness, visual changes, language deficit, and cognitive changes. Glioblastomas tend to affect older individuals (age 45 to 70) with rare occurrences in children. Treatment methods typically include a combination of surgery, chemotherapy, radiation therapy, and alternating electric fields therapy.
Scientists at Northwestern University developed a technique to study their fast spreading cancer using a 3D structure made of agglomeration of human brain cells and biomaterials, which can help doctors better understand how the tumor grows and speed up the potential discovery of novel drugs to fight it. A water-based substance serves as a matrix to hold the cells into place. However, inside the living brain, scientists can’t observe how the tumor cells grow or respond the treatment and they have to use mice/rats to understand tumor development. Animal studies are expensive and time consuming, but the 3D printed live tissue allows researchers to study glioblastoma to be studied more directly.
To understand what happens inside the 3D model, the researchers used a laser to scan the sample and create a snapshot of the cellular structure. This combination allows them to assess the effectiveness of a commonly used chemotherapy drug, temozolomide. The drug, temozolomide kills glioblastoma cells in two-dimensional models, but when put into a three-dimensional one, the tumor rebounded which implies that the drug did not work in the long term.
This 3D model may be able to speed up that process to weed out ineffective drugs first, confirming that only the most promising ones move to animal, and eventually human, trials.
Metastatic Gastric Cancer Treatments Indicates Mixed Results
Reporter: Irina Robu, PhD
Two novel therapies for patients with metastatic gastric cancer were evaluated by Dr. David H. Ilson of Memorial Sloan Kettering Cancer Center in New York City. In one study, trifluridine/tipiracil (FTD/TPI) was revealed to be an effective treatment for patients with metastatic gastric cancer. On the other hand, the monoclonal antibody andecaliximab plus the chemotherapy regimen mFOLFOX6 (mFOLFOX + ADX) as a first-line treatment in patients with advanced gastric or gastroesophageal junction adenocarcinoma failed to improve overall survival. He has shown the only potentially curative treatment for early stage gastric cancer is surgery, with 5-year survival rates after gastrectomy of 90% or more in Japan and Korea and 40% to 75% in non-Asian countries.
Still, the disease reappears in up to half of patients, while 40% of patients with metastatic disease have had a previous gastrectomy. The phase III TAGS study had established that FTD/TPI is safe for patients with severely pretreated metastatic gastric cancer. In this study, Ilson and his colleagues appraised the efficacy and safety of the FTD/TPI in patients with or without gastrectomy. Of the 507 patients in the study, 147 in the FTD/TPI arm had a prior gastrectomy compared to 74 in the placebo arm. The study enhances the benefit of TPI as prolonging surviving versus placebo.
According to Dr. Manish A. Shah, the mixture of mFOLFOX6 and ADX exposed encouraging anti-tumor activity in patients with gastric or gastroesophageal junction adenocarcinoma according to a prior I/IB study. He showed a phase III, randomized, double-blind, multicenter study associating the efficiency and safety of mFOLFOX with or without ADX in patients with untreated HER2-negative gastric or gastroesophageal junction adenocarcinoma.
The main endpoint was complete survival with secondary endpoints of evolution free survival, objective response rate and safety. According to Dr. Shah, thee apparent increased activity of the mixture of mFOLFOX with ADX in patients ages 65 or older needs further study.
Almudena’s Story: A Life of Hope, Rejuvenation and Strength
Author: Gail S. Thornton, M.A.
Co-Editor: The VOICES of Patients, HealthCare Providers, Caregivers and Families: Personal Experience with Critical Care and Invasive Medical Procedures
Patient had ovarian clear cell adenocarcinomas (OCCAs) and underwent a complete hysterectomy at age 52. Interview was conducted 15 months’ post-surgery. Earlier in life, patient had thyroid cancer and removal of her thyroid gland and all the lymph nodes in her neck.
Almudena Seeder-Alonso, originally from Madrid, Spain, and now living in Amsterdam, The Netherlands, with her Dutch husband, René, is the eternal optimist, embracing life, reinventing herself, and looking for opportunity in every moment. She is an influential blogger of international relations issues, a career professional in human resources management in both corporate and consulting businesses in Legal, Accounting and Technology, and a lawyer and political scientist with an advanced degree in international relations who is also pursuing a Ph.D. in international relations and diplomacy. And she speaks four languages fluently – Spanish, Dutch, Portuguese and English.
Her story is one of hope, rejuvenation and strength that defines her effervescent personality. One year ago, a routine gynecology exam changed her outlook and perspective on life. She would have never thought that her diagnosis would be ovarian carcinoma of the clear cell, the most aggressive form of cancer.
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Image SOURCE: Photographs courtesy of Almudena Seeder-Alonso. Top Left: Almudena’s parents, María and Angel, and sister, Cristina, and her husband. Top Right: Almudena during chemotherapy last summer (2015). Middle: Almudena attending a wedding in Asturias (northwest Spain – May 2016), Almudena and René in Comporta, Portugal (Summer 2014) and in New York (April 2014). Below left: Almudena in New York (April 2014). Below Right: Almudena’s sisters, María and Cristina with nephew, Jaime (May 2016).
A Small Cyst Turns Into Diagnosis of Ovarian Cancer
In early 2015, Almudena visited her gynecologist in Amsterdam for a regular, yearly appointment.
“I was feeling fine. I had no physical complaints, except for my monthly periods which were heavy. I didn’t think much about it. During my examination, my doctor told me that she found a small cyst on my right ovary and we would just observe it to make sure it was not growing.”
Almudena went back to her gynecologist at the OLVG (Onze Lieve Vrouw Gasthuis https://www.olvg.nl/) in Amsterdam twice over the next month to monitor the cyst, only to find that the cyst was growing slightly. Her gynecologist recommended blood tests, an ultrasound, and a specimen of the cyst to be removed through a laparoscopy, a procedure requiring small incisions made below the navel using specialized tools.
“The pathology report said that the cyst was an aggressive cancer, called ovarian carcinoma of the clear cell. I remember sitting in my doctor’s office once she told me the results of the test, and I got very quiet. I could not believe that this was happening to me. While I was meeting with the doctor, I called my husband to let the doctor inform him about the situation. I was listening to this conversation but from far away. He immediately left his meeting with his client (he is one of two founding partners of SeederdeBoer, a Dutch Consulting & Technology firm), to come home. I left the doctor’s office, went home and cried in my husband’s arms.”
Almudena then called her parents, María and Angel, and her two sisters, María and Cristina who live in Madrid, to tell them the news.
“My Mother was very emotional when she heard about my diagnosis. My Father, who is a quiet man by nature, asked me, ‘How could this be happening to you again?’ I did not have an answer for him.”
Almudena’s father was referring to his daughter’s diagnosis of thyroid cancer in her late 20s.
Diagnosis of Thyroid Cancer As A Young Woman
When Almudena was 27 years old, she was diagnosed with follicular thyroid cancer, a slow-growing, highly treatable type of cancer that forms in follicular cells in the thyroid gland. After a 12-hour surgery to remove the gland through a procedure called a full thyroidectomy, she also needed radiation therapy. Many years later, she is feeling fine and continues to be on thyroid medication for the rest of her life.
“I was not aware at that young age of the scope of the diagnosis, but my life really changed. I was kind of a party animal at the end of the 1980s, and I did not have any amount of energy for that anymore. I needed several months to get back into shape as the scar from the surgery was a large one on the right side of my neck. I could not use my right arm and hand properly for months, even writing was complicated. The worst news came later when I could not get pregnant given the situation that many of my eggs were gone because of radiation. At that moment, egg freezing technology was not as advanced as it is today; it was not normal to freeze eggs for a later time. That was really painful, as I could not become a mother, even after four in vitro fertilization (IVF) cycles.”
According to the National Cancer Institute’s web site, thyroid cancer is a disease in which malignant cancer cells form in the tissues of the thyroid gland. The thyroid is a gland at the base of the throat near the trachea (windpipe). It is shaped like a butterfly, with a right lobe and a left lobe. The isthmus, a thin piece of tissue, connects the two lobes. A healthy thyroid is a little larger than a quarter coin. It usually cannot be felt through the skin. The thyroid uses iodine, a mineral found in some foods and in iodized salt, to help make several hormones. Thyroid hormones control heart rate, body temperature, and how quickly food is changed into energy (metabolism) as well as, it controls the amount of calcium in the blood. http://www.cancer.gov/types/thyroid/patient/thyroid-treatment-pdq
Ovarian Cancer Diagnosis Continues
Almudena then spoke with her physicians in Madrid, as that is where she grew up, to get a second opinion about her ovarian carcinoma diagnosis. The physicians knew her history well and they told her that they did not believe that the follicular thyroid cancer was directly related to the ovarian cancer.
“My local gynecologist in Amsterdam then referred me to a specialist, Dr. J. van der Velden, a gynecologist/oncologist at the Amsterdam Medisch Centrum (AMC), http://www.cgoa.nl/page/view/name/34-wie-we-zijn, one of the top university hospitals in The Netherlands for this surgery and treatment. My husband, René, and I met with Dr. van der Velden, and he told us that my cancer was a fast-spreading condition and I needed to have it removed immediately. He answered our questions, calmed my fears and said he would do everything to help me.
“I have an open attitude towards people so it was easy to create a good connection with the doctors and medical personnel, which I consider very fundamental in such a process. I talked to them about my concerns or doubts and shared my worries about the process that I was going through. I have to say that all of them were wonderful in every aspect!”
Dr. van der Velden explained to Almudena that as clear cell is an aggressive form of ovarian cancer, it would need to be treated that way. One month later, Almudena underwent a procedure called open surgery, rather than laparoscopic surgery, requiring an incision large enough for the doctor to see the cyst and surrounding tissue.
“My incision from the surgery is a constant reminder of the struggle I went through. The cyst, which was 3cm, was a solid mass on my right ovary. It had adhered itself to the ovary and had to be broken to be removed, so some cells spilled out into my reproductive organs, namely, in my uterus and fallopian tubes. During this surgery, which was a complete hysterectomy, the doctor took additional tissue samples of my reproductive organs to be analyzed by pathology. Weeks later, he found no other metastases or extra cancer cells.”
One month later, Almudena’s body was still recovering from the operation. Now, she had to start chemotherapy back at the OLVG.
“The doctor, Dr. W. Terpstra, hematologist/oncologist instructed me that I would be going through six full cycles of chemotherapy, which means full doses of carboplatin & paclitaxel every 21 days. At first, I felt reasonably good, then as each week progressed, I became more and more tired, nauseous, and just feeling terrible. I was not sleeping well and even lost the sensation of my fingers and toes as chemo attacks the nerves, too. Then, I started losing my eyelashes and hair so I shaved my long, flowing hair and wore a scarf wrapped around my head.”
Almudena would report to the hospital for her weekly chemotherapy session, starting at 9am and leaving at 6pm. The medical team would put her in a room with a full-size bed so she can relax during the infusion. Her husband, two sisters and some close friends would take turns accompanying her during this time, as she had a nurturing and caring support network.
“I could not have gone through this condition without my family and friends. It tests your relationships and shows you who your friends really are.”
The chemotherapy affected Almudena’s red blood cell count halfway through the process and she felt weak and tired.
“Anemia is normal during this time, but always being tired made me concentrate and focus on things less. I would watch a movie or read a book through the chemo session, and then I would fall asleep quickly.”
After Almudena finished the complete cycle of chemotherapy infusions, she had a follow-up appointment with her doctor, which included blood work, CT scan, and other diagnostic tests.
“My doctor said the tests results were very good. Now, I see him every three months for a routine visit. That was such a wonderful report to hear.
“During this process I learned to love myself, and pampered myself and my body. I learned to improve in terms of beauty, even in the worst circumstances. I wanted to feel beautiful and attractive for myself and for my close family. After three chemo cycles, I started even to think about how my new hair style would be in the moment that I finished chemo.”
Ovarian Carcinoma Pathophysiology Facts
According to published studies, ovarian clear cell adenocarcinomas (OCCAs) account for less than 5 percent of all ovarian malignancies, and 3.7–12.1 percent of all epithelial ovarian carcinomas. By contrast, early‐stage clear cell ovarian cancer carries a relatively good prognosis. When compared with their serous counterparts, a greater proportion of OCCA tumors present as early‐stage (I–II) tumors, are often associated with a large pelvic mass, which may account for their earlier diagnosis, and rarely occur bilaterally. Very little is known about the pathobiology of OCCA. Between 5 percent and 10 percent of ovarian cancers are associated with endometriotic lesions in which there is a predominance of clear and endometrioid cell subtypes, suggesting that both tumor types may arise in endometriosis. http://www.cancer.gov/types/ovarian/hp/ovarian-epithelial-treatment-pdq
The National Cancer Institute’s web site offers these statistics. In most families affected with the breast and ovarian cancer syndrome or site-specific ovarian cancer, genetic linkage has been found to the BRCA1 locus on chromosome 17q21. BRCA2, also responsible for some instances of inherited ovarian and breast cancer, has been mapped by genetic linkage to chromosome 13q12. The lifetime risk for developing ovarian cancer in patients harboring germline mutations in BRCA1 is substantially increased over that of the general population. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2001101/
Words Of Wisdom
“Throughout this journey, I found myself again in some way and found my strength as well. When it seemed I could not stand it anymore, either physically and mentally, I realized that I could.
“At the beginning of my diagnosis, I asked myself, ‘Why me?’, and I then changed it to, ‘Why not me?’ I discovered that I have the same opportunities as anyone who becomes ill. The important perspective to have is not whining and dwelling on my bad luck. The important thing is to heal, survive, and recover my life, which is very good!
“I learned the real value and importance of things: to differentiate and give real meaning and value to the care and support of my husband, René, who was always there for me, and my parents and sisters, who came to Amsterdam very often during the process. I also made sure that René was well-supported and accompanied by my family. René was feeling terrible for me, but he never showed it — and I learned this fact after I was starting to be back on track.”
Almudena’s Life Today
“At a significant moment in my life during my cancer diagnosis and after a long professional life in many corporate and consulting business in several countries, I decided to re-invent myself and start a new career, this time, in the battle of the opinions. I always liked foreign affairs and diplomacy, so why not share my thoughts and write about current international issues.”
That’s when Almudena started a blog to discuss relevant international political issues with her background specialization in International Relations, International Politics, International Law and Governance.
“I consider myself politically liberal and have been influenced by J.S. Mill and A. Tocqueville’s tradition of thought, as well as their ethical conception of the defense of freedom. This is what I try to capture in my political approach and in this blog. http://almudenas.website/index.php/about-me/
“Regarding my profession, I have already reinvented myself, leaving the corporate life with all that is included regarding life’s standards, and do what really makes me happy, which I´m doing right now. It seems after all, looking back with perspective, I did the right thing.
“I am grateful for my life and never take anything for granted. I am the happiest when I am doing things that please me or give me the utmost satisfaction. I now have balance in my personal and professional life, something that I’ve never had before. My husband, René, likes it too and I have his full support.”
She recently ‘liked’ this saying on LinkedIn, the professional network site, ‘I never lose. I either win or learn,’ which was attributed to Nelson Mandela, the deceased South African anti-apartheid revolutionary, politician and philanthropist.
Almudena’s life continues on a path of balance, richness and thankfulness for the person she is and the many blessings she continues to have along the way.
Editor’s note:
We would like to thank Gabriela Contreras, a global communications consultant and patient advocate, for the tremendous help and support she provided in locating and scheduling time to talk with Almudena Seeder-Alonso.
Almudena Seeder-Alonso provided her permission to publish this interview on August 10, 2016.
Technologies For Targeting And Delivering Chemotherapeutics Directly To The Tumour Site
Curator: David Orchard-Webb, PhD
Chemotherapy is normally associated with debilitating side effects due to systemic toxicity to normal cells, however targeting the chemotherapeutics directly to the tumour should dramatically reduce these side effects. Several technologies designed to accomplish this are under development (Table 1).
Researchers of the NTU-Northwestern Institute of Nanomedicine at Nanyang Technological University in Singapore are developing magnetic microbubbles which can contain chemotherapeutics. The microbubbles can be systemically delivered and imaged in real time. The chemotherapeutic is released from the microbubbles at the tumour site by directing ultrasound at the location [1]. Therefore this technology has the potential to specifically deliver any chemotherapeutic to a desired tumour site in the body.
For more on nanoparticle delivery make sure to read the following pharmaceutical intelligence article concerning iCluster technology:
Researchers at PanTher Therapeutics are developing a novel drug-eluting device for targeting chemotherapeutics to solid tumours. The cremaphor formulation of paclitaxel has dose limiting toxicity which prevent its use for pancreatic cancer. Paclitaxel’s toxicity like the majority of chemotherapeutics stems from its systemic delivery and toxicity to normal cells. However recently an albumin-bound formulation (nab-paclitaxel) has demonstrated increased survival times in combination with gemcitabine compared to gemcitabine alone [2]. And now PanTher Therapeutics’ novel biodegradable device has been developed which can deliver chemotherapeutics including paclitaxel directly to the pancreas limiting systemic toxicities [3].
The device has been tested with paclitaxel and shown favourable results in mouse xenograft models over systemically delivered paclitaxel. The device is flexible and can be surgically placed over the pancreatic tumour where it rests delivering a steady flow of paclitaxel for the duration of the treatment. The one time insertion is an attractive aspect compared with repeated intravenous deliveries.
