Author: The Wistar Institute

PHILADELPHIA — (Jan. 30, 2020) — Combining EZH2 inhibition and PARP1 inhibition may provide a new therapeutic strategy for ovarian cancers that have functional DNA damage repair and thus would not typically respond to PARP inhibitor treatment alone. According to a study by The Wistar Institute, in epithelial ovarian cancers characterized by overexpression of the CARM1 oncogene, EZH2 inhibitors can shift the equilibrium between different DNA damage repair pathways in a way that renders cancer cells vulnerable to PARP inhibitors. These results were published online in Cancer Cell.

High-grade serous ovarian cancer (HGSOC) is the most common and lethal type of ovarian cancer. PARP inhibitors have recently been approved for maintenance of HGSOC following platinum-based chemotherapy, but their use is limited to specific subtypes that have defects in a DNA repair pathway called homologous recombination (HR).

“Despite high response rates in a subset of patients, right now PARP inhibitors are not for everyone,” said lead researcher Rugang Zhang, Ph.D., deputy director of The Wistar Institute Cancer Center, professor and co-program leader of the Gene Expression and Regulation Program. “Expanding the use of these new drugs represents a major unmet clinical need as it would affect a large population of ovarian cancer patients that do not currently benefit from PARP inhibitors and possibly those who develop resistance to the treatment.”

PARP inhibitors work by hindering certain DNA repair processes. Cancer cells that accumulate excessive DNA damage will die. However, this approach is most effective in cancer cells that have a defect in HR, an error-free mechanism that repairs DNA breaks, whereas HR-proficient cancers are not sensitive to treatment.

Zhang and colleagues wanted to find a way to sensitize this group of cancers through a combinatorial approach. Previous research in the Zhang lab has demonstrated the oncogenic role of the CARM1 gene that is amplified in a set of ovarian cancers and showed that in these cancers, inhibitors of the EZH2 enzyme are an effective treatment.

In this study, the authors tested the effects of combining PARP and EZH2 inhibition and observed that the EZH2 inhibitor enhanced the cytotoxic effect of the PARP inhibitor in cancer cells with functional HR, but only in the presence of elevated CARM1 expression, suggesting that this effect is dependent on the expression level of CARM1.

Mechanistically, elevated CARM1 expression results in transcriptional silencing of the MAD2L2 gene by EZH2. MAD2L2 activates a DNA repair pathway called non-homologous end joining (NHEJ) that is an error-prone mechanism alternative to HR. Therefore, EZH2 inhibition relieves MAD2L2 expression and shifts the choice of DNA repair process towards NHEJ, even in the presence of functional HR.

As a consequence of repairing DNA damage via a low-fidelity mechanism, cancer cells accumulate unrepaired DNA breaks and chromosomal abnormalities, which ultimately leads to mitotic catastrophe, a mode of cell death that occurs when cells with a heavily damaged genome try to divide.

“Based on our findings, we propose a combinatorial approach using EZH2 inhibitors and PARP inhibitors as a precision treatment strategy for patients whose cancer has an elevated expression of CARM1 and functional HR DNA repair mechanism, including those who developed resistance to PARP inhibitors,” said Sergey Karakashev, Ph.D., first author of the study and a postdoctoral researcher in the Zhang Lab.

This approach was tested in vivo in different mouse models of epithelial ovarian cancer with high CARM1 levels, confirming that the combination of inhibitors was significantly more effective in suppressing tumor growth and improving survival compared with either inhibitor alone.
No toxic effects were observed, suggesting that the combination treatment was well tolerated.

“Notably, CARM1 is often overexpressed in several cancer types, therefore our discovery may have broader implications expanding the clinical use of PARP inhibitors for cancer treatment,” said Zhang.

Co-authors: Takeshi Fukumoto, Bo Zhao, Jianhuang Lin, Shuai Wu, Nail Fatkhutdinov, Pyoung-Hwa Park, Galina Semenova, Andrew V. Kossenkov, and Qin Liu from Wistar; Stephanie Jean, Mark G. Cadungog and Mark E. Borowsky from Helen F. Graham Cancer Center & Research Institute.

