McEwen Award for Innovation: Irving Weissman, M.D., Stanford School of Medicine, and Hans Clevers, M.D., Ph.D., Hubrecht Institute
Larry H. Bernstein, MD, FCAP, Curator
Leaders in Pharmaceutical Innovation
Series E. 2; 7.3
Past winners include Azim Surani, James Thomson, Rudolf Jaenisch and Kazutoshi Takahashi with Shinya Yamanaka
The International Society for Stem Cell Research (ISSCR) has presented EuroStemCell partner Hans Clevers with the McEwen Award for Innovation at the opening of its annual meeting, today (24 June) in Stockholm, Sweden.
The prizes awarded by ISSCR in 2015 are:
McEwen Award for Innovation: Irving Weissman, M.D., Stanford School of Medicine, and Hans Clevers, M.D., Ph.D., Hubrecht Institute
ISSCR-BD Biosciences Outstanding Young Investigator Award: Paul Tesar, Ph.D., Case Western Reserve University School of Medicine
ISSCR Public Service Award: Alan Trounson, Ph.D., MIMR-PHI Institute of Medical Research
In 2015, the ISSCR recognizes long-standing contributors to the field, Weissman and Clevers, for the identification, prospective purification and characterization of somatic (adult) tissue-associated stem cells and advancement of their research findings toward clinical applications.
Award recipient Weissman’s many discoveries have helped map the direction of the stem cell field and have served as the basis for important research and work by scientists all over the world. He was the first to isolate and characterize hematopoietic (blood) stem cells from mice and humans. He developed the approaches and technologies, now widely used within the field, for isolating blood stem and progenitor cells and defining their properties. Weissman pioneered the extension of his approaches to isolation of other stem cell types, including human nervous system cells and skeletal muscle myogenic stem/progenitor cells. Further, he discovered several independent leukemia stem cells and, more recently, bladder cancer stem cells, head and neck cancer stem cells and malignant melanoma stem cells. Weissman has pursued these discoveries to develop several promising means of cancer therapy.
Award recipient Clevers has been a leader in biomedical sciences and the area of Wnt signaling in colon cancer for more than three decades. He and his lab developed tools to identify and track an adult stem cell population able to give rise to the entire lining of the gut and later to demonstrate that these cells can be isolated and grown in culture as “miniguts,” recapitulating the normal structure and function of the gut. These discoveries are a move toward promising therapies for colon conditions, like ulcers, in which the lining of the intestine has been destroyed in patches, and provide a powerful resource for modeling disease pathology and for drug screening.
“Irv Weissman and Hans Clevers have made enormous contributions to stem cell science. Working in the blood and gut systems, respectively, and extending their findings in different tissues, they have defined the concepts and technologies that underpin many avenues of research,” Hans Schöler, chair of the ISSCR’s McEwen Awards selection committee, said. “Each has made pioneering conceptual advances in disease modeling and regenerative medicine.”
The ISSCR-BD Biosciences Outstanding Young Investigator Award recognizes exceptional achievements by an ISSCR member and investigator in the early part of their independent career in stem cell research. The winner receives a $7,500 USD personal award and is invited to present at the ISSCR’s annual meeting. Past winners include Valentina Greco, Marius Wernig, Cédric Blanpain, Robert Blelloch, Joanna Wysocka and Konrad Hochedlinger.
Award recipient Tesar established his independent laboratory five years ago and has rapidly risen to his current position as the Dr. Donald and Ruth Weber Goodman Professor of Innovative Therapeutics and tenured Associate Professor in the Department of Genetics and Genome Sciences at Case Western Reserve University School of Medicine. Tesar’s studies have shaped the global understanding of both pluripotent stem cell and oligodendrocyte biology. His seminal and highly cited report on epiblast stem cells, published in Nature in 2007, along with similar findings by Pedersen, Vallier and colleagues, led to a complete shift in the understanding of how pluripotency is regulated in the mammalian embryo. He has continued to provide high impact contributions to the field, pioneering new methods to generate and mature oligodendrocyte progenitor cells, and to use these to enhance repair in animal models of multiple sclerosis.
Stanford stem cell pioneer Irving Weissman wins international honors
by Krista Conger on Feb 10, 2015
http://news.stanford.edu/thedish/2015/02/10/stanford-stem-cell-pioneer-irving-weissman-wins-international-honors/
IRVING WEISSMAN, a professor of pathology and of developmental biology at Stanford Medical School, was recently awarded the Charles Rodolphe Brupbacher Prize for Cancer Research in Zurich.
Weissman, who directs the Stanford Institute for Stem Cell Biology and Regenerative Medicine, was honored for his role in identifying and isolating the first hematopoetic, or blood-forming, stem cell in mice in 1988, and then in humans in 1992. In 2000, he also isolated leukemia cancer stem cells from humans. Recently, he and his colleagues have devoted themselves to understanding how cancer cells escape destruction by the immune system by expressing a “don’t eat me” signal on their cell membranes.
“His discoveries on aging processes in stem-cell systems and ultimately his contribution toward understanding cancer stem cells and the way in which the immune system can control these cells are pioneering achievements with far-reaching clinical implications,” Markus Manz, director of the Department of Hematology at the University Hospital Zurich, said of Weissman at a symposium titled “Breakthroughs in Cancer Research and Therapy” where the prize was announced.
Weissman also is the director of Stanford’s Ludwig Center for Cancer Stem Cell Research and Medicine and holds the Virginia and Daniel K. Ludwig Professorship in Clinical Investigation in Cancer Research.
The prize, presented by the Charles Rodolphe Brupbacher Foundation, included 100,000 Swiss francs, or about $108,000.
The Charles Rodolphe Brupbacher Foundation was founded in 1991 by Brupbacher’s wife, Frederique, in honor of her late husband. This is the 12th time the prize, which is meant to recognize internationally acknowledged achievements in fundamental cancer research, has been awarded. Brupbacher was a Swiss banker, economist and international currency expert.
