Genetic instability is a hallmark of cancer. We have shown in previous work that the hypoxic tumormicroenvironment is one cause of this genetic instability, and we have recently found that hypoxiaspecifically causes decreased expression of the DMArepair factors, RAD51 and BRCA1. These factorsmaintain genomic integrity by mediating the repair of double-strand breaks and other lesions through thehigh-fidelity homology-dependent repair (HDR) pathway. Germline mutations in BRCA1 have been linked tohereditary breast and ovarian cancer, and decreased expression of BRCA1 has been seen in many sporadiccancers of these sites. In this project, we propose to investigate the mechanisms and consequences of RAD51 and BRCA1regulation in response to hypoxia. We will examine key transcription regulatory mechanisms, with a focus onpromoter repression by E2Fs and associated pocket proteins, and we will test the hypothesis that RAD51and BRCA1 are coordinately regulated by these factors. The impact of decreased RAD51 and BRCA1expression on genetic instability will be assessed using selected DNA recombination and repair assays totest the hypothesis that hypoxia-induced decreases in RAD51 and/or BRCA1 may shift the balance betweenthe high-fidelity HDR and the error-prone non-homologous end-joining repair pathways. We will also testwhether the suppression of HDR in hypoxic cells renders them especially vulnerable to novel therapeuticstrategies, including inhibition of base excision repair (BER) (in collaboration with Project 3) by eitherpoly(ADP-ribose) polymerase-1 (PARP-1) or polymerase beta inhibitors (to cause accumulation ofunrepaired strand breaks) or inhibition of O6-alkylguanine-DNA alkyltransferase (AGT) in combination withagents that target the O-6 position of guanine and give rise to crosslinks (in collaboration with Project 1). These studies will provide further insight into how the hypoxic tumor microenvironment contributes togenetic instability and may offer an explanation for the down-regulation of BRCA1 detected in sporadiccancers. This work may also serve as a basis for novel therapeutic strategies to target hypoxic cells in solidtumors and possibly to treat familial breast and ovarian cancers associated with mutations in BRCA1 orBRCA2.

National Institute of Health (NIH)
National Cancer Institute (NCI)
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Yale University
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Penketh, Philip G; Shyam, Krishnamurthy; Baumann, Raymond P et al. (2016) When alcohol is the answer: Trapping, identifying and quantifying simple alkylating species in aqueous environments. Anal Biochem 508:34-7
Penketh, P G; Shyam, K; Baumann, R P et al. (2015) A simple and inexpensive method to control oxygen concentrations within physiological and neoplastic ranges. Anal Biochem 491:1-3
Penketh, Philip G; Shyam, Krishnamurthy; Zhu, Rui et al. (2014) Influence of phosphate and phosphoesters on the decomposition pathway of 1,2-bis(methylsulfonyl)-1-(2-chloroethyhydrazine (90CE), the active anticancer moiety generated by Laromustine, KS119, and KS119W. Chem Res Toxicol 27:818-33
Lin, Z Ping; Ratner, Elena S; Whicker, Margaret E et al. (2014) Triapine disrupts CtIP-mediated homologous recombination repair and sensitizes ovarian cancer cells to PARP and topoisomerase inhibitors. Mol Cancer Res 12:381-393
Penketh, Philip G; Patridge, Eric; Shyam, Krishnamurthy et al. (2014) Influence of glutathione and glutathione S-transferases on DNA interstrand cross-link formation by 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine, the active anticancer moiety generated by laromustine. Chem Res Toxicol 27:1440-9
Lamb, Kristy L; Liu, Yanfeng; Ishiguro, Kimiko et al. (2014) Tumor-associated mutations in O? -methylguanine DNA-methyltransferase (MGMT) reduce DNA repair functionality. Mol Carcinog 53:201-10
Zhu, Rui; Baumann, Raymond P; Penketh, Philip G et al. (2013) Hypoxia-selective O6-alkylguanine-DNA alkyltransferase inhibitors: design, synthesis, and evaluation of 6-(benzyloxy)-2-(aryldiazenyl)-9H-purines as prodrugs of O6-benzylguanine. J Med Chem 56:1355-9
Zhu, Rui; Baumann, Raymond P; Patridge, Eric et al. (2013) Chloroethylating and methylating dual function antineoplastic agents display superior cytotoxicity against repair proficient tumor cells. Bioorg Med Chem Lett 23:1853-9
Daley, James M; Niu, Hengyao; Sung, Patrick (2013) Roles of DNA helicases in the mediation and regulation of homologous recombination. Adv Exp Med Biol 767:185-202
Daley, James M; Sung, Patrick (2013) RIF1 in DNA break repair pathway choice. Mol Cell 49:840-1

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