Researchers at PharmaCyte Biotech, Inc. are developing a cell encapsidation technology called Cell-in-a-Box® which protects the cells inside from the host immune system while allowing the free exchange of soluble proteins and chemicals. The chemotherapeutic ifosfamide is activated in the liver by cytochrome P450 enzymes and must travel systemically to the tumour site. The greater the distance of the tumour from the liver the greater the dose requirement for effective delivery. The toxicities induced by an effective dose for pancreatic cancer are too great. Using Cell-in-a-Box®, activated ifosfamide can however be targeted to the pancreatic cancer reducing the dose requirement.
Cell-in-a-Box® is made of polymers of cellulose sulphate [4]. Clinical studies have shown that it is possible to encapsulate 293 cells overexpressing cytochrome P450 and deliver the capsules to the pancreas via the blood vessels without adverse effects. Lower doses of ifosfamide can then be systemically delivered and yet have a high active local concentration at the pancreas. A phase II trial is planned to confirm effectiveness in pancreatic cancer patients refractory to gemcitabine and abraxane or FOLFIRINOX [5].
Researchers of the University of North Carolina at Chapel Hill have developed a new device based on inserting positive and negative electrodes on either side of a tumour, injecting a chemotherapeutic and then applying an electric field in order to drive the therapeutic into the tumour. This Iontophoresis device has been tested in pancreatic cancer mouse xenograft models with gemcitabine and the newer combination FOLFIRINOX. Significant tumour volume reductions compared to intravenous delivery of the chemotherapeutic were found in both cases [6, 7]. Clinical trials are planned in the near future [8].
REFERENCES
Gao, Yu, Chon U Chan, Qiushi Gu, Xudong Lin, Wencong Zhang, David Chen Loong Yeo, Astrid Marlies Alsema, et al. ‘Controlled Nanoparticle Release from Stable Magnetic Microbubble Oscillations’. NPG Asia Materials 8, no. 4 (8 April 2016): e260. doi:10.1038/am.2016.37.
Ma, W. W., and M. Hidalgo. ‘The Winning Formulation: The Development of Paclitaxel in Pancreatic Cancer’. Clinical Cancer Research 19, no. 20 (15 October 2013): 5572–79. doi:10.1158/1078-0432.CCR-13-1356.
Ligorio, Matteo, Laura Indolfi, David T. Ting, Kristina Xega, Nicola Aceto, Francesca Bersani, Cristina R. Ferrone, et al. ‘Abstract 4584: A Novel Drug-Eluting Platform for Localized Treatment of Pancreatic Cancer’. Cancer Research 74, no. 19 Supplement (10 January 2014): 4584–4584. doi:10.1158/1538-7445.AM2014-4584.
Byrne, J. D., M. N. R. Jajja, A. T. O’Neill, L. R. Bickford, A. W. Keeler, N. Hyder, K. Wagner, et al. ‘Local Iontophoretic Administration of Cytotoxic Therapies to Solid Tumors’. Science Translational Medicine 7, no. 273 (4 February 2015): 273ra14–273ra14. doi:10.1126/scitranslmed.3009951.
Byrne, James D., Mohammad R. N. Jajja, Allison N. Schorzman, Amanda W. Keeler, J. Christopher Luft, William C. Zamboni, Joseph M. DeSimone, and Jen Jen Yeh. ‘Iontophoretic Device Delivery for the Localized Treatment of Pancreatic Ductal Adenocarcinoma’. Proceedings of the National Academy of Sciences 113, no. 8 (23 February 2016): 2200–2205. doi:10.1073/pnas.1600421113.
Curbing Cancer Cell Growth & Metastasis-on-a-Chip’ Models Cancer’s Spread, Volume 2 (Volume Two: Latest in Genomics Methodologies for Therapeutics: Gene Editing, NGS and BioInformatics, Simulations and the Genome Ontology), Part 1: Next Generation Sequencing (NGS)
Curbing Cancer Cell Growth & Metastasis-on-a-Chip’ Models Cancer’s Spread
Using a new approach, scientists at The Scripps Research Institute (TSRI) and collaborating institutions have discovered a novel drug candidate that could be used to treat certain types of breast cancer, lung cancer and melanoma.
The new study focused on serine, one of the 20 amino acids (protein building blocks) found in nature. Many types of cancer require synthesis of serine to sustain rapid, constant and unregulated growth.
To find a drug candidate that interfered with this pathway, the team screened a large library of compounds from a variety of sources, searching for molecules that inhibited a specific enzyme known as 3-phosphoglycerate dehydrogenase (PHGDH), which is responsible for the first committed step in serine biosynthesis.
“In addition to discovering an inhibitor that targets cancer metabolism, we also now have a tool to help answer interesting questions about serine metabolism,” said Luke L. Lairson, assistant professor of chemistry at TSRI and principal investigator of cell biology at the California Institute for Biomedical Research (CALIBR).
Lairson was senior author of the study, published recently in the Proceedings of the National Academy of Sciences (PNAS), with Lewis Cantley of Weill Cornell Medical College and Costas Lyssiotis of the University of Michigan.
Addicted to Serine
Serine is necessary for nucleotide, protein and lipid biosynthesis in all cells. Cells use two main routes for acquiring serine: through import from the extracellular environment or through conversion of 3-phosphoglycerate (a glycolytic intermediate) by PHGDH.
“Since the late 1950s, it has been known that cancer cells use the process of aerobic glycolysis to generate metabolites needed for proliferative growth,” said Lairson.
This process can lead to an overproduction of serine. The genetic basis for this abundance had remained mysterious until recently, when it was demonstrated that some cancers acquire mutations that increased the expression of PHGDH; reducing PHGDH in these “serine-addicted” cancer cells also inhibited their growth.
The labs of Lewis C. Cantley at Weill Cornell Medical College (in work published in Nature Genetics) and David Sabatini at the Whitehead Institute (in work published in Nature) suggested PHGDH as a potential drug target for cancer types that overexpress the enzyme.
Lairson and colleagues hypothesized that a small molecule drug candidate that inhibited PHGDH could interfere with cancer metabolism and point the way to the development of an effective cancer therapeutic. Importantly, this drug candidate would be inactive against normal cells because they would be able to import enough serine to support ordinary growth.
As Easy as 1-2-800,000
Lairson, in collaboration with colleagues including Cantley, Lyssiotis, Edouard Mullarky of Weill Cornell and Harvard Medical School and Natasha Lucki of CALIBR, screened through a library of 800,000 small molecules using a high-throughput in vitro enzyme assay to detect inhibition of PHGDH. The group identified 408 candidates and further narrowed this list down based on cell-type specific anti-proliferative activity and by eliminating those inhibitors that broadly targeted other dehydrogenases.
With the successful identification of seven candidate inhibitors, the team sought to determine if these molecules could inhibit PHGDH in the complex cellular environment. To do so, the team used a mass spectrometry-based assay (test) to measure newly synthesized serine in a cell in the presence of the drug candidates.
One of the seven small molecules tested, named CBR-5884, was able to specifically inhibit serine synthesis by 30 percent, suggesting that the molecule specifically targeted PHGDH. The group went on to show that CBR-5884 was able to inhibit cell proliferation of breast cancer and melanoma cells lines that overexpress PHGDH.
As expected, CBR-5884 did not inhibit cancer cells that did not overexpress PHGDH, as they can import serine; however, when incubated in media lacking serine, the presence of CBR-5884 decreased growth in these cells.
The group anticipates much optimization work before this drug candidate can become an effective therapeutic. In pursuit of this goal, the researchers plan to take a medicinal chemistry approach to improve potency and metabolic stability.
How Cancer Stem Cells Thrive When Oxygen Is Scarce
Working with human breast cancer cells and mice, scientists at The Johns Hopkins University say new experiments explain how certain cancer stem cells thrive in low oxygen conditions. Proliferation of such cells, which tend to resist chemotherapy and help tumors spread, are considered a major roadblock to successful cancer treatment.
The new research, suggesting that low-oxygen conditions spur growth through the same chain of biochemical events in both embryonic stem cells and breast cancer stem cells, could offer a path through that roadblock, the investigators say.
“There are still many questions left to answer but we now know that oxygen poor environments, like those often found in advanced human breast cancers serve as nurseries for the birth of cancer stem cells,” said Gregg Semenza, M.D., Ph.D., the C. Michael Armstrong Professor of Medicine and a member of the Johns Hopkins Kimmel Cancer Center. “That gives us a few more possible targets for drugs that diminish their threat in human cancer.”
A summary of the findings was published online March 21 in the Proceedings of the National Academy of Sciences.
“Aggressive cancers contain regions where the cancer cells are starved for oxygen and die off, yet patients with these tumors generally have the worst outcome. Our new findings tell us that low oxygen conditions actually encourage certain cancer stem cells to multiply through the same mechanism used by embryonic stem cells.”
All stem cells are immature cells known for their ability to multiply indefinitely and give rise to progenitor cells that mature into specific cell types that populate the body’s tissues during embryonic development. They also replenish tissues throughout the life of an organism. But stem cells found in tumors use those same attributes and twist them to maintain and enhance the survival of cancers.
Recent studies showed that low oxygen conditions increase levels of a family of proteins known as HIFs, or hypoxia-inducible factors, that turn on hundreds of genes, including one called NANOG that instructs cells to become stem cells.
Studies of embryonic stem cells revealed that NANOG protein levels can be lowered by a chemical process known as methylation, which involves putting a methyl group chemical tag on a protein’s messenger RNA (mRNA) precursor. Semenza said methylation leads to the destruction of NANOG’s mRNA so that no protein is made, which in turn causes the embryonic stem cells to abandon their stem cell state and mature into different cell types.
Zeroing in on NANOG, the scientists found that low oxygen conditions increased NANOG’s mRNA levels through the action of HIF proteins, which turned on the gene for ALKBH5, which decreased the methylation and subsequent destruction of NANOG’s mRNA. When they prevented the cells from making ALKBH5, NANOG levels and the number of cancer stem cells decreased. When the researchers manipulated the cell’s genetics to increase levels of ALKBH5 without exposing them to low oxygen, they found this also decreased methylation of NANOG mRNA and increased the numbers of breast cancer stem cells.
Finally, using live mice, the scientists injected 1,000 triple-negative breast cancer cells into their mammary fat pads, where the mouse version of breast cancer forms. Unaltered cells created tumors in all seven mice injected with such cells, but when cells missing ALKBH5 were used, they caused tumors in only 43 percent (six out of 14) of mice. “That confirmed for us that ALKBH5 helps preserve cancer stem cells and their tumor-forming abilities,” Semenza said.
The new research, suggesting that low-oxygen conditions spur growth through the same chain of biochemical events in both embryonic stem cells and breast cancer stem cells, could offer a path through that roadblock, the investigators say.
“There are still many questions left to answer but we now know that oxygen poor environments, like those often found in advanced human breast cancers serve as nurseries for the birth of cancer stem cells,” says Gregg Semenza, M.D., Ph.D., the C. Michael Armstrong Professor of Medicine and a member of the Johns Hopkins Kimmel Cancer Center.
Chuanzhao Zhang, Debangshu Samanta, Haiquan Lu, John W. Bullen, Huimin Zhang, Ivan Chen, Xiaoshun He, Gregg L. Semenza. Hypoxia induces the breast cancer stem cell phenotype by HIF-dependent and ALKBH5-mediated m6A-demethylation of NANOG mRNA. Proceedings of the National Academy of Sciences, 2016; 201602883 DOI: 10.1073/pnas.1602883113
Significance
Pluripotency factors, such as NANOG, play a critical role in the maintenance and specification of cancer stem cells, which are required for primary tumor formation and metastasis. In this study, we report that exposure of breast cancer cells to hypoxia (i.e., reduced O2 availability), which is a critical feature of the tumor microenvironment, induces N6-methyladenosine (m6A) demethylation and stabilization of NANOG mRNA, thereby promoting the breast cancer stem cell (BCSC) phenotype. We show that inhibiting the expression of AlkB homolog 5 (ALKBH5), which demethylates m6A, or the hypoxia-inducible factors (HIFs) HIF-1α and HIF-2α, which activate ALKBH5 gene transcription in hypoxic breast cancer cells, is an effective strategy to decrease NANOG expression and target BCSCs in vivo.
N6-methyladenosine (m6A) modification of mRNA plays a role in regulating embryonic stem cell pluripotency. However, the physiological signals that determine the balance between methylation and demethylation have not been described, nor have studies addressed the role of m6A in cancer stem cells. We report that exposure of breast cancer cells to hypoxia stimulated hypoxia-inducible factor (HIF)-1α- and HIF-2α–dependent expression of AlkB homolog 5 (ALKBH5), an m6A demethylase, which demethylated NANOG mRNA, which encodes a pluripotency factor, at an m6A residue in the 3′-UTR. Increased NANOG mRNA and protein expression, and the breast cancer stem cell (BCSC) phenotype, were induced by hypoxia in an HIF- and ALKBH5-dependent manner. Insertion of the NANOG 3′-UTR into a luciferase reporter gene led to regulation of luciferase activity by O2, HIFs, and ALKBH5, which was lost upon mutation of the methylated residue. ALKBH5 overexpression decreased NANOG mRNA methylation, increased NANOG levels, and increased the percentage of BCSCs, phenocopying the effect of hypoxia. Knockdown of ALKBH5 expression in MDA-MB-231 human breast cancer cells significantly reduced their capacity for tumor initiation as a result of reduced numbers of BCSCs. Thus, HIF-dependent ALKBH5 expression mediates enrichment of BCSCs in the hypoxic tumor microenvironment.
Specific Proteins Found to Jump Start Spread of Cancer Cells
Scientists at the University of California, San Diego School of Medicine and Moores Cancer Center, with colleagues in Spain and Germany, have discovered how elevated levels of particular proteins in cancer cells trigger hyperactivity in other proteins, fueling the growth and spread of a variety of cancers. Their study (“Prognostic Impact of Modulators of G Proteins in Circulating Tumor Cells from Patients with Metastatic Colorectal Cancer”) is published in Scientific Reports.
Specifically, the international team, led by senior author Pradipta Ghosh, M.D., associate professor at the University of California San Diego School of Medicine, found that increased levels of expression of some members of a protein family called guanine nucleotide exchange factors (GEFs) triggered unsuspected hyperactivation of G proteins and subsequent progression or metastasis of cancer.
The discovery suggests GEFs offer a new and more precise indicator of disease state and prognosis. “We found that elevated expression of each GEF is associated with a shorter, progression-free survival in patients with metastatic colorectal cancer,” said Dr. Ghosh. “The GEFs fared better as prognostic markers than two well-known markers of cancer progression, and the clustering of all GEFs together improved the predictive accuracy of each individual family member.”
In recent years, circulating tumor cells (CTCs), which are shed from primary tumors into the bloodstream and act as seeds for new tumors taking root in other parts of the body, have become a prognostic and predictive biomarker. The presence of CTCs is used to monitor the efficacy of therapies and detect early signs of metastasis.
But counting CTCs in the bloodstream has limited utility, said Dr. Ghosh. “Enumeration alone does not capture the particular characteristics of CTCs that are actually tumorigenic and most likely to cause additional malignancies.”
Numerous efforts are underway to improve the value and precision of CTC analysis. According to Dr. Ghosh the new findings are a step in that direction. First, GEFs activate trimeric G proteins, and second, G protein signaling is involved in CTCs. G proteins are ubiquitous and essential molecular switches involved in transmitting external signals from stimuli into cells’ interiors. They have been a subject of heightened scientific interest for many years.
Dr. Ghosh and colleagues found that elevated expression of nonreceptor GEFs activates Gαi proteins, fueling CTCs and ultimately impacting the disease course and survival of cancer patients.
“Our work shows the prognostic impact of elevated expression of individual and clustered GEFs on survival and the benefit of transcriptome analysis of G protein regulatory proteins in cancer biology,” said Dr. Ghosh. “The next step will be to carry this technology into the clinic where it can be applied directly to deciphering a patient’s state of cancer and how best to treat.”
In the journal Biotechnology Bioengineering, the team reports on its “metastasis-on-a-chip” system believed to be one of the first laboratory models of cancer spreading from one 3D tissue to another.
The current version of the system models a colorectal tumor spreading from the colon to the liver, the most common site of metastasis. Skardal said future versions could include additional organs, such as the lung and bone marrow, which are also potential sites of metastasis. The team also plans to model other types of cancer, such as the deadly brain tumor glioblastoma
To create the system, researchers encapsulated human intestine and colorectal cancer cells inside a biocompatible gel-like material to make a mini-organ. A mini-liver composed of human liver cells was made in the same way. These organoids were placed in a “chip” system made up of a set of micro-channels and chambers etched into the chip’s surface to mimic a simplified version of the body’s circulatory system. The tumor cells were tagged with fluorescent molecules so their activity could be viewed under a microscope.
To test whether the system could model metastasis, the researchers first used highly aggressive cancer cells in the colon organoid. Under the microscope, they saw the tumor grow in the colon organoid until the cells broke free, entered the circulatory system and then invaded the liver tissue, where another tumor formed and grew. When a less aggressive form of colon cancer was used in the system, the tumor did not metastasize, but continued to grow in the colon.
