Grant Update: New Funding Bolsters Promising Research Projects

Why are many BRCA1-mutated ovarian cancer tumors resistant to chemotherapy?
How does cholesterol metabolism impact cells’ susceptibility to EGFR inhibitors?

These are among the scientific questions that Fox Chase researchers, reinforced by new federal support, are probing, with implications for ovarian, colorectal, and kidney cancer, lymphoma, and more. Fox Chase NOW rounded up some of the most exciting projects underway in Fox Chase labs.

Johnson-Neil-1Identifying Determinants of PARP-Inhibitor Sensitivity in Ovarian Cancer

  • PI: Neil Johnson, PhD, assistant professor, Molecular Therapeutics
  • Grant: Department of Defense Ovarian Cancer Academy Award – Early-Career Investigator
  • Award: $1.25 million over five years
Experimental analysis of BRCA1 protein localization after treatment with DNA-damaging chemotherapy. Green dots represent BRCA1  protein accumulation around double-stranded DNA breaks. In the BRCA1 mutant cell, the protein fails to accumulate at DNA breaks.

Experimental analysis of BRCA1 protein localization after treatment with DNA-damaging chemotherapy. Green dots represent BRCA1 protein accumulation around double-stranded DNA breaks. In the BRCA1 mutant cell, the protein fails to accumulate at DNA breaks. (Click to enlarge)

Johnson works on cancers associated with BRCA1 and BRCA2 gene mutations. BRCA proteins are important for repairing DNA damage caused by some types of chemotherapy. The BRCA1 gene is commonly mutated in hereditary ovarian cancers, and these tumors typically respond well to chemotherapy or a newer class of agents called poly(ADP-ribose) polymerase (PARP) inhibitors. Despite substantial response rates, many patients with BRCA1 mutations appear resistant to PARP-inhibitor treatment, possibly because mutant forms of the BRCA1 protein can still repair DNA damage, resulting in chemotherapy resistance. Johnson’s research will identify mutant BRCA1 proteins that can repair DNA damage, investigate accompanying mutations that facilitate this process, and identify biomarkers for PARP-inhibitor sensitivity and treatment response.

AstsaturovSynergistic Targeting of Cholesterol Metabolism and EGFR Signaling in Cancer

  • PI: Igor Astsaturov, MD, PhD, medical oncologist; assistant professor, Molecular Therapeutics
  • Grant: R01 – National Institutes of Health
  • Award: $2.2 million over five years
Blockade of SC4MOL or NSDHL (horizontal bar) increases meiosis activating sterols (MAS) levels and activates LXR. This causes perturbation of membrane cholesterol downstream of LXR via LDLR degradation and ABCA 1 efflux, and antagonizes EGFR traffic and signaling and cancer cell growth.

Blockade of SC4MOL or NSDHL (horizontal bar) increases meiosis activating sterols (MAS) levels and activates LXR. This causes perturbation of membrane cholesterol downstream of LXR via LDLR degradation and ABCA 1 efflux, and antagonizes EGFR traffic and signaling and cancer cell growth. (Click to enlarge) Image by Jessia Hui

Astsaturov is studying a new pathway for limiting the function of EGFR (epidermal growth factor receptor), a protein on which many cancers depend for growth and which often proves resistant to targeting by inhibitor drugs. His team found that enzymes involved in cholesterol metabolism, specifically NAD(P) dependent steroid dehydrogenase-like (NSDHL) and sterol-C4-methyl oxidase-like (SC4MOL), also affect how cells handle EGFR. When these enzymes are inactivated in cancer cells, it makes them more susceptible to EGFR inhibitors. One plausible mechanism is that the metabolites normally processed by these enzymes are activating the liver X receptor protein (LXR), which signals the cell to get rid of cholesterol. Astsaturov and his team will use the five-year NIH grant to learn how this pathway works; examine the roles of NSDHL and SC4MOL in normal and cancerous cell growth; and determine whether targeting cholesterol metabolism and EGFR signaling using LXR will have a synergistic effect against EGFR-dependent cancers.

clapper08Efficacy of Eldecalcitol (ED-71) in Colorectal Cancer Prevention in ApcMin Mice

  • PI: Margie L. Clapper, PhD, co-leader, Cancer Prevention & Control
  • Grant: R21 – National Cancer Institute
  • Award: $303,000 over one year