Work supported by: National Institutes of Health (NIH) grants R01CA160331, R01CA163377, R01CA202919, R01CA239128, P50CA228991, and R50CA211199; U.S. Department of Defense grants OC150446 and OC180109. Additional support was provided by The Honorable Tina Brozman Foundation for Ovarian Cancer Research (Tina’s Wish) and The Tina Brozman Ovarian Cancer Research Consortium 2.0, Ovarian Cancer Research Alliance (Collaborative Research Development Grant and Ann and Sol Schreiber Mentored Investigator Award), and 2018 AACR-AstraZeneca Ovarian Cancer Research Fellowship to the first author. Core support for The Wistar Institute was provided by the Cancer Center Support Grant P30CA010815.

Publication information: EZH2 inhibition sensitizes CARM1-high, homologous recombination proficient ovarian cancers to PARP inhibition, Cancer Cell, 2020. Online publication.

###

The Wistar Institute is an international leader in biomedical research with special expertise in cancer research and vaccine development. Founded in 1892 as the first independent nonprofit biomedical research institute in the United States, Wistar has held the prestigious Cancer Center designation from the National Cancer Institute since 1972. The Institute works actively to ensure that research advances move from the laboratory to the clinic as quickly as possible. wistar.org.

PHILADELPHIA — (Jan. 24, 2020) — In a study by The Wistar Institute and collaborators, a rare, African-specific variant of the TP53 gene called P47S causes iron accumulation in macrophages and other cell types and is associated with poorer response to bacterial infections, along with markers of iron overload in African Americans. Macrophage iron accumulation disrupts their function, resulting in more severe bacterial infections. The study, published online in Nature Communications, also showed that P47S macrophages exhibit improved response to the malaria toxin. This effect may confer protection against generalized inflammation associated with signs of acute malaria pathology.

The TP53 gene possesses numerous genetic variants, some of which are common in the population. Wistar scientists have previously shown that the P47S gene variant, which exists in populations of African descent, is associated with increased cancer risk in African Americans due to defects in an iron-mediated modality of cell death called ferroptosis. They have now discovered another notable effect of disrupted iron metabolism in cells that carry the P47S variant.

“We discovered that macrophages from mice carrying the P47S variant accumulate iron and this impairs their ability to mount an inflammatory response against bacterial infections, making them more susceptible to these diseases,” said Farokh Dotiwala, M.B.B.S., Ph.D., assistant professor in the Vaccine & Immunotherapy Center and corresponding author of the study. “The flip side of diminished inflammation is that these mice have a more favorable response to malaria toxin hemozoin, that is responsible for most of the lethal symptoms in the acute phase of disease.”

Along with Wistar’s Maureen E. Murphy, Ph.D., Ira Brind Professor and leader of the Molecular & Cellular Oncogenesis Program at Wistar, and a co-senior author on the study, Dotiwala and his team found the frequency of the P47S variant to be significantly higher in African Americans from the HEIRS study (Hemochromatosis and Iron Overload Screening). Studying a mouse model carrying the human P47S variant of TP53, generated by the Murphy lab, researchers observed increased iron accumulation in macrophages.

Macrophages from P47S mice with higher iron content were less effective at controlling the growth of different bacterial species in vitro, which reflected faster disease progression and worse outcome.

To dissect the mechanisms of increased susceptibility of P47S mice to bacteria, Dotiwala and colleagues used proteomics to reveal changes in protein levels in macrophages. This approach showed modulation of several proteins involved in the immune response, particularly in metabolic pathways that are essential for macrophages to kill bacteria, such as the arginine pathway, and in ferroptosis. These changes reduced the ability of P47S macrophages to kill bacteria and were reversed by targeting three different affected pathways, thus highlighting future therapeutic potential.

Given the prevalence of the P47S gene variant in malaria-endemic regions of sub-Saharan Africa, the team asked whether this variant could confer a survival advantage to malaria infection. P47S mice injected with the malaria toxin hemozoin showed a weaker inflammatory response than mice carrying the common p53 gene variant. This may limit disease severity, which is a consequence of the massive generalized inflammatory response triggered by the toxin and mostly mediated by macrophages.