To test the system’s potential for screening drugs, the team introduced Marimastat, a drug used to inhibit metastasis in human patients, into the system and found that it significantly prevented the migration of metastatic cells over a 10-day period. Likewise, the team also tested 5-fluorouracil, a common colorectal cancer drug, which reduced the metabolic activity of the tumor cells.
“We are currently exploring whether other established anti-cancer drugs have the same effects in the system as they do in patients,” said Skardal. “If this link can be validated and expanded, we believe the system can be used to screen drug candidates for patients as a tool in personalized medicine. If we can create the same model systems, only with tumor cells from an actual patient, then we believe we can use this platform to determine the best therapy for any individual patient.”
The scientists are currently working to refine their system. They plan to use 3D printing to create organoids more similar in function to natural organs. And they aim to make the process of metastasis more realistic. When cancer spreads in the human body, the tumor cells must break through blood vessels to enter the blood steam and reach other organs. The scientists plan to add a barrier of endothelial cells, the cells that line blood vessels, to the model.
This concept of modeling the body’s processes on a miniature level is made possible because of advances in micro-tissue engineering and micro-fluidics technologies. It is similar to advances in the electronics industry made possible by miniaturizing electronics on a chip.
A schematic shows a trioxacarcin C molecule, whose structure was revealed for the first time through a new process developed by the Rice lab of synthetic organic chemist K.C. Nicolaou. Trioxacarcins are found in bacteria but synthetic versions are needed to study them for their potential as medications. Trioxacarcins have anti-cancer properties. Source: Nicolaou Group/Rice University http://www.dddmag.com/sites/dddmag.com/files/ddd1603_rice-anticancer.jpg
A team led by Rice University synthetic organic chemist K.C. Nicolaou has developed a new process for the synthesis of a series of potent anti-cancer agents originally found in bacteria.
The Nicolaou lab finds ways to replicate rare, naturally occurring compounds in larger amounts so they can be studied by biologists and clinicians as potential new medications. It also seeks to fine-tune the molecular structures of these compounds through analog design and synthesis to improve their disease-fighting properties and lessen their side effects.
Such is the case with their synthesis of trioxacarcins, reported this month in the Journal of the American Chemical Society.
“Not only does this synthesis render these valuable molecules readily available for biological investigation, but it also allows the previously unknown full structural elucidation of one of them,” Nicolaou said. “The newly developed synthetic technologies will allow us to construct variations for biological evaluation as part of a program to optimize their pharmacological profiles.”
At present, there are no drugs based on trioxacarcins, which damage DNA through a novel mechanism, Nicolaou said.
Trioxacarcins were discovered in the fermentation broth of the bacterial strain Streptomyces bottropensis. They disrupt the replication of cancer cells by binding and chemically modifying their genetic material.
“These molecules are endowed with powerful anti-tumor properties,” Nicolaou said. “They are not as potent as shishijimicin, which we also synthesized recently, but they are more powerful than taxol, the widely used anti-cancer drug. Our objective is to make it more powerful through fine-tuning its structure.”
He said his lab is working with a biotechnology partner to pair these cytotoxic compounds (called payloads) to cancer cell-targeting antibodies through chemical linkers. The process produces so-called antibody-drug conjugates as drugs to treat cancer patients. “It’s one of the latest frontiers in personalized targeting chemotherapies,” said Nicolaou, who earlier this year won the prestigious Wolf Prize in Chemistry.
Fluorescent Nanoparticle Tracks Cancer Treatment’s Effectiveness in Hours
Using reporter nanoparticles loaded with either a chemotherapy or immunotherapy, researchers could distinguish between drug-sensitive and drug-resistant tumors in a pre-clinical model of prostate cancer. (Source: Brigham and Women’s Hospital)
Bioengineers at Brigham and Women’s Hospital have developed a new technique to help determine if chemotherapy is working in as few as eight hours after treatment. The new approach, which can also be used for monitoring the effectiveness of immunotherapy, has shown success in pre-clinical models.
The technology utilizes a nanoparticle, carrying anti-cancer drugs, that glows green when cancer cells begin dying. Researchers, using the “reporter nanoparticles” that responds to a particular enzyme known as caspase, which is activated when cells die, were able to distinguish between a tumor that is drug-sensitive or drug-resistant much faster than conventional detection methods such as PET scans, CT and MRI. The findings were published online March 28 in the Proceedings of the National Academy of Sciences.
“Using this approach, the cells light up the moment a cancer drug starts working,” co-corresponding author Shiladitya Sengupta, Ph.D., principal investigator in BWH’s Division of Bioengineering, said in a prepared statement. “We can determine if a cancer therapy is effective within hours of treatment. Our long-term goal is to find a way to monitor outcomes very early so that we don’t give a chemotherapy drug to patients who are not responding to it.”
Cancer killers send signal of success
Nanoparticles deliver drug, then give real-time feedback when tumor cells die BY SARAH SCHWARTZ
New lab-made nanoparticles deliver cancer drugs into tumors, then report their effects in real time by lighting up in response to proteins produced by dying cells. More light (right, green) indicates a tumor is responding to chemotherapy.
Tiny biochemical bundles carry chemotherapy drugs into tumors and light up when surrounding cancer cells start dying. Future iterations of these lab-made particles could allow doctors to monitor the effects of cancer treatment in real time, researchers report the week of March 28 in theProceedings of the National Academy of Sciences.
“This is the first system that allows you to read out whether your drug is working or not,” says study coauthor Shiladitya Sengupta, a bioengineer at Brigham and Women’s Hospital in Boston.
Each roughly 100-nanometer-wide particle consists of a drug and a fluorescent dye linked to a coiled molecular chain. Before the particles enter cells, the dye is tethered to a “quencher” molecule that prevents it from lighting up. When injected into the bloodstream of a mouse with cancer, the nanoparticles accumulate in tumor cells and release the drug, which activates a protein that tears a cancer cell apart. This cell-splitting protein not only kills the tumor cell, but also severs the link between the dye and the quencher, allowing the nanoparticles to glow under infrared light.
Reporter nanoparticle that monitors its anticancer efficacy in real time
The ability to identify responders and nonresponders very early during chemotherapy by direct visualization of the activity of the anticancer treatment and to switch, if necessary, to a regimen that is effective can have a significant effect on the outcome as well as quality of life. Current approaches to quantify response rely on imaging techniques that fail to detect very early responses. In the case of immunotherapy, the early anatomical readout is often discordant with the biological response. This study describes a self-reporting nanomedicine that not only delivers chemotherapy or immunotherapy to the tumor but also reports back on its efficacy in real time, thereby identifying responders and nonresponders early on
The ability to monitor the efficacy of an anticancer treatment in real time can have a critical effect on the outcome. Currently, clinical readouts of efficacy rely on indirect or anatomic measurements, which occur over prolonged time scales postchemotherapy or postimmunotherapy and may not be concordant with the actual effect. Here we describe the biology-inspired engineering of a simple 2-in-1 reporter nanoparticle that not only delivers a cytotoxic or an immunotherapy payload to the tumor but also reports back on the efficacy in real time. The reporter nanoparticles are engineered from a novel two-staged stimuli-responsive polymeric material with an optimal ratio of an enzyme-cleavable drug or immunotherapy (effector elements) and a drug function-activatable reporter element. The spatiotemporally constrained delivery of the effector and the reporter elements in a single nanoparticle produces maximum signal enhancement due to the availability of the reporter element in the same cell as the drug, thereby effectively capturing the temporal apoptosis process. Using chemotherapy-sensitive and chemotherapy-resistant tumors in vivo, we show that the reporter nanoparticles can provide a real-time noninvasive readout of tumor response to chemotherapy. The reporter nanoparticle can also monitor the efficacy of immune checkpoint inhibition in melanoma. The self-reporting capability, for the first time to our knowledge, captures an anticancer nanoparticle in action in vivo.
Evan Johnson had battled a cold for weeks, endured occasional nosebleeds and felt so fatigued he struggled to finish his workouts at the gym. But it was the unexplained bruises and chest pain that ultimately sent the then 23-year-old senior at the University of North Dakota to the Mayo Clinic. There a genetic test revealed a particularly aggressive form of acute myeloid leukemia. That was two years ago.
The harrowing roller-coaster that followed for Mr. Johnson and his family highlights new directions oncologists are taking with genetic testing to find and attack cancer. Tumors can evolve to resist treatments, and doctors are beginning to turn such setbacks into possible advantages by identifying new targets to attack as the tumors change.
His course involved a failed stem cell transplant, a half-dozen different drug regimens, four relapses and life-threatening side effects related to his treatment.
Nine months in, his leukemia had evolved to develop a surprising new mutation. The change meant the cancer escaped one treatment, but the new anomaly provided doctors with a fresh target, one susceptible to drugs approved for other cancers. Doctors adjusted Mr. Johnson’s treatment accordingly, knocked out the disease and paved the way for a second, more successful stem cell transplant. He has now been free of leukemia for a year.
Now patients with advanced cancer who are treated at major centers can expect to have their tumors sequenced, in hopes of finding a match in a growing medicine chest of drugs that precisely target mutations that drive cancer’s growth. When they work, such matches can have a dramatic effect on tumors. But these “precision medicines” aren’t cures. They are often foiled when tumors evolve, pushing doctors to take the next step to identify new mutations in hopes of attacking them with an effective treatment.
Before qualifying for a transplant, a patient’s blasts need to be under 5%.
To get under 5%, he started on a standard chemotherapy regimen and almost immediately, things went south. His blast cells plummeted, but “the chemo just wiped out my immune system,”
Then as mysteriously as it began, a serious mycotic throat infection stopped. But Mr. Johnson couldn’t tolerate the chemo, and his blast cells were on the rise. A two-drug combination that included the liver cancer drug Nexavar, which targets the FLT3 mutation, knocked back the blast cells. But the stem cell transplant in May, which came from one of his brothers, failed to take, and he relapsed after 67 days, around late July.
He was put into a clinical trial of an experimental AML drug being developed by Astellas Pharma of Japan. He started to regain weight. In November 2014, doctors spotted the initial signs in blood tests that Mr. Johnson’s cancer was evolving to acquire a new mutation. By late January, he relapsed again , but there was a Philadelphia chromosome mutation, a well-known genetic alteration associated with chronic myeloid leukemia. It also is a target of the blockbuster cancer drug Gleevec and several other medicines.
Clonal evolution of AML on novel FMS-like tyrosine kinase-3 (FLT3) inhibitor therapy with evolving actionable targets
• The article reports on a case of AML that underwent clonal evolution.
• We report on novel acquisition of the Philadelphia t(9;22) translocation in AML.
• Next generation sequencing maybe helpful in these refractory/relapse cases.
• Novel FLT3-inhibitor targeted therapies are another option in patients with AML.
• Personalizing cancer treatment based on evolving targets is a viable option.
For acute myeloid leukemia (AML), identification of activating mutations in the FMS-like tyrosine kinase-3 (FLT3) has led to the development of several FLT3-inhibitors. Here we present clinical and next generation sequencing data at the time of progression of a patient on a novel FLT3-inhibitor clinical trial (ASP2215) to show that employing therapeutic interventions with these novel targeted therapies can lead to consequences secondary to selective pressure and clonal evolution of cancer. We describe novel findings alongside data on treatment directed towards actionable aberrations acquired during the process. (Clinical Trial: NCT02014558; registered at: 〈https://clinicaltrials.gov/ct2/show/NCT02014558〉)
The development of kinase inhibitors for the treatment of leukemia has revolutionized the care of these patients. Since the introduction of imatinib for the treatment of chronic myeloid leukemia, multiple other tyrosine kinase inhibitors (TKIs) have become available[1]. Additionally, for acute myeloid leukemia (AML), identification of activating mutations in the FMS-like tyrosine kinase-3 (FLT3) has led to the development of several FLT3-inhibitors [2], [3], [4] and [5]. The article herein reports a unique case of AML that underwent clonal evolution while on a novel FLT3-inhibitor clinical trial.
Our work herein presents clinical and next generation sequencing data at the time of progression to illustrate these important concepts stemming from Darwinian evolution [6]. We describe novel findings alongside data on treatment directed towards actionable aberrations acquired during the process.
Our work focuses on a 23-year-old male who presented with 3 months history of fatigue and easy bruising, a white blood count of 22.0×109/L with 51% circulating blasts, hemoglobin 7.6 g/dL, and a platelet count of 43×109/L. A bone marrow biopsy confirmed a diagnosis of AML. Initial cytogenetic studies identified trisomy 8 in all the twenty metaphases examined. Mutational analysis revealed an internal tandem duplication of the FLT3 gene (FLT3-ITD).
He received standard induction chemotherapy (7+3) with cytarabine (ARA-C; 100 mg/m2for 7 days) and daunorubicin (DNM; 60 mg/m2 for 3 days). His induction chemotherapy was complicated by severe palatine and uvular necrosis of indeterminate etiology (possible mucormycosis).
Bone marrow biopsy at day 28 demonstrated persistent disease with 10% bone marrow blasts (Fig. 1). Due to his complicated clinical course and the presence of a FLT3-ITD, salvage therapy with 5-azacitidine (5-AZA) and sorafenib (SFN) was instituted. Table 1.
The highlighted therapies were employed in this particular case at various time points as shown in Fig. 1.
Treatment with FLT3 inhibitor in patients with FLT3-mutated acute myeloid leukemia is associated with development of secondary FLT3-tyrosine kinase domain mutations
Curators: Larry H. Berstein, M.D. FACP & Stephen J. Williams, Ph.D.
For most of the history of chemotherapy drug development, predicting the possible mechanisms of drug resistance that ensued could be surmised from the drug’s pharmacologic mechanism of action. In other words, a tumor would develop resistance merely by altering the pathways/systems which the drug relied on for mechanism of action. For example, as elucidated in later chapters in this book, most cytotoxic chemotherapies like cisplatin and cyclophosphamide were developed to bind DNA and disrupt the cycling cell, thereby resulting in cell cycle arrest and eventually cell death or resulting in such a degree of genotoxicity which would result in great amount of DNA fragmentation. These DNA-damaging agents efficacy was shown to be reliant on their ability to form DNA adducts and lesions. Therefore increasing DNA repair could result in a tumor cell becoming resistant to these drugs. In addition, if drug concentration was merely decreased in these cells, by an enhanced drug efflux as seen with the ABC transporters, then there would be less drug available for these DNA adducts to be generated. A plethora of literature has been generated on this particular topic.
However in the era of chemotherapies developed against targets only expressed in tumor cells (such as Gleevec against the Bcr-Abl fusion protein in chronic myeloid leukemia), this paradigm had changed as clinical cases of resistance had rapidly developed soon after the advent of these compounds and new paradigms of resistance mechanisms were discovered.
Imatinib resistance can be seen quickly after initiation of therapy
Speed of imatinib resistance a result of rapid gene amplification of BCR/ABL target, thereby decreasing imatinib efficacy
Although there are many other new mechanisms of resistance to personalized medicine agents (which are discussed later in the chapter) this post is a curation of cellular changes which are not commonly discussed in reviews of chemoresistance and separated in three main categories:
The advent of Gleevec (imatinib) had issued in a new era of chemotherapy, a personalized medicine approach by determining the and a lifesaver to chronic myeloid leukemia (CML) patients whose tumors displayed expression of the Bcr-Abl fusion gene. However it was not long before clinical resistance was seen to this therapy and, it was shown amplification of the drug target can lead to tumor outgrowth despite adequate drug exposure. le Coutre, Weisberg and Mahon23, 24, 25 all independently generated imatinib-resistant clones through serial passage of the cells in imatinib-containing media and demonstrated elevated Abl kinase activity due to a genetic amplification of the Bcr–Abl sequence. However, all of these samples were derived in vitro and may not represent a true mode of clinical resistance. Nevertheless, Gorre et al.26 obtained specimens, directly patients demonstrating imatinib resistance, and using fluorescence in situ hybridization analysis, genetic duplication of the Bcr–Abl gene was identified as one possible source of the resistance. Additional sporadic examples of amplification of the Bcr–Abl sequence have been clinically described, but the majority of patients presenting with either primary or secondary imatinib resistance fail to clinically demonstrate Abl amplification as a primary mode of treatment failure.
