Genetic instability is a hallmark of cancer. We have shown in previous work that the hypoxic tumor microenvironment is one cause of this genetic instability, and we have recently found that hypoxia specifically causes decreased expression of the DMArepair factors, RAD51 and BRCA1. These factors maintain genomic integrity by mediating the repair of double-strand breaks and other lesions through the high-fidelity homology-dependent repair (HDR) pathway. Germline mutations in BRCA1 have been linked to hereditary breast and ovarian cancer, and decreased expression of BRCA1 has been seen in many sporadic cancers of these sites. In this project, we propose to investigate the mechanisms and consequences of RAD51 and BRCA1 regulation in response to hypoxia. We will examine key transcription regulatory mechanisms, with a focus on promoter repression by E2Fs and associated pocket proteins, and we will test the hypothesis that RAD51 and BRCA1 are coordinately regulated by these factors. The impact of decreased RAD51 and BRCA1 expression on genetic instability will be assessed using selected DNA recombination and repair assays to test the hypothesis that hypoxia-induced decreases in RAD51 and/or BRCA1 may shift the balance between the high-fidelity HDR and the error-prone non-homologous end-joining repair pathways. We will also test whether the suppression of HDR in hypoxic cells renders them especially vulnerable to novel therapeutic strategies, including inhibition of base excision repair (BER) (in collaboration with Project 3) by either poly(ADP-ribose) polymerase-1 (PARP-1) or polymerase beta inhibitors (to cause accumulation of unrepaired strand breaks) or inhibition of O6-alkylguanine-DNA alkyltransferase (AGT) in combination with agents 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 to genetic instability and may offer an explanation for the down-regulation of BRCA1 detected in sporadic cancers. This work may also serve as a basis for novel therapeutic strategies to target hypoxic cells in solid tumors and possibly to treat familial breast and ovarian cancers associated with mutations in BRCA1 or BRCA2.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Program Projects (P01)
Project #
5P01CA129186-02
Application #
7669301
Study Section
Special Emphasis Panel (ZCA1)
Project Start
Project End
Budget Start
2008-08-01
Budget End
2009-07-31
Support Year
2
Fiscal Year
2008
Total Cost
$302,309
Indirect Cost
Name
Yale University
Department
Type
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520
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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