Archive for the ‘Cell Biology, Signaling & Cell Circuits’ Category

Live Conference Coverage AACR 2020 in Real Time: Monday June 22, 2020 Late Day Sessions


Reporter: Stephen J. Williams, PhD


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June 22-24: Free Registration for AACR Members, the Cancer Community, and the Public
This virtual meeting will feature more than 120 sessions and 4,000 e-posters, including sessions on cancer health disparities and the impact of COVID-19 on clinical trials


This Virtual Meeting is Part II of the AACR Annual Meeting.  Part I was held online in April and was centered only on clinical findings.  This Part II of the virtual meeting will contain all the Sessions and Abstracts pertaining to basic and translational cancer research as well as clinical trial findings.






Virtual Educational Session

Prevention Research, Science Policy, Epidemiology, Survivorship

Carcinogens at Home: Science and Pathways to Prevention

Chemicals known to cause cancer are used and released to the environment in large volumes, exposing people where they live, work, play, and go to school. The science establishing an important role for such exposures in the development of cancers continues to strengthen, yet cancer prevention researchers are largely unfamiliar with the data drawn upon in identifying carcinogens and making decisions about their use. Characterizing and reducing harmful exposures and accelerating the devel

Julia Brody, Kathryn Z. Guyton, Polly J. Hoppin, Bill Walsh, Mary H. Ward


Monday, June 22

1:30 PM – 3:30 PM EDT

Virtual Educational Session

Tumor Biology, Molecular and Cellular Biology/Genetics, Clinical Research Excluding Trials

EMT Still Matters: Let’s Explore! – Dedicated to the Memory of Isaiah J. Fidler

During carcinoma progression, initially benign epithelial cells acquire the ability to invade locally and disseminate to distant tissues by activating epithelial-mesenchymal transition (EMT). EMT is a cellular process during which epithelial cells lose their epithelial features and acquire mesenchymal phenotypes and behavior. Growing evidence supports the notion that EMT programs during tumor progression are usually activated to various extents and often partial and reversible, thus pr

Jean-Paul Thiery, Heide L Ford, Jing Yang, Geert Berx


Monday, June 22

1:30 PM – 3:00 PM EDT

Virtual Educational Session

Tumor Biology, Experimental and Molecular Therapeutics, Molecular and Cellular Biology/Genetics

One of These Things Is Not Like the Other: The Many Faces of Senescence in Cancer

Cellular senescence is a stable cell growth arrest that is broadly recognized to act as a barrier against tumorigenesis. Senescent cells acquire a senescence-associated secretory phenotype (SASP), a transcriptional response involving the secretion of inflammatory cytokines, immune modulators, and proteases that can shape the tumor microenvironment. The SASP can initially stimulate tumor immune surveillance and reinforce growth arrest. However, if senescent cells are not removed by the

Clemens A Schmitt, Andrea Alimonti, René Bernards


Monday, June 22

1:30 PM – 3:00 PM EDT

Virtual Educational Session

Clinical Research Excluding Trials, Molecular and Cellular Biology/Genetics

Recent Advances in Applications of Cell-Free DNA

The focus of this educational session will be on recent developments in cell-free DNA (cfDNA) analysis that have the potential to impact the care of cancer patients. Tumors continually shed DNA into the circulation, where it can be detected as circulating tumor DNA (ctDNA). Analysis of ctDNA has become a routine part of care for a subset of patients with advanced malignancies. However, there are a number of exciting potential applications that have promising preliminary data but that h

Michael R Speicher, Maximilian Diehn, Aparna Parikh


Monday, June 22

1:30 PM – 3:30 PM EDT

Virtual Methods Workshop

Clinical Research Excluding Trials, Clinical Trials, Experimental and Molecular Therapeutics, Molecular and Cellular Biology/Genetics

Translating Genetics and Genomics to the Clinic and Population

This session will describe how advances in understanding cancer genomes and in genetic testing technologies are being translated to the clinic. The speakers will illustrate the clinical impact of genomic discoveries for diagnostics and treatment of common tumor types in adults and in children. Cutting-edge technologies for characterization of patient and tumor genomes will be described. New insights into the importance of patient factors for cancer risk and outcome, including predispos

Heather L. Hampel, Gordana Raca, Jaclyn Biegel, Jeffrey M Trent


Monday, June 22

1:30 PM – 3:22 PM EDT

Virtual Educational Session

Regulatory Science and Policy, Drug Development, Epidemiology

Under-representation in Clinical Trials and the Implications for Drug Development

The U.S. Food and Drug Administration relies on data from clinical trials to determine whether medical products are safe and effective. Ideally, patients enrolled in those trials are representative of the population in which the product will be used if approved, including people of different ages, races, ethnic groups, and genders. Unfortunately, with few patients enrolling in clinical trials, many groups are not well-represented in clinical trials. This session will explore challenges

Ajay K. Nooka, Nicole J. Gormley, Kenneth C Anderson, Ruben A. Mesa, Daniel J. George, Yelak Biru, RADM Richardae Araojo, Lola A. Fashoyin-Aje


Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Cancer Chemistry

Targeted Protein Degradation: Target Validation Tools and Therapeutic Opportunity

This educational session will cover the exciting emerging field of targeted protein degradation. Key learning topics will include: 1. an introduction to the technology and its relevance to oncology; 2. PROTACS, degraders, and CELMoDs; 3. enzymology and protein-protein interactions in targeted protein degraders; 4. examples of differentiated biology due to degradation vs. inhibition; 5. how to address questions of specificity; and 6. how the field is approaching challenges in optimizing therapies

George Burslem, Mary Matyskiela, Lyn H. Jones, Stewart L Fisher, Andrew J Phillips


Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Bioinformatics and Systems Biology, Experimental and Molecular Therapeutics, Drug Development, Molecular and Cellular Biology/Genetics

Obstacles and opportunities for protein degradation drug discovery

Lyn H. Jones
  • PROTACs ubiquitin mediated by E3 ligases;  first discovered by DeShaies and targeted to specific proteins
  • PROTACs used in drug discovery against a host of types of targets including kinases and membrane receptors
  • PROTACs can be modular but lack molecular structural activity relationships
  • can use chemical probes for target validation
  • four requirements: candidate exposure at site of action (for example lipophilicity for candidates needed to cross membranes and accumulate in lysosomes), target engagement (ternary occupancy as measured by FRET), functional pharmacology, relevant phenotype
  • PROTACs hijack the proteosomal degradation system

Proteolysis-targeting chimeras as therapeutics and tools for biological discovery

George Burslem
  • first PROTAC developed to coopt the VHL ubiquitin ligase system which degrades HIF1alpha but now modified for EREalpha
  • in screen for potential PROTACS there were compounds which bound high affinity but no degradation so phenotypic screening very important
  • when look at molecular dynamics can see where PROTAC can add additional protein protein interaction, verifed by site directed mutagenesis
  • able to target bcr-Abl
  • he says this is a rapidly expanding field because of all the new E3 ligase targets being discovered

Expanding the horizons of cereblon modulators

Mary Matyskiela

Translating cellular targeted protein degradation to in vivo models using an enzymology framework

Stewart L Fisher
  • new targeting compounds have an E3 ligase binding domain, a target binding domain and a linker domain
  • in vivo these compounds are very effective; BRD4 degraders good invitro and in vivo with little effect on body weight
  • degraders are essential activators of E3 ligases as these degraders bring targets in close proximity so activates a catalytic cycle of a multistep process (has now high turnover number)
  • in enzymatic pathway the degraders make a productive complex so instead of a kcat think of measuring a kprod or productivity of degraders linked up an E3 ligase
  • the degraders are also affecting the rebound protein synthesis; so Emax never to zero and see a small rebound of protein synthesis


Data-Driven Approaches for Choosing Combinatorial Therapies

Drug combinations remain the gold standard for treating cancer, as they significantly outperform single agents. However, due to the enormous size of drug combination space, it is virtually impossible to interrogate all possible combinations. This session will discuss approaches to identify novel combinations using both experimental and computational approaches. Speakers will discuss i) approaches to drug screening in cell lines, the impact of the microenvironment, and attempts to more

Bence Szalai, James E Korkola, Lisa Tucker-Kellogg, Jeffrey W Tyner


Monday, June 22

3:45 PM – 5:21 PM EDT

Virtual Educational Session

Tumor Biology

Cancer Stem Cells and Therapeutic Resistance

Cancer stem cells are a subpopulation of cells with a high capacity for self-renewal, differentiation and resistance to therapy. In this session, we will define cancer stem cells, discuss cellular plasticity, interactions between cancer stem cells and the tumor microenvironment, and mechanisms that contribute to therapeutic resistance.

Robert S Kerbel, Dolores Hambardzumyan, Jennifer S. Yu


Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Drug Development, Experimental and Molecular Therapeutics

Molecular Imaging in Cancer Research

This session will cover the fundamentals as well as the major advances made in the field of molecular imaging. Topics covered will include the basics for optical, nuclear, and ultrasound imaging; the pros and cons of each modality; and the recent translational advancements. Learning objectives include the fundamentals of each imaging modality, recent advances in the technology, the processes involved to translate an imaging agent from bench to bedside, and how molecular imaging can gui

Julie Sutcliffe, Summer L Gibbs, Mark D Pagel, Katherine W Ferrara


Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Tumor Biology, Immunology, Experimental and Molecular Therapeutics, Drug Development

Tumor Endothelium: The Gatekeepers of Tumor Immune Surveillance

Tumor-associated endothelium is a gatekeeper that coordinates the entry and egress of innate and adaptive immune cells within the tumor microenvironment. This is achieved, in part, via the coordinated expression of chemokines and cell adhesion molecules on the endothelial cell surface that attract and retain circulating leukocytes. Crosstalk between adaptive immune cells and the tumor endothelium is therefore essential for tumor immune surveillance and the success of immune-based thera

Dai Fukumura, Maria M Steele, Wen Jiang, Andrew C Dudley


Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Immunology, Experimental and Molecular Therapeutics

Novel Strategies in Cancer Immunotherapy: The Next Generation of Targets for Anticancer Immunotherapy

T-cell immunotherapy in the form of immune checkpoint blockade or cellular T-cell therapies has been tremendously successful in some types of cancer. This success has opened the door to consider what other modalities or types of immune cells can be harnessed for exert antitumor functions. In this session, experts in their respective fields will discuss topics including novel approaches in immunotherapy, including NK cells, macrophage, and viral oncotherapies.