The 2-phenylaminopyrimidine derivative STI571 has been shown to selectively inhibit the tyrosine kinase domain of the oncogenic bcr/abl fusion protein. The activity of this inhibitor has been demonstrated so far both in vitro with bcr/abl expressing cells derived from leukemic patients, and in vivo on nude mice inoculated with bcr/abl positive cells. Yet, no information is available on whether leukemic cells can develop resistance to bcr/abl inhibition. The human bcr/abl expressing cell line LAMA84 was cultured with increasing concentrations of STI571. After approximately 6 months of culture, a new cell line was obtained and named LAMA84R. This newly selected cell line showed an IC50 for the STI571 (1.0 microM) 10-fold higher than the IC50 (0.1 microM) of the parental sensitive cell line. Treatment with STI571 was shown to increase both the early and late apoptotic fraction in LAMA84 but not in LAMA84R. The induction of apoptosis in LAMA84 was associated with the activation of caspase 3-like activity, which did not develop in the resistant LAMA84R cell line. LAMA84R cells showed increased levels of bcr/abl protein and mRNA when compared to LAMA84 cells. FISH analysis with BCR- and ABL-specific probes in LAMA84R cells revealed the presence of a marker chromosome containing approximately 13 to 14 copies of the BCR/ABL gene. Thus, overexpression of the Bcr/Abl protein mediated through gene amplification is associated with and probably determines resistance of human leukemic cells to STI571 in vitro. (Blood. 2000;95:1758-1766)
This is actually the opposite case with other personalized therapies like the EGFR inhibitor gefinitib where actually the AMPLIFICATION of the therapeutic target EGFR is correlated with better response to drug in
The epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases, including EGFR, HER2/erbB2, and HER3/erbB3, is an attractive target for antitumor strategies. Aberrant EGFR signaling is correlated with progression of various malignancies, and somatic tyrosine kinase domain mutations in the EGFR gene have been discovered in patients with non-small cell lung cancer responding to EGFR-targeting small molecular agents, such as gefitinib and erlotinib. EGFR overexpression is thought to be the principal mechanism of activation in various malignant tumors. Moreover, an increased EGFR copy number is associated with improved survival in non-small cell lung cancer patients, suggesting that increased expression of mutant and/or wild-type EGFR molecules could be molecular determinants of responses to gefitinib. However, as EGFR mutations and/or gene gains are not observed in all patients who respond partially to treatment, alternative mechanisms might confer sensitivity to EGFR-targeting agents. Preclinical studies showed that sensitivity to EGFR tyrosine kinase inhibitors depends on how closely cell survival and growth signalings are coupled with EGFR, and also with HER2 and HER3, in each cancer. This review also describes a possible association between EGFR phosphorylation and drug sensitivity in cancer cells, as well as discussing the antiangiogenic effect of gefitinib in association with EGFR activation and phosphatidylinositol 3-kinase/Akt activation in vascular endothelial cells.
New Generation of Platinated Compounds to Circumvent Resistance
Curator/Writer: Stephen J. Williams, Ph.D.
Resistance to chemotherapeutic drugs continues to be a major hurdle in the treatment of neoplastic disorders, irregardless if the drug is a member of the cytotoxic “older” drugs or the cytostatic “newer” personalized therapies like the tyrosine kinase inhibitors. For the platinatum compounds such as cisplatin and carboplatin, which are mainstays in therapeutic regimens for ovarian and certain head and neck cancers, development of resistance is often regarded as the final blow, as new options for these diseases have been limited.
Although there are many mechanisms by which resistance to platinated compounds may develop the purpose of this posting is not to do an in-depth review of this area except to refer the reader to the book Ovarian Cancer and just to summarize the well accepted mechanisms of cisplatin resistance including:
Decreased cellular cisplatin influx
Increased cellular cisplatin efflux
Increased cellular glutathione and subsequent conjugation, inactivation
Increased glutathione-S-transferase activity (GST) and subsequent inactivation, conjugation
Increased γ-GGT
Increased metallothionenes with subsequent conjugation, inactivation
Increased DNA repair: increased excision repair
DNA damage tolerance: loss of mismatch repair (MMR)
altered cell signaling activities and cell cycle protein expression
Williams, S.J., and Hamilton, T.C. Chemotherapeutic resistance in ovarian cancer. In: S.C. Rubin, and G.P. Sutton (eds.), Ovarian Cancer, pp.34-44. Lippincott, Wilkins, and Williams, New York, 2000.
Also for a great review on clinical platinum resistance by Drs. Maritn, Hamilton and Schilder please see the following Clinical Cancer Research link here.
This curation represents the scientific rationale for the development of a new class of platinated compounds which are meant to circumvent mechanisms of resistance, in this case the loss of mismatch repair (MMR) and increased tolerance to DNA damage.
An early step in the production of cytotoxicity by the important anticancer drug cisplatin and its analog carboplatin is the formation of intra- and inter-strand adducts with tumor cell DNA 1-3. This damage triggers a cascade of events, best characterized by activation of damage-sensing kinases (reviewed in 4), p53 stabilization, and induction of p53-related genes involved in apoptosis and cell cycle arrest, such as bax and the cyclin-dependent kinase inhibitor p21waf1/cip1/sdi1 (p21), respectively 5,6. DNA damage significantly induces p21 in various p53 wild-type tumor cell lines, including ovarian carcinoma cells, and this induction is responsible for the cell cycle arrest at G1/S and G2/M borders, allowing time for repair 7,8. DNA lesions have the ability of to result in an opening of chromatin structure, allowing for transcription factors to enter 56-58. Therefore the anti-tumoral ability of cisplatin and other DNA damaging agents is correlated to their ability to bind to DNA and elicit responses, such as DNA breaks or DNA damage responses which ultimately lead to cell cycle arrest and apoptosis. Therefore either repair of such lesions, the lack of recognition of such lesions, or the cellular tolerance of such lesions can lead to resistance of these agents.
Mechanisms of Cisplatin Sensitivity and Resistance. Red arrows show how a DNA lesion results in chemo-sensitivity while the beige arrow show common mechanisms of resistance including increased repair of the lesion, effects on expression patterns, and increased inactivation of the DNA damaging agent by conjugation reactions
Increased DNA Repair Mechanisms of Platinated Lesion Lead to ChemoResistance
Description of Different Types of Cellular DNA Repair Pathways. Nucleotide Excision Repair is commonly up-regulated in highly cisplatin resistant cells
Loss of Mismatch Repair Can Lead to DNA Damage Tolerance
In the following Cancer Research paper Dr. Vaisman in the lab of Dr. Steve Chaney at North Carolina (and in collaboration with Dr. Tom Hamilton) describe how cisplatin resistance may arise from loss of mismatch repair and how oxaliplatin lesions are not recognized by the mismatch repair system.
Defects in mismatch repair are associated with cisplatin resistance, and several mechanisms have been proposed to explain this correlation. It is hypothesized that futile cycles of translesion synthesis past cisplatin-DNA adducts followed by removal of the newly synthesized DNA by an active mismatch repair system may lead to cell death. Thus, resistance to platinum-DNA adducts could arise through loss of the mismatch repair pathway. However, no direct link between mismatch repair status and replicative bypass ability has been reported. In this study, cytotoxicity and steady-state chain elongation assays indicate that hMLH1 or hMSH6 defects result in 1.5-4.8-fold increased cisplatin resistance and 2.5-6-fold increased replicative bypass of cisplatin adducts. Oxaliplatin adducts are not recognized by the mismatch repair complex, and no significant differences in bypass of oxaliplatin adducts in mismatch repair-proficient and -defective cells were found. Defects in hMSH3 did not alter sensitivity to, or replicative bypass of, either cisplatin or oxaliplatin adducts. These observations support the hypothesis that mismatch repair defects in hMutL alpha and hMutS alpha, but not in hMutS beta, contribute to increased net replicative bypass of cisplatin adducts and therefore to drug resistance by preventing futile cycles of translesion synthesis and mismatch correction.
The following are slides I had co-prepared with my mentor Dr. Thomas C. Hamilton, Ph.D. of Fox Chase Cancer Center on DNA Mismatch Repair, Oxaliplatin and Ovarina Cancer.
Multiple Platinum Analogs of Cisplatin (like Oxaliplatin )Had Been Designed to be Sensitive in MMR Deficient Tumors
Please see below video on 2015 Nobel Laureates and their work to elucidate the celluar DNA repair mechanisms.
Clinical genetics expert Kenneth Offit gives an overview of Lynch syndrome, a genetic disorder that can cause colon (HNPCC) and other cancers by defects in the MSH2 DNA mismatch repair gene. (View Video)
References
Johnson, S. W. et al. Relationship between platinum-DNA adduct formation, removal, and cytotoxicity in cisplatin sensitive and resistant human ovarian cancer cells. Cancer Res54, 5911-5916 (1994).
Eastman, A. The formation, isolation and characterization of DNA adducts produced by anticancer platinum complexes. Pharmacology and Therapeutics34, 155-166 (1987).
Zhen, W. et al. Increased gene-specific repair of cisplatin interstrand cross-links in cisplatin-resistant human ovarian cancer cell lines. Molecular and Cellular Biology12, 3689-3698 (1992).
Durocher, D. & Jackson, S. P. DNA-PK, ATM and ATR as sensors of DNA damage: variations on a theme? Curr Opin Cell Biol13, 225-231 (2001).
el-Deiry, W. S. p21/p53, cellular growth control and genomic integrity. Curr Top Microbiol Immunol227, 121-37 (1998).
Ewen, M. E. & Miller, S. J. p53 and translational control. Biochim Biophys Acta1242, 181-4 (1996).
Gartel, A. L., Serfas, M. S. & Tyner, A. L. p21–negative regulator of the cell cycle. Proc Soc Exp Biol Med213, 138-49 (1996).
Chang, B. D. et al. p21Waf1/Cip1/Sdi1-induced growth arrest is associated with depletion of mitosis-control proteins and leads to abnormal mitosis and endoreduplication in recovering cells. Oncogene19, 2165-70 (2000).
Davies, N. P., Hardman, L. C. & Murray, V. The effect of chromatin structure on cisplatin damage in intact human cells. Nucleic Acids Res28, 2954-2958 (2000).
Vichi, P. et al. Cisplatin- and UV-damaged DNA lure the basal transcription factor TFIID/TBP. Embo J16, 7444-7456 (1997).
Xiao, G. et al. A DNA damage signal is required for p53 to activate gadd45. Cancer Res60, 1711-9 (2000).
Other articles in this Open Access Journal on ChemoResistance Include:
The cancer stem-cell hypothesis proposes the existence of a subset of cells within a heterogeneous tumor cell population that have stem-cell like properties [1], and may be essential for the progression and metastases of epithelial malignancies, by providing a reservoir of cells that self-renew and differentiate into the bulk of the tumor [2]. The stem-cell hypothesis implies that similar genetic regulatory pathways might define critical stem-cell like functions, such as self-renewal and pluripotency, in both normal and cancer stem-cells. Indeed, cancer stem-cells have been identified in many tumor types, such as breast [3], pancreas [4] and ovarian [5], based on screening with cellular markers typically found in normal stem-cells such as CD44, ALDH1, and CD133 (reviewed in [2]). A number of studies have suggested that the expression of these stem-cell markers is correlated with poor prognosis [6-9]. The ability to identify and isolate these populations may have a significant impact on design of individualized therapies.
Great general posts and good review on this site about Cancer Stem Cells, their markers, and ability to target them with chemotherapy can be seen here.
However, there has been growing acknowledgement of the ability of cancer stem cell populations to resist the cytotoxic effects of most chemotherapeutic agents, including cisplatin, topoisomerase inhibitors, DNA damaging agents, and even tyrosine kinase inhibitors (TKI). Indeed, some feel that intrinsic resistance to cytotoxic drugs may be a biological feature of cancer stem cells.
Definitions:
Acquired resistance: a resistance to a particular drug which results following continued exposure to said drug. Can take days (in cases of some TKIs) or months to develop. Acquired resistant cells lines are developed by exposure to increasing drug concentration over a time period (either intermittent exposure or continuous exposure)
Intrinsic resistance: a pre-existing resistance usually termed refractory where cancer cells THAT HAVE NOT BEEN EXPOSED to drug, do not respond to initial drug exposure. Can be seen experimentally in panels of unrelated cancer cells lines isolated from untreated patients which show no cytotoxicity to drug exposure in vitro.
Below is one of the first reports which described the drug resistant phenotype of cancer stem cells in an in vivo (mouse) model of breast cancer with videos.
Cancer Res. 2008 May 1;68(9):3243-50. doi: 10.1158/0008-5472.CAN-07-5480.
The majority of BRCA1-associated breast cancers are basal cell-like, which is associated with a poor outcome. Using a spontaneous mouse mammary tumor model, we show that platinum compounds, which generate DNA breaks during the repair process, are more effective than doxorubicin in Brca1/p53-mutated tumors. At 0.5 mg/kg of daily cisplatin treatment, 80% primary tumors (n = 8) show complete pathologic response. At greater dosages, 100% show complete response (n = 19). However, after 2 to 3 months of complete remission following platinum treatment, tumors relapse and become refractory to successive rounds of treatment. Approximately 3.8% to 8.0% (mean, 5.9%) of tumor cells express the normal mammary stem cell markers, CD29(hi)24(med), and these cells are tumorigenic, whereas CD29(med)24(-/lo) and CD29(med)24(hi) cells have diminished tumorigenicity or are nontumorigenic, respectively. In partially platinum-responsive primary transplants, 6.6% to 11.0% (mean, 8.8%) tumor cells are CD29(hi)24(med); these populations significantly increase to 16.5% to 29.2% (mean, 22.8%; P < 0.05) in platinum-refractory secondary tumor transplants. Further, refractory tumor cells have greater colony-forming ability than the primary transplant-derived cells in the presence of cisplatin. Expression of a normal stem cell marker, Nanog, is decreased in the CD29(hi)24(med) populations in the secondary transplants. Top2A expression is also down-regulated in secondary drug-resistant tumor populations and, in one case, was accompanied by genomic deletion of Top2A. These studies identify distinct cancer cell populations for therapeutic targeting in breast cancer and implicate clonal evolution and expansion of cancer stem-like cells as a potential cause of chemoresistance.
Please Watch Videos
Below is a curation of talks and abstracts from the 2015 Annual AACR Meeting in Philadelphia, PA.
The Talk by Dr. Cheresh is an example of this school of thought; that inducing cancer cell stemness can result in development of drug resistance, in this case to a TKI. (For a press release on this finding see here.)
Induction of cancer stemness and drug resistance by EGFR blockade
Presentation Time:
Tuesday, Apr 21, 2015, 12:00 PM -12:15 PM
Abstract Body:
Tumor drug resistance is often accompanied by genetic and biological changes in the tumor cell population reflecting the acquisition of a stem-like state. However, it is not clear whether cancer therapies select for the growth of drug resistance cancer stem cells and/or directly induce the reprograming of tumor cells to a cancer stem-like, drug resistance state. We provide evidence that breast, pancreas and lung carcinomas in the presence of prolonged exposure to EGFR inhibitors undergo an epigenetic reprogramming resulting in a drug resistant stem-like tumor population expressing the cell surface marker CD61 (b3 integrin). In fact, CD61 in the context of KRAS, is necessary and sufficient to account for drug resistance, tumor initiation, self-renewal and expression of the pluripotent genes Oct 4 and Nanog. Once expressed, CD61 in the unligated state recruits KRAS to the plasma membrane leading to the activation of RalB, TBK1 and c-Rel driving both stemness and EGFR inhibitor resistance. Pharmacological targeting this pathway with drugs such as bortezomib or revlimid not only reverses stemness but resensitizes these epithelial tumors to EGFR inhibition. This epigenetic pathway can also be initiated by range of cellular stresses found within the tumor microenvironment such as hypoxia, nutrient deprivation, low pH, and oxidative stress. In normal tissues CD61 is induced during tissue remodeling and repair. For example, CD61 was found to be critical for mammary gland remodeling during pregnancy and as a mediator of pathological neovascularization. Together these findings reveal a stress-induced epigenetic pathway characterized by the upregulation of CD61 that promotes the remodeling of normal tissues but in tumors contributes to EGFR inhibitor resistance and tumor progression.
Molecular and Cellular Biology – Poster Presentations – Proffered Abstracts – Poster Presentations – Cell Death Mechanisms: Abstract 4: ABT-263 is effective in a subset of non-small cell lung cancer cell lines
Aoi Kuroda,
Keiko Ohgino,
Hiroyuki Yasuda,
Junko Hamamoto,
Daisuke Arai,
Kota Ishioka,
Tetsuo Tani,
Shigenari Nukaga,
Ichiro Kawada,
Katsuhiko Naoki,
Kenzo Soejima,
and Tomoko Betsuyaku
Cancer Res August 1, 2015 75:4; doi:10.1158/1538-7445.AM2015-4
Molecular and Cellular Biology – Poster Presentations – Proffered Abstracts – Poster Presentations – Cell Death Mechanisms: Abstract 6: Quantitative assessment of BCL-2:BIM complexes as a pharmacodynamic marker for venetoclax (ABT-199)
Sha Jin,
Paul Tapang,
Donald J. Osterling,
Wenqing Gao,
Daniel H. Albert,
Andrew J. Souers,
Joel D. Leverson,
Darren C. Phillips,
and Jun Chen
Cancer Res August 1, 2015 75:6; doi:10.1158/1538-7445.AM2015-6
Molecular and Cellular Biology – Poster Presentations – Proffered Abstracts – Poster Presentations – Cell Death Mechanisms: Abstract 24: The phosphorylation of p53 at serine 46 is essential to induce cell death through palmdelphin in response to DNA damage
Nurmaa Khund Dashzeveg and
Kiyotsugu Yoshida
Cancer Res August 1, 2015 75:24; doi:10.1158/1538-7445.AM2015-24
Molecular and Cellular Biology – Poster Presentations – Proffered Abstracts – Poster Presentations – Cell Signaling in Cancer 1: Abstract 48: Identification of a novel binding protein playing a critical role in HER2 activation in lung cancer cells
Tomoaki Ohtsuka,
Masakiyo Sakaguchi,
Katsuyoshi Takata,
Shinsuke Hashida,
Mototsugu Watanabe,
Ken Suzawa,
Yuho Maki,
Hiromasa Yamamoto,
Junichi Soh,
Hiroaki Asano,
Kazunori Tsukuda,
Shinichiro Miyoshi,
and Shinichi Toyooka
Cancer Res August 1, 2015 75:48; doi:10.1158/1538-7445.AM2015-48
Abstract 1 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Cell Death Mechanisms
Abstract 4: ABT-263 is effective in a subset of non-small cell lung cancer cell lines
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
Rationale:
ABT-263 (Navitoclax) is one of the BH3 mimetics targeting anti-apoptotic B-cell lymphoma-2 (Bcl-2) family proteins such as Bcl-2, Bcl-XL, and Bcl-w, thereby inducing apoptosis. It has been reported that the response to ABT-263 is associated with expressions of myeloid cell leukemia-1 (Mcl-1), an anti-apoptotic protein. Given its effectiveness as a single agent in preclinical studies, ABT-263 is currently being evaluated in clinical trials for small cell lung cancer (SCLC) and leukemia. However, the efficacy of ABT-263 in non-small cell lung cancer (NSCLC) has not been fully evaluated. We examined the effect of ABT-263 on cell proliferation of NSCLC cell lines and investigated the underlying mechanisms.