“While warranting further studies in humans, we believe that mechanistic knowledge obtained from studying the P47S variant provides a stepping stone in the field of personalized medicine to help address disparities arising from such polymorphisms,” said Donna George, Ph.D., associate professor of genetics at the Perelman School of Medicine of the University of Pennsylvania and co-senior author on the study.

This study may also help understand the connection between the TP53 gene variant and iron overload disorders as well as the increased occurrence of certain bacterial infections and cancers found in African Americans.

Co-authors: Kumar Sachin Singh and Thibaut Barnoud (co-first authors), Prashanthi Vonteddu, Keerthana Gnanapradeepan, Cindy Lin, and Qin Liu from Wistar; co-first author Julia I-Ju Leu from University of Pennsylvania; and James C. Barton from Southern Iron Disorders Center.

Work supported by: Grant from The Pew Charitable Trusts and National Institutes of Health (NIH) grants R01 CA102184, R01 CA201430, R21 HL144991, F32 CA220972, R01 CA139319, P01 CA114046, P30 DK050306, P01 CA098101, and P01 DK049210. Core support for The Wistar Institute was provided by the Cancer Center Support Grant P30CA010815.

Publication information: African-centric TP53 variant increases iron accumulation and bacterial pathogenesis but improves response to malaria toxin, Nature Communications, 2020. Online publication.

###

The Wistar Institute is an international leader in biomedical research with special expertise in cancer research and vaccine development. Founded in 1892 as the first independent nonprofit biomedical research institute in the United States, Wistar has held the prestigious Cancer Center designation from the National Cancer Institute since 1972. The Institute works actively to ensure that research advances move from the laboratory to the clinic as quickly as possible. wistar.org.

PHILADELPHIA — (Jan. 11, 2020) — Mutations that inactivate the ARID1A gene in ovarian cancer increase utilization of the glutamine amino acid making cancer cells dependent on glutamine metabolism, according to a study by The Wistar Institute published online in Nature Cancer. Researchers also showed that pharmacologic inhibition of glutamine metabolism may represent an effective therapeutic strategy for ARID1A-mutant ovarian cancer.

Up to 60% of ovarian clear cell carcinomas (OCCC) have inactivating mutations in the ARID1A tumor suppressor gene. These mutations are known genetic drivers of this type of cancer, which typically does not respond to chemotherapy and carries the worst prognosis among all subtypes of ovarian cancer.

The laboratory of Rugang Zhang, Ph.D., deputy director of The Wistar Institute Cancer Center, professor and leader of the Immunology, Microenvironment & Metastasis Program, studies the effects of ARID1A inactivation to devise new mechanism-guided therapeutic strategies and combination approaches to enhance immunotherapy for ovarian cancer.

“Metabolic reprogramming is a hallmark of many cancers, including OCCC, so in this study we assessed whether ARID1A plays a role in regulation of metabolism,” said Zhang, corresponding author on the paper. “We found that its inactivation in cancer cells creates a specific metabolic requirement for glutamine and exposed this as a vulnerability that could be exploited for therapeutic purposes.”

The authors inactivated ARID1A in wild type ovarian cancer cells and observed increased glutamine consumption. Glutamine is normally required for cancer cells to grow, but Zhang and colleagues unveiled a stronger dependence of ARID1A-mutant cells on this amino acid, which significantly enhanced the growth suppression induced by glutamine deprivation.

ARID1A is part of a protein complex called SWI/SNF that modulates gene expression. The authors investigated the transcriptional effect of ARID1A inactivation and found that GLS1, which encodes for the glutaminase enzyme, was the top upregulated gene among those controlling glutamine metabolism. Accordingly, GLS1 was expressed at significantly higher levels in tumor samples from patients with other cancer types that also carry mutations in the SWI/SNF complex.

The team evaluated the therapeutic potential of inhibiting the glutamine metabolism by blocking the glutaminase enzyme with the CB-839 inhibitor. It has been reported that this molecule is under investigation in clinical trials and is well tolerated as a single agent and in combination with other anticancer therapies.