Evanthia Galanis, Kerry S Campbell, Milan G Chheda, Jennifer L Guerriero


Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Tumor Biology, Drug Development, Immunology, Clinical Research Excluding Trials

Benign Cells as Drivers of Cancer Progression: Fat and Beyond

Carcinomas develop metastases and resistance to therapy as a result of interaction with tumor microenvironment, composed of various nonmalignant cell types. Understanding the complexity and origins of tumor stromal cells is a prerequisite for development of effective treatments. The link between obesity and cancer progression has revealed the engagement of adipose stromal cells (ASC) and adipocytes from adjacent fat tissue. However, the molecular mechanisms through which they stimulate

Guojun Wu, Matteo Ligorio, Mikhail Kolonin, Maria T Diaz-Meco


Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Educational Session

Clinical Research Excluding Trials, Experimental and Molecular Therapeutics, Tumor Biology

Dharma Master Jiantai Symposium on Lung Cancer: Know Thy Organ – Lessons Learned from Lung and Pancreatic Cancer Research

The term “cancer” encompasses hundreds of distinct disease entities involving almost every possible site in the human body. Effectively interrogating cancer, either in animals models or human specimens, requires a deep understanding of the involved organ. This includes both the normal cellular constituents of the affected tissue as well as unique aspects of tissue-specific tumorigenesis. It is critical to “Know Thy Organ” when studying cancer. This session will focus on two of the most

Trudy G Oliver, Hossein Borghaei, Laura Delong Wood, Howard C Crawford


Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Methods Workshop

Clinical Trials

Clinical Trial Design: Part 1: Novel Approaches and Methods in Clinical Trial Design

Good clinical trial design has always had to balance the competing interests of effectively and convincingly answering the question with the limitations imposed by scarce resources, complex logistics, and risks and potential benefits to participants. New targeted therapies, immuno-oncology, and novel combination treatments add new challenges on top of the old ones. This session will introduce these concerns and 1) suggest ways to consider what outcomes are relevant, 2) how we can best

Mary W. Redman, Nolan A. Wages, Susan G Hilsenbeck, Karyn A. Goodman


Monday, June 22

3:45 PM – 5:45 PM EDT

Virtual Methods Workshop

Tumor Biology, Drug Development

High-Throughput Screens for Drivers of Progression and Resistance

The sequencing of human cancers now provides a landscape of the genetic alterations that occur in human cancer, and increasingly knowledge of somatic genetic alterations is becoming part of the evaluation of cancer patients. In some cases, this information leads directly to the selection of particular therapeutic approaches; however, we still lack the ability to decipher the significance of genetic alterations in many cancers. This session will focus on recent developments that permit the identification of molecular targets in specific cancers. This information, coupled with genomic characterization of cancer, will facilitate the development of new therapeutic agents and provide a path to implement precision cancer medicine to all patients.

William C Hahn, Mark A Dawson, Mariella Filbin, Michael Bassik


Monday, June 22

3:45 PM – 5:15 PM EDT

Defining a cancer dependency map

William C Hahn


William C Hahn

Genome-scale CRISPR screens in 3D spheroids identify cancer vulnerabilities

Michael Bassik

Utilizing single-cell RNAseq and CRISPR screens to target cancer stem cells in pediatric brain tumors

Mariella Filbin
  • many gliomas are defined by discreet mutational spectra that also discriminates based on age and site as well (for example many cortical tumors have mainly V600E Braf mutations while thalamus will be FGFR1
  • they did single cell RNAseq on needle biopsy from 7 gliomas which gave about 3500 high quality single cells; obtained full length RNA
  • tumors clustered mainly where the patient it came from but had stromal cell contamination probably so did a deconvolution?  Copy number variation showed which were tumor cells and did principle component analysis
  • it seems they used a human glioma model as training set
  • identified a stem cell like glioma cell so concentrated on the genes altered in these for translational studies
  • developed multiple PDX models from patients
  • PDX transcriptome closest to patient transcriptome but organoid grown in serum free very close while organoids grown in serum very distinct transcriptome
  • developed a CRISPR barcoded library to determine genes for survival genes
  • pulled out BMI1  and EZH2 (polycomb complex proteins) as good targets

Virtual Methods Workshop

Prevention Research, Survivorship, Clinical Research Excluding Trials, Epidemiology

Implementation Science Methods for Cancer Prevention and Control in Diverse Populations: Integration of Implementation Science Methods in Care Settings

Through this Education Session we will use examples from ongoing research to provide an overview of implementation science approaches to cancer prevention and control research. We draw on examples to highlight study design approaches, research methods, and real-world solutions when applying implementation science to achieve health equity. Approaches to defining change in the care setting and measuring sustained changes are also emphasized. Using real examples of patient navigation prog

Graham A Colditz, Sanja Percac-Lima, Nathalie Huguet


Monday, June 22

3:45 PM – 5:30 PM EDT

Virtual Educational Session

Regulatory Science and Policy, Epidemiology

COVID-19 and Cancer: Guidance for Clinical Trial Conduct and Considerations for RWE

This session will consider the use of real-world evidence in the context of oncology clinical trials affected by the COVID-19 pandemic. Key aspects of the FDA’s recent “Guidance on Conduct of Clinical Trials of Medical Products of Medical Products during COVID-19 Public Health Emergency” will be discussed, including telemedicine, accounting for missing data, obtaining laboratory tests and images locally, using remote informed consent procedures, and additional considerations for contin

Wendy Rubinstein, Paul G. Kluetz, Amy P. Abernethy, Jonathan Hirsch, C.K. Wang



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RNA from the SARS-CoV-2 virus taking over the cells it infects: Virulence – Pathogen’s ability to infect a Resistant Host: The Imbalance between Controlling Virus Replication versus Activation of the Adaptive Immune Response

Curator: Aviva Lev-Ari, PhD, RN – I added colors and bold face


UPDATED on 6/29/2020

Another duality and paradox in the Treatment of COVID-19 Patients in ICUs was expressed by Mike Yoffe, MD, PhD, David H. Koch Professor of Biology and Biological Engineering, Massachusetts Institute of Technology. Dr. Yaffe has a joint appointment in Acute Care Surgery, Trauma, and Surgical Critical Care, and in Surgical Oncology @BIDMC

on 6/29 at SOLUTIONS with/in/sight at Koch Institute @MIT

How Are Cancer Researchers Fighting COVID-19? (Part II)” Jun 29, 2020 11:30 AM EST

Mike Yoffe, MD, PhD 

In COVID-19 patients: two life threatening conditions are seen in ICUs:

  • Blood Clotting – Hypercoagulability or Thrombophilia
  • Cytokine Storm – immuno-inflammatory response
  • The coexistence of 1 and 2 – HINDERS the ability to use effectively tPA as an anti-clotting agent while the cytokine storm is present.

Mike Yoffe’s related domain of expertise:

Signaling pathways and networks that control cytokine responses and inflammation

Misregulation of cytokine feedback loops, along with inappropriate activation of the blood clotting cascade causes dysregulation of cell signaling pathways in innate immune cells (neutrophils and macrophages), resulting in tissue damage and multiple organ failure following trauma or sepsis. Our research is focused on understanding the role of the p38-MK2 pathway in cytokine control and innate immune function, and on cross-talk between cytokines, clotting factors, and neutrophil NADPH oxidase-derived ROS in tissue damage, coagulopathy, and inflammation, using biochemistry, cell biology, and mouse knock-out/knock-in models.  We recently discovered a particularly important link between abnormal blood clotting and the complement pathway cytokine C5a which causes excessive production of extracellular ROS and organ damage by neutrophils after traumatic injury.





The Genome Structure of CORONAVIRUS, SARS-CoV-2

Reporter: Aviva Lev-Ari, PhD, RN



Imbalanced Host Response to SARS-CoV-2 Drives Development of COVID-19

Open Access Published:May 15, 2020DOI:https://doi.org/10.1016/j.cell.2020.04.026


  • SARS-CoV-2 infection induces low IFN-I and -III levels with a moderate ISG response
  • Strong chemokine expression is consistent across in vitroex vivo, and in vivo models
  • Low innate antiviral defenses and high pro-inflammatory cues contribute to COVID-19


Viral pandemics, such as the one caused by SARS-CoV-2, pose an imminent threat to humanity. Because of its recent emergence, there is a paucity of information regarding viral behavior and host response following SARS-CoV-2 infection. Here we offer an in-depth analysis of the transcriptional response to SARS-CoV-2 compared with other respiratory viruses. Cell and animal models of SARS-CoV-2 infection, in addition to transcriptional and serum profiling of COVID-19 patients, consistently revealed a unique and inappropriate inflammatory response. This response is defined by low levels of type I and III interferons juxtaposed to elevated chemokines and high expression of IL-6. We propose that reduced innate antiviral defenses coupled with exuberant inflammatory cytokine production are the defining and driving features of COVID-19.

Graphical Abstract



Defining the Transcriptional Response to SARS-CoV-2 Relative to Other Respiratory Viruses

To compare the transcriptional response of SARS-CoV-2 with other respiratory viruses, including MERS-CoV, SARS-CoV-1, human parainfluenza virus 3 (HPIV3), respiratory syncytial virus (RSV), and IAV, we first chose to focus on infection in a variety of respiratory cell lines (Figure 1). To this end, we collected poly(A) RNA from infected cells and performed RNA sequencing (RNA-seq) to estimate viral load. These data show that virus infection levels ranged from 0.1% to more than 50% of total RNA reads (Figure 1A).


In the present study, we focus on defining the host response to SARS-CoV-2 and other human respiratory viruses in cell lines, primary cell cultures, ferrets, and COVID-19 patients. In general, our data show that the overall transcriptional footprint of SARS-CoV-2 infection was distinct in comparison with other highly pathogenic coronaviruses and common respiratory viruses such as IAV, HPIV3, and RSV. It is noteworthy that, despite a reduced IFN-I and -III response to SARS-CoV-2, we observed a consistent chemokine signature. One exception to this observation is the response to high-MOI infection in A549-ACE2 and Calu-3 cells, where replication was robust and an IFN-I and -III signature could be observed. In both of these examples, cells were infected at a rate to theoretically deliver two functional virions per cell in addition to any defective interfering particles within the virus stock that were not accounted for by plaque assays. Under these conditions, the threshold for PAMP may be achieved prior to the ability of the virus to evade detection through production of a viral antagonist. Alternatively, addition of multiple genomes to a single cell may disrupt the stoichiometry of viral components, which, in turn, may itself generate PAMPs that would not form otherwise. These ideas are supported by the fact that, at a low-MOI infection in A549-ACE2 cells, high levels of replication could also be achieved, but in the absence of IFN-I and -III induction. Taken together, these data suggest that, at low MOIs, the virus is not a strong inducer of the IFN-I and -III system, as opposed to conditions where the MOI is high.
Taken together, the data presented here suggest that the response to SARS-CoV-2 is imbalanced with regard to controlling virus replication versus activation of the adaptive immune response. Given this dynamic, treatments for COVID-19 have less to do with the IFN response and more to do with controlling inflammation. Because our data suggest that numerous chemokines and ILs are elevated in COVID-19 patients, future efforts should focus on U.S. Food and Drug Administration (FDA)-approved drugs that can be rapidly deployed and have immunomodulating properties.



