Hypoxia, DNA repair, and gene silencing. Hypoxia is a key feature of solid tumors that confers radiation resistance, stimulates angiogenesis, promotes metastasis, and is linked to poor prognosis. With the support of this grant, we have shown that hypoxia is also a driver of genetic instability via down-regulation of critical DNA repair genes. In the past funding period, we have discovered that hypoxia can also induce durable silencing of the BRCA1 and MLH1 promoters via specific epigenetic factors. In recent preliminary studies, we have further determined that hypoxia can lead to silencing of the pro-apoptotic BIM gene and resistance to the EGFR inhibitor, gefitinib, in lung cancer cells. The broad, long-term goal of this renewal application is to elucidate the impact of hypoxic stress on carcinogenesis and cancer biology, with a focus on DNA repair and gene silencing.
In Aim 1, we will dissect the molecular mechanisms by which hypoxic stress drives epigenetic change to cause gene silencing, with a focus on the MLH1 promoter. We will determine promoter elements and regulatory factors that mediate silencing, and we will use a facile selection-based shRNA screen to identify key targets for reversal of this process. We will also assay for the impact of the hypoxic tumor microenvironment on gene silencing during tumor growth in vivo. Next, since heavy metals are known human carcinogens that can induce hypoxia-related pathways, in Aim 2 we will ask whether exposure to heavy metals can also drive gene silencing and/or down-regulate DNA repair.
In Aim 3, we will build on novel preliminary results suggesting that growth of lung cancer cells in hypoxia can promote resistance to the epidermal growth factor receptor (EGFR) inhibitor, gefitinib, in conjunction with silencing of the pro-apoptotic factor, BIM. We wil test specific hypotheses regarding the underlying mechanisms, and, guided by Aim 1, we will identify strategies to prevent or reverse this resistance. The proposed work will elucidate key pathways of gene silencing and DNA repair regulation in response to hypoxia (and possibly to carcinogenic heavy metals) that may underlie critical steps in carcinogenesis, genetic instability, tumor progression, and resistance to radiation and other cancer therapies. Identification of strategies to prevent or reverse these pathways may provide the basis for new approaches to cancer prevention and therapy.

Public Health Relevance

Hypoxia, DNA repair, and gene silencing. Hypoxia is a key feature of solid tumors that confers radiation resistance and is linked to poor prognosis. We have discovered that hypoxia can also induce silencing of the tumor suppressor genes, BRCA1 and MLH1. The proposed work will elucidate key pathways of gene silencing and DNA repair regulation in response to hypoxia (and possibly to carcinogenic heavy metals) that may underlie critical steps in carcinogenesis, genetic instability, tumor progression, and resistance to radiation and other cancer therapies. Identification of strategies to prevent or reverse these pathways may provide the basis for new approaches to cancer prevention and therapy.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES005775-25
Application #
9591304
Study Section
Radiation Therapeutics and Biology Study Section (RTB)
Program Officer
Reinlib, Leslie J
Project Start
1992-09-30
Project End
2019-10-31
Budget Start
2018-11-01
Budget End
2019-10-31
Support Year
25
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Yale University
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520
Sulkowski, Parker L; Sundaram, Ranjini K; Oeck, Sebastian et al. (2018) Krebs-cycle-deficient hereditary cancer syndromes are defined by defects in homologous-recombination DNA repair. Nat Genet 50:1086-1092
Kim, Hoon; Lin, Qun; Glazer, Peter M et al. (2018) The hypoxic tumor microenvironment in vivo selects the cancer stem cell fate of breast cancer cells. Breast Cancer Res 20:16
Sulkowski, Parker L; Scanlon, Susan E; Oeck, Sebastian et al. (2018) PTEN Regulates Nonhomologous End Joining By Epigenetic Induction of NHEJ1/XLF. Mol Cancer Res 16:1241-1254
Lu, Yuhong; Liu, Yanfeng; Oeck, Sebastian et al. (2018) Hypoxia Promotes Resistance to EGFR Inhibition in NSCLC Cells via the Histone Demethylases, LSD1 and PLU-1. Mol Cancer Res 16:1458-1469
Scanlon, Susan E; Hegan, Denise C; Sulkowski, Parker L et al. (2018) Suppression of homology-dependent DNA double-strand break repair induces PARP inhibitor sensitivity in VHL-deficient human renal cell carcinoma. Oncotarget 9:4647-4660
Scanlon, Susan E; Scanlon, Christine D; Hegan, Denise C et al. (2017) Nickel induces transcriptional down-regulation of DNA repair pathways in tumorigenic and non-tumorigenic lung cells. Carcinogenesis 38:627-637
Gupta, Anisha; Quijano, Elias; Liu, Yanfeng et al. (2017) Anti-tumor Activity of miniPEG-?-Modified PNAs to Inhibit MicroRNA-210 for Cancer Therapy. Mol Ther Nucleic Acids 9:111-119
Sulkowski, Parker L; Corso, Christopher D; Robinson, Nathaniel D et al. (2017) 2-Hydroxyglutarate produced by neomorphic IDH mutations suppresses homologous recombination and induces PARP inhibitor sensitivity. Sci Transl Med 9:
Yu, Chang; Zelterman, Daniel (2017) A parametric model to estimate the proportion from true null using a distribution for p-values. Comput Stat Data Anal 114:105-118
Czochor, Jennifer R; Sulkowski, Parker; Glazer, Peter M (2016) miR-155 Overexpression Promotes Genomic Instability by Reducing High-fidelity Polymerase Delta Expression and Activating Error-Prone DSB Repair. Mol Cancer Res 14:363-73

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