When tested in vivo on OCCC mouse models, CB-839 significantly reduced tumor burden and prolonged survival. These studies were expanded to mice carrying patient-derived tumor transplants, confirming that CB-839 impaired the growth of ARID1A-mutant but not ARID1A-wildtype tumors.

Researchers also combined CB-839 with anti-PDL1 treatment and revealed a synergy between glutaminase inhibitors and immune checkpoint blockade in suppressing the growth of ARID1A-mutant OCCC tumors.

“Our findings suggest that glutaminase inhibitors warrant further studies as a standalone or combinatorial therapeutic intervention for OCCC, for which effective options are very limited,” said Shuai Wu, Ph.D., first author of the study and a staff scientist in the Zhang Lab.

Glutaminase inhibitors could become a new strategy to precisely target a specific vulnerability of OCCC cells associated with loss of ARID1A function.

Co-authors: Takeshi Fukumoto, Jianhuang Lin, Timothy Nacarelli, Heng Liu, Nail Fatkhutdinov, Joseph A. Zundell, Sergey Karakashev, Wei Zhou, Hsin-Yao Tang, Qin Liu, Andrew V. Kossenkov, David W. Speicher, Zachary T. Schug, and Chi Van Dang from The Wistar Institute; Yemin Wang, Dionzie Ong and David G. Huntsman from University of British Columbia, Vancouver, British Columbia, Canada; and Lauren E. Schwartz and Ronny Drapkin from University of Pennsylvania.

Work supported by: National Institutes of Health (NIH) grants R01CA160331, R01CA163377, R01CA202919, R01CA239128, P01AG031862, P50CA228991, K99CA241395, R50CA221838, S10OD023658, S10OD023586; R01CA195670, F31CA247336, and T32CA009191; U.S. Department of Defense grants OC180109 and OC190181. Additional support was provided by The Honorable Tina Brozman Foundation for Ovarian Cancer Research and The Tina Brozman Ovarian Cancer Research Consortium 2.0; and the Ovarian Cancer Research Alliance (Collaborative Research Development Grant #596552 and Ann and Sol Schreiber Mentored Investigator Award #598026). Core support for The Wistar Institute was provided by the Cancer Center Support Grant P30CA010815.

Publication information: Targeting glutamine dependence through GLS1 inhibition suppresses ARID1A-inactivated clear cell ovarian carcinoma, Nature Cancer, 2020. Online publication.

###

The Wistar Institute is an international leader in biomedical research with special expertise in cancer research and vaccine development. Founded in 1892 as the first independent nonprofit biomedical research institute in the United States, Wistar has held the prestigious Cancer Center designation from the National Cancer Institute since 1972. The Institute works actively to ensure that research advances move from the laboratory to the clinic as quickly as possible. wistar.org.

PHILADELPHIA — (Dec. 19, 2019) — In the past six months, scientists at The Wistar Institute received funding from private foundations totaling $2,418,000 that will fuel new discoveries in cancer, immunology and infectious diseases.