SARS-CoV-2 ORF3b is a potent interferon antagonist whose activity is further increased by a naturally occurring elongation variant

Yoriyuki KonnoIzumi KimuraKeiya UriuMasaya FukushiTakashi IrieYoshio KoyanagiSo NakagawaKei Sato


One of the features distinguishing SARS-CoV-2 from its more pathogenic counterpart SARS-CoV is the presence of premature stop codons in its ORF3b gene. Here, we show that SARS-CoV-2 ORF3b is a potent interferon antagonist, suppressing the induction of type I interferon more efficiently than its SARS-CoV ortholog. Phylogenetic analyses and functional assays revealed that SARS-CoV-2-related viruses from bats and pangolins also encode truncated ORF3b gene products with strong anti-interferon activity. Furthermore, analyses of more than 15,000 SARS-CoV-2 sequences identified a natural variant, in which a longer ORF3b reading frame was reconstituted. This variant was isolated from two patients with severe disease and further increased the ability of ORF3b to suppress interferon induction. Thus, our findings not only help to explain the poor interferon response in COVID-19 patients, but also describe a possibility of the emergence of natural SARS-CoV-2 quasi-species with extended ORF3b that may exacerbate COVID-19 symptoms.


  • ORF3b of SARS-CoV-2 and related bat and pangolin viruses is a potent IFN antagonist

  • SARS-CoV-2 ORF3b suppresses IFN induction more efficiently than SARS-CoV ortholog

  • The anti-IFN activity of ORF3b depends on the length of its C-terminus

  • An ORF3b with increased IFN antagonism was isolated from two severe COVID-19 cases

Competing Interest Statement

The authors have declared no competing interest.

Paper in collection COVID-19 SARS-CoV-2 preprints from medRxiv and bioRxiv






A deep dive into how the new coronavirus infects cells has found that it orchestrates a hostile takeover of their genes unlike any other known viruses do, producing what one leading scientist calls “unique” and “aberrant” changes.Recent studies show that in seizing control of genes in the human cells it invades, the virus changes how segments of DNA are read, doing so in a way that might explain why the elderly are more likely to die of Covid-19 and why antiviral drugs might not only save sick patients’ lives but also prevent severe disease if taken before infection.“It’s something I have never seen in my 20 years of” studying viruses, said virologist Benjamin tenOever of the Icahn School of Medicine at Mount Sinai, referring to how SARS-CoV-2, the virus that causes Covid-19, hijacks cells’ genomes.The “something” he and his colleagues saw is how SARS-CoV-2 blocks one virus-fighting set of genes but allows another set to launch, a pattern never seen with other viruses. Influenza and the original SARS virus (in the early 2000s), for instance, interfere with both arms of the body’s immune response — what tenOever dubs “call to arms” genes and “call for reinforcement” genes.The first group of genes produces interferons. These proteins, which infected cells release, are biological semaphores, signaling to neighboring cells to activate some 500 of their own genes that will slow down the virus’ ability to make millions of copies of itself if it invades them. This lasts seven to 10 days, tenOever said, controlling virus replication and thereby buying time for the second group of genes to act.

This second set of genes produce their own secreted proteins, called chemokines, that emit a biochemical “come here!” alarm. When far-flung antibody-making B cells and virus-killing T cells sense the alarm, they race to its source. If all goes well, the first set of genes holds the virus at bay long enough for the lethal professional killers to arrive and start eradicating viruses.

“Most other viruses interfere with some aspect of both the call to arms and the call for reinforcements,” tenOever said. “If they didn’t, no one would ever get a viral illness”: The one-two punch would pummel any incipient infection into submission.

SARS-CoV-2, however, uniquely blocks one cellular defense but activates the other, he and his colleagues reported in a study published last week in Cell. They studied healthy human lung cells growing in lab dishes, ferrets (which the virus infects easily), and lung cells from Covid-19 patients. In all three, they found that within three days of infection, the virus induces cells’ call-for-reinforcement genes to produce cytokines. But it blocks their call-to-arms genes — the interferons that dampen the virus’ replication.

The result is essentially no brakes on the virus’s replication, but a storm of inflammatory molecules in the lungs, which is what tenOever calls an “unique” and “aberrant” consequence of how SARS-CoV-2 manipulates the genome of its target.

In another new study, scientists in Japan last week identified how SARS-CoV-2 accomplishes that genetic manipulation. Its ORF3b gene produces a protein called a transcription factor that has “strong anti-interferon activity,” Kei Sato of the University of Tokyo and colleagues found — stronger than the original SARS virus or influenza viruses. The protein basically blocks the cell from recognizing that a virus is present, in a way that prevents interferon genes from being expressed.

In fact, the Icahn School team found no interferons in the lung cells of Covid-19 patients. Without interferons, tenOever said, “there is nothing to stop the virus from replicating and festering in the lungs forever.”

That causes lung cells to emit even more “call-for-reinforcement” genes, summoning more and more immune cells. Now the lungs have macrophages and neutrophils and other immune cells “everywhere,” tenOever said, causing such runaway inflammation “that you start having inflammation that induces more inflammation.”

At the same time, unchecked viral replication kills lung cells involved in oxygen exchange. “And suddenly you’re in the hospital in severe respiratory distress,” he said.

In elderly people, as well as those with diabetes, heart disease, and other underlying conditions, the call-to-arms part of the immune system is weaker than in younger, healthier people, even before the coronavirus arrives. That reduces even further the cells’ ability to knock down virus replication with interferons, and imbalances the immune system toward the dangerous inflammatory response.

The discovery that SARS-CoV-2 strongly suppresses infected cells’ production of interferons has raised an intriguing possibility: that taking interferons might prevent severe Covid-19 or even prevent it in the first place, said Vineet Menachery of the University of Texas Medical Branch.

In a study of human cells growing in lab dishes, described in a preprint (not peer-reviewed or published in a journal yet), he and his colleagues also found that SARS-CoV-2 “prevents the vast amount” of interferon genes from turning on. But when cells growing in lab dishes received the interferon IFN-1 before exposure to the coronavirus, “the virus has a difficult time replicating.”

After a few days, the amount of virus in infected but interferon-treated cells was 1,000- to 10,000-fold lower than in infected cells not pre-treated with interferon. (The original SARS virus, in contrast, is insensitive to interferon.)

Ending the pandemic and preventing its return is assumed to require an effective vaccine to prevent infectionand antiviral drugs such as remdesivir to treat the very sick, but the genetic studies suggest a third strategy: preventive drugs.

It’s possible that treatment with so-called type-1 interferon “could stop the virus before it could get established,” Menachery said.

Giving drugs to healthy people is always a dicey proposition, since all drugs have side effects — something considered less acceptable than when a drug is used to treat an illness. “Interferon treatment is rife with complications,” Menachery warned. The various interferons, which are prescribed for hepatitis, cancers, and many other diseases, can cause flu-like symptoms.

But the risk-benefit equation might shift, both for individuals and for society, if interferons or antivirals or other medications are shown to reduce the risk of developing serious Covid-19 or even make any infection nearly asymptomatic.

Interferon “would be warning the cells the virus is coming,” Menachery said, so such pretreatment might “allow treated cells to fend off the virus better and limit its spread.” Determining that will of course require clinical trials, which are underway.

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Live Notes, Real Time Conference Coverage 2020 AACR Virtual Meeting April 28, 2020 Session on Novel Targets and Therapies 2:35 PM

Reporter: Stephen J. Williams, PhD


Session VMS.ET04.01 – Novel Targets and Therapies

Targeting chromatin remodeling-associated genetic vulnerabilities in cancer: PBRM1 defects are synthetic lethal with PARP and ATR inhibitors

Presenter/AuthorsRoman Merial Chabanon, Daphné Morel, Léo Colmet-Daage, Thomas Eychenne, Nicolas Dorvault, Ilirjana Bajrami, Marlène Garrido, Suzanna Hopkins, Cornelia Meisenberg, Andrew Lamb, Theo Roumeliotis, Samuel Jouny, Clémence Astier, Asha Konde, Geneviève Almouzni, Jyoti Choudhary, Jean-Charles Soria, Jessica Downs, Christopher J. Lord, Sophie Postel-Vinay. Gustave Roussy, Villejuif, France, The Francis Crick Institute, London, United Kingdom, Institute of Cancer Research, London, United Kingdom, Sage Bionetworks, Seattle, WA, Institute of Cancer Research, London, United Kingdom, Institute of Cancer Research, London, United Kingdom, Institut Curie, Paris, France, Université Paris-Sud/Université Paris-Saclay, Le Kremlin-Bicêtre, France, Gustave Roussy Cancer Campus and U981 INSERM, ATIP-Avenir group, Villejuif, FranceDisclosures R.M. Chabanon: None. D. Morel: None. L. Colmet-Daage: None. T. Eychenne: None. N. Dorvault: None. I. Bajrami: None. M. Garrido: None. S. Hopkins: ; Fishawack Group of Companies. C. Meisenberg: None. A. Lamb: None. T. Roumeliotis: None. S. Jouny: None. C. Astier: None. A. Konde: None. G. Almouzni: None. J. Choudhary: None. J. Soria: ; Medimmune/AstraZeneca. ; Astex. ; Gritstone. ; Clovis. ; GSK. ; GamaMabs. ; Lilly. ; MSD. ; Mission Therapeutics. ; Merus. ; Pfizer. ; PharmaMar. ; Pierre Fabre. ; Roche/Genentech. ; Sanofi. ; Servier. ; Symphogen. ; Takeda. J. Downs: None. C.J. Lord: ; AstraZeneca. ; Merck KGaA. ; Artios. ; Tango. ; Sun Pharma. ; GLG. ; Vertex. ; Ono Pharma. ; Third Rock Ventures. S. Postel-Vinay: ; Merck KGaA. ; Principal investigator of clinical trials for Gustave Roussy.; Boehringer Ingelheim. ; Principal investigator of clinical trials for Gustave Roussy.; Roche. ; Principal investigator of clinical trials for Gustave Roussy. Benefited from reimbursement for attending symposia.; AstraZeneca. ; Principal investigator of clinical trials for Gustave Roussy.; Clovis. ; Principal investigator of clinical trials for Gustave Roussy.; Bristol-Myers Squibb. ; Principal investigator of clinical trials for Gustave Roussy.; Agios. ; Principal investigator of clinical trials for Gustave Roussy.; GSK.AbstractAim: Polybromo-1 (PBRM1), a specific subunit of the pBAF chromatin remodeling complex, is frequently inactivated in cancer. For example, 40% of clear cell Renal Cell Carcinoma (ccRCC) and 15% of cholangiocarcinoma present deleterious PBRM1 mutations. There is currently no precision medicine-based therapeutic approach that targets PBRM1 defects. To identify novel, targeted therapeutic strategies for PBRM1-defective cancers, we carried out high-throughput functional genomics and drug screenings followed by in vitro and in vivo validation studies.
Methods: High-throughput siRNA-drug sensitization and drug sensitivity screens evaluating > 150 cancer-relevant small molecules in dose-response were performed in Pbrm1 siRNA-transfected mouse embryonic stem cells (mES) and isogenic PBRM1-KO or -WT HAP1 cells, respectively. After identification of PBRM1-selective small molecules, revalidation was carried out in a series of in-house-generated isogenic models of PBRM1 deficiency – including 786-O (ccRCC), A498 (ccRCC), U2OS (osteosarcoma) and H1299 (non-small cell lung cancer) human cancer cell lines – and non-isogenic ccRCC models, using multiple clinical compounds. Mechanistic dissection was performed using immunofluorescence, RT-qPCR, western blotting, DNA fiber assay, transcriptomics, proteomics and DRIP-sequencing to evaluate markers of DNA damage response (DDR), replication stress and cell-autonomous innate immune signaling. Preclinical data were integrated with TCGA tumor data.
Results: Parallel high-throughput drug screens independently identified PARP inhibitors (PARPi) as being synthetic lethal with PBRM1 defects – a cell type-independent effect which was exacerbated by ATR inhibitors (ATRi) and which we revalidated in vitro in isogenic and non-isogenic systems and in vivo in a xenograft model. PBRM1 defects were associated with increased replication fork stress (higher γH2AX and RPA foci levels, decreased replication fork speed and increased ATM checkpoint activation), R-loop accumulation and enhanced genomic instability in vitro; these effects were exacerbated upon PARPi exposure. In patient tumor samples, we also found that PBRM1-mutant cancers possessed a higher mutational load. Finally, we found that ATRi selectively activated the cGAS/STING cytosolic DNA sensing pathway in PBRM1-deficient cells, resulting in increased expression of type I interferon genes.
Conclusion: PBRM1-defective cancer cells present increased replication fork stress, R-loop formation, genome instability and are selectively sensitive to PARPi and ATRi through a synthetic lethal mechanism that is cell type-independent. Our data provide the pre-clinical rationale for assessing PARPi as a monotherapy or in combination with ATRi or immune-modulating agents in molecularly-selected patients with PBRM1-defective cancers.