In addition to the Brupbacher Prize, it was recently announced that Weissman will receive theMcEwen Award for Innovation, supported by the McEwen Centre for Regenerative Medicine in Toronto. The award will be presented in June at the annual meeting of the International Society for Stem Cell Research in Stockholm. It recognizes the work of Weissman and Hans Clevers, of the Hubrecht Institute in the Netherlands, in the identification, purification and characterization of adult stem cells from a variety of human tissues and cancers. Weissman and Clevers will share a $100,000 award.
Anti-CD47 antibody may offer new route to successful cancer vaccination
Scientists at the School of Medicine have shown that their previously identified therapeutic approach to fight cancer via immune cells called macrophages also prompts the disease-fighting killer T cells to attack the cancer.
The research, published online May 20 in the Proceedings of the National Academy of Sciences, demonstrates that the approach may be a promising strategy for creating custom cancer vaccines.
Various researchers have been working over the years to create vaccines against cancer, but the resulting vaccines have not been highly effective. Current approaches to developing the vaccines rely on using immune cells called dendritic cells to introduce cancer protein fragments to T cells — a process known as antigen presentation. The hope has been that the process would stimulate the body’s T cells to identify cancer cells as diseased or damaged and target them for elimination. However, this process often only modestly activates the most potent cancer-fighting kind of T cell, called killer T cells or CD8+ T cells.
The Stanford team discovered that there was another viable vaccine approach, using the macrophage pathway to program killer T cells against cancer. Irving Weissman, MD, professor of pathology and of developmental biology, and his team previously showed that nearly all cancers use the molecule CD47 as a “don’t-eat-me” signal to escape from being eaten and eliminated by macrophages. The researchers found that anti-CD47 antibodies, which can block the “don’t-eat-me” signal and enable macrophages to engulf cancer cells, eliminated or inhibited the growth of various blood cancers and solid tumors.
In the new study, the Stanford team showed that after engulfing the cancer cells, the macrophages presented pieces of the cancer to CD8+ T cells, which, in addition to attacking cancer, are also potent attackers of virally infected or damaged cells. As a result, the CD8+ T cells were activated to attack the cancer cells on their own. “It was completely unexpected that CD8+ T cells would be mobilized when macrophages engulfed the cancer cells in the presence of CD47-blocking antibodies,” said MD/PhD student Diane Tseng, the lead author of the study. Following engulfment of cancer cells, macrophages activate T cells to mobilize their own immune attack against cancer, she said.
The Stanford group plans to start human clinical trials of the anti-CD47 cancer therapy in 2014. The new research provides hope that the therapy will cause the immune system to wage a two-pronged attack on cancer — through both macrophages and T cells. The approach may also give physicians early indicators of how the treatment is working in patients. “Monitoring T-cell parameters in patients receiving anti-CD47 antibody may help us identify the immunological signatures that tell us whether patients are responding to therapy,” said co-author Jens Volkmer, MD, an instructor at the Stanford Institute for Stem Cell Biology and Regenerative Medicine.
The research revives interest in an aspect of macrophages that has been neglected for decades: their role in presenting antigens to T cells. For many years, researchers have focused on the dendritic cell as the main antigen-presenting cell, and have generally believed that macrophages specialize in degrading antigens rather presenting them. This research shows that macrophages can be effective at antigen presentation and are powerful initiators of the CD8+T cell response.
The fact that T cells become involved in fighting cancer as a result of CD47-blocking antibody therapy could have important clinical implications. The antibody might be used as a personalized cancer vaccine allowing T cells to recognize the unique molecular markers on an individual patient’s cancer. “Because T cells are sensitized to attack a patient’s particular cancer, the administration of CD47-blocking antibodies in a sense could act as a personalized vaccination against that cancer,” Tseng added.
Weissman, who is senior author of the new study, is the director of the Stanford Institute for Stem Cell Biology and Regenerative Medicine and the director of the Stanford Ludwig Center for Cancer Stem Cell Research and Medicine.
Other Stanford investigators involved in the research were senior scientist Stephen Willingham, PhD; postdoctoral scholars John Fathman, PhD, Nathaniel Fernhoff, PhD, Matthew Inlay, PhD, and Masanori Miyanishi, MD, PhD; instructor Jun Seita, MD, PhD; graduate student Kipp Weisskopf, MPhil; and life sciences research associate Humberto Contreras-Trujillo.
The research was supported by the Virginia and D.K. Ludwig Fund for Cancer Research, the Joseph and Laurie Lacob Gynecologic/Ovarian Cancer Fund, the National Institutes of Health (grants R01CA86017, P01CA139490, P30CA124435 and F30CA168059), and the Student Training and Research in Tumor Immunology Program of the Cancer Research Institute.
Christopher Vaughan is communications manager at the Stanford Institute for Stem Cell Biology and Regenerative Medicine.
Clinical Investigation of a Humanized Anti-CD47 Antibody in Targeting Cancer Stem Cells in Hematologic Malignancies and Solid Tumors
Funding Type:
Disease Team Therapy Development III
Grant Number: DR3-06965
Investigator(s): Irving Weissman – PI
Institution: Stanford University
Disease Focus:
Cancer
Solid Tumor
Blood Cancer
Most normal tissues are maintained by a small number of stem cells that can both self-renew to maintain stem cell numbers, and also give rise to progenitors that make mature cells. We have shown that normal stem cells can accumulate mutations that cause progenitors to self-renew out of control, forming cancer stem cells (CSC). CSC make tumors composed of cancer cells, which are more sensitive to cancer drugs and radiation than the CSC. As a result, some CSC survive therapy, and grow and spread. We sought to find therapies that include all CSC as targets. We found that all cancers and their CSC protect themselves by expressing a ‘don’t eat me’ signal, called CD47, that prevents the innate immune system macrophages from eating and killing them. We have developed a novel therapy (anti-CD47 blocking antibody) that enables macrophages to eliminate both the CSC and the tumors they produce. This anti-CD47 antibody eliminates human cancer stem cells when patient cancers are grown in mice. At the time of funding of this proposal, we will have fulfilled FDA requirements to take this antibody into clinical trials, showing in animal models that the antibody is safe and well-tolerated, and that we can manufacture it to FDA specifications for administration to humans.