Clapper’s project examines the potential ability of an analogue of Vitamin D3 (eldecalcitol, ED-71) to prevent colorectal cancer. Although several studies have demonstrated the protective effect of Vitamin D3 against colorectal cancer, its use in humans has been hindered by its adverse effect on bone structure. Unlike Vitamin D3, ED-71 stimulates bone remodeling and suppresses bone resorption, leading to its approval in Japan for treatment of osteoporosis. Each year, approximately 112,000 new cases of colon cancer are diagnosed in the U.S., the majority of which are initiated by mutation of the “gatekeeping” Apc gene. Clapper and her colleagues have developed a unique strain of Min (Multiple Intestinal Neoplasia) mice (Apc+/Min FCCC) which, due to their extended lifespan and enhanced susceptibility to colorectal cancer, are ideal for testing chemopreventive agents and extrapolating the results to human disease. This study will use Apc+/Min FCCC mice to assess the effectiveness of ED-71 in reducing colon cancer risk and modulating vitamin D receptor signaling. The researchers will also identify biomarkers of ED-71 effectiveness by comparing RNA and microRNA expression in colon tissues from treated and untreated mice using RNASeq and NanoString technology.

Balachandran_SiddharthInterferon Activated Necrosis as a New Therapeutic Avenue for Kidney Cancer

  • PI: Siddharth Balachandran, PhD, associate professor, Blood Cell Development and Function
  • Grant: R01 – National Institutes of Health
  • Award: $1,852,000 over five years

Balachandran is studying the cytokine interferon-gamma (IFN-γ), which in previous studies has shown the potential to provide lasting remission in metastatic renal cell carcinoma (RCC), but also produces severe toxic side-effects when employed at high doses as a monotherapy. Balachandran’s team is investigating how IFN-γ triggers necrotic death in tumor cells; how the tumor cell survival factor NF kappaB (NF-κB) protects against IFN-γ; and how to exploit IFN-γ’s tumoricidal properties for treatment of RCC in vivo. The team found that NF-κB inhibitor bortezomib successfully sensitized RCC cells to IFN-γ-mediated necrosis, suggesting that the combination of IFN-γ and bortezomib will have clinical benefit in RCC at doses of IFN-γ that are significantly lower than those used before. Based on this work, Fox Chase medical oncologist Daniel M. Geynisman, MD, is launching a new clinical trial to examine whether Ixazomib, an oral NF-κB inhibitor, will be beneficial for advanced RCC patients when used in combination with pegylated IFN.

kappesDissecting the Role of ThPOK in Thymic Development and T Cell Differentiation

  • PI: Dietmar J. Kappes, PhD, professor, Blood Cell Development and Function
  • Grant: R01 – National Institutes of Health
  • Award: $1,356,000 over four years
Mutation of the ThPOK silencer element dramatically alters representation of mature T cell subsets in mice. A site-specific Zn finger nuclease (ZFN) approach was used to introduce different mutations into the silencer of the endogenous ThPOK locus; proportions of mature T helper and killer cells in the blood of homozygous mutant mice were assessed by flow cytometric analysis of T cell receptor positive lymphocytes. Note that different mutations are neutral (PS17), promote (QC48), or antagonize (OB11) development/differentiation of T helper cells.

Mutation of the ThPOK silencer element dramatically alters representation of mature T cell subsets in mice. A site-specific Zn finger nuclease (ZFN) approach was used to introduce different mutations into the silencer of the endogenous ThPOK locus; proportions of mature T helper and killer cells in the blood of homozygous mutant mice were assessed by flow cytometric analysis of T cell receptor positive lymphocytes. Note that different mutations are neutral (PS17), promote (QC48), or antagonize (OB11) development/differentiation of T helper cells. (Click to enlarge)

Kappes is studying the role of T helper inducing POZ-Kruppel Factor (ThPOK) in thymic development and T cell differentiation. ThPOK is a transcriptional regulator that encourages the differentiation of immature T cells into T helper (Th) cells and affects the further differentiation of Th cells; misregulated ThPOK expression can result in aggressive lymphomas. The goals of this project are three-fold: to elucidate the function of the ThPOK silencer, which regulates the expression of ThPOK during T cell development, and test the theory that nuclear factor of activated T cells (NFAT) and/or early growth response (EGR) transcription factors control the silencer; to analyze the role of the zinc finger protein Zfp281 in control of ThPOK transcription and in T cell development and function; and to define the influence of ThPOK on mature T cell function. Kappes and colleagues have developed a new mouse line for these studies in which ThPOK expression is selectively blocked in mature T cells via site-specific zinc finger proteins.