1057 – Targeting MTHFD2 using first-in-class inhibitors kills haematological and solid cancer through thymineless-induced replication stress

Presenter/AuthorsThomas Helleday. University of Sheffield, Sheffield, United KingdomDisclosures T. Helleday: None.AbstractSummary
Thymidine synthesis pathways are upregulated pathways in cancer. Since the 1940s, targeting nucleotide and folate metabolism to induce thymineless death has remained first-line anti-cancer treatment. Recent discoveries that showing cancer cells have rewired networks and exploit unique enzymes for proliferation, have renewed interest in metabolic pathways. The cancer-specific expression of MTHFD2 has gained wide-spread attention and here we describe an emerging role for MTHFD2 in the DNA damage response (DDR). The folate metabolism enzyme MTHFD2 is one of the most consistently overexpressed metabolic enzymes in cancer and an emerging anticancer target. We show a novel role for MTHFD2 being essential for DNA replication and genomic stability in cancer cells. We describe first-in-class nanomolar MTHFD2 inhibitors (MTHFD2i), with protein co-crystal structures demonstrating binding in the active site of MTHFD2 and engaging with the target in cells and tumours. We show MTHFD2i reduce replication fork speed and induce replication stress, followed by S phase arrest, apoptosis and killing of a range of haematological and solid cancer cells in vitro and in vivo, with a therapeutic window spanning up to four orders of magnitude compared to non-transformed cells. Mechanistically, MTHFD2i prevent thymidine production leading to mis-incorporation of uracil into DNA and replication stress. As MTHFD2 expression is cancer specific there is a potential of MTHFD2i to synergize with other treatments. Here, we show MTHFD2i synergize with dUTPase inhibitors as well as other DDR inhibitors and demonstrate the mechanism of action. These results demonstrate a new link between MTHFD2-dependent cancer metabolism and replication stress that can be exploited therapeutically.
MTHFD2, one-carbon metabolism, folate metabolism, DNA replication, replication stress, synthetic lethal, thymineless death, small-molecule inhibitor, DNA damage response



1060 – Genetic and pharmacologic inhibition of Skp2, an E3 ubiquitin ligase and RB1-target, has antitumor activity in RB1-deficient human and mouse small cell lung cancer (SCLC)

Hongling ZhaoVineeth SukrithanNiloy IqbalCari NicholasYingjiao XueJoseph LockerJuntao ZouLiang ZhuEdward L. Schwartz. Albert Einstein College of Medicine, Bronx, NY, Albert Einstein College of Medicine, Bronx, NY, Albert Einstein College of Medicine, Bronx, NY, University of Pittsburgh Medical Center, Pittsburgh, PA, Albert Einstein College of Medicine, Bronx, NY
 H. Zhao: None. V. Sukrithan: None. N. Iqbal: None. C. Nicholas: None. Y. Xue: None. J. Locker: None. J. Zou: None. L. Zhu: None. E.L. Schwartz: None.
The identification of driver mutations and their corresponding targeted drugs has led to significant improvements in the treatment of non-small cell lung cancer (NSCLC) and other solid tumors; however, similar advances have not been made in the treatment of small cell lung cancer (SCLC). Due to their aggressive growth, frequent metastases, and resistance to chemotherapy, the five-year overall survival of SCLC is less than 5%. While SCLC tumors can be sensitive to first-line therapy of cisplatin and etoposide, most patients relapse, often in less than 3 months after initial therapy. Dozens of drugs have been tested clinically in SCLC, including more than 40 agents that have failed in phase III trials.
The near uniform bi-allelic inactivation of the tumor suppressor gene RB1 is a defining feature of SCLC. RB1 is mutated in highly aggressive tumors, including SCLC, where its functional loss, along with that of TP53, is both required and sufficient for tumorigenesis. While it is known that RB1 mutant cells fail to arrest at G1/S in response to checkpoint signals, this information has not led to effective strategies to treat RB1-deficient tumors, and it has been challenging to develop targeted drugs for tumors that are driven by the loss of gene function.
Our group previously identified Skp2, a substrate recruiting subunit of the SCF-Skp2 E3 ubiquitin ligase, as an early repression target of pRb whose knockout blocked tumorigenesis in Rb1-deficient prostate and pituitary tumors. Here we used genetic mouse models to demonstrate that deletion of Skp2 completely blocked the formation of SCLC in Rb1/p53-knockout mice (RP mice). Skp2 KO caused an increased accumulation of the Skp2-degradation target p27, a cyclin-dependent kinase inhibitor, and we confirmed this was the mechanism of protection in the RP-Skp2 KO mice by using the knock-in of a mutant p27 that was unable to bind to Skp2. Building on the observed synthetic lethality between Rb1 and Skp2, we found that small molecules that bind to and/or inhibit Skp2 induced apoptosis and inhibited SCLC cell growth. In a panel of SCLC cell lines, growth inhibition by a Skp2 inhibitor was not correlated with sensitivity/resistance to etoposide. Targeting Skp2 also had in vivo antitumor activity in mouse tumors and human patient-derived xenograft models of SCLC. Using the genetic and pharmacologic approaches, antitumor activity was seen in vivo in established SCLC primary lung tumors, in liver metastases, and in chemotherapy-resistant tumors. The identification and validation of an actionable target downstream of RB1 could have a broad impact on treatment of SCLC and other advanced tumors with mutant RB1, for which there are currently no targeted therapies available.

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Live Notes, Real Time Conference Coverage 2020 AACR Virtual Meeting April 27, 2020 Minisymposium on Signaling in Cancer 11:45am-1:30 pm

Reporter: Stephen J. Williams, PhD.

SESSION VMS.MCB01.01 – Emerging Signaling Vulnerabilities in Cancer
April 27, 2020, 11:45 AM – 1:30 PM
Virtual Meeting: All Session Times Are U.S. EDT

All session times are U.S. Eastern Daylight Time (EDT). Access to AACR Virtual Annual Meeting I sessions are free with registration. Register now at http://www.aacr.org/virtualam2020

Session Type

Virtual Minisymposium


Molecular and Cellular Biology/Genetics

16 Presentations
11:45 AM – 1:30 PM
– Chairperson

J. Silvio Gutkind. UCSD Moores Cancer Center, La Jolla, CA

11:45 AM – 1:30 PM
– Chairperson

  • in 80’s and 90’s signaling focused on defects and also oncogene addiction.  Now the field is switching to finding vulnerabilities in signaling cascades in cancer

Adrienne D. Cox. University of North Carolina at Chapel Hill, Chapel Hill, NC

11:45 AM – 11:55 AM
– Introduction

J. Silvio Gutkind. UCSD Moores Cancer Center, La Jolla, CA

11:55 AM – 12:05 PM
1085 – Interrogating the RAS interactome identifies EFR3A as a novel enhancer of RAS oncogenesis

Hema Adhikari, Walaa Kattan, John F. Hancock, Christopher M. Counter. Duke University, Durham, NC, University of Texas MD Anderson Cancer Center, Houston, TX

Abstract: Activating mutations in one of the three RAS genes (HRAS, NRAS, and KRAS) are detected in as much as a third of all human cancers. As oncogenic RAS mediates it tumorigenic signaling through protein-protein interactions primarily at the plasma membrane, we sought to document the protein networks engaged by each RAS isoform to identify new vulnerabilities for future therapeutic development. To this end, we determined interactomes of oncogenic HRAS, NRAS, and KRAS by BirA-mediated proximity labeling. This analysis identified roughly ** proteins shared among multiple interactomes, as well as a smaller subset unique to a single RAS oncoprotein. To identify those interactome components promoting RAS oncogenesis, we created and screened sgRNA library targeting the interactomes for genes modifying oncogenic HRAS-, NRAS-, or KRAS-mediated transformation. This analysis identified the protein EFR3A as not only a common component of all three RAS interactomes, but when inactivated, uniformly reduced the growth of cells transformed by any of the three RAS isoforms. EFR3A recruits a complex containing the druggable phosphatidylinositol (Ptdlns) 4 kinase alpha (PI4KA) to the plasma membrane to generate the Ptdlns species PI4P. We show that EFR3A sgRNA reduced multiple RAS effector signaling pathways, suggesting that EFR3A acts at the level of the oncoprotein itself. As lipids play a critical role in the membrane localization of RAS, we tested and found that EFR3A sgRNA reduced not only the occupancy of RAS at the plasma membrane, but also the nanoclustering necessary for signaling. Furthermore, the loss of oncogenic RAS signaling induced by EFR3A sgRNA was rescued by targeting PI4K to the plasma membrane. Taken together, these data support a model whereby EFR3A recruits PI4K to oncogenic RAS to promote plasma membrane localization and nonclustering, and in turn, signaling and transformation. To investigate the therapeutic potential of this new RAS enhancer, we show that EFR3A sgRNA reduced oncogenic KRAS signaling and transformed growth in a panel of pancreatic ductal adenocarcinoma (PDAC) cell lines. Encouraged by these results we are exploring whether genetically inactivating the kinase activity of PI4KA inhibits oncogenic signaling and transformation in PDAC cell lines. If true, pharmacologically targeting PI4K may hold promise as a way to enhance the anti-neoplastic activity of drugs targeting oncogenic RAS or its effectors.