Here, we propose the initial clinical investigation of the anti-CD47 antibody with parallel first-in-human Phase 1 clinical trials in patients with either Acute Myelogenous Leukemia (AML) or separately a diversity of solid tumors, who are no longer candidates for conventional therapies or for whom there are no further standard therapies. The primary objectives of our Phase I clinical trials are to assess the safety and tolerability of anti-CD47 antibody. The trials are designed to determine the maximum tolerated dose and optimal dosing regimen of anti-CD47 antibody given to up to 42 patients with AML and up to 70 patients with solid tumors. While patients will be clinically evaluated for halting of disease progression, such clinical responses are rare in Phase I trials due to the advanced illness and small numbers of patients, and because it is not known how to optimally administer the antibody. Subsequent progression to Phase II clinical trials will involve administration of an optimal dosing regimen to larger numbers of patients. These Phase II trials will be critical for evaluating the ability of anti-CD47 antibody to either delay disease progression or cause clinical responses, including complete remission. In addition to its use as a stand-alone therapy, anti-CD47 antibody has shown promise in preclinical cancer models in combination with approved anti-cancer therapeutics to dramatically eradicate disease. Thus, our future clinical plans include testing anti-CD47 antibody in Phase IB studies with currently approved cancer therapeutics that produce partial responses. Ultimately, we hope anti-CD47 antibody therapy will provide durable clinical responses in the absence of significant toxicity.
New insights into the biology of cancer have provided a potential explanation for the challenge of treating cancer. An increasing number of scientific studies suggest that cancer is initiated and maintained by a small number of cancer stem cells that are relatively resistant to current treatment approaches. Cancer stem cells have the unique properties of continuous propagation, and the ability to give rise to all cell types found in that particular cancer. Such cells are proposed to persist in tumors as a distinct population, and because of their increased ability to survive existing anti-cancer therapies, they regenerate the tumor and cause relapse and metastasis. Cancer stem cells and their progeny produce a cell surface ‘invisibility cloak’ called CD47, a ‘don’t eat me signal’ for cells of the native immune system to counterbalance ‘eat me’ signals which appear during cancer development. Our anti-CD47 antibody counters the ‘cloak’, enabling the patient’s natural immune system to eliminate the cancer stem cells and cancer cells. Our preclinical data provide compelling support that anti-CD47 antibody might be a treatment strategy for many different cancer types, including breast, bladder, colon, ovarian, glioblastoma, leiomyosarcoma, squamous cell carcinoma, multiple myeloma, lymphoma, and acute myelogenous leukemia.
Development of specific therapies that target all cancer stem cells is necessary to achieve improved outcomes, especially for sufferers of metastatic disease. We hope our clinical trials proposed in this grant will indicate that anti-CD47 antibody is a safe and highly effective anti-ancer therapy that offers patients in California and throughout the world the possibility of increased survival and even complete cure.
We have previously developed a new therapeutic candidate, the anti-CD47 humanized antibody, Hu5F9-G4, which demonstrates potent anti-cancer activity in animal models of malignancy. The goal of CIRM DTIII Grant DR3-06965 is to conduct initial phase I clinical trials of this antibody in advanced cancer patients. We originally proposed to conduct two separate Phase I clinical trials: one in solid tumor patients with advanced malignancy (commenced in August 2014), the other in relapsed, refractory AML patients (anticipated to start in September 2015). The primary endpoints for these trials will be to assess safety and tolerability, and additional endpoints include obtaining information about the dosing regimen for subsequent clinical investigations, and initial efficacy assessments.
CD47 is a dominant anti-phagocytosis signal that is expressed on all types of human cancers assessed thus far. It binds to SIRPα, an inhibitory receptor on macrophages, and in so doing, blocks the ability of macrophages to engulf and eliminate cancer cells. Hu5F9-G4 blocks binding of CD47 to SIRPα, and restores the ability of macrophages to engulf or phagocytose cancer cells. In pre-clinical cancer models, treatment with Hu5F9-G4 shrunk tumors, eliminated metastases, and in some cases resulted in long-term protection from cancer recurrence. These results suggest that Hu5F9-G4 leads to elimination of cancer stem cells in addition to differentiated cancer cells.
We have developed Hu5F9-G4 for human clinical trials by demonstrating safety and tolerability in pre-clinical toxicology studies. These studies also indicated that we can achieve serum levels associated with potent efficacy in pre-clinical models. The regulatory agencies (FDA in the U.S., and MHRA in the U.K.) reviewed the large package of pre-clinical data describing Hu5F9-G4, and approved our requests to commence separate Phase I clinical trials in solid tumor and AML patients. The solid tumor trial commenced at Stanford in August 2014 and has been designed to assess patients in separate groups, or cohorts, treated with increasing doses of Hu5F9-G4. The trial is ongoing as primary endpoints have not been met. The acute myeloid leukemia trial has been given regulatory approval in the U.K., and will start enrolling patients in September 2015. In summary, during the last year, the Hu5F9-G4 clinical trials have made substantial progress and all milestones have been met.
Stem Cell Research: Promise and Progress
Hans Clevers: “Every day new research is showing us that many types of cancers are fed by tumour stem cells”
http://www.irbbarcelona.org/en/news/hans-clevers-every-day-new-research-is-showing-us-that-many-types-of-cancers-are-fed-by-tumour
The biggest challenge in designing new cancer therapies lies in successfully identifying and targeting tumour stem cells, which are responsible for the regrowth of the tumour.
The Barcelona BioMed Conference on “Normal and Tumour Stem Cells”, aims to analyze the function of stem cells in cancer. The conference, which begins today and runs until November 14 at the Institut d’Estudis Catalans, is co-organized by colon cancer research experts Eduard Batlle (IRB Barcelona) andHans Clevers (Hubrecht Institute, the Netherlands), with the support of the BBVA Foundation. During the three-day event, 21 world experts in the field will meet with a further 130 participants to share their latest research findings on tumour stem cells.