• The Pew Charitable Trusts awarded a $1M grant to the Institute to support the recruitment of three new faculty members at the assistant or associate professor levels. The addition of the new investigators will enhance and expand Wistar’s focus on immunotherapy for infectious diseases and cancer.
• David B. Weiner, Ph.D., Wistar executive vice president, director of the Vaccine & Immunotherapy Center, and the W.W. Smith Charitable Trust Professor in Cancer Research, received a $452,000 grant that will fund research on combining different DNA-based approaches for delivery of vaccinal activity against HIV. The grant was awarded by the Bill & Melinda Gates Foundation.
• The W.W. Smith Charitable Trust awarded three $110,000 grants to assistant professors Mohamed Abdel-Mohsen, Ph.D., and Kar Muthumani, Ph.D., of the Vaccine & Immunotherapy Center, and Kavitha Sarma, Ph.D., of the Gene Expression & Regulation Program. These grants will allow the scientists to further their research on immune reconstitution after HIV antiretroviral therapy, novel DNA-encoded therapeutics for dyslipidemia and epigenetic mechanisms involved in brain cancer, respectively.
• Zachary Schug, Ph.D., assistant professor in the Molecular & Cellular Oncogenesis Program, received a $200,000 grant from the V Foundation for Cancer Research to fund his research focused on targeting cancer metabolism as a precision medicine approach.
• Luis J. Montaner, D.V.M., D.Phil., Herbert Kean, M.D., Family Professor and director of the HIV-1 Immunopathogenesis Laboratory at Wistar’s Vaccine & Immunotherapy Center, was awarded a $130,000 grant from the Robert I. Jacobs Fund of the Philadelphia Foundation. This funding extends previous support of the “HIV-1 Patient Partnership for Basic Research” program that includes biomedical research, community education in partnership with local organizations, and internship opportunities for local students.
• A $100,000 grant from the Melanoma Research Foundation bestowed upon Vito Rebecca, Ph.D., a staff scientist in the Molecular & Cellular Oncogenesis Program, will support his work investigating melanoma pathways involved in therapy resistance.
• Kavitha Sarma, Ph.D., assistant professor in the Gene Expression & Regulation Program, received a $100,000 award from the Basser Center for BRCA at the University of Pennsylvania for her research on the role of particular DNA/RNA molecules in BRCA1 and BRCA2-mutant cancers.
• Daniel Kulp, Ph.D., associate professor in the Vaccine & Immunotherapy Center, was the recipient of a $40,000 subaward from a Penn Center for AIDS Research (CFAR) grant. This funding is directed to study and develop multivalent HIV vaccine immunogens.

###

The Wistar Institute is an international leader in biomedical research with special cancer, immunology, infectious disease research, and vaccine development. Founded in 1892 as the first independent nonprofit biomedical research institute in the United States, Wistar has held the prestigious Cancer Center designation from the National Cancer Institute since 1972. The Institute works actively to ensure that research advances move from the laboratory to the clinic as quickly as possible. wistar.org.

PHILADELPHIA — (Dec. 19, 2019) — A study from The Wistar Institute demonstrated that NAMPT, an enzyme critical for NAD+ biosynthesis, mediates selection of stem-like chemoresistant cells following cisplatin treatment. Researchers showed that a combination of cisplatin treatment with pharmacological inhibition of NAMPT suppresses the outgrowth of resistant cancer cells in vitro and prolongs survival in a preclinical model. These findings were published online in Cancer Research.

Epithelial ovarian cancer is the leading cause of death by gynecologic cancers in the United States, with treatment options still limited to surgery and chemotherapy. Unfortunately, chemoresistance to platinum-based drugs represents a major challenge as most patients ultimately relapse and succumb to the disease.

“Based on previous findings from our laboratory, we have identified a molecule that can be pharmacologically blocked to get rid of resistant cells while preserving the beneficial anticancer power of cisplatin, which still remains the standard of care for this disease,” said Rugang Zhang, Ph.D., deputy director of The Wistar Institute Cancer Center, professor and co-program leader of the Gene Expression and Regulation Program, and senior author on the paper.

Platinum-based therapies trigger cellular senescence that is accompanied by the emergence of drug-resistant, more malignant cells. Senescent cells stop dividing suppressing tumor growth, but, at the same time, produce a variety of inflammatory molecules. Collectively known as the senescence-associated secretory phenotype (SASP), these molecules can promote proliferation and survival of neighboring cells, ultimately contributing to tumor progression.

Zhang and colleagues previously showed that the NAMPT enzyme drives the activation of the SASP in ovarian cancer cells and that pharmacological inhibition of NAMPT suppresses the SASP.

Drug-resistant cancer cells also possess stem-like properties including expression of the CD133 surface marker and elevated activity of the aldehyde dehydrogenase (ALDH1) enzyme. Since inhibition of ALDH activity sensitizes cancer cells to chemotherapy, it’s been suggested that acquisition of the stem-like phenotype is a key step in the emergence of resistance.

In this new study, the team demonstrated that the NAMPT-regulated SASP mediates therapy-induced emergence of senescence-associated stem-like cancer cells.

