Date of Award

January 2014

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Elena S. Ratner

Subject Area(s)

Obstetrics and gynecology, Pharmacology, Oncology

Abstract

Platinum resistance is a major obstacle in the treatment of epithelial ovarian cancer (EOC). Activation of the Akt pathway promotes a platinum resistance while inhibition of Akt sensitizes chemoresistant cells. Patients with BRCA mutant EOC, and thus a defect in the homologous recombination repair (HRR) pathway, demonstrate greater clinical response to platinum and olaparib therapy than patients with BRCA wild-type EOC. MK-2206, an allosteric inhibitor of Akt phosphorylation, sensitizes a variety of cell types to various anticancer agents and is currently in phase II trials as monotherapy for advanced endometrial cancer. This study examines the differential effects of Akt inhibition with cisplatin and olaparib therapy in BRCA1/2-deficient versus wild-type EOC. Clonogenic assays were conducted with a BRCA1-knockdown variant (BR-kd) of SK-OV3, a human ovarian adenocarcarcinoma, as well as a paired non-targeted control (NTC). MTS colormetric assays were conducted using PEO1, a chemosensitive BRCA2-mutant serous ovarian adenocarcinoma, and PEO4, a reverted BRCA2-proficient line from the same patient after chemotherapeutic resistance developed. Cells were treated 24 hours after plating and incubated continuously with drug combinations for 72 hours. Western blotting assessed the impact of drug treatment on Akt activation, as well as on downstream targets of Akt. In PEO1, MK-2206 demonstrated moderate to strong synergism with cisplatin and olaparib at all doses, while demonstrating antagonism at all doses in PEO4. Baseline phospho-Akt activity in untreated cells is upregulated in both BRCA-deficient cell lines. MK-2206 prevents the cisplatin- and olaparib-induced Akt activation in the BRCA2-deficient PEO1 cells. We propose that BRCA-deficient EOC cells upregulate baseline Akt activity to enhance survival in the absence of HR. Higher Akt activity is also required to withstand cytotoxic agent-induced DNA damage, leading to strong synergism between MK-2206 and cisplatin or olaparib therapy in BRCA-deficient cells. MK-2206 shows promise as a chemosensitization agent in BRCA-deficient epithelial ovarian cancers and merits clinical investigation in this patient population.

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