“In 2007 we held the first Barcelona BioMed Conference on this topic. At the time there was only very preliminary data on the relationship between stem cells and cancer. Five years on, many convincing data have emerged to indicate that the majority of tumours are indeed fed by tumour stem cells,” explains Hans Clevers, the scientist who first identified stem cells in the intestine and who today is one of the world leaders in research on normal stem cells and their potential for regenerative therapy.
A number of important studies have demonstrated that at the heart of cancers of the breast, colon, skin, brain, lung and leukemias lie a small group of malignant cells that have retained the properties of the stem cell that gave rise to the cancers in the first place. It is these cells that allow the tumour to grow and can regenerate it. The efforts of many research groups worldwide now focusses on unraveling this process, identifying the specific genes that allow it to occur, and finding ways to detect and eliminate these malignant stem cells.
Stem cells and the origin of tumours
One of the principal characteristics of stem cells is that they are able to copy themselves indefinitely, giving rise to one stem cell and one specialized cell. This capacity for unlimited replication ensures the constant renewal of healthy tissues, which is fundamental for survival and is the basis of regenerative medicine. When the stem cells undergo cancerous mutations or when normal tumour cells acquire stem cell properties, however, this can lead to the formation of tumours.
“This conference gives us a valuable opportunity to learn about the latest work on the two types of stem cells, normal and tumour, in different tissues. What we have been observing over recent years is that the tumour mimcs the hierarchies that exist in normal tissues. In order to understand the tumour, we need to understand the healthy tissue. Most of the scientists invited to the conference are working on both aspects,” explains Batlle. The list of speakers includes pioneers in the field, such as Irving L. Weissman, director of the Institute for Stem Cell Biology & Regenerative Medicine in Stanford, California. Weissman, known as the “father of haematopoiesis”, first identified stem cells in the blood and determined how they give rise to the different types of blood cells, making major contributions to our understanding of leukemias and other ‘liquid’ tumours.
Stem cells and metastasis
In addition to being at the root of the tumour and allowing it to grow, stem cells may also cause metastasis. In order for metastasis to occur, cells from the original tumour must escape into the blood stream and invade new organs to seed new tumours there. “Only cells with stem cell properties are able to make this happen, since they are the only type of cell that can generate all the cell types of the tumor,” explains Batlle. But in order to cause metastasis, these cells also need to be able to do other things. “We have discovered that in the case of colon cancer, stem cells must be able to trick the healthy tissue of the organ they have invaded into helping them survive in this hostile environment.” Batlle’s study, to be published tomorrow inCancer Cell, will be presented during the conference. This is the first piece of work to reveal a key role for the tumour microenvironment in fostering the process of metastasis, a discovery which will open doors to similar findings in other types of tumours.
Normal stem cells vs. tumour stem cells
One of the keys in the fight against cancer is the ability to identify tumour stem cells and differentiate them from healthy stem cells. The conference co-organizers maintain that “this is still a central question. We don’t yet know enough about normal stem cells, and technical issues make things difficult. We are making rapid progress, however, and in the next few years we expect to be able to make great strides both in figuring out the similarities and differences in the two types of cells, and in coming up with new strategies to fight the growth and spread of tumours.”
PROFILES OF CONFERENCE CO-ORGANIZERS
EDUARD BATLLE – Group Leader of the Colorectal Cancer Laboratory and Coordinator of the Oncology Programme at IRB Barcelona. ICREA Research Professor (Instituto Catalán para la Investigación y Estudios Avanzados).
Dr. Batlle’s research over the past decade has focused on the characterization of the mechanisms that cause the initiation, progression and metastasis of colon cancer. He has published studies in several high-impact journals such as Cell, Nature, Nature Genetics and Cancer Cell. His achievements include the discovery of the transcription factor Snail in tumour cells and the elucidation of the function of EphB membrane receptors in colorrectal cancer. During the Barcelona BioMed Conference, Dr. Batlle will present the results of a study to be published in Cancer Cell on a process indispensable for colon cancer metastasis.
Among his recognitions, Batlle has received the Banc Sabadell Prize for Biomedical Research (2010) and the “Debiopharm Life Sciences Award for Outstanding Research in Oncology” given by the Ecole Polytechnique Fédérale de Lausanne in Switzerland (2006). He is the recipient of an ERC Starting Grant awarded by the European Research Council in 2007.
HANS CLEVERS – Group leader at the Hubrecht Institute (director 2002-2012 ) and President of the Royal Netherlands Academy of Arts and Sciences. Dr. Clevers was the first scientist to identify intestinal stem cells and remains one of the leading researchers in this field. His discoveries have had significant impact in cancer as well as in regenerative therapy with stem cells and in vitro organ culture. Clevers’ work in developmental biology and cancer led him to discover the beta-catenin/Tcf4 transcriptional complex, which causes the majority of colorrectal cancer.
http://apoorvamandavilli.com/wp-content/uploads/2010/10/2010stem-cells-and-cancer.pdf
In 1991 Clevers became a professor of immunology at the University Medical Center in Utrecht. Since 2002 he has been a professor of molecular genetics at UMC Utrecht. Also in 2002 he became director of the Hubrecht Institute for Developmental Biology and Stem-Cell Research at the Royal Dutch Academy of Sciences, where until May 2012 he led the WNT Signaling and Cancer research group and was project leader of the Netherlands Proteomics Centre and Cancer Genomics Centre. Clevers discovered similarities between the normal renewal of intestinal tissue and the onset of colon cancer. In 2007 he received a grant of two million euros from the KWF Cancer Society to study the function of stem cells in the normal intestines and in colon cancer, and in 2008 he received an ERC Advanced Investigator Grant. In March 2012, Clevers, who since 2000 had been a member of the Royal Netherlands Academy of Arts and Sciences, was elected its president, a position he assumed on June 1 of that year, succeeding Robbert Dijkgraaf. In connection with his election to this position, he resigned from the Hubrecht Institute and began to carry out research two days a week at the UMC-U.[4][5][6][7][9]
Asked in a 2008 interview what had been the highlights of his research up to that point, Clevers said “there would probably be three. There was a first one, when I just started my lab, within the first few months we cloned the gene that they call TCF1, t-cell factor 1, I used to be a t-cell embryologist when we first started out. And that paper was published in EMBO in ’91, first author. So in that paper we described cloning of this vector, which at that time maybe on the world scale was not great but for my own lab to clone this gene was my first thing I ever did alone. This gene then in ’96 we found to be the crucial missing component of what’s called the Wnt signaling pathway, and this [was] generally seen as a major breakthrough we had. There were papers in ’96 and ’97 in Cell, and we had two papers in Science in the same two years.”