Methods:
The following 9 NSCLC cell lines were examined: SK-LU-1, A549, H358, Calu3, H3122, H1975, H460, H441, and BID007. The effects of ABT-263 in NSCLC cell lines were evaluated by MTS assay. Apoptosis was examined by flowcytometry using staining for annexin V and propidium iodide (PI), and also western blotting for cleaved PARP. Quantitative RT-PCR was carried out to assess the mRNA expression levels of anti-apoptotic genes and pro-apoptotic genes. Immunoprecipitation and western blotting were performed to compare the levels of anti-apoptotic and pro-apoptotic proteins between the sensitive and resistant cell lines. In addition, knockdown of Mcl-1 was performed by siRNA.
Results:
By screening 9 NSCLC cell lines using MTS assay, we found Calu3 and BID007were sensitive to ABT-263. We also confirmed that apoptosis was induced only in the ABT-263 sensitive lines but not in the ABT-263 resistant cell lines after ABT-263 treatment. However, the expression levels of Bcl-2 family proteins, including Mcl-1, did not differ significantly among the ABT-263 sensitive and resistant cell lines. Unlike the results in previous reports regarding SCLC, Mcl-1 was not decreased in the sensitive cell lines. The ABT-263 resistant cell lines became sensitive to ABT-263 after knockdown of Mcl-1 by siRNA, while the ABT-263 sensitive cell lines maintained the same sensitivity.
Conclusion:
We found that Calu3 and BID007 were sensitive to ABT-263. In the sensitive NSCLC cell lines, ABT-263 induces apoptosis irrespective of Mcl-1 expression levels.
Citation Format: Aoi Kuroda, Keiko Ohgino, Hiroyuki Yasuda, Junko Hamamoto, Daisuke Arai, Kota Ishioka, Tetsuo Tani, Shigenari Nukaga, Ichiro Kawada, Katsuhiko Naoki, Kenzo Soejima, Tomoko Betsuyaku. ABT-263 is effective in a subset of non-small cell lung cancer cell lines. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4. doi:10.1158/1538-7445.AM2015-4
Abstract 2 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Cell Death Mechanisms
Abstract 6: Quantitative assessment of BCL-2:BIM complexes as a pharmacodynamic marker for venetoclax (ABT-199)
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
The BCL-2-selective inhibitor venetoclax (ABT-199) binds with high affinity to the BH3-binding groove of BCL-2, thereby competing for binding with the BH3-only protein BIM (Souers et al., 2013). Venetoclax is currently being evaluated in clinical trials for CLL, AML, multiple myeloma and NHL. To facilitate these studies, we developed and validated a 384-well electrochemiluminescent ELISA (MSD, Gaithersburg, MD,USA) that quantifies expression of BCL-2, BCL-XL, and MCL-1protein alone or in complex with BIM. We subsequently quantified expression of BCL-2 and BCL-2:BIM complexes in 16 hematologic tumor cell lines. We found the EC50 of venetoclax in these tumor cell lines to correlate strongly with baseline BCL-2:BIM complex levels. This correlation was superior to the correlation between venetoclax EC50 and absolute BCL-2 expression. We also applied the assay to measure disruption of BCL-2:BIM complexes in vivo. Treatment of the Non-Hodgkin’s Lymphoma (NHL) xenograft model SU-DHL-4 with a BCL-2-selective inhibitor resulted in disruption of tumor BCL-2:BIM complexes that aligned with serum and tumor concentrations of inhibitor. Collectively, these data demonstrate that quantifying BCL-2:BIM complexes offers an accurate means of assessing target engagement by venetoclax and, potentially, predicting its efficacy. The utility of this assay is currently being assessed in clinical trials.
Citation Format: Sha Jin, Paul Tapang, Donald J. Osterling, Wenqing Gao, Daniel H. Albert, Andrew J. Souers, Joel D. Leverson, Darren C. Phillips, Jun Chen. Quantitative assessment of BCL-2:BIM complexes as a pharmacodynamic marker for venetoclax (ABT-199). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 6. doi:10.1158/1538-7445.AM2015-6
Abstract 3 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Cell Death Mechanisms
Abstract 19: Antitumor activity of selective inhibitors of XPO1/CRM1-mediated nuclear export in diffuse malignant peritoneal mesothelioma: the role of survivin
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
Survivin, which is highly expressed and promotes cell survival in diffuse malignant peritoneal mesothelioma (DMPM), exclusively relies on the nuclear exportin 1 (XPO1/CRM1) to be released in the cytoplasm and perform its anti-apoptotic function. Here, we explored the efficacy of selective inhibitors of nuclear export (SINEs) in patient-derived DMPM preclinical models. Exposure to individual SINE (KPT-251, KPT-276, KPT-330) was able to induce a time- and dose-dependent inhibition of the growth of two DMPM cell lines without affecting normal cell proliferation. Such a cell growth inhibition was preceded by a decline in the nuclear XPO1/CRM1 levels and an increase in the nuclear accumulation of its cargo proteins p53 and p21, which led to a cell cycle arrest at G1-phase. Our results also indicated that survivin is an essential component of the downstream signaling pathway of XPO1/CRM1 inhibition in DMPM cells. In fact, in both cell lines, exposure to SINEs led to a time-dependent reduction of cytoplasmic survivin levels and, after an initial survivin nuclear accumulation, also to a progressive decrease in the nuclear protein abundance, through the ubiquitin-proteasomal degradation pathway, leading to the complete depletion of total survivin levels. In both DMPM cell models, according to survivin anti-apoptotic activity, drug-induced reduction of cytoplasmic survivin levels correlated with the onset of caspase-dependent apoptosis. We further observed that SINEs can be combined with other survivin inhibitors, such as the survivin suppressant YM155 to achieve enhanced growth inhibition in DMPM cells. Initial in vivo experiments with orally administered KPT-251, KPT-276 and the orally available, clinical stage KPT-330 (selinexor) indicated that each compound was able to significantly reduce the growth of early-stage subcutaneous DMPM xenografts. Interestingly, additional experiments carry out with selinexor demonstrated that the compound was also able to inhibit the growth of late-stage subcutaneous DMPM xenografts in nude mice. Most importantly, oral administration of selinexor to SCID mice reduced the growth of orthotopic DMPM xenografts, which properly recapitulate the dissemination pattern in the peritoneal cavity of human DMPM and, for this reason, represent a valuable model for investigating novel therapeutic approaches for the disease. Consistent with an important role of survivin as a determinant of anti-cancer activity of SINE compounds, a reduction of the protein expression was observed in tumor specimens obtained from selinexor treated mice. Overall, our results (i) demonstrate a marked efficacy of SINEs in DMPM preclinical models, which is, at least in part, dependent on the interference with survivin intracellular distribution and function, and (ii) suggest SINE-mediated XPO1/CRM1 inhibition as a novel therapeutic option for the disease.
Citation Format: Nadia Zaffaroni, Michelandrea De Cesare, Denis Cominetti, Valentina Doldi, Alessia Lopergolo, Marcello Deraco, Paolo Gandellini, Yosef Landesman, Sharon Friedlander, Michael G. Kauffman, Sharon Shacham, Marzia Pennati. Antitumor activity of selective inhibitors of XPO1/CRM1-mediated nuclear export in diffuse malignant peritoneal mesothelioma: the role of survivin. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 19. doi:10.1158/1538-7445.AM2015-19
Abstract 4 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Cell Death Mechanisms
Abstract 24: The phosphorylation of p53 at serine 46 is essential to induce cell death through palmdelphin in response to DNA damage
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
Tumor suppressor p53 plays a pivotal role in cell cycle arrest, DNA repair, and apoptosis in response to DNA damage. Promoter selectivity of p53 depends mainly on post-translational modification. Notably, the apoptotic function of p53 is related to its phosphorylation at serine-46 (ser46) to promote pro-apoptotic genes. However, little is known about the pro-apoptotic genes induced by Ser46 phosphorylation. Our research achieved to investigate the pro-apoptotic genes induced by p53 in a phospho-ser46-specific manner using microarray and ChIP sequencing in human cancer cell lines. As a result, palmdelphin (PALMD), an isoform of paralemmin protein, was strongly elicited from the phosphorylation of ser46. The mRNA and protein expression of PALMD increased only in wild type p53 transfected cells, but not in ser46-mutated cells. Importantly, PALMD moved to the nucleus in response to DNA damage and the apoptotic function of PALMD was tightly exerted with localization into nucleus. Interestingly, down-regulation of PALMD by siRNA resulted in necroptosis-like cell death through ATP depletion. Moreover, we found vimentin as a PALMD interacting protein and the depletion of vimentin increased PALMD level to accelerate apoptosis. These results demonstrate that p53 regulates cell death fate (apoptosis or necroptosis-like cell death) through promoting PALMD expression in a phospho-ser46-specific manner in response to DNA damage.
Citation Format: Nurmaa Khund Dashzeveg, Kiyotsugu Yoshida. The phosphorylation of p53 at serine 46 is essential to induce cell death through palmdelphin in response to DNA damage. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 24. doi:10.1158/1538-7445.AM2015-24
Abstract 5 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Cell Signaling in Cancer 1
Abstract 48: Identification of a novel binding protein playing a critical role in HER2 activation in lung cancer cells
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
Human epidermal growth factor receptor 2 (HER2) is a member of epidermal growth factor receptor (EGFR) family. Previous studies have revealed that many kinds of malignant tumors have genetic mutations or amplification of HER2, indicating that HER2 alterations are oncogenic. Many kinds of HER2 targeted therapies are effective to HER2 positive tumors, but those treated tumors often get resistance to drugs. Thus, to elucidate HER2 related pathway in cancer biology is important to develop new therapeutic strategy for cancers.
Recently, we newly identified a protein X (a temporary name) as a novel binding protein to HER2 with immunoprecipitation and following LC-Ms/Ms analysis. The protein generally expressed in lung and breast cancers at remarkable level.
We constructed plasmid vectors carrying wild type HER2 and gene X. These vectors were simultaneously introduced to HEK293T cells to examine the binding ability of protein X and HER2 as well as the effect of gene X on HER2-mediated signal-transduction pathway. The approach clearly showed that the expression of gene X, resulted in phosphorylation of HER2 and subsequent activation of oncogenic effector molecules.
We next constructed several kinds of gene X-truncated variants and subjected to the binding assay to look for the binding domain of gene X to HER2. The analysis showed that N-terminal head domain of gene X was essential for the HER2 binding. This domain has an ability to induce HER2 phosphorylation and subsequent activation of the effector kinase, ERK.
In conclusion, we found that gene X is a novel binding protein to HER2 and has a role in HER2 activation.
Citation Format: Tomoaki Ohtsuka, Masakiyo Sakaguchi, Katsuyoshi Takata, Shinsuke Hashida, Mototsugu Watanabe, Ken Suzawa, Yuho Maki, Hiromasa Yamamoto, Junichi Soh, Hiroaki Asano, Kazunori Tsukuda, Shinichiro Miyoshi, Shinichi Toyooka. Identification of a novel binding protein playing a critical role in HER2 activation in lung cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 48. doi:10.1158/1538-7445.AM2015-48
Abstract 6 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Cell Signaling in Cancer 1
Abstract 54: Ezrin enhances signaling and nuclear translocation of the epidermal growth factor receptor in non-small cell lung cancer cells
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
The cytoskeletal cross linker protein ezrin is a member of the ezrin-radixin-moesin (ERM) family and plays important roles not only in cell motility, cell adhesion, and apoptosis, but also in various cell-signaling pathways. Ezrin interacts with EGFR in the cell membrane and involves in cell motility events, but little is known about the effects of this interaction on the EGFR signaling pathway. We investigated the role of Ezrin in EGFR signaling and nuclear trafficking in non-small cell lung cancer (NSCLC) cell lines. The ligand induced interaction between Ezrin and EGFR was evaluated by immunoprecipitation (IP) and immunofluorescence (IF) in H292 and A549 cells. Ezrin levels were reduced using siRNA in these two cell lines. Downstream signaling protein phosphorylation and nuclear localization of EGFR were detected after EGF treatment. Expressions of nuclear EGFR target genes were evaluated by qPCR. Endogenous Ezrin was found in a complex with EGFR in IP and IF. When Ezrin protein expression was inhibited, phosphorylation levels of EGFR at Y1068, Y1101 and Y845 were reduced as well as phosphorylation levels of downstream signaling pathway proteins ERK and STAT3. Cell fractionation revealed that EGFR nuclear translocation after EGF treatment significantly reduced in Ezrin-knockdown cells. Further, mRNA levels of EGFR target genes AuroraK-A, COX2, Cyclin D1 and iNOS were decreased in Ezrin-knockdown A549 cells. Small molecule ezrin inhibitors showed strong synergy with EGFR inhibitors in cytotoxicity assays. These results suggest that Ezrin has a role as an enhancer in the EGFR pathway and targeting ezrin may potentiate anti-EGFR based therapies in NSCLC.
Citation Format: Yasemin Saygideger Kont, Haydar Celik, Hayriye V. Erkizan, Tsion Minas, Jenny Han, Jeffrey Toretsky, Aykut Uren. Ezrin enhances signaling and nuclear translocation of the epidermal growth factor receptor in non-small cell lung cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 54. doi:10.1158/1538-7445.AM2015-54
Abstract 7 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Cell Signaling in Cancer 1
Abstract 57: Substrates of protein kinase C drive cell rac1-dependent motility
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
This laboratory has identified and/or characterized substrates of PKC that upon phosphorylation give rise to motility, an aspect of metastasis. By use of the traceable kinase method, we discovered that alpha-tubulin and Cdc42 effector protein-4 (CEP4) are PKC substrates. Phosphorylation of alpha-tubulin stimulates its incorporation into microtubules (MTs), consequently increasing the stability and prolonged growth of MTs and leading to the activation of the small GTPase Rac1. CEP4 undergoes phosphorylation by PKC that results in its release from Cdc42, whereupon CEP4 binds a guanine nucleotide exchange factor (GEF) that in turn activates Rac1 GTPase. These results imply that Rac1 acts as a node in pathways driven by phosphorylated PKC substrates. Since translocation of IQGAP to the membrane is known to be promoted by Rac1, a role is explored in non-transformed human MCF-10A cells that express a specific phospho-mimetic mutant substrate. In addition, the phospho-mimetic mutant for each substrate expressed in human metastatic MDA-MB-231 cells produces different morphologies in 3-D growth assays. This research is being supported by NIH CA125632.
Citation Format: Susan A. Rotenberg, Xin Zhao, Shatarupa De. Substrates of protein kinase C drive cell rac1-dependent motility. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 57. doi:10.1158/1538-7445.AM2015-57
Abstract 8 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Deregulation of Gene Expression in Prostate Cancer and Sarcoma
Abstract 88: The Nkx3.1 homeobox gene maintains prostatic identity while its loss leads to prostate cancer initiation
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
Background
Maintenance of epithelial cell identity is tightly coordinated by tissue-specific gene expression programs, which are often deregulated during tumorigenesis. The homeodomain-containing transcription factor, Nkx3.1, is a key regulator of normal prostatic development and is frequently lost at early stages of prostate cancer initiation. In this study, we aim to elucidate detailed mechanisms governing Nkx3.1-driven maintenance of prostate identity and how deregulation of such can lead to prostate tumorigenesis.
Models and Methods
We evaluated the consequences of Nkx3.1 loss or gain of function in vivo using genetically-engineered mouse models and cell-recombination assays. RNA sequencing was performed to generate gene expression profiles, which were analyzed using Gene Set Enrichment analysis (GSEA), and validated by quantitative real-time PCR. In parallel, protein expression was assessed by immunofluorescence and western blot. Immunoprecipitation (IP) and chromatin-immunoprecipitation (ChIP) assays were performed using RWPE1 prostate epithelial cells.
Results
Here, we show that loss of function of Nkx3.1 leads to the progressive down-regulation of a prostate-specific gene expression program and to aberrant expression of genes that are not typically expressed in the prostate epithelium. Conversely, gain of function of Nkx3.1 in non-prostatic epithelium leads to the acquisition of a prostate-like morphology and expression of prostate-related genes. Our findings indicate that the underlying mechanism by which Nkx3.1 promotes prostatic identity is via epigenetic regulation of gene expression. In particular, we show that Nkx3.1 interacts with the histone methyl-transferase complex G9a/Glp. Finally, we demonstrate that this interaction is necessary for maintenance of prostate identity in vivo and that Nkx3.1 and G9a cooperate to control expression of genes that coordinate prostatic epithelial integrity.