  • different isoforms of ras mutations exist differentially in various tumor types e.g. nras vs kras
  • the C terminal end serve as hotspots of mutations and probably isoform specific functions
  • they determined the interactomes of nras and kras and determined how many candidates are ras specific
  • they overlayed results from proteomic and CRSPR screen; EFR3a was a potential target that stuck out
  • using TCGA patients with higher EFR3a had poorer prognosis
  • EFR3a promotes Ras signaling; and required for RAS driven tumor growth (in RAS addicted tumors?)
  • EGFR3a promotes clustering of oncogenic RAS at plasma membrane


12:05 PM – 12:10 PM
– Discussion

12:10 PM – 12:20 PM
1086 – Downstream kinase signaling is dictated by specific KRAS mutations; Konstantin Budagyan, Jonathan Chernoff. Drexel University College of Medicine, Philadelphia, PA, Fox Chase Cancer Center, Philadelphia, PA @FoxChaseCancer

Abstract: Oncogenic KRAS mutations are common in colorectal cancer (CRC), found in ~50% of tumors, and are associated with poor prognosis and resistance to therapy. There is substantial diversity of KRAS alleles observed in CRC. Importantly, emerging clinical and experimental analysis of relatively common KRAS mutations at amino acids G12, G13, A146, and Q61 suggest that each mutation differently influences the clinical properties of a disease and response to therapy. For example, KRAS G12 mutations confer resistance to EGFR-targeted therapy, while G13D mutations do not. Although there is clinical evidence to suggest biological differences between mutant KRAS alleles, it is not yet known what drives these differences and whether they can be exploited for allele-specific therapy. We hypothesized that different KRAS mutants elicit variable alterations in downstream signaling pathways. To investigate this hypothesis, we created a novel system by which we can model KRAS mutants in isogenic mouse colon epithelial cell lines. To generate the cell lines, we developed an assay using fluorescent co-selection for CRISPR-driven genome editing. This assay involves simultaneous introduction of single-guide RNAs (sgRNAs) to two different endogenous loci resulting in double-editing events. We first introduced Cas9 and blue fluorescent protein (BFP) into mouse colon epithelial cell line containing heterozygous KRAS G12D mutation. We then used sgRNAs targeting BFP and the mutant G12D KRAS allele along with homology-directed repair (HDR) templates for a GFP gene and a KRAS mutant allele of our choice. Cells that successfully undergo HDR are GFP-positive and contain the desired KRAS mutation. Therefore, selection for GFP-positive cells allows us to identify those with phenotypically silent KRAS edits. Ultimately, this method allows us to toggle between different mutant alleles while preserving the wild-type allele, all in an isogenic background. Using this method, we have generated cell lines with endogenous heterozygous KRAS mutations commonly seen in CRC (G12D, G12V, G12C, G12R, G13D). In order to elucidate cellular signaling pathway differences between the KRAS mutants, we screened the mutated cell lines using a small-molecule library of ~160 protein kinase inhibitors. We found that there are mutation-specific differences in drug sensitivity profiles. These observations suggest that KRAS mutants drive specific cellular signaling pathways, and that further exploration of these pathways may prove to be valuable for identification of novel therapeutic opportunities in CRC.

  • Flourescent coselection of KRAS edits by CRSPR screen in a colorectal cancer line; a cell that is competent to undergo HR can undergo combination multiple KRAS
  • target only mutant allele while leaving wild type intact;
  • it was KRAS editing event in APC  +/- mouse cell line
  • this enabled a screen for kinase inhibitors that decreased tumor growth in isogenic cell lines; PKC alpha and beta 1 inhibitors, also CDK4 inhibitors inhibited cell growth
  • questions about heterogeneity in KRAS clones; they looked at off target guides and looked at effects in screens; then they used top two clones that did not have off target;  questions about 3D culture- they have not done that; Question ? dependency on AKT activity? perhaps the G12E has different downstream effectors


12:20 PM – 12:25 PM
– Discussion

12:25 PM – 12:35 PM
1087 – NF1 regulates the RAS-related GTPases, RRAS and RRAS2, independent of RAS activity; Jillian M. Silva, Lizzeth Canche, Frank McCormick. University of California, San Francisco, San Francisco, CA @UCSFMedicine

Abstract: Neurofibromin, which is encoded by the neurofibromatosis type 1 (NF1) gene, is a tumor suppressor that acts as a RAS-GTPase activating protein (RAS-GAP) to stimulate the intrinsic GTPase activity of RAS as well as the closely related RAS subfamily members, RRAS, RRAS2, and MRAS. This results in the conversion of the active GTP-bound form of RAS into the inactive GDP-bound state leading to the downregulation of several RAS downstream effector pathways, most notably MAPK signaling. While the region of NF1 that regulates RAS activity represents only a small fraction of the entire protein, a large extent of the NF1 structural domains and their corresponding mechanistic functions remain uncharacterized despite the fact there is a high frequency of NF1 mutations in several different types of cancer. Thus, we wanted to elucidate the underlying biochemical and signaling functions of NF1 that are unrelated to the regulation of RAS and how loss of these functions contributes to the pathogenesis of cancer. To accomplish this objective, we used CRISPR-Cas9 methods to knockout NF1 in an isogenic “RASless” MEF model system, which is devoid of the major oncogenic RAS isoforms (HRAS, KRAS, and NRAS) and reconstituted with the KRAS4b wild-type or mutant KRASG12C or KRASG12D isoform. Loss of NF1 led to elevated RAS-GTP levels, however, this increase was not as profound as the levels in KRAS-mutated cells or provided a proliferative advantage. Although ablation of NF1 resulted in sustained activation of MAPK signaling, it also unexpectedly, resulted in a robust increase in AKT phosphorylation compared to KRAS-mutated cells. Surprisingly, loss of NF1 in KRAS4b wild-type and KRAS-mutated cells potently suppressed the RAS-related GTPases, RRAS and RRAS2, with modest effects on MRAS, at both the transcript and protein levels. A Clariom™D transcriptome microarray analysis revealed a significant downregulation in the NF-κB target genes, insulin-like growth factor binding protein 2 (IGFBP2), argininosuccinate synthetase 1 (ASS1), and DUSP1, in both the NF1 knockout KRAS4b wild-type and KRAS-mutated cells. Moreover, NF1Null melanoma cells also displayed a potent suppression of RRAS and RRAS2 as well as these NF-κB transcription factors. Since RRAS and RRAS2 both contain the same NF-κB transcription factor binding sites, we hypothesize that IGFBP2, ASS1, and/or DUSP1 may contribute to the NF1-mediated regulation of these RAS-related GTPases. More importantly, this study provides the first evidence of at least one novel RAS-independent function of NF1 to regulate the RAS-related subfamily members, RRAS and RRAS2, in a manner exclusive of its RAS-GTPase activity and this may provide insight into new potential biomarkers and molecular targets for treating patients with mutations in NF1.
  • NF1 and SPRED work together to signal from RTK cKIT through RAS
  • NF1 knockout cells had higher KRAS and had increased cell proliferation
  • NF1 -/-  or SPRED loss had increased ERK phosphorylation and some increase in AKT activity compared to parental cells
  • they used isogenic cell lines devoid of all RAS isoforms and then reconstituted with specific RAS WT or mutants
  • NF1 and SPRED KO both reduce RRAS expression; in an AKT independent mannner
  • NF1 SPRED KO cells have almost no IGFBP2 protein expression and SNAIL so maybe affecting EMT?
  • this effect is independent of its RAS GTPAse activity (noncanonical)

12:35 PM – 12:40 PM
– Discussion

12:40 PM – 12:50 PM
1088 – Elucidating the regulation of delayed-early gene targets of sustained MAPK signaling; Kali J. Dale, Martin McMahon. University of Utah, Salt Lake City, UT, Huntsman Cancer Institute, Salt Lake City, UT

Abstract: RAS and its downstream effector, BRAF, are commonly mutated proto-oncogenes in many types of human cancer. Mutationally activated RAS or BRAF signal through the MEK→ERK MAP kinase (MAPK) pathway to regulate key cancer cell hallmarks such as cell division cycle progression, reduced programmed cell death, and enhanced cell motility. Amongst the list of RAS/RAF-regulated genes are those encoding integrins, alpha-beta heterodimeric transmembrane proteins that regulate cell adhesion to the extracellular matrix. Altered integrin expression has been linked to the acquisition of more aggressive behavior by melanoma, lung, and breast cancer cells leading to diminished survival of cancer patients. We have previously documented the ability of the RAS-activated MAPK pathway to induce the expression of ITGB3 encoding integrin β3 in several different cell types. RAS/RAF-mediated induction of ITGB3 mRNA requires sustained, high-level activation of RAF→MEK→ERK signaling mediated by oncogene activation and is classified as “delayed-early”, in that it is sensitive to the protein synthesis inhibitor cycloheximide. However, to date, the regulatory mechanisms that allow for induced ITGB3 downstream of sustained, high-level activation of MAPK signaling remains obscure. We have identified over 300 DEGs, including those expressing additional cell surface proteins, that display similar regulatory characteristics as ITGB3. We use integrin β3 as a model to test our hypothesis that there is a different mechanism of regulation for delayed-early genes (DEG) compared to the canonical regulation of Immediate-Early genes. There are three regions in the chromatin upstream of the ITGB3 that become more accessible during RAF activation. We are relating the chromatin changes seen during RAF activation to active enhancer histone marks. To elucidate the essential genes of this regulation process, we are employing the use of a genome-wide CRISPR knockout screen. The work presented from this abstract will help elucidate the regulatory properties of oncogenic progression in BRAF mutated cancers that could lead to the identification of biomarkers.