Clevers and his team thus showed that “there is that this TCF transcription factor, there is a small family of them, they occur in every animal on the planet, they are the end point of the signal transcription cascade, and they control virtually every decision in a developing animal. When we realized this we started changing our model systems, we used to work on lymphocytes, and we changed it, first to frogs and flies, drosophila, where the Wnt pathway had been studied by many other people that way we could use assays of those people. We then realized that in mammals Wnt signaling…was not only important in embryos but also crucial in adults, which is novel. And we switched to the gut, we found that one of our knockouts, the TCF4 knockout, one of the four members of that family had no stem cells in the gut. And this is the first link in the literature, this was also a ’97 paper in Nature Genetics, between Wnt signaling and stem cells in adults. And in that same year we found that colon cancer comes about by the disregulation of TCF4, and those two phenomena are really linked. So stem cells need TCF4, cancers disregulate TCF4 by mutating a gene upstream in that pathway called APC.”
After this Clevers’s team “continued to work on the intestine and on the physiology of the intestine, which was essentially an unstudied field, much to my surprise. May I emphasize, there are thousands of very competent embryologists, and they work on tiny details, and they fight over the smallest details, are extremely competent. In this intestinal field there are thousands of gastroentromologists that study cancer or colitis or Crohn’s Disease, but there are very few, if any, labs studying normal tissue, which is amazing because that is a tissue that we use every five days. It’s the most rapidly proliferating tissue in a normal body. So my lab actually build up a lot of mouse models and we learn a lot about how that’s being done, and then finally…last year we finally identified the stem cells in the gut. And we now can purify them in large numbers and study their characteristics.”[4]
A recent posting at the website of the Royal Netherlands Academy of Arts and Sciences provides a capsule summary of Clevers’s research to date: “His research deals with the intestine, in both its healthy and diseased state. He has discovered that there are numerous similarities between the normal process whereby intestinal tissue is renewed and the development of intestinal cancer. Improved understanding of these processes is crucial to developing new ways of treating cancer. Hans Clevers has described the molecular signalling pathways that are disrupted by cancer and has identified a protein that is specific to stem cells in the intestine. He has then been able to grow ‘mini-intestines’ from individual stem cells. These are the first steps on the road to regenerative medicine, in this case the regeneration of intestinal tissue.”[7]
Q&A: Hans Clevers
Eric Bender
Nature 521, S15 (14 May 2015) http://dx.doi.org://10.1038/521S15a
n 2009, Hans Clevers and Toshiro Sato (then a postdoc in Clevers’ lab) demonstrated a powerful new model to study development and disease: a three-dimensional ‘organoid’ derived from adult stem cells that replicates the structure of cells lining the intestine. More than 100 labs worldwide are now working with different types of organoid to study cancer and other diseases. Clevers, at the Hubrecht Institute in Utrecht, the Netherlands, discusses the potential of this approach.
Why might it be better to screen drugs in organoids rather than in cell lines?
We don’t currently understand why certain tumours are sensitive or resistant to particular drugs. With targeted therapies, you can make a prediction, but for classical chemotherapy drugs, such as cisplatin or 5-fluorouracil, it is totally unpredictable which tumours will respond. Tumours can be sequenced in great detail, but drugs against them cannot be tested effectively other than in clinical trials. Organoids are a very good genetic representation of the tumour, so they let us bridge the gap between deep-sequencing efforts and patient outcomes.
How do you see organoids contributing to the study of colorectal cancer?
We are collaborating with groups at the Broad Institute in Cambridge, Massachusetts, and the Sanger Institute in Hinxton, UK, to build a biobank of organoids from 20 or so people with colon cancer. We have organoids of the cancer and of normal cells from individual patients, as well as sequences of their protein-coding genes. We have established the non-profit Hubrecht Organoid Technology (HUB) to expand our organoid biobanks. The HUB shares these biobanks with academic groups around the world, and now works with about 15 companies on drug-development programmes. We can culture tumours from almost every person with colon cancer, sequence them and test them against drugs. Additionally, we can use research techniques that have been developed for cell lines, such as genetic tools, fluorescence-activated cell sorting and microarrays.
Is this research moving towards clinical trials?
Yes, my group and the HUB are collaborating with Emile Voest at the Netherlands Cancer Institute in Amsterdam on an observational trial. We already have some organoid models from people with colon cancer who receive chemotherapy. The organoids are screened against a panel of common colon-cancer drugs. The patients will be treated the same way the oncologists would normally treat them, but we’ll see if we could have predicted the response from our organoids. We’re also starting another trial in which we will enrol advanced-colon-cancer patients, for whom there is no standard treatment. We will make organoids, test drug sensitivity and resistance, and then advise the oncologists as to what drug to use for that particular patient. We will be looking at multiple drugs, so we need large numbers of patients — that’s the only way we will be able to produce enough data to help us match drugs to tumour types.
To benefit individual patients, won’t you need to test the drugs very quickly?
Yes — and that’s really where we want to take this technology. When you have pneumonia, your bacterial cultures are tested and you get answers in three days. With this technology, we can tell the oncologist the best odds for a combination of therapeutics, maybe not in three days, but in several weeks. We have an organoid-based test in cystic fibrosis that gives us a result in about two weeks.
How does the organoid approach differ from patient-derived xenografts, in which patients’ tumours are transplanted into immune-suppressed mice for testing drugs?