Importantly, combining cisplatin treatment with NAMPT inhibitors blocked the expression of stem-like markers, suppressed the outgrowth of chemoresistant stem-like cells in vitro and delayed tumor relapse in vivo, significantly prolonging survival of a mouse model of epithelial ovarian cancer.

“NAMPT blockage removes the tumor-promoting effects of cellular senescence while not interfering with its tumor-suppressive functions,” said Zhang. “Our findings suggest that clinically applicable NAMPT inhibitors may be applied to enhance the therapeutic effect of cisplatin and improve the platinum-based standard of care in epithelial ovarian cancer.”

Co-authors: Timothy Nacarelli and Takeshi Fukumoto (co-first authors), Joseph Zundell, and Nail Fatkhutdinov from Wistar; Stephanie Jean, Mark G. Cadungog, and Mark E. Borowsky from Helen F. Graham Cancer Center & Research Institute.

Work supported by: National Institutes of Health (NIH) grants R01CA160331, R01CA163377, R01CA202919, R01CA239128, P01AG031862, P50CA228991, and T32CA009191; U.S. Department of Defense grants OC150446 and OC180109. Additional support was provided by The Honorable Tina Brozman Foundation for Ovarian Cancer Research (Tina’s Wish) and The Tina Brozman Ovarian Cancer Research Consortium 2.0, and Ovarian Cancer Research Alliance (Collaborative Research Development Grant). Core support for The Wistar Institute was provided by the Cancer Center Support Grant P30CA010815.

Publication information: NAMPT inhibition suppresses cancer stem-like cells associated with therapy-induced, Cancer Research (2019). Advance online publication.

###

The Wistar Institute is an international leader in biomedical research with special expertise in cancer, immunology, infectious disease research, and vaccine development. Founded in 1892 as the first independent nonprofit biomedical research institute in the United States, Wistar has held the prestigious Cancer Center designation from the National Cancer Institute since 1972. The Institute works actively to ensure that research advances move from the laboratory to the clinic as quickly as possible. wistar.org.

PHILADELPHIA — (Dec. 17, 2019) — See cellular images as distinct as abstract art, minerals appear as future urban landscapes, single-celled organisms of the microscopic netherworld, and much more from the 2019 Nikon Small World competition of photomicrography. These photographs taken through microscopes will be on display at The Wistar Institute, with an opening reception on Jan. 31, 2020 from 6:00 to 8:00 pm. From Feb. 3 through April 10, 2020, the top-20 images will be on view at Wistar, and the exhibit is FREE to the public. The Wistar Institute is the only Pennsylvania venue to host these remarkable works.

At Wistar, researchers look through microscopes and hypothesize over microscopic images with the goal of advancing cancer and infectious disease research to develop future therapeutics. Each year, winners are both scientists and artists possessing the skill, scientific discipline and creativity for which the Nikon Small World competition is known.

Opportunities at Wistar’s opening reception include:

• Top 20 honoree images on view,
• A feature wall of 15 high-definition TV screens projecting 2019 Nikon Small World in Motion winners and Photomicrography Competition winners,
• A hands-on microscope demonstration by Wistar scientists,
• A self-guided tour of cell photographs created by Wistar scientists and other pieces of Wistar history, and
• Brief talks by Teresa Zgoda & Teresa Kugler, 1st place winners, James E. Hayden, Wistar Imaging Facility managing director, and Eric Flem, Nikon Instruments Inc. communications manager.

Small World spans 45 years as a leading global competition for photomicrography. This year’s images were chosen from more than 2,500 entries from 89 countries. Wistar has been hosting the exhibit for more than 17 years.

2nd place photo by Dr. Igor Siwanowicz, Howard Hughes Medical Institute (HHMI), of depth-color coded projections of three stentors (single-cell freshwater protozoans).

###

The Wistar Institute is an international leader in biomedical research with special expertise in cancer and infectious disease research and vaccine development. Founded in 1892 as the first independent nonprofit biomedical research institute in the United States, Wistar has held the prestigious Cancer Center designation from the National Cancer Institute since 1972. The Institute works actively to ensure that research advances move from the laboratory to the clinic as quickly as possible. wistar.org.