Ovarian cancer is often lethal, in part due to frequent resistance to chemotherapy. Due to the high rate of recurrence and paucity of treatment options, the development of more effective therapies to eliminate ovarian cancer cells is desperately needed. Most cancer therapies reduce tumor size using cytotoxic compounds, which promote programmed cell death (apoptosis) of tumor cells. Because cancer cells can evade apoptosis, understanding the signaling pathways utilized by cancer cells to survive and proliferate is imperative for effective treatment. Ovarian carcinomas require an ample supply of fatty acids for rapid proliferation;therefore, 80% of these tumors have upregulated the metabolic enzyme fatty acid synthase (FASN). This upregulation correlates with poor cancer prognosis. While inhibiting FASN can both reduce proliferation and promote apoptosis of tumor cells, currently available FASN inhibitors are not clinically useful for cancer treatment due to undesirable side effects, low bioavailability, or high reactivity. Ovarian cancer cells can also vay in sensitivity to FASN inhibitor-induced apoptosis. To aid in the discovery of new therapies that exploit this pathway, we must elucidate the signaling events downstream of FASN inhibition. Recently, we observed that ovarian cancer cell death following FASN inhibition correlated with expression of REDD1, a 14-3-3-binding protein and mTORC1 inhibitor. Moreover, activation of the pro- apoptotic initiator caspase, caspase-2, was dependent on REDD1 expression. However, two important questions remain: 1) how does REDD1 promote caspase-2 activation, and 2) is resistance to FASN inhibitor- induced apoptosis in ovarian cancer cells due to reduced REDD1 levels? Therefore, we will first determine the mechanism through which REDD1 leads to caspase-2 activation using biochemical and mass spectrometry approaches. We will specifically examine: 1) the role of mTORC1 signaling, 2) the involvement of 14-3-3 sequestration in REDD1 function and 3) post-translational modifications and binding partners of caspase-2 that are modulated by FASN inhibition. Next, we will define the relationship between REDD1 abundance and resistance to FASN inhibitor-induced apoptosis in ovarian cancer using in vitro biochemistry and an in vivo xenograft model. Specifically, we will determine 1) whether REDD1 overexpression can sensitize FASN inhibitor resistant cells in vitro 2) the mechanism of reduced REDD1 expression in resistant cells and 3) if overexpression of REDD1 can re-sensitize cells to FASN inhibition and promote tumor regression in a xenograft model of ovarian cancer. At the completion of this training project, I will have defined the role of REDD1 in promoting ovarian cancer cell apoptosis following FASN inhibition. This study will enhance our understanding of apoptotic regulation in ovarian cancer cells and is likely to suggest potentially druggable targets that may circumvent chemoresistance to effectively treat ovarian cancer.
Ovarian cancer is often lethal due to recurrence after initial chemotherapy treatment. To address this problem, we propose to identify new therapeutic targets by examining how cancer cells respond to toxic treatments. Our overall goal is to lay the groundwork for the development of new treatment strategies to increase survival of ovarian cancer patients.