It’s the same principle — you get a functional readout of the patient’s tumour. But organoids can be tested against an unlimited amount of compounds and combinations. Furthermore, in contrast to xenografts, organoids can be established from almost all patients.
What are some of the next steps in your cancer research?
Organoids model the key component of the tumour but they lack some important elements. We want to combine organoids with other elements to make more-complete tools. For instance, we would like to introduce the immune system so that we can study the effects of the fantastic new immunotherapy drugs. We think that we can build it up in a reductionist way — take lymphocytes isolated from a tumour, bring these together with cancer organoids derived from the same tumour and watch what happens. And maybe we can also put microorganisms in these organoids. For example, we could add Helicobacter, a major cause of stomach cancer, to stomach organoids.
Can organoids also help to test drug combinations?
Yes, tumours are genetically heterogeneous, and there can be vast differences in drug sensitivity between clones for the same tumour. We can possibly advance sequence-based therapy by testing millions of drug combinations in organoids.
Single Lgr5 stem cells build crypt–villus structures in vitro without a mesenchymal niche
Toshiro Sato1, Robert G. Vries1, Hugo J. Snippert1, Marc van de Wetering1, Nick Barker1, Daniel E. Stange1, Johan H. van Es1, Arie Abo2, Pekka Kujala3, Peter J. Peters3 & Hans Clevers1
Nature 459, 262-265 (14 May 2009) | http://dx.doi.org:/10.1038/nature07935 Received 16 July 2008; Accepted 24 February 2009
The intestinal epithelium is the most rapidly self-renewing tissue in adult mammals. We have recently demonstrated the presence of about six cycling Lgr5+ stem cells at the bottoms of small-intestinal crypts1. Here we describe the establishment of long-term culture conditions under which single crypts undergo multiple crypt fission events, while simultanously generating villus-like epithelial domains in which all differentiated cell types are present. Single sorted Lgr5+ stem cells can also initiate these crypt–villus organoids. Tracing experiments indicate that the Lgr5+ stem-cell hierarchy is maintained in organoids. We conclude that intestinal crypt–villus units are self-organizing structures, which can be built from a single stem cell in the absence of a non-epithelial cellular niche.
Dis. Model. Mech. September 2013, doi: 10.1242/dmm.013367 vol. 6 no. 5 1053-1056
A gutsy approach to stem cells and signalling: an interview with Hans Clevers
Hans Clevers, Professor of Molecular Genetics at Utrecht University, began his career in immunology and developmental biology, but a shift towards intestinal research in the late 1990s led to his group’s pioneering discovery that Lgr5 is a marker of tissue stem cells – a finding that paved the way for a cascade of key insights into the molecular signalling pathways that are dysregulated in cancer. Interviewed here by Ross Cagan, Editor-in-Chief of Disease Models & Mechanisms, Hans recalls the mentors and discoveries that motivated his transition from basic to applied science, discusses his style of lab management and mentorship, and highlights the potential of organoid-based therapy for personalised medicine.
Johannes (Hans) Clevers was born in 1957 in Eindhoven, home to Philips Electronics, in the south of The Netherlands. From a young age he showed enthusiasm and a natural talent for science, and as an undergraduate became fascinated with molecular biology. He obtained his PhD in immunology from Utrecht University during the mid-1980s, and simultaneously studied medicine. Making the pivotal decision to move back into the lab after completing his clinical training, he undertook postdoctoral research in Cox Terhorst’s lab at the Dana-Farber Cancer Institute at Harvard University. He then returned to Utrecht to set up his own lab, and was a Professor of Immunology at the university between 1991 and 2002. From 2002 to 2012 he was Director of the nearby Hubrecht Institute for Stem Cell Research. During this time, Hans moved gradually into the gastroenterology field, and made groundbreaking discoveries regarding the role of Wnt signalling in stem cells and colon cancer. His unique contributions to cancer, stem cell research and regenerative medicine have been recognised in the form of numerous awards, and in 2013 he was one of the eleven winners of a $3 million award from the Breakthrough Prize in Life Sciences Foundation. Currently, he is Professor of Molecular Genetics at Utrecht University, and is also President of the Royal Netherlands Academy of Arts and Sciences (KNAW). Hans has also been involved in setting up several biotechnology companies.
Before we get to your background, I want to congratulate you on being, unsurprisingly, one of the Breakthrough Prize award winners. You have a long list of prizes now – is it something you’ve gotten used to?
This last one was unusual for me – prior to the Breakthrough award I had only ever received one American prize and that was in gastroenterology. To be the only researcher in Europe awarded, and to see my name on the list together with people like Robert Weinberg and Bert Vogelstein, who were the big shots when I was a postdoc, was a truly great honour. I went to the ceremony for the physics prize in Geneva, and it was like being at the Oscars – very surreal, as a scientist.
The first thing I did when I found out about my award was to invite the current and previous members of my lab to a huge party in Amsterdam, which will take place in September [2013]. There will be around 100 attendees – most of which are still in science. There will be good food and drink, stand-up comedy, and a small symposium.
Taking a step back into your past, why did you choose a career in science and medicine?
My high school system was very geared towards languages. I started learning biology at university in 1975 at the age of 18, and I was disappointed. Molecular biology was being developed in England, Switzerland and the US, but in Dutch universities there was no legal framework to do this, and so the courses – where available – focused only on technical details. Biology in general lacked charisma. At the time, my friends and brothers were junior medics, and as I had an interest in medicine I decided to take it on in addition to biology. I ended up spending a year in Nairobi and half a year at NIH for my biology rotations, and essentially I never went to any lectures (although this is something I never tell my students!). Anyway, I really started getting sucked into the clinical training, and found that working in a clinical environment is much more sociable than being in a lab. You’re part of a big organisation and there are lots of people to talk to, whereas in the lab there are only a few people, and small issues – such as somebody not cleaning up – can really cause friction. After medical school, I was picked, mainly because of my research background, for a training position in paediatrics. They suggested that I should start work for a PhD, so I went back into the lab. That’s when I realised that, despite the social attractiveness of working in a hospital, I was much more of a scientist than a doctor. I got my PhD – together with four published papers – in just 1 year. However, it was during my first postdoc position in Boston that I think I was really exposed to science for the first time. It was tough, but I knew I’d made the right decision.