Conclusions
Our results suggest that Nkx3.1 promotes prostatic identity by interacting with histone modifying enzymes to coordinate the expression of prostate-specific genes and that the loss of this function results in a failure to maintain prostate identity associated with early stages of prostate tumorigenesis.
Citation Format: Clémentine Le Magnen, Aditya Dutta, Cory Abate-Shen. The Nkx3.1 homeobox gene maintains prostatic identity while its loss leads to prostate cancer initiation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 88. doi:10.1158/1538-7445.AM2015-88
Abstract 9 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Deregulation of Gene Expression in Prostate Cancer and Sarcoma
Abstract 90: K63-linked JARID1B ubiquitination by TRAF6 contributes to aberrant elevation of JARID1B in prostate cancer
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
Aberrant elevation of JARID1B and histone H3 Lys4 trimethylations (H3K4me3) is frequently observed in many diseases including prostate cancer (PCa), yet the mechanisms on the regulations of JARID1B and H3K4me3 through epigenetic modifications still remain poorly understood. In this study we performed immunohistochemistry staining, immunofluorescence imaging, immunoprecipitation, shRNA and Western blotting analysis in mouse embryonic fibroblasts (MEFs), mouse models, and cultured human prostate cancer cells. As a result, we discovered that SKP2 modulates JARID1B and H3K4me3 levels in vitro in PTEN null prostate cancer cells and in vivo in Pten/Trp53 mouse models. We demonstrated that levels of SKP2, JARID1B and H3K4me3 are strikingly elevated in vitro and in vivo when both PTEN and P53 are inactivated. Importantly, SKP2 inactivation resulted in a reduction of cell growth, cell migration and malignant transformation of Pten/Trp53 double null MEFs, and further restrained prostate tumorigenesis of Pten/Trp53 mutant mice. Mechanistically, JARID1B is ubiquitinated by E3 ligase TRAF6 through the K63-linkage in prostate cancer cells. Interestingly, SKP2 contributes to JARID1B ubiquitination machinery as a non-E3 ligase regulator by decreasing TRAF6-mediated ubiquitination of JARID1B. SKP2 deficiency resulted in an increase of JARID1B ubiquitination and in turn a reduction of H3K4me3, and induced senescence through JARID1B accumulation in nucleoli of PCa cells and prostate tumors of mice. Furthermore, we showed that the aberrant levels of SKP2, JARID1B, and H3K4me3 are associated with malignant features of castration-resistant prostate cancer (CRPC) in mice. Overall, our findings reveal a novel network of SKP2- JARID1B, and targeting SKP2 and JARID1B may be a potential strategy for PCa control.
Citation Format: Wenfu Lu, Shenji Liu, Bo Li, Yingqiu Xie, Christine Adhiambo, Qing Yang, Billy R. Ballard, Keiichi I. Nakayama, Robert J. Matusik, Zhenbang Chen. K63-linked JARID1B ubiquitination by TRAF6 contributes to aberrant elevation of JARID1B in prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 90. doi:10.1158/1538-7445.AM2015-90
Abstract 10 of 10Molecular and Cellular Biology / Poster Presentations – Proffered Abstracts / Poster Presentations – Histone Methylation and Acetylation
Abstract 97: CARM1 preferentially methylates H3R17 over H3R26 through a random kinetic mechanism
Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA
CARM1 (PRMT4) is a type I arginine methyltransferase involved in the regulation of transcription, pre-mRNA splicing, cell cycle progression and the DNA damage response. Overexpression of CARM1 has been implicated in breast, prostate, and colorectal cancers. Since CARM1 appears to be a good target for the development of therapies against these cancers, we studied the substrate specificity and kinetic mechanism of the full-length human enzyme. CARM1 has been shown to methylate both residues R17 and R26 of histone H3. Substrate specificity was examined by testing CARM1 activity with several H3-based peptide substrates using a radiometric assay. Comparison of kcat/KM values reveal that methylation of H3R17 is preferred over H3R26. An R17/R26K peptide produced 8-fold greater kcat/KM value compared to the corresponding R17K/R26 peptide. These effects are KM-driven as kcat values remain relatively constant for the peptides tested. Shortening the peptide at the C-terminus by 5 amino acid residues greatly reduced the specificity (16-24-fold), demonstrating the contribution of distal residues to substrate binding. In contrast, adding residues to the N-terminus of the shortened peptide had a negative effect on activity. CARM1 displays little preference for monomethylated over unmethylated H3R17 (2-5-fold by kcat/KM) suggesting that it operates through a distributive mechanism. Previous crystallographic studies with mouse CARM1 showed that part of the substrate binding groove was formed by cofactor binding, thereby suggesting an ordered kinetic mechanism (Yue et al., EMBO J., 2007). Our results from dead-end and product inhibition studies performed with human CARM1, however, are consistent with a random kinetic mechanism. SAH and sinefungin demonstrate competitive inhibition with respect to SAM and produced noncompetitive inhibition patterns with respect to peptide. Both dimethylated R17 product peptide and dead-end R17K peptide exhibited noncompetitive inhibition patterns with respect to SAM. Furthermore, binding of SAM and peptide substrates were shown to be independent of each other in initial velocity experiments where both substrates were varied. Together, these results elucidate the kinetic mechanism of CARM1 and highlight elements important for binding affinity.
Citation Format: Suzanne L. Jacques, Katrina P. Aquino, Jodi Gureasko, P Ann Boriack-Sjodin, Robert A. Copeland, Thomas V. Riera. CARM1 preferentially methylates H3R17 over H3R26 through a random kinetic mechanism. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 97. doi:10.1158/1538-7445.AM2015-97
Bonnet D, Dick JE: Human acute myeloid leukemia is organized as a hierarchy that originates from a primitive hematopoietic cell. Nat Med 1997, 3(7):730-737.
Al-Hajj M, Clarke MF: Self-renewal and solid tumor stem cells. Oncogene 2004, 23(43):7274-7282.
Hughes L, Malone C, Chumsri S, Burger AM, McDonnell S: Characterisation of breast cancer cell lines and establishment of a novel isogenic subclone to study migration, invasion and tumourigenicity. Clin Exp Metastasis 2008, 25(5):549-557.
Li C, Lee CJ, Simeone DM: Identification of human pancreatic cancer stem cells. Methods Mol Biol 2009, 568:161-173.
Zhang S, Balch C, Chan MW, Lai HC, Matei D, Schilder JM, Yan PS, Huang TH, Nephew KP: Identification and characterization of ovarian cancer-initiating cells from primary human tumors. Cancer Res 2008, 68(11):4311-4320.
Kakarala M, Wicha MS: Implications of the cancer stem-cell hypothesis for breast cancer prevention and therapy. J Clin Oncol 2008, 26(17):2813-2820.
Ginestier C, Hur MH, Charafe-Jauffret E, Monville F, Dutcher J, Brown M, Jacquemier J, Viens P, Kleer CG, Liu S et al: ALDH1 is a marker of normal and malignant human mammary stem cells and a predictor of poor clinical outcome. Cell Stem Cell 2007, 1(5):555-567.
Dontu G: Breast cancer stem cell markers – the rocky road to clinical applications. Breast Cancer Res 2008, 10(5):110.
Ferrandina G, Bonanno G, Pierelli L, Perillo A, Procoli A, Mariotti A, Corallo M, Martinelli E, Rutella S, Paglia A et al: Expression of CD133-1 and CD133-2 in ovarian cancer. Int J Gynecol Cancer 2008, 18(3):506-514.
Additional Articles on this Open Access Journal on Cancer Stem Cells Include
Can IntraTumoral Heterogeneity Be Thought of as a Mechanism of Resistance?
Curator/Reporter: Stephen J. Williams, Ph.D.
Therapeutic resistance remains one of the most challenging problems for the oncologist, despite the increase of new therapeutics in the oncologist’s toolkit. As new targeted therapies are developed, and new novel targets are investigated as potential therapies, especially cytostatic therapies which it has become evident our understanding of chemoresistance is expanding beyond mechanisms to circumvent a drug’s pharmacologic mechanism of action (i.e. increased DNA repair and cisplatin) or pharmacokinetic changes (i.e. increased efflux by acquisition of a MDR phenotype).
To recount a bit of background I list the overall points of the one of previous posts on tumor heterogeneity (and an interview with Dr. Charles Swanton) are as follows:
Multiple biopsies of primary tumor and metastases are required to determine the full mutational landscape of a patient’s tumor
The intratumor heterogeneity will have an impact on the personalized therapy strategy for the clinician
Metastases arising from primary tumor clones will have a greater genomic instability and mutational spectrum than the tumor from which it originates
Tumors and their metastases do NOT evolve in a linear path but have a branched evolution and would complicate biomarker development and the prognostic and resistance outlook for the patient
The following is a curation of various talks and abstracts from the 2015 AACR National Meeting in Philadelphia on effects of clonal evolution and intratumoral heterogeneity of a tumor with respect to development of chemoresistance. As this theory of heterogeneity and clonal evolution is particularly new I attempted to present all works (although apologize for the length upfront) to forgo bias and so the reader may extract any information pertinent to their clinical efforts and research. However I will give a brief highlight summary below:
From the 2015 AACR National Meeting in Philadelphia
PresentationNumber:NGO2
Presentation Title:
Polyclonal and heterogeneous resistance to targeted therapy in leukemia
Presentation Time:
Monday, Apr 20, 2015, 10:40 AM -10:55 AM
Location:
Room 201, Pennsylvania Convention Center
Author Block:
Catherine C. Smith, Amy Paguirigan, Chen-Shan Chin, Michael Brown, Wendy Parker, Mark J. Levis, Alexander E. Perl, Kevin Travers, Corynn Kasap, Jerald P. Radich, Susan Branford, Neil P. Shah. University of California, San Francisco, CA, Fred Hutchinson Cancer Research Center, Seattle, WA, Pacific Biosciences, Menlo Park, CA, Royal Adelaide Hospital, Adelaide, Australia, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, Abramson Cancer Center of the University of Pennsylvania, Philadelphia, PA, University of California, San Francisco, CA
Abstract Body:
Genomic studies in solid tumors have revealed significant branching intratumoral clonal genetic heterogeneity. Such complexity is not surprising in solid tumors, where sequencing studies have revealed thousands of mutations per tumor genome. However, in leukemia, the genetic landscape is considerably less complex. Chronic myeloid leukemia (CML) is the human malignancy most definitively linked to a single genetic lesion, the BCR-ABL gene fusion. Genome wide sequencing of acute myeloid leukemia (AML) has revealed that AML is the most genetically straightforward of all extensively sequenced adult cancers to date, with an average of 13 coding mutations and 3 or less clones identified per tumor.
In CML, tyrosine kinase inhibitors (TKIs) of BCR-ABL have resulted in high rates of remission. However, despite excellent initial response rates with TKI monotherapy, patients still relapse, including virtually all patients with Philadelphia-positive acute lymphoblastic leukemia and blast crisis CML. Studies of clinical resistance highlight BCR-ABL as the sole genetic driver in CML as secondary kinase domain (KD) mutations that prevent drug binding are the predominant mechanism of relapse on BCR-ABL TKIs.
In AML, a more diverse panel of disease-defining genetic mutations has been uncovered. However, in individual patients, a single oncogene can still drive disease. This is the case in FLT3 mutant AML, in which the investigational FLT3 TKI quizartinib achieved an initial response rate of ~50% in relapsed/refractory AML patients with activating FLT3 internal tandem duplication (ITD) mutations, though most patients eventually relapsed. Confirming the importance of FLT3 in disease maintenance, we showed that 8 of 8 patients who relapsed on quizartinib did so due to acquired drug-resistant FLT3 KD mutations.
Studies in CML have revealed that sequential TKI therapy is associated with additional complexity where multiple mutations can coexist separately in an individual patient (“polyclonality”) or in tandem on a single allele (“compound mutations”). In AML, we observed polyclonal FLT3-ITD KD mutations in 2 of 8 patients examined in our initial study of quizartinib resistance.
In light of the polyclonal KD mutations observed in CML and AML at the time of TKI relapse, we undertook next generation sequencing studies to determine the true genetic complexity in CML and AML patients at the time of relapse on targeted therapy. We used Pacific Biosciences RS Single Molecule Real Time (SMRT) third generation sequencing technology to sequence the entire ABL KD or the entire FLT3 juxtamembrane and KD on a single strand of DNA. Using this method, we assessed a total of 103 samples from 79 CML patients on ABL TKI therapy and 36 paired pre-treatment and relapse samples from 18 FLT3-ITD+ AML patients who responded to investigational FLT3 TKI therapy.
In CML, using SMRT sequencing, we detected all mutations previously detected by direct sequencing. Of samples in which multiple mutations were detectable by direct sequencing, 85% had compound mutant alleles detectable in a variety of combinations. Compound mutant alleles were comprised of both dominant and minor mutations, some which were not detectable by direct sequencing. In the most complex case, 12 individual mutant alleles comprised of 7 different mutations were identified in a single sample.
For 12 CML patients, we interrogated longitudinal samples (2-4 time points per patient) and observed complex clonal relationships with highly dynamic shifts in mutant allele populations over time. We detected compound mutations arising from ancestral single mutant clones as well as parallel evolution of de novo polyclonal and compound mutations largely in keeping with what would be expected to cause resistance to the second generation TKI therapy received by that patient.
We used a phospho-flow cytometric technique to assesses the phosphorylation status of the BCR-ABL substrate CRKL in as a method to test the ex vivo biochemical responsiveness of individual mutant cell populations to TKI therapy and assess functional cellular heterogeneity in a given patient at a given timepoint. Using this technique, we observed co-existing cell populations with differential ex vivo response to TKI in 2 cases with detectable polyclonal mutations. In a third case, we identified co-existence of an MLL-AF9 containing cell population that retained the ability to modulate p-CRKL in response to BCR-ABL TKIs along with a BCR-ABL containing only population that showed biochemical resistance to all TKIs, suggesting the co-existence of BCR-ABL independent and dependent resistance in a single patient.
In AML, using SMRT sequencing, we identified acquired quizartinib resistant KD mutations on the FLT3-ITD (ITD+) allele of 9 of 9 patients who relapsed after response to quizartinib and 4 of 9 patients who relapsed after response to the investigational FLT3 inhibitor, PLX3397. In 4 cases of quizartinib resistance and 3 cases of PLX3397 resistance, polyclonal mutations were observed, including 7 different KD mutations in one patient with PLX3397 resistance. In 7 quizartinib-resistant cases and 3 PLX3397-resistant cases, mutations occurred at the activation loop residue D835. When we examined non-ITD containing (ITD-) alleles, we surprisingly uncovered concurrent drug-resistant FLT3 KD mutations on ITD- alleles in 7 patients who developed quizartinib resistance and 4 patients with PLX3397 resistance. One additional PLX3397-resistant patient developed a D835Y mutation only in ITD- alleles at the time of resistance, suggesting selection for a non-ITD containing clone. All of the individual substitutions found on ITD- alleles were the same substitutions identified on ITD+ alleles for each individual patient.
Given that the same individual mutations found on ITD- alleles were also found on ITD+ alleles, we sought to determine whether these mutations were found in the same cell or were indicative of polyclonal blast populations in each patient. To answer this question, we performed single cell sorting of viably frozen blasts from 3 quizartinib-resistant patients with D835 mutations identified at the time of relapse and genotyped single cells for the presence or absence of ITD and D835 mutations. This analysis revealed striking genetic heterogeneity. In 2/3 cases, polyclonal D835 mutations were found in both ITD+ and ITD- cells. In all cases, FLT3-ITD and D835 mutations were found in both heterozygous and homozygous combinations. Most surprisingly, in all 3 patients, approximately 30-40% of FLT3-ITD+ cells had no identified quizartinib resistance-causing FLT3 KD mutation to account for resistance, suggesting the presence of non-FLT3 dependent resistance in all patients.
To determine that ITD+ cells lacking FLT3 KD mutations observed in patients relapsed on quizartinib are indeed consistent with leukemic blasts functionally resistant to quizartinib and do not instead represent a population of differentiated or non-proliferating cells, we utilized relapse blasts from another patient who initially achieved clearance of bone marrow blasts on quizartinib and developed a D835Y mutation at relapse. We performed a colony assay in the presence of 20nM quizartinib. As expected, this dose of quizartinib was unable to suppress the colony-forming ability of blasts from this relapsed patient when compared to DMSO treatment. Genotyping of individual colonies grown from this relapse sample in the presence of 20nM quizartinib again showed remarkable genetic heterogeneity, including ITD+ and ITD- colonies with D835Y mutations in homozygous and heterozygous combinations as well as ITD+ colonies without D835Y mutations, again suggesting the presence of blasts with non-FLT3 dependent resistance. Additionally, 4 colonies with no FLT3 mutations at all were identified in this sample, suggesting the presence of a quizartinib-resistant non-FLT3 mutant blast population. To see if we could identify specific mechanisms of off-target resistance, we performed targeted exome sequencing 33-AML relevant genes from relapse and pre-treatment DNA from all four patients and detected no new mutations in any genes other than FLT3 acquired at the time of disease relapse. Clonal genetic heterogeneity is not surprising in solid tumors, where multiple driver mutations frequently occur, but in CML and FLT3-ITD+ AML, where disease has been shown to be exquisitely dependent on oncogenic driver mutations, our studies suggest a surprising amount of clonal diversity. Our findings show that clinical TKI resistance in these diseases is amazingly intricate on the single allele level and frequently consists of both polyclonal and compound mutations that give rise to an complicated pool of TKI-resistant alleles that can change dynamically over time. In addition, we demonstrate that cell populations with off-target resistance can co-exist with other TKI-resistant populations, underscoring the emerging complexity of clinical TKI resistance. Such complexity argues strongly that monotherapy strategies in advanced CML and AML may be ultimately doomed to fail due to heterogeneous cell intrinsic resistance mechanisms. Ultimately, combination strategies that can address both on and off target resistance will be required to effect durable therapeutic responses.