12:50 PM – 12:55 PM
– Discussion

12:55 PM – 1:05 PM
1090 – Regulation of PTEN translation by PI3K signaling maintains pathway homeostasis

Radha Mukherjee, Kiran Gireesan Vanaja, Jacob A. Boyer, Juan Qiu, Xiaoping Chen, Elisa De Stanchina, Sarat Chandarlapaty, Andre Levchenko, Neal Rosen. Memorial Sloan Kettering Cancer Center, New York, NY, Yale University, West Haven, CT, Memorial Sloan Kettering Cancer Center, New York, NY, Memorial Sloan Kettering Cancer Center, New York, NY @sloan_kettering

Abstract: The PI3K pathway is a key regulator of metabolism, cell proliferation and migration and some of its components (e.g. PIK3CA and PTEN) are frequently altered in cancer by genetic events that deregulate its output. However, PI3K signaling is not usually the primary driver of these tumors and inhibitors of components of the pathway have only modest antitumor effects. We now show that both physiologic and oncogenic activation of the PI3K signaling by growth factors and an activating hotspot PIK3CA mutation respectively, cause an increase in the expression of the lipid phosphatase PTEN, thus limiting the duration of the signal and the output of the pathway in tumors. Pharmacologic and physiologic inhibition of the pathway by HER2/PI3K/AKT/mTOR inhibitors and nutrient starvation respectively reduce PTEN, thus buffering the effects of inhibition and contributing to the rebound in pathway activity that occurs in tumors. This regulation is found to be a feature of multiple types of cancer, non-cancer cell line and PDX models thereby highlighting its role as a key conserved feedback loop within the PI3K signaling network, both in vitro and in vivo. Regulation of expression is due to mTOR/4EBP1 dependent control of PTEN translation and is lost when 4EBP1 is knocked out. Translational regulation of PTEN is therefore a major homeostatic regulator of physiologic PI3K signaling and plays a role in reducing the output of oncogenic mutants that deregulate the pathway and the antitumor activity of PI3K pathway inhibitors.

  • mTOR can be a potent regulator of PTEN and therefore a major issue when developing PI3K inhibitors

1:05 PM – 1:10 PM
– Discussion

1:10 PM – 1:20 PM
1091 – BI-3406 and BI 1701963: Potent and selective SOS1::KRAS inhibitors induce regressions in combination with MEK inhibitors or irinotecan

Daniel Gerlach, Michael Gmachl, Juergen Ramharter, Jessica Teh, Szu-Chin Fu, Francesca Trapani, Dirk Kessler, Klaus Rumpel, Dana-Adriana Botesteanu, Peter Ettmayer, Heribert Arnhof, Thomas Gerstberger, Christiane Kofink, Tobias Wunberg, Christopher P. Vellano, Timothy P. Heffernan, Joseph R. Marszalek, Mark Pearson, Darryl B. McConnell, Norbert Kraut, Marco H. Hofmann. Boehringer Ingelheim RCV GmbH & Co KG, Vienna, Austria, The University of Texas MD Anderson Cancer Center, Houston, TX, The University of Texas MD Anderson Cancer Center, Houston, TX, Boehringer Ingelheim RCV GmbH & Co KG, Vienna, Austria

  • there is rational for developing an SOS1 inhibitor (GEF); BI3406 shows better PK and PD as a candidate
  • most sensitive cell lines to inhibitor carry KRAS mutation; NRAS or BRAF mutations are not sensititve
  • KRAS mutation defines sensitivity so they created KRAS mut isogenic cell lines
  • found best to co inhibit SOS and MEK as observed plasticity with only SOS
  • dual combination in lung NSCLC pancreatic showed enhanced efficacy compared to monotherapy
  • SOS1 inhibition plus irinotecan enhances DNA double strand breaks; no increased DNA damage in normal stroma but preferentially in tumor cells
  • these SOS1 had broad activity against KRAS mutant models;
  • phase 1 started in 2019;


1:20 PM – 1:25 PM
– Discussion

1:25 PM – 1:30 PM
– Closing Remarks

Adrienne D. Cox. University of North Carolina at Chapel Hill, Chapel Hill, NC

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Lesson 7 of Cell Signaling 7 Motility: Tubulin and Tutorial Quizes for #TUBiol3373

Stephen J. Williams, Ph.D.

This lesson (lesson 7) will discuss the last type of cytoskeletal structure: microtubules and tubulin.  In addition I want to go over the last quiz answers and also introduce some new poll quizes.

I had given the lecture 7 over Canvas and each of you can download and go over the lecture but I will highlight a few slides in the lecture.

Let’s first review:

Remember that microtubules are the largest of the three cytoskeletal structures:

actin microfilaments < intermediate filaments < microtubules

This is very important to understand as the microtubules, as shown later, shuttle organelles and cellular structures like synaptic vesicles, as well as forming the centrisome and spindle fibers of mitosis.














Now remember the quiz question from last time

Remember that actin monomers (the G actin binds ATP)  while tubulin, the protein which makes up the microtubules binds GTP {although it is a little more complex than that as the following diagram shows}













































See how the growth at the plus end is dependent on tubulin heterodimer GTP while when GDP is only bound to tubulin (both forms) you get a destabilization of the plus end and removal of tubulin dimers (catastrophe) if there is no source of tubulin GTP dimers (alpha tubulin GTP with beta tubulin GTP).





Also remember that like actin microfilaments you can have treadmilling (the plus end  continues growing while minus end undergoes catasrophe).  The VIDEO below describes these processes:




Certain SNPs and mutants of tubulin are found and can result in drastic phenotypic changes in microtubule stability and structure. Below is an article where a mutation in tubulin can result in microtubule catastrophe or destabilization of microtubule structures.


From: A mutation uncouples the tubulin conformational and GTPase cycles, revealing allosteric control of microtubule dynamics;, E.A. Geyer et al..; elife 2015;4:e10113


Microtubule dynamic instability depends on the GTPase activity of the polymerizing αβ-tubulin subunits, which cycle through at least three distinct conformations as they move into and out of microtubules. How this conformational cycle contributes to microtubule growing, shrinking, and switching remains unknown. Here, we report that a buried mutation in αβ-tubulin yields microtubules with dramatically reduced shrinking rate and catastrophe frequency. The mutation causes these effects by suppressing a conformational change that normally occurs in response to GTP hydrolysis in the lattice, without detectably changing the conformation of unpolymerized αβ-tubulin. Thus, the mutation weakens the coupling between the conformational and GTPase cycles of αβ-tubulin. By showing that the mutation predominantly affects post-GTPase conformational and dynamic properties of microtubules, our data reveal that the strength of the allosteric response to GDP in the lattice dictates the frequency of catastrophe and the severity of rapid shrinking.



Remember the term allosterism: change in the affinity for binding of a ligand or substrate that is caused by the binding of another ligand away from the active site (for example like 2,3 DPG effect on oxygen binding to hemoglobin


Cellular transport of organelles and vesicles: a function of microtubules


















Now the above figure (figure 9 in your Powerpoint) shows the movement of organelles and vesicles in two different types of cells along microtubules.

Note the magenta arrow which goes from the nucleus toward the plus end of the microtubule (at cell membrane) is referred to as anterograde transport and is movement away from center of cell to the periphery.  Retrograde transport is movement of organelles and vesicles from periphery of cell to the center of the cell.

Note that kinesin is involved in anterograde transport while dyenin is involved in retrograde transport

Also refer to the Wiki page which shows a nice cartoon of this walking down a microtubule on the right hand side of the page









Cilia; a cellular structure of microtubules (we will talk about cilia later)

for more information on structure of Cillia please see https://www.ncbi.nlm.nih.gov/books/NBK21698/

This is from a posting by Dr. Larry Bernstein of Yale University at https://pharmaceuticalintelligence.com/2015/11/04/cilia-and-tubulin/








Defective cilia can lead to a host of diseases and conditions in the human body, from rare, inherited bone malformations to blindness, male infertility, kidney disease and obesity. It is known that these tiny cell organelles become deformed and cause these diseases because of a problem related to their assembly, which requires the translocation of vast quantities of the vital cell protein tubulin. What they didn’t know was how tubulin and another cell organelle known as flagella fit into the process.

Now, a new study from University of Georgia shows the mechanism behind tubulin transport and its assembly into cilia, including the first video imagery of the process. The study was published in the Journal of Cell Biology.

Cilia are found throughout the body, so defects in cilia formation affect cells that line airways, brain ventricles or the reproductive track.  One of the main causes of male infertility is the cilia won’t function properly.

The team used total internal reflection fluorescence microscopy to analyze moving protein particles inside the cilia of Chlamydomonas reinhardtii, a green alga widely used as a model for cilia analysis.

The team exploited the natural behaviour of the organism, which is to attach by its cilia to a smooth surface, such as a microscope glass cover. This positions the cilia within the 200-nanometer reach of the total internal reflection fluorescence microscope allowing for the imaging of individual proteins as they move inside the cilia.  A video explaining the process was published along with the study.

Tubulin is transported by this process called intraflagellar transport, or IFT.  Though it has long been suspected in the field and there was indirect evidence to support the theory, this is the first time it has been shown directly, through live imaging, that IFT does function as a tubulin pump.  The team observed that about 400,000 tubulin dimers need to be transported within 60 minutes to assemble a single cilium. Being able to see tubulin moving into cilia allowed for first insights into how this transport is regulated to make sure cilia will have the correct size.

The new findings are expected to have wide implications for a variety of diseases and conditions related to cilia defects in the body.  The team state that they are on the very basic side of this research.  But because more and more diseases are being connected to cilia-related conditions, including obesity and even diabetes, the number of people working on cilia has greatly expanded over the last few years.


So here are the answer to last weeks polls

  1. Actin filaments are the SMALLEST of the cytoskeletal structures.  As shown in this lecture it is tubulin that binds GTP.  Actin binds ATP.
  2.  ARP2/3 or actin related proteins 2 and 3 are nucleating proteins that assist in initiating growth of branched chain micofiliment networks.  Formins are associated with unbranched actin formations.
  3.  The answer is GAPs or GTPase activating proteins.  Remember RAS in active state when GTP is bound and when you hydrolyze the GTP to GDP Ras is inactive state






4.  Okay so I did a type here but the best answer was acetylcholinesterase (AchE) degrading acetylcholine.  Acetylcholinesterase degrades the neurotransmitter acetylcholine into choline and acetate not as I accidentally put into acetylCoA.  The freed choline can then be taken back up into the presynaptic neuron and then, with a new acetyl group (with Coenzyme A) will form acetylcholine.


Synthesis of the neurotransmitter acetylcholine




The neuromuscular junction





















Thanks to all who took the quiz.  Remember it is for your benefit.





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Lesson 6 of Cell Signaling & Motility – Cytoskeleton II: #TUBiol3373

Stephen J. Williams, Ph.D.