Are there particular mentors who influenced your decision to choose the lab over clinics, and shaped your career moves?
When I received the Heineken Prize from the Royal Netherlands Academy of Arts and Sciences in 2012, I had to think deeply about my mentors and realised that there were two that I had almost forgotten. The first was my high school chemistry teacher, who sold laboratory chemicals to students from his home, during the evenings (in a well-regulated way). I had built a small lab in the attic of my parents’ house and I really had fun mixing things together and doing all the experiments that are possible to do at home. Because of this chemistry teacher, I learned the joy of being in a lab.
The second crucial mentor was my thesis advisor, who didn’t supervise me very much but did give me key advice that has stayed with me until now. He taught me that it’s important to trust everybody you work with, at least until they show you that they can’t be trusted. I emphasize this in my own lab – I encourage my students and postdocs to be open and transparent and to discuss their work. Some scientists are intuitively secretive and paranoid – cultural differences perhaps play a part in this. In my view, only when someone damages your trust can you justify being paranoid, and until then it is important to share information.
“…it’s important to trust everybody you work with, at least until they show you that they can’t be trusted”
There are many ways to run a lab; for example, you can micro-manage it or you can focus on the big picture and step back from the day-to-day issues. What is your style of running a lab?
When I first became a PI, I really liked doing experimental work. Even after 5 years as a postdoc, I enjoyed doing minipreps! As a consequence, I really micro-managed the few lab members I had, and I’m sure they were ultimately happy to get away from me. But when the lab grew a little bigger and I became Head of Department, it took me away from the lab much of the time. Nowadays, I informally talk with my lab colleagues as much as I can, preferably at the bench. As we speak, I know that there is someone in my group who will find out the results of a 3-month effort, today. I always insist on looking at the raw data, never the digested, analysed data. It could be 5 minutes or 2 hours, but when I’m needed in the lab I will always try to make time for it and be part of the troubleshooting process. When you can no longer troubleshoot in your own lab, you’re lost.
Well clearly success builds on success – some impressive scientists have come out of your lab. Do you encourage all of your group members to pursue academic positions?
I’ve had many ‘super postdocs’ in my lab but some of these individuals would not be happy as PIs. It’s not about capability, but about wanting to deal with the paperwork, the responsibility and the decision-making that come with being a PI. Such individuals can make a valuable contribution to a lab, given their years of experience, as well as acting as great mentors and role models for the newer group members. When, having gained experience in the pharmaceutical industry, Nick Barker re-joined my group in 2006 as Senior Staff Scientist, we spent 6–7 years looking for stem cell markers, and then broke open the field by identifying Lgr5 as a marker of cancer stem cell populations. Nick has now set up his own group in Singapore, but I have had several other very talented experimentalists in my lab for many years. Overall, I think that intermediate positions are fantastic for successful postdocs who might end up unhappy as PIs.
How did you get involved with intestinal stem cell research? You didn’t start in this field but somehow ended up there.
As an undergraduate student, I did a brief rotation project on T cells. This led to a PhD and postdoc focused on T cells. I learned molecular biology, which inspired me to clone a T-lymphocyte transcription factor, TCF-1, when I subsequently set up my own lab in Holland. We (Marc van der Wetering and I) cloned TCF-1 within a few months and showed that it binds DNA; but, despite trying all kinds of functional assays, we couldn’t show that it regulates transcription. It took 6 or 7 years to figure out that β-catenin, a signal transducer in the Wnt signalling pathway, was needed. We heard that Walter Birchmeier had made a complementary discovery in Berlin, and our papers came out at the same time.
Around that time, I was Clinical Professor in Immunology at Utrecht, and I started studying TCFs in mice, frogs, flies and worms. We soon established that TCFs are always the endpoint of the Wnt pathway. In 1996–1997, we knocked out TCF-4 in mice and, remarkably, observed a gut phenotype – the mice had no crypts. Simultaneously, we realised that the pathway is overactivated in colon cancer. That’s when I decided to move into studying the gut. It wasn’t easy as an immunologist, but I gradually got to know the gastroenterology field. At the time, this field was dominated by clinical research, and in fact our work didn’t really become known to gastroenterologists until around 3–4 years ago. They were totally unaware that mice could give clues about human disease, which surprised me, as in haematology and immunology, there is a good balance between basic and clinical science. There are other clinically well-developed fields, such as prostate and lung cancer research, that could really benefit from a stronger basic approach.
A key discovery for you was that Lgr5 is a marker of stem cells. When did you realise the implications of this discovery?
There were two ‘eureka’ moments with the stem cell story. The dogma at the time was the ‘+4’ stem cell model, which was pioneered by Chris Potten, who recently passed away. I tried to provide experimental support for this model, together with Nick Barker, but it never really went anywhere. Having realised that β-catenin and TCFs controlled crypts in the gut and cancer, we set out to determine the genetic programme controlled by this pathway. At the time (1997), there was no technology to do this properly, but in 2000 we performed one of the first microarrays with Pat Brown. Our array looked at expression in a colon cancer cell line. The array contained only two samples – plus or minus the Wnt pathway – but it opened the field for us by providing a list of markers to investigate further. This was the first, key step. From the list of markers, we picked a few that we thought were marking +4 cells, but these led us nowhere. Eventually, based on its unique expression pattern, we came up with Lgr5. We made numerous mouse strains, including Lgr5-GFP tagged mice. The moment we saw tiny cells lighting up under the microscope, I started writing our next ten big papers in my head. It was a remarkable moment – the cells exist, and we could visualise them using these mice.
And why exactly is Lgr5 so important, both from a basic and an applied standpoint?