Session Title:
Tumor Heterogeneity and Evolution
Session Type:
Educational Session
Session Start/End Time:
Saturday, Apr 18, 2015, 1:00 PM – 3:00 PM
Location:
Terrace Ballroom II-III (400 Level), Pennsylvania Convention Center
CME:
CME-Designated
CME/CE Hours:
2
Session Description:
One of the major challenges for both the measurement and management of cancer is its heterogeneity. Recent studies have revealed both extensive inter- and intra-tumor heterogeneity at the genotypic and phenotypic levels. Leaders in the field will discuss this challenge, its origins, dynamics and clinical importance. They will also review how we can best measure and deal with tumor heterogeneity, particularly intra-tumor heterogeneity.
Bozic I, Reiter JG, Allen B, Antal T, Chatterjee K, Shah P, Moon YS, Yaqubie A, Kelly N, Le DT, Lipson EJ, Chapman PB, Diaz LA Jr, Vogelstein B, Nowak MA.
Elife. 2013 Jun 25;2:e00747. doi: 10.7554/eLife.00747.
Despite dramatic advances in the treatment of cancer, therapy resistance remains the most significant hurdle in improving the outcome of cancer patients. In this session, we will discuss many different aspects of therapy resistance, including a summary of our current understanding of therapy resistant tumor cell populations as well as analyses of the challenges associated with intratumoral heterogeneity and adaptive responses to targeted therapies.
Clonal evolution of the HER2 L755S mutation as a mechanism of acquired HER-targeted therapy resistance
Presentation Time:
Sunday, Apr 19, 2015, 1:00 PM – 5:00 PM
Location:
Section 30
Poster Board Number:
29
Author Block:
Xiaowei Xu1, Agostina Nardone1, Huizhong Hu1, Lanfang Qin1, Sarmistha Nanda1, Laura Heiser2, Nicholas Wang2, Kyle Covington1, Edward Chen1, Alexander Renwick1, Tamika Mitchell1, Marty Shea1, Tao Wang1, Carmine De Angelis1, Alejandro Contreras1, Carolina Gutierrez1, Suzanne Fuqua1, Gary Chamness1, Chad Shaw1, Marilyn Li1, David Wheeler1, Susan Hilsenbeck1, Mothaffar Fahed Rimawi1, Joe Gray2, C.Kent Osborne1, Rachel Schiff1. 1Baylor College of Medicine, Houston, TX; 2Oregon Health & Science University, Portland, OR
Abstract Body:
Background: Targeting HER2 with lapatinib (L), trastuzumab (T), or the LT combination, is effective in HER2+ breast cancer (BC), but acquired resistance commonly occurs. In our 12-week neoadjuvant
trial (TBCRC006) of LT without chemotherapy in HER2+ BC, the overall pathologic complete response (pCR) rate was 27%. To investigate resistance mechanisms, we developed 10 HER2+ BC cell line
models resistant (R) to one or both drugs (LR/TR/LTR). To discover potential predictive markers/therapeutic targets to circumvent resistance, we completed genomic profiling of the cell lines and a
subset of pre-treatment specimens from TBCRC006.
Methods: Parental (P) and LR/TR/LTR lines of 10 cell line models were profiled with whole exome/RNA sequencing. Mutations detected in R lines but not in P lines of the same model were identified. Mutation-specific Q-PCR was designed for sensitive quantification. Resistant cell and xenograft tumor growth were measured in response to drugs. Whole exome sequencing (>100X) and Ampliseq of 17 baseline tumor/normal pairs from TBCRC006 were performed.
Results: We found and validated the HER2 L755S mutation in the BT474/ATCC-LTR line and BT474/AZ-LR line (in ~30% of DNA/RNA), in which the HER pathway was reactivated for resistance. Overexpression of this mutation was previously shown to induce LR in HER2-negative BC cell lines, and resistant growth of BT474/AZ-LR line is significantly inhibited by HER2-L755S-specific siRNA knock-down, suggesting its role as an acquired L/LT resistance driver in HER2+ BC. Sequencing of BT474/AZ-LR single cell clones found the mutation in ~30% of HER2 copies in every cell. Using mutation-specific Q-PCR, we found statistically higher HER2 L755S levels in two BT474 parentals compared to P lines of SKBR3, AU565, and UACC812. These data suggest that HER2 L755S resistant subclones preexist in the BT474 parentals and were selected by L treatment to become the major clone in the two R lines. The HER1/2 irreversible tyrosine kinase inhibitor (TKI) afatinib (Afa) robustly inhibited growth of BT474/AZ-LR and BT474/ATCC-LTR cells (IC50: Afa 0.02µM vs. L 3 µM) and BT474/AZ-LR xenografts. Whole exome sequencing/Ampliseq of TBCRC006 found the HER2 L755S mutation in 1/17 primaries. This patient did not achieve pCR. The variant was present in 2% of DNA on both platforms, indicating a subclonal event of the resistance mutation.
Conclusion: Acquired L/LT resistance in the two BT474 R lines is due to selection of HER2 L755S subclones present in parental cells. The higher HER2 L755S
levels in BT474 parentals compared with other parentals, and detection of its subclonal presence in a pre-treatment HER2+ BC patient, suggest that sensitive mutation detection methods will be needed to identify patients with potentially actionable HER family mutations in primary tumor. Treating this patient group
with an irreversible TKI like Afa may prevent resistance and improve clinical outcome of this subset of HER2+ BC.
Presentation Number:
SY07-04
Presentation Title:
The evolutionary landscape of CLL: Therapeutic implications
Presentation Time:
Sunday, Apr 19, 2015, 2:25 PM – 2:45 PM
Location:
Grand Ballroom (300 Level), Pennsylvania Convention Center
Author Block:
Catherine J. Wu. Dana-Farber Cancer Institute, Boston, MA
Abstract Body:
Clonal evolution is a key feature of cancer progression and relapse. Recent studies across cancers have demonstrated the extensive degree of intratumoral heterogeneity present within individual cancers. We hypothesized that evolutionary dynamics contribute to the variations in disease tempo and response to therapy that are highly characteristic of chronic lymphocytic leukemia (CLL). We have recently investigated this phenomenon by developing a pipeline that estimates the fraction of cancer cells harboring each somatic mutation within a tumor through integration of whole-exome sequence (WES) and local copy number data (Landau et al., Cell 2013). By applying this analysis approach to 149 CLL cases, we discovered earlier and later cancer drivers, uncovered patterns of clonal evolution in CLL and linked the presence of subclones harboring driver mutations with adverse clinical outcome. Thus, our study, generated from a heterogeneous sample cohort, strongly supports the concept that CLL clonal evolution arises from mass extinction and therapeutic bottlenecks which lead to the emergence of highly fit (and treatment resistant) subclones. We further hypothesized that epigenetic heterogeneity also shapes CLL clonal evolution through interrelation with genetic heterogeneity. Indeed, in recent work, we have uncovered stochastic methylation disorder as the primary cause of methylation changes in CLL and cancer in general, and that this phenomena impacts gene transcription, genetic evolution and clinical outcome. Thus, integrated studies of genetic and epigenetic heterogeneity in CLL have revealed the complex and diverse evolutionary trajectories of these cancer cells.
Immunotherapy is exquisitely suited for specifically and simultaneously targeting multiple lesions. We have developed an approach that leverages whole-exome sequencing to systematically identify personal tumor mutations with immunogenic potential, which can be incorporated as antigen targets in multi-epitope personalized therapeutic vaccines. We are pioneering this approach in an ongoing trial in melanoma and will now expand this concept to address diverse malignancies. Our expectation is that the choice of tumor neoantigens for a vaccine bypasses thymic tolerance and thus generates highly specific and potent high-affinity T cell responses to eliminate tumors in any cancer, including both ‘trunk’ and ‘branch’ lesions.
Abstract Number:
LB-056
Presentation Title:
TP53 and RB1 alterations promote reprogramming and antiandrogen resistance in advanced prostate cancer
Presentation Time:
Sunday, Apr 19, 2015, 4:50 PM – 5:05 PM
Location:
Room 122, Pennsylvania Convention Center
Author Block:
Ping Mu, Zhen Cao, Elizabeth Hoover, John Wongvipat, Chun-Hao Huang, Wouter Karthaus, Wassim Abida, Elisa De Stanchina, Charles Sawyers. Memorial Sloan Kettering Cancer Center, New York, NY
Abstract Body:
Castration-resistant prostate cancer (CRPC) is one of the most difficult cancers to treat with conventional methods and is responsible for nearly all prostate cancer deaths in the US. The Sawyers laboratory first showed that the primary mechanism of resistance to antiandrogen therapy is elevated androgen receptor (AR) expression. Research based on this finding has led to the development of next-generation antiandrogen: enzalutamide. Despite the exciting clinical success of enzalutamide, about 60% of patients exhibit various degrees of resistance to this agent. Highly variable responses to enzalutamide limit the clinical benefit of this novel antiandrogen, underscoring the importance of understanding the mechanisms of enzalutamide resistance. Most recently, an unbiased SU2C-Prostate Cancer Dream Team metastatic CRPC sequencing project led by Dr. Sawyers and Dr. Chinnaiyan revealed that mutations in the TP53 locus are the most significantly enriched alteration in CRPC tumors when compared to primary prostate cancers. Moreover, deletions and decreased expressions of the TP53 and RB1 loci (co-occurrence and individual occurrence) are more commonly associated with CRPC than with primary tumors. These results established that alteration of the TP53 and RB1 pathways are associated with the development of antiandrogen resistance.
By knockdowning TP53 or/and RB1 in the castration resistant LNCaP/AR model, we demonstrate that the disruption of either TP53 or RB1 alone confers significant resistance to enzalutamide both in vitro and in vivo. Strikingly, the co-inactivation of these pathways confers the most dramatic resistance. Since up-regulation of either AR or AR target genes is not observed in the resistant tumors, loss of TP53 and RB1 function confers enzalutamide resistance likely through an AR independent mechanism. In the clinic, resistance to enzalutamide is increasingly being associated with a transition to a poorly differentiated or neuroendocrine-like histology. Interestingly, we observed significant up-regulations of the basal cell marker Ck5 and the neuroendocrine-like cell marker Synaptophysin in the TP53 and RB1 inactivated cells, as well as down-regulation of the luminal cell marker Ck8. The differences between these markers became even greater after enzalutamide treatment. By using the p53-stabilizing drug Nutlin, level of p53 is rescued and consequently the the decrease of AR protein caused by RB1 and TP53 knockdown is reversed. These results strongly suggest that interference of TP53 and RB1 pathways confers antiandrogen resistance by “priming” prostate cancer cells to reprogramming or transdifferentiation, likely neuroendocrine-like differentiation, in response to treatment. Futher experiments will be performed to assess the molecular mechanism of TP53/RB1 alterations in mediating cell programming and conferring antiandrogen resistance.
Abstract Number:
LB-146
Presentation Title:
TGF-β-induced tumor heterogeneity and drug resistance of cancer stem cells
Presentation Time:
Monday, Apr 20, 2015, 1:00 PM – 5:00 PM
Location:
Section 41
Author Block:
Naoki Oshimori1, Daniel Oristian1, Elaine Fuchs2. 1Rockefeller University, New York, NY; 2HHMI/Rockefeller University, New York, NY
Abstract Body:
Among the most common and life-threatening cancers world-wide, squamous cell carcinoma (SCC) exhibit high rates of tumor recurrence following anti-cancer therapy. Subsets of cancer stem cells (CSCs) often escape anti-cancer therapeutics and promote recurrence. However, its sources and mechanisms that generate tumor heterogeneity and therapy-resistant cell population are largely unknown. Tumor microenvironment may drive intratumor heterogeneity by transmitting signaling factors, oxygen and metabolites to tumor cells depending on their proximity to the local sources. While the hypothesis is attractive, experimental evidence is lacking, and non-genetic mechanisms that drive functional heterogeneity remain largely unknown. As a potential non-genetic factor, we focused on TGF-β because of its multiple roles in tumor progression.
Here we devise a functional reporter system to monitor, track and modify TGF-β signaling in mouse skin SCC in vivo. Using this approach, we found that perivascular TGF-β in the tumor microenvironment generates heterogeneity in TGF-β signaling in neighboring CSCs. This heterogeneity is functionally important: small subsets of TGF-β-responding CSCs proliferate more slowly than their non-responding counterparts. They also exhibit invasive morphology and a malignant differentiation program compared to their non-responding neighbors. By lineage tracing, we show that although TGF-β-responding CSCs clonally expand more slowly they gain a growth advantage in a remarkable ability to escape cisplatin-induced apoptosis. We show that indeed it is their progenies that make a substantial contribution in tumor recurrence. Surprisingly, the slower proliferating state of this subset of CSCs within the cancer correlated with but did not confer the survival advantage to anti-cancer drugs. Using transcriptomic, biochemical and genetic analyses, we unravel a novel mechanism by which heterogeneity in the tumor microenvironment allows a subset of CSCs to respond to TGF-β, and evade anti-cancer drugs.
Our findings also show that TGF-β established ability to suppress proliferation and promote invasion and metastasis do not happen sequentially, but rather simultaneously. This new work build upon the roles of this factor in tumor progression, and sets an important paradigm for a non-genetic factor that produces tumor heterogeneity.
Abstract Number:
LB-129
Presentation Title:
Identifying tumor subpopulations and the functional consequences of intratumor heterogeneity using single-cell profiling of breast cancer patient-derived xenografts
Presentation Time:
Monday, Apr 20, 2015, 1:00 PM – 5:00 PM
Location:
Section 41
Author Block:
Paul Savage1, Sadiq M. Saleh1, Ernesto Iacucci1, Timothe Revil1, Yu-Chang Wang1, Nicholas Bertos1, Anie Monast1, Hong Zhao1, Margarita Souleimanova1, Keith Szulwach2, Chandana Batchu2, Atilla Omeroglu1, Morag Park1, Ioannis Ragoussis1. 1McGill University, Montreal, QC, Canada; 2Fluidigm Corporation, South San Francisco, CA
Abstract Body:
Human breast tumors have been shown to exhibit extensive inter- and intra-tumor heterogeneity. While recent advances in genomic technologies have allowed us to deconvolute this heterogeneity, few studies have addressed the functional consequences of diversity within tumor populations. Here, we identified an index case for which we have derived a patient-derived xenograft (PDX) as a renewable tissue source to identify subpopulations and perform functional assays. On pathology, the tumor was an invasive ductal carcinoma which was hormone receptor-negative, HER2-positive (IHC 2+, FISH average HER2/CEP17 2.4), though the FISH signal was noted to be heterogeneous. On gene expression profiling of bulk samples, the primary tumor and PDX were classified as basal-like. We performed single cell RNA and exome sequencing of the PDX to identify population structure. Using a single sample predictor of breast cancer subtype, we have identified single basal-like, HER2-enriched and normal-like cells co-existing within the PDX tumor. Genes differentially expressed between these subpopulations are involved in proliferation and differentiation. Functional studies distinguishing these subpopulations are ongoing. Microfluidic whole genome amplification followed by whole exome capture of 81 single cells showed high and homogeneous target enrichment with >75% of reads mapping uniquely on target. Variant calling using GATK and Samtools revealed founder mutations in key genes as BRCA1 and TP53, as well as subclonal mutations that are being investigated further. Loss of heterozygocity was observed in 16 TCGA cancer driver genes and novel mutations in 7 cancer driver genes. These findings may be important in understanding the functional consequences of intra-tumor heterogeneity with respect to clinically important phenotypes such as invasion, metastasis and drug-resistance.
Abstract Number:
2847
Presentation Title:
High complexity barcoding to study clonal dynamics in response to cancer therapy
Presentation Time:
Monday, Apr 20, 2015, 4:35 PM – 4:50 PM
Location:
Room 118, Pennsylvania Convention Center
Author Block:
Hyo-eun C. Bhang1, David A. Ruddy1, Viveksagar Krishnamurthy Radhakrishna1, Rui Zhao2, Iris Kao1, Daniel Rakiec1, Pamela Shaw1, Marissa Balak1, Justina X. Caushi1, Elizabeth Ackley1, Nicholas Keen1, Michael R. Schlabach1, Michael Palmer1, William R. Sellers1, Franziska Michor2, Vesselina G. Cooke1, Joshua M. Korn1, Frank Stegmeier1. 1Novartis Institutes for BioMedical Research, Cambridge, MA; 2Dana-Farber Cancer Institute, Boston, MA
Abstract Body:
Targeted therapies, such as erlotinib and imatinib, lead to dramatic clinical responses, but the emergence of resistance presents a significant challenge. Recent studies have revealed intratumoral heterogeneity as a potential source for the emergence of therapeutic resistance. However, it is still unclear if relapse/resistance is driven predominantly by pre-existing or de novo acquired alterations. To address this question, we developed a high-complexity barcode library, ClonTracer, which contains over 27 million unique DNA barcodes and thus enables the high resolution tracking of cancer cells under drug treatment. Using this library in two clinically relevant resistance models, we demonstrate that the majority of resistant clones pre-exist as rare subpopulations that become selected in response to therapeutic challenge. Furthermore, our data provide direct evidence that both genetic and non-genetic resistance mechanisms pre-exist in cancer cell populations. The ClonTracer barcoding strategy, together with mathematical modeling, enabled us to quantitatively dissect the frequency of drug-resistant subpopulations and evaluate the impact of combination treatments on the clonal complexity of these cancer models. Hence, monitoring of clonal diversity in drug-resistant cell populations by the ClonTracer barcoding strategy described here may provide a valuable tool to optimize therapeutic regimens towards the goal of curative cancer therapies.