In this lesson we will go over the biochemical makeup and formation of various actin containing cellular structures involved in cellular motility, structure, as well as the dynamics of muscular contraction.  The lesson had been put on your Canvas and I am emailing you the Google Docs version.  If you are having problems downloading you can download here (I believe maybe the Canvas version had problems with embedding videos properly so that is why I am sending you also by email)

Download Below

cell signaling 6 lesson 2020

After opening the powerpoint (or Google Doc) please review with the following notes which highlight some concepts as well as some reviews and reminders of past lectures.  It may be handy to also have lecture 5 handy if you need to refer to it.  In between some sections there will be polls (really multiple choice quizzes DON’T WORRY you will not be graded on them but they are for your benefit.  There will also be a section under Comments all the way at the end and at the last quiz where you can also ask questions.

Remember you can always email me or Tweet me any questions @StephenJWillia2 using the hashtag #TUBiol3373.

In addition you can also leave comments at the very bottom which can be answered.

Slide 2 of lesson 6 is a refresher of the end of our last lecture, talking about Actin Binding Regulatory Proteins.



















The picture above shows a brief review of some of the structures and actin binding proteins involved in helping to form these actin filament structures (like filamin in cross linked structures, profilin which binds the actin monomers [G-actin] and helps with addition of these monomers to the leading plus end.

*** Remember G-actin (Globular Actin) is the monomer and F-actin (filamentious actin) is the polymerized actin strand [filament]

Also remember from the last lecture that G-Actin as monomer has affinity for ATP {Adenosine triphosphate} and these G-Actin-ATP will be able to polymerize to form the F-Actin form.  Also F-actin can then hydrolyze the ATP to ADP and inorganic phosphate.  At this point the actin-ADP unit looses affinity for the remaining F-Actin chain and depolymerization can occur


An event referred to as TREADMILLING or when the G actin units are removed from minus end and added to the plus (or growing barbed) end

Also remember that there is a critical concentration of G-Actin-ATP needed for bypassing the lag phase of nucleation before the elongation phase and the rate of addition to the plus end is faster than addition to minus end and greater than the rate of depolymerization at the minus end

Cell Structures That Involve Actin (see links for more information)

  1. filopodia
  2. parallel actin bundles
  3. actin cortex
  4. lamellipodia
  5. stress fibers
  6. microvilli
  7. contractile ring in cytokinesis



















Nucleating proteins Arp (actin related protein and Formins

Arp ====> formation of lamellipodia

Formins ====> formation of stress fibers

Process involving formins starts with a signaling event by activation of a G-protein, the GTP binding protein Rho

Rho is a subfamily member of the Ras superfamily.  The Rho family consists of cdc42, rac1, and RhoA (we will discuss at a later date).  Rho acts like G proteins, as a molecular switch.

Note that just like the Ras member of G-proteins and the Ras GTP/GDP cycle, the Rho activation, deactivation cycle also depends on GEFs [Guanine nucleotide exchange factors] and GAPs [GTPase activating proteins] and also GDIs [guanine nucleotide dissociation inhibitors which we will discuss later but involved in preventing Rho diffusion in the cell, acting as a tether].

Myosin and Motor (muscle) Function; Neuromuscular junctions, the sarcoplasmic reticulum and Ohhh the plethora of signaling events

In this section, from slides 29 to 54, we talk about myosin and the interactions between myosin and actin in formation of the contractile unit of the muscle (skeletal).

We also talk about some familiar signaling events, in particular the neuromuscular junction.

At this junction is a special type of acetylcholine receptor

Remember we talked about two types of acetylcholine receptors:

  1. muscarinic receptors – typical GPCRs that tranduce the signal via Gi or Gq depending on the muscarinic subtype
  2. nicotinic receptors – these are ligand {receptor} operated channels and when activated opens a Na+ channel which leads to depolarization


Now the depolarization activates another set of channels, the voltage operated calcium channels so we have two types of ion channels: Receptor {ligand} operated channels and Voltage operated channels.  These are sometimes abbreviated as ROCs and VOCs.

The unit of the myofibril on the contactile unit of the skeletal muscle is the sarcomere and upon the calcium transient, the sarcomere shortens with the two z-disks moving closer to each other as shown in the video in the lecture.

Also briefly review the introduction part on microtubules. We will finish that next week. Note that the microtubule is comprised of the protein tubulin, which is another GTP binding protein.

For other articles and more information please see

Lesson 5 Cell Signaling And Motility: Cytoskeleton & Actin: Curations and Articles of reference as supplemental information: #TUBiol3373

Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Identification of Biomarkers that are Related to the Actin Cytoskeleton










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Reporter and Curator: Dr. Sudipta Saha, Ph.D.


Parkinson’s Disease (PD), characterized by both motor and non-motor system pathology, is a common neurodegenerative disorder affecting about 1% of the population over age 60. Its prevalence presents an increasing social burden as the population ages. Since its introduction in the 1960’s, dopamine (DA)-replacement therapy (e.g., L-DOPA) has remained the gold standard treatment. While improving PD patients’ quality of life, the effects of treatment fade with disease progression and prolonged usage of these medications often (>80%) results in side effects including dyskinesias and motor fluctuations. Since the selective degeneration of A9 mDA neurons (mDANs) in the substantia nigra (SN) is a key pathological feature of the disease and is directly associated with the cardinal motor symptoms, dopaminergic cell transplantation has been proposed as a therapeutic strategy.


Researchers showed that mammalian fibroblasts can be converted into embryonic stem cell (ESC)-like induced pluripotent stem cells (iPSCs) by introducing four transcription factors i.e., Oct4, Sox2, Klf4, and c-Myc. This was then accomplished with human somatic cells, reprogramming them into human iPSCs (hiPSCs), offering the possibility of generating patient-specific stem cells. There are several major barriers to implementation of hiPSC-based cell therapy for PD. First, probably due to the limited understanding of the reprogramming process, wide variability exists between the differentiation potential of individual hiPSC lines. Second, the safety of hiPSC-based cell therapy has yet to be fully established. In particular, since any hiPSCs that remain undifferentiated or bear sub-clonal tumorigenic mutations have neoplastic potential, it is critical to eliminate completely such cells from a therapeutic product.


In the present study the researchers established human induced pluripotent stem cell (hiPSC)-based autologous cell therapy. Researchers reported a platform of core techniques for the production of mDA progenitors as a safe and effective therapeutic product. First, by combining metabolism-regulating microRNAs with reprogramming factors, a method was developed to more efficiently generate clinical grade iPSCs, as evidenced by genomic integrity and unbiased pluripotent potential. Second, a “spotting”-based in vitro differentiation methodology was established to generate functional and healthy mDA cells in a scalable manner. Third, a chemical method was developed that safely eliminates undifferentiated cells from the final product. Dopaminergic cells thus produced can express high levels of characteristic mDA markers, produce and secrete dopamine, and exhibit electrophysiological features typical of mDA cells. Transplantation of these cells into rodent models of PD robustly restored motor dysfunction and reinnervated host brain, while showing no evidence of tumor formation or redistribution of the implanted cells.


Together these results supported the promise of these techniques to provide clinically applicable personalized autologous cell therapy for PD. It was recognized by researchers that this methodology is likely to be more costly in dollars and manpower than techniques using off-the-shelf methods and allogenic cell lines. Nevertheless, the cost for autologous cell therapy may be expected to decrease steadily with technological refinement and automation. Given the significant advantages inherent in a cell source free of ethical concerns and with the potential to obviate the need for immunosuppression, with its attendant costs and dangers, it was proposed that this platform is suitable for the successful implementation of human personalized autologous cell therapy for PD.




















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Reporter and Curator: Dr. Sudipta Saha, Ph.D.


Effective humoral immune responses to infection and immunization are defined by high-affinity antibodies generated as a result of B cell differentiation and selection that occurs within germinal centers (GC). Within the GC, B cells undergo affinity maturation, an iterative and competitive process wherein B cells mutate their immunoglobulin genes (somatic hypermutation) and undergo clonal selection by competing for T cell help. Balancing the decision to remain within the GC and continue participating in affinity maturation or to exit the GC as a plasma cell (PC) or memory B cell (MBC) is critical for achieving optimal antibody avidity, antibody quantity, and establishing immunological memory in response to immunization or infection. Humoral immune responses during chronic infections are often dysregulated and characterized by hypergammaglobulinemia, decreased affinity maturation, and delayed development of neutralizing antibodies. Previous studies have suggested that poor antibody quality is in part due to deletion of B cells prior to establishment of the GC response.


In fact the impact of chronic infections on B cell fate decisions in the GC remains poorly understood. To address this question, researchers used single-cell transcriptional profiling of virus-specific GC B cells to test the hypothesis that chronic viral infection disrupted GC B cell fate decisions leading to suboptimal humoral immunity. These studies revealed a critical GC differentiation checkpoint that is disrupted by chronic infection, specifically at the point of dark zone re-entry. During chronic viral infection, virus-specific GC B cells were shunted towards terminal plasma cell (PC) or memory B cell (MBC) fates at the expense of continued participation in the GC. Early GC exit was associated with decreased B cell mutational burden and antibody quality. Persisting antigen and inflammation independently drove facets of dysregulation, with a key role for inflammation in directing premature terminal GC B cell differentiation and GC exit. Thus, the present research defines GC defects during chronic viral infection and identify a critical GC checkpoint that is short-circuited, preventing optimal maturation of humoral immunity.


Together, these studies identify a key GC B cell differentiation checkpoint that is dysregulated during chronic infection. Further, it was found that the chronic inflammatory environment, rather than persistent antigen, is sufficient to drive altered GC B cell differentiation during chronic infection even against unrelated antigens. However, the data also indicate that inflammatory circuits are likely linked to perception of antigen stimulation. Nevertheless, this study reveals a B cell-intrinsic program of transcriptional skewing in chronic viral infection that results in shunting out of the cyclic GC B cell process and early GC exit with consequences for antibody quality and hypergammaglobulinemia. These findings have implications for vaccination in individuals with pre-existing chronic infections where antibody responses are often ineffective and suggest that modulation of inflammatory pathways may be therapeutically useful to overcome impaired humoral immunity and foster affinity maturation during chronic viral infections.
















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New Mutant KRAS Inhibitors Are Showing Promise in Cancer Clinical Trials: Hope For the Once ‘Undruggable’ Target

Curator: Stephen J. Williams, Ph.D.

The November 1st issue of Science highlights a series of findings which give cancer researchers some hope in finally winning a thirty year war with the discovery of drugs that target KRAS, one of the most commonly mutated oncogenes  (25% of cancers), and thought to be a major driver of tumorigenesis. Once considered an undruggable target, mainly because of the smooth surface with no obvious pockets to fit a drug in, as well as the plethora of failed attempts to develop such an inhibitor, new findings with recently developed candidates, highlighted in this article and other curated within, are finally giving hope to researchers and oncologists who have been hoping for a clinically successful inhibitor of this once considered elusive target.