Lgr5 is an exquisite protein. We and several other labs have shown that it is a marker for stem cells in many tissues. Originally, we saw it only in spontaneously dividing tissues, but we’ve recently found that it also appears in organs that have undergone damage. Lgr5 is unique in that it – on its own – it specifically marks homogenous populations of stem cells but not their progenitors, unlike most other markers. We now know that this is because it is a cell surface receptor protein in the Wnt pathway, and only stem cells require Wnts. In the gut, the stem cells are particularly active – in mice, they divide every day for 2.5 years, so they go through a thousand cell divisions.
Discovering Lgr5 led to another eureka moment: the generation of long-term culture systems that maintain crypt physiology. A Japanese gastroenterologist who I invited to my lab, Toshiro Sato, was the first to set up the right culture conditions, and now multiple labs are creating these systems, which are called organoids or ‘mini-guts’. Once the system was up and running, Toshiro showed that Paneth cells provide the niche for stem cells at crypt bottoms, and that stem cells produce their own daughters which then produce growth factors. With his former Japanese lab, we showed that normal tissue can be generated from a single stem cell, and it can survive in a mouse for as long as you want. Based on this finding, our lab evolved and now we’re culturing prostate, liver, pancreas, kidney, lung and breast tissue, all for prolonged periods of time, all from humans. There are no changes in chromosomal structure in the cultured cells, and deep sequencing reveals very few mutations. The next step will be to take single cells, genetically modify them like we do with embryonic stem cells, pick a safe clone, expand it and use it for therapy, particularly transplantation.
Do you think we will be able to take organoid-based therapy to the personalised level? Colorectal cancer, for example, only has a 3% success rate in clinical trials. Are organoids going to provide the answer?
We’re finalising a pilot sequencing study now involving 20 patients with normal crypts and colon cancer. With the wild-type and colon cancer organoids, we can potentially predict patient outcome and response to drugs. In the future, we hope to rapidly build large, living biobanks for other cancers, too. In line with this, we’re building up a ‘Stand Up 2 Cancer’ dream team involving several American labs and the Sanger Institute, with the aim of taking the organoid approach to the next level in cancer therapy. Sanger has robotised screening set-ups that allow thousands of compounds to be screened across hundreds of cell lines. We can now do this with patient-derived organoids. From these tests we could establish new effective drug combinations, and we could link genetics to function to help design smarter trials. The great thing about organoids is that they contain only epithelium – there is no immune system, no blood system, only the diseased tissue, making it a very clean system.
We’ve also recently collaborated with clinicians on a cystic fibrosis project. We can predict using cystic fibrosis ‘mini-guts’ that certain drugs that are currently in trials will work for one patient and not for another, and that certain drug combinations work better than others. From biopsy to drug response, it takes only 10 days. Industry is now very interested in using this assay to pre-screen and design trials.
“The great thing about organoids is that they contain only epithelium – there is no immune system, no blood system, only the diseased tissue, making it a very clean system”
In the past, you’ve suggested that classic hypothesis-driven science isn’t the right way to do science. Could you say a little bit more about this?
Now that I’m a bit older I’m more interested in how the process of science works. I always ask my colleagues: how do you run the lab and how do you make discoveries? In my lab, I try to establish a reproducible, quantitative system, like GFP mice and arrays. Then, I throw something at the system and look, without formulating a hypothesis. This is difficult because our brains like to produce causal relationships, even though these are often wrong. I’m constantly telling my group members that they should keep their minds open and make observations without assuming that they know what’s going on. In molecular biology, we can go anywhere we want and there are billions of effects to discover. You cannot do this in a hypothesis-driven way because you’re essentially retracing evolution. There are many solutions to a particular problem but evolution picked one – it’s very arrogant to think we can reconstruct this in our minds.
Some of my most elegant hypotheses have fallen by the wayside. The importance of establishing formal rules for innovation is a discussion worth having in biology. I understand that you have embraced movies to explain scientific concepts. What’s the story behind this?
I was inspired by Leonard Zon – I came across one of his movies about 8 years ago. I realised it’s much easier to convey messages visually than in words so I started working with a small company in Holland to produce science movies. The lab provides the idea and the images, and the company writes the script. We end up going back and forth a few times to make the message as accurate as possible, and it really shows us as scientists how ambiguous language can be. Often, feedback from the company sends us back into the lab to find out something we hadn’t looked into, for example how fast do the cells move, how many cells are there? Gradually, the movie comes together. Nowadays, I typically use the movies in my talks to explain a problem, and I’ve found that it’s much more effective to show the movie before explaining the experiments. People understand the experiments much better that way, and listen effortlessly. Now, whenever we have a story to write up I try to turn it into a 30-second movie before putting pen to paper. This really forces us to think about the core of the paper.
“In molecular biology, we can go anywhere we want and there are billions of effects to discover…There are many solutions to a particular problem but evolution picked one – it’s very arrogant to think we can reconstruct this in our minds”
In your view, is being a scientist a good career choice? What advice would you give to a young scientist thinking about this career?
Science is frustrating because things don’t work 90% of the time: ideas are wrong, experiments fail. You have to have the personality that thrives by those few fantastic moments of success that you have once a year or even once a career. Moving from being a clinician to being a scientist was one of the hardest decisions I ever made. A clinician gets rewards multiple times a day, so if you’re a person who needs that kind of reward and social interaction, then you shouldn’t be a scientist. Luckily there are now many alternative careers, such as pharma, government and teaching, that didn’t exist when I was a young scientist. However, there needs to be a radical change in the way we view these alternative routes. Maybe in the US it’s different, but here, if you step out of the system you are treated like a failure. I tell young scientists that failure comes with ending up as a miserable PI, with no funding and no papers.
PhD students and junior postdocs have to be aware that the people they see at meetings who give the great talks are in the minority – as scientists we have to be ready to do something else at any point during our career. I think the whole system has to realise that every other job can be as interesting as a job in science. That’s not what we always convey to young people – we describe academia as where it’s happening and everything else as dull or uncreative.
If you hadn’t chosen science as a career, what would you have done instead?
I would probably be a novelist. It’s even more competitive than being a scientist, but it’s also creative, so the perfect blend for me.
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