Abstract Number:
3590
Presentation Title:
Resistance mechanisms to ALK inhibitors
Presentation Time:
Tuesday, Apr 21, 2015, 8:00 AM -12:00 PM
Location:
Section 31
Poster Board Number:
13
Author Block:
Ryohei Katayama1, Noriko Yanagitani1, Sumie Koike1, Takuya Sakashita1, Satoru Kitazono1, Makoto Nishio1, Yasushi Okuno2, Jeffrey A. Engelman3, Alice T. Shaw3, Naoya Fujita1. 1Japanese Foundation for Cancer Research, Tokyo, Japan; 2Graduate School of Medicine, Kyoto University, Kyoto, Japan; 3Massachusetts General Hospital Cancer Center, Boston, MA
Abstract Body:
Purpose: ALK-rearranged non-small cell lung cancer (NSCLC) was first reported in 2007. Approximately 3-5% of NSCLCs harbor an ALK gene rearrangement. The first-generation ALK tyrosine kinase inhibitor (TKI) crizotinib is a standard therapy for patients with advanced ALK-rearranged NSCLC. Several next-generation ALK-TKIs have entered the clinic and have shown promising antitumor activity in crizotinib-resistant patients. As patients still relapse even on these next-generation ALK-TKIs, we examined mechanisms of resistance to one next-generation ALK-TKI – alectinib – and potential strategies to overcome this resistance.
Experimental Procedure: We established a cell line model of alectinib resistance, and analyzed resistant tumor specimens from patients who had relapsed on alectinib. Cell lines were also established under an IRB-approved protocol when there was sufficient fresh tumor tissue. We established Ba/F3 cells expressing EML4-ALK and performed ENU mutagenesis to compare potential crizotinib or alectinib-resistance mutations. In addition, we developed Ba/F3 models harboring ALK resistance mutations and evaluated the potency of multiple next-generation ALK-TKIs including 3rd generation ALK inhibitor in these models and in vivo. To elucidate structure-activity-relationships of ALK resistance mutations, we performed computational thermodynamic simulation with MP-CAFEE.
Results: We identified multiple resistance mutations, including ALK I1171N, I1171S, and V1180L, from the ENU mutagenesis screen and the cell line model. In addition we found secondary mutations at the I1171 residue from the Japanese patients who developed resistance to alectinib or crizotinib. Both ALK mutations (V1180L and I1171 mutations) conferred resistance to alectinib as well as to crizotinib, but were sensitive to ceritinib and other next-generation ALK-TKIs. Based on thermodynamics simulation, each resistance mutation is predicted to lead to distinct structural alterations that decrease the binding affinity of ALK-TKIs for ALK.
Conclusions: We have identified multiple alectinib-resistance mutations from the cell line model, patient derived cell lines, and tumor tissues, and ENU mutagenesis. ALK secondary mutations arising after alectinib exposure are sensitive to other next generation ALK-TKIs. These findings suggest a potential role for sequential therapy with multiple next-generation ALK-TKIs in patients with advanced, ALK-rearranged cancers.
Session Title:
Mechanisms of Resistance: From Signaling Pathways to Stem Cells
Session Type:
Major Symposium
Session Start/End Time:
Tuesday, Apr 21, 2015, 10:30 AM -12:30 PM
Location:
Terrace Ballroom II-III (400 Level), Pennsylvania Convention Center
CME:
CME-Designated
CME/CE Hours:
2
Session Description:
Even the most effective cancer therapies are limited due to the development of one or more resistance mechanisms. Acquired resistance to targeted therapies can, in some cases, be attributed to the selective propagation of a small population of intrinsically resistant cells. However, there is also evidence that cancer drugs themselves can drive resistance by triggering the biochemical- or genetic-reprogramming of cells within the tumor or its microenvironment. Therefore, understanding drug resistance at the molecular and biological levels may enable the selection of specific drug combinations to counteract these adaptive responses. This symposium will explore some of the recent advances addressing the molecular basis of cancer cell drug resistance. We will address how tumor cell signaling pathways become rewired to facilitate tumor cell survival in the face of some of our most promising cancer drugs. Another topic to be discussed involves how drugs select for or induce the reprogramming of tumor cells toward a stem-like, drug resistant fate. By targeting the molecular driver(s) of rewired signaling pathways and/or cancer stemness it may be possible to select drug combinations that prevent the reprogramming of tumors and thereby delay or eliminate the onset of drug resistance.
Tumour heterogeneity and therapy resistance in melanoma
Presentation Time:
Tuesday, Apr 21, 2015, 11:20 AM -11:35 AM
Location:
Terrace Ballroom II-III (400 Level), Pennsylvania Convention Center
Author Block:
Claudia Wellbrock. Univ. of Manchester, Manchester, United Kingdom
Abstract Body:
Solid tumors are structurally very complex; they consist of heterogeneous cancer cell populations, other non-cancerous cell types and a distinct extracellular matrix. Interactions of cancer cells with non-cancerous cells is well investigated, and our recent work in melanoma has demonstrated that the cellular environment that surrounds cancer cells has a major impact on the way a patient responds to MAP-kinase pathway targeting therapy.
We have shown that intra-tumor signaling within a heterogeneous tumor can have a major impact on the efficacy of BRAF and MEK inhibitors. With the increasing evidence of genetic and phenotypic heterogeneity within tumors, intra-tumor signaling between individual cancer-cell subpopulations is therefore a crucial factor that needs to be considered in future therapy approaches. Our work has identified the ‘melanocyte-lineage survival oncogene’ MITF as an important player in phenotypic heterogeneity (MITFhigh and MITFlow cells) in melanoma, and MITF expression levels are crucial for the response to MAP-kinase pathway targeted therapy. We found that ‘MITF heterogeneity’ can be caused by cell-autonomous mechanisms or by the microenvironment, including the immune-microenvironment.
We have identified various mechanisms underlying MITF action in resistance to BRAF and MEK inhibitors in melanoma. In MITFhigh expressing cells, MITF confers cell-autonomous resistance to MAP-kinase pathway targeted therapy. Moreover, it appears that in melanomas heterogeneous for MITF expression (MITFhigh and MITFlow cells), individual subpopulations of resistant and sensitive cells communicate and MITF can contribute to overall tumor-resistance through intra-tumor signaling. Finally, we have identified a novel approach of interfering with MITF action, which profoundly sensitizes melanoma to MAP-kinase pathway targeted therapy.
Cellular Reprogramming in Carcinogenesis: Implications for Tumor Heterogeneity, Prognosis, and Therapy
Session Type:
Major Symposium
Session Start/End Time:
Tuesday, Apr 21, 2015, 10:30 AM -12:30 PM
Location:
Room 103, Pennsylvania Convention Center
CME:
CME-Designated
CME/CE Hours:
2
Session Description:
Cancers, both solid and liquid, consist of phenotypically heterogeneous cell types that make up the full cellular complement of disease. Deep sequencing of bulk cancers also frequently reveals a genetic intratumoral heterogeneity that reflects clonal evolution in space and in time and under the influence of treatment. How the distinct phenotypic and genotypic cells contribute to individual cancer growth and progression is incompletely understood. In this symposium, we will discuss issues of cancer heterogeneity and effects on growth and treatment resistance, with emphasis on cancer cell functional properties and influences of the microenvironment, interclonal genomic heterogeneity, and lineage relationships between cancer cells with stem cell and differentiated properties. Understanding these complex cellular relationships within cancers will have critical implications for devising more effective treatments.
Glioblastoma (GBM) is a cancer comprised of morphologically, genetically, and phenotypically diverse cells. However, an understanding of the functional significance of intratumoral heterogeneity is lacking. We devised a method to isolate and functionally profile tumorigenic clones from patient glioblastoma samples. Individual clones demonstrated unique proliferation and differentiation abilities. Importantly, naïve patient tumors included clones that were temozolomide resistant, indicating that resistance to conventional GBM therapy can preexist in untreated tumors at a clonal level. Further, candidate therapies for resistant clones were detected with clone-specific drug screening. Genomic analyses revealed genes and pathways that associate with specific functional behavior of single clones. Our results suggest that functional clonal profiling used to identify tumorigenic and drug-resistant tumor clones will lead to the discovery of new GBM clone-specific treatment strategies.
An SDSU chemist has developed a technique to identify potential cancer drugs that are less likely to produce side effects.
A class of therapeutic drugs known as protein kinase inhibitors has in the past decade become a powerful weapon in the fight against various life-threatening diseases, including certain types of leukemia, lung cancer, kidney cancer and squamous cell cancer of the head and neck. One problem with these drugs, however, is that they often inhibit many different targets, which can lead to side effects and complications in therapeutic use. A recent study by San Diego State University chemist Jeffrey Gustafson has identified a new technique for improving the selectivity of these drugs and possibly decreasing unwanted side effects in the future.
Why are protein kinase–inhibiting drugs so unpredictable? The answer lies in their molecular makeup.
Many of these drug candidates possess examples of a phenomenon known as atropisomerism. To understand what this is, it’s helpful to understand a bit of the chemistry at work. Molecules can come in different forms that have exactly the same chemical formula and even the same bonds, just arranged differently. The different arrangements are mirror images of each other, with a left-handed and a right-handed arrangement. The molecules’ “handedness” is referred to as chirality. Atropisomerism is a form of chirality that arises when the spatial arrangement has a rotatable bond called an axis of chirality. Picture two non-identical paper snowflakes tethered together by a rigid stick.
Some axes of chirality are rigid, while others can freely spin about their axis. In the latter case, this means that at any given time, you could have one of two different “versions” of the same molecule.
Watershed treatment
As the name suggests, kinase inhibitors interrupt the function of kinases—a particular type of enzyme—and effectively shut down the activity of proteins that contribute to cancer.
“Kinase inhibition has been a watershed for cancer treatment,” said Gustafson, who attended SDSU as an undergraduate before earning his Ph.D. in organic chemistry from Yale University, then working there as a National Institutes of Health poctdoctoral fellow in chemical biology.
“However, it’s really hard to inhibit a single kinase,” he explained. “The majority of compounds identified inhibit not just one but many kinases, and that can lead to a number of side effects.”
Many kinase inhibitors possess axes of chirality that are freely spinning. The problem is that because you can’t control which “arrangement” of the molecule is present at a given time, the unwanted version could have unintended consequences.
In practice, this means that when medicinal chemists discover a promising kinase inhibitor that exists as two interchanging arrangements, they actually have two different inhibitors. Each one can have quite different biological effects, and it’s difficult to know which version of the molecule actually targets the right protein.
“I think this has really been under-recognized in the field,” Gustafson said. “The field needs strategies to weed out these side effects.”
Applying the brakes
So that’s what Gustafson did in a recently published study. He and his colleagues synthesized atropisomeric compounds known to target a particular family of kinases known as tyrosine kinases. To some of these compounds, the researchers added a single chlorine atom which effectively served as a brake to keep the atropisomer from spinning around, locking the molecule into either a right-handed or a left-handed version.
When the researchers screened both the modified and unmodified versions against their target kinases, they found major differences in which kinases the different versions inhibited. The unmodified compound was like a shotgun blast, inhibiting a broad range of kinases. But the locked-in right-handed and left-handed versions were choosier.
“Just by locking them into one or another atropisomeric configuration, not only were they more selective, but they inhibited different kinases,” Gustafson explained.
If drug makers incorporated this technique into their early drug discovery process, he said, it would help identify which version of an atropisomeric compound actually targets the kinase they want to target, cutting the potential for side effects and helping to usher drugs past strict regulatory hurdles and into the hands of waiting patients.
Potential for halting disease in molecule isolated from sea sponges.
A molecule isolated from sea sponges and later synthesized in the lab can halt the growth of cancerous cells and could open the door to a new treatment for leukemia, according to a team of Harvard researchers and other collaborators led by Matthew Shair, a professor of chemistry and chemical biology.
“Once we learned this molecule, named cortistatin A, was very potent and selective in terms of inhibiting the growth of AML [acute myeloid leukemia] cells, we tested it in mouse models of AML and found that it was as efficacious as any other molecule we had seen, without having deleterious effects,” Shair said. “This suggests we have identified a promising new therapeutic approach.”
It’s one that could be available to test in patients relatively soon.
“We synthesized cortistatin A and we are working to develop novel therapeutics based on it by optimizing its drug-like properties,” Shair said. “Given the dearth of effective treatments for AML, we recognize the importance of advancing it toward clinical trials as quickly as possible.”
The drug-development process generally takes years, but Shair’s lab is very close to having what is known as a development candidate that could be taken into late-stage preclinical development and then clinical trials. An industrial partner will be needed to push the technology along that path and toward regulatory approval. Harvard’s Office of Technology Development (OTD) is engaged in advanced discussions to that end.
The molecule works, Shair explained, by inhibiting a pair of nearly identical kinases, called CDK8 and CDK19, that his research indicates play a key role in the growth of AML cells.
The kinases operate as part of a poorly understood, massive structure in the nucleus of cells called the mediator complex, which acts as a bridge between transcription factors and transcriptional machinery. Inhibiting these two specific kinases, Shair and colleagues found, doesn’t shut down all transcription, but instead has gene-specific effects.
“We treated AML cells with cortistatin A and measured the effects on gene expression,” Shair said. “One of the first surprises was that it’s affecting a very small number of genes — we thought it might be in the thousands, but it’s in the low hundreds.”
When Shair, Henry Pelish, a senior research associate in chemistry and chemical biology, and then-Ph.D. student Brian Liau looked closely at which genes were affected, they discovered many were associated with DNA regulatory elements known as “super-enhancers.”
“Humans have about 220 different types of cells in their body — they all have the same genome, but they have to form things like skin and bone and liver cells,” Shair explained. “In all cells, there are a relatively small number of DNA regulatory elements, called super-enhancers. These super-enhancers drive high expression of genes, many of which dictate cellular identity. A big part of cancer is a situation where that identity is lost, and the cells become poorly differentiated and are stuck in an almost stem-cell-like state.”
While a few potential cancer treatments have attacked the disease by down-regulating such cellular identity genes, Shair and colleagues were surprised to find that their molecule actually turned up the activity of those genes in AML cells.
“Before this paper, the thought was that cancer is ramping these genes up, keeping the cells in a hyper-proliferative state and affecting cell growth in that way,” Shair said. “But our molecule is saying that’s one part of the story, and in addition cancer is keeping the dosage of these genes in a narrow range. If it’s too low, the cells die. If they are pushed too high, as with cortistatin A, they return to their normal identity and stop growing.”
Shair’s lab became interested in the molecule several years ago, shortly after it was first isolated and described by other researchers. Early studies suggested it appeared to inhibit just a handful of kinases.
“We tested approximately 400 kinases, and found that it inhibits only CDK8 and CDK19 in cells, which makes it among the most selective kinase inhibitors identified to date,” Shair said. “Having compounds that precisely hit a specific target, like cortistatin A, can help reduce side effects and increase efficacy. In a way, it shatters a dogma because we thought it wasn’t possible for a molecule to be this selective and bind in a site common to all 500 human kinases, but this molecule does it, and it does it because of its 3-D structure. What’s interesting is that most kinase-inhibitor drugs do not have this type of 3-D structure. Nature is telling us that one way to achieve this level of specificity is to make molecules more like cortistatin A.”
Shair’s team successfully synthesized the molecule, which helped them study how it worked and why it affected the growth of a very specific type of cell. Later on, with funding and drug-development expertise provided by Harvard’s Blavatnik Biomedical Accelerator, Shair’s lab created a range of new molecules that may be better suited to clinical application.
“It’s a complex process to make [cortistatin A] — 32 chemical steps,” said Shair. “But we have been able to find less complex structures that act just like the natural compound, with better drug-like properties, and they can be made on a large scale and in about half as many steps.”
“Over the course of several years, we have watched this research progress from an intriguing discovery to a highly promising development candidate,” said Isaac Kohlberg, senior associate provost and chief technology development officer. “The latest results are a real testament to Matt’s ingenuity and dedication to addressing a very tough disease.”
While there is still much work to be done — in particular, to better understand how CDK8 and CDK19 regulate gene expression — the early results have been dramatic.
“This is the kind of thing you do science for,” Shair said, “the idea that once every 10 or 20 years you might find something this interesting, that sheds new light on important, difficult problems. This gives us an opportunity to generate a new understanding of cancer and also develop new therapeutics to treat it. We’re very excited and curious to see where it goes.”
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