For a great review on development of G12C KRas inhibitors please see Dr. Hobb’s and Channing Der’s review in Cell Selective Targeting of the KRAS G12C Mutant: Kicking KRAS When It’s Down

Figure 1Mechanism of Action of ARS853 showing that the inhibitors may not need bind to the active conformation of KRAS for efficacy

Abstract: Two recent studies evaluated a small molecule that specifically binds to and inactivates the KRAS G12C mutant. The new findings argue that the perception that mutant KRAS is persistently frozen in its active GTP-bound form may not be accurate.


Although the development of the KRASG12C-specific inhibitor, compound 12 (Ostrem et al., 2013), was groundbreaking, subsequent studies found that the potency of compound 12 in cellular assays was limited (Lito et al., 2016, Patricelli et al., 2016). A search for more-effective analogs led to the development of ARS853 (Patricelli et al., 2016), which exhibited a 600-fold increase of its reaction rate in vitro over compound 12 and cellular activities in the low micromolar range.


A Summary and more in-depth curation of the Science article is given below:

After decades, progress against an ‘undruggable’ cancer target


Cancer researchers are making progress toward a goal that has eluded them for more than 30 years: shrinking tumors by shutting off a protein called KRAS that drives growth in many cancer types. A new type of drug aimed at KRAS made tumors disappear in mice and shrank tumors in lung cancer patients, two companies report in papers published this week. It’s not yet clear whether the drugs will extend patients’ lives, but the results are generating a wave of excitement. And one company, Amgen, reports an unexpected bonus: Its drug also appears to stimulate the immune system to attack tumors, suggesting it could be even more powerful if paired with widely available immunotherapy treatments.

Jocelyn Kaiser. After decades, progress against an ‘undruggable’ cancer target. Science  01 Nov 2019: Vol. 366, Issue 6465, pp. 561 DOI: 10.1126/science.366.6465.561

The article highlights the development of three inhibitors: by Wellspring Biosciences, Amgen, and Mirati Therapeutics.

Wellspring BioSciences


In 2013, Dr. Kevan Shokat’s lab at UCSF discovered a small molecule that could fit in the groove of the KRAS mutant G12C.  The G12C as well as the G12D is a common mutation found in KRAS in cancers. KRAS p.G12C mutations predominate in NSCLC comprising 11%–16% of lung adenocarcinomas (45%–50% of mutant KRAS is p.G12C) (Campbell et al., 2016; Jordan et al., 2017), as well as 1%–4% of pancreatic and colorectal adenocarcinomas, respectively (Bailey et al., 2016; Giannakis et al., 2016).  This inhibitor was effective in shrinking, in mouse studies conducted by Wellspring Biosciences,  implanted tumors containing this mutant KRAS.


See Wellspring’s news releases below:

March, 2016 – Publication – Selective Inhibition of Oncogenic KRAS Output with Small Molecules Targeting the Inactive State

February, 2016 – Publication – Allele-specific inhibitors inactivate mutant KRAS G12C by a trapping mechanism



Amgen press release on AMG510 Clinical Trial at ASCO 2019


THOUSAND OAKS, Calif., June 3, 2019 /PRNewswire/ — Amgen (NASDAQ: AMGN) today announced the first clinical results from a Phase 1 study evaluating investigational AMG 510, the first KRASG12C inhibitor to reach the clinical stage. In the trial, there were no dose-limiting toxicities at tested dose levels. AMG 510 showed anti-tumor activity when administered as a monotherapy in patients with locally-advanced or metastatic KRASG12C mutant solid tumors. These data are being presented during an oral session at the 55th Annual Meeting of the American Society of Clinical Oncology (ASCO) in Chicago.

“KRAS has been a target of active exploration in cancer research since it was identified as one of the first oncogenes more than 30 years ago, but it remained undruggable due to a lack of traditional small molecule binding pockets on the protein. AMG 510 seeks to crack the KRAS code by exploiting a previously hidden groove on the protein surface,” said David M. Reese, M.D., executive vice president of Research and Development at Amgen. “By irreversibly binding to cysteine 12 on the mutated KRAS protein, AMG 510 is designed to lock it into an inactive state. With high selectivity for KRASG12C, we believe investigational AMG 510 has high potential as both a monotherapy and in combination with other targeted and immune therapies.”

The Phase 1, first-in-human, open-label multicenter study enrolled 35 patients with various tumor types (14 non-small cell lung cancer [NSCLC], 19 colorectal cancer [CRC] and two other). Eligible patients were heavily pretreated with at least two or more prior lines of treatment, consistent with their tumor type and stage of disease. 

Canon, J., Rex, K., Saiki, A.Y. et al. The clinical KRAS(G12C) inhibitor AMG 510 drives anti-tumour immunity. Nature 575, 217–223 (2019) doi:10.1038/s41586-019-1694-1

Besides blocking tumor growth, AMG510 appears to stimulate T cells to attack the tumor, thus potentially supplying a two pronged attack to the tumor, inhibiting oncogenic RAS and stimulating anti-tumor immunity.


Mirati Therapeutics


Mirati’s G12C KRAS inhibitor (MRTX849) is being investigated in a variety of solid malignancies containing the KRAS mutation.


For recent publication on results in lung cancer see Patricelli M.P., et al. Cancer Discov. 2016; (Published online January 6, 2016)

For more information on Mirati’s KRAS G12C inhibitor see https://www.mirati.com/pipeline/kras-g12c/


KRAS G12C Inhibitor (MRTX849)

Study 849-001 – Phase 1b/2 of single agent MRTX849 for solid tumors with KRAS G12C mutation

Phase 1b/2 clinical trial of single agent MRTX849 in patients with advanced solid tumors that have a KRAS G12C mutation.

See details for this study at clinicaltrials.gov


Additional References:

Allele-specific inhibitors inactivate mutant KRAS G12C by a trapping mechanism.

Lito P et al. Science. (2016)

Targeting KRAS Mutant Cancers with a Covalent G12C-Specific Inhibitor.

Janes MR et al. Cell. (2018)

Potent and Selective Covalent Quinazoline Inhibitors of KRAS G12C.

Zeng M et al. Cell Chem Biol. (2017)

Campbell, J.D., Alexandrov, A., Kim, J., Wala, J., Berger, A.H., Pedamallu, C.S., Shukla, S.A., Guo, G., Brooks, A.N., Murray, B.A., et al.; Cancer Genome Atlas Research Network (2016). Distinct patterns of somatic genome alterations in lung adenocarcinomas and squamous cell carcinomas. Nat. Genet.48, 607–616

Jordan, E.J., Kim, H.R., Arcila, M.E., Barron, D., Chakravarty, D., Gao, J., Chang, M.T., Ni, A., Kundra, R., Jonsson, P., et al. (2017). Prospective comprehensive molecular characterization of lung adenocarcinomas for efficient patient matching to approved and emerging therapies. Cancer Discov. 7, 596–609.

Bailey, P., Chang, D.K., Nones, K., Johns, A.L., Patch, A.M., Gingras, M.C., Miller, D.K., Christ, A.N., Bruxner, T.J., Quinn, M.C., et al.; Australian Pancreatic Cancer Genome Initiative (2016). Genomic analyses identify molecular subtypes of pancreatic cancer. Nature 531, 47–52.

Giannakis, M., Mu, X.J., Shukla, S.A., Qian, Z.R., Cohen, O., Nishihara, R., Bahl, S., Cao, Y., Amin-Mansour, A., Yamauchi, M., et al. (2016). Genomic correlates of immune-cell infiltrates in colorectal carcinoma. Cell Rep. 15, 857–865.

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Reporter and Curator: Dr. Sudipta Saha, Ph.D.


One of the most contagious diseases known to humankind, measles killed an average of 2.6 million people each year before a vaccine was developed, according to the World Health Organization. Widespread vaccination has slashed the death toll. However, lack of access to vaccination and refusal to get vaccinated means measles still infects more than 7 million people and kills more than 100,000 each year worldwide as reported by WHO. The cases are on the rise, tripling in early 2019 and some experience well-known long-term consequences, including brain damage and vision and hearing loss. Previous epidemiological research into immune amnesia suggests that death rates attributed to measles could be even higher, accounting for as much as 50 percent of all childhood mortality.


Over the last decade, evidence has mounted that the measles vaccine protects in two ways. It prevents the well-known acute illness with spots and fever and also appears to protect from other infections over the long term by giving general boost to the immune system. The measles virus can impair the body’s immune memory, causing so-called immune amnesia. By protecting against measles infection, the vaccine prevents the body from losing or “forgetting” its immune memory and preserves its resistance to other infections. Researchers showed that the measles virus wipes out 11% to 73% of the different antibodies that protect against viral and bacterial strains a person was previously immune to like from influenza to herpes virus to bacteria that cause pneumonia and skin infections.


This study at Harvard Medical School and their collaborators is the first to measure the immune damage caused by the virus and underscores the value of preventing measles infection through vaccination. The discovery that measles depletes people’s antibody repertoires, partially obliterating immune memory to most previously encountered pathogens, supports the immune amnesia hypothesis. It was found that those who survive measles gradually regain their previous immunity to other viruses and bacteria as they get re-exposed to them. But because this process may take months to years, people remain vulnerable in the meantime to serious complications of those infections and thus booster shots of routine vaccines may be required.


VirScan detects antiviral and antibacterial antibodies in the blood that result from current or past encounters with viruses and bacteria, giving an overall snapshot of the immune system. Researchers gathered blood samples from unvaccinated children during a 2013 measles outbreak in the Netherlands and used VirScan to measure antibodies before and two months after infection in 77 children who’d contracted the disease. The researchers also compared the measurements to those of 115 uninfected children and adults. Researchers found a striking drop in antibodies from other pathogens in the measles-infected children that clearly suggested a direct effect on the immune system resembling measles-induced immune amnesia.


Further tests revealed that severe measles infection reduced people’s overall immunity more than mild infection. This could be particularly problematic for certain categories of children and adults, the researchers said. The present study observed the effects in previously healthy children only. But, measles is known to hit malnourished children much harder, the degree of immune amnesia and its effects could be even more severe in less healthy populations. Inoculation with the MMR (measles, mumps, rubella) vaccine did not impair children’s overall immunity. The results align with decades of research. Ensuring widespread vaccination against measles would not only help prevent the expected 120,000 deaths that will be directly attributed to measles this year alone, but could also avert potentially hundreds of thousands of additional deaths attributable to the lasting damage to the immune system.
















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