Abstract 4525: mTOR complex inhibition as a novel therapeutic strategy in high-grade papillary serous ovarian cancer

Abstract

Abstract Objectives: To compare mTOR complex 1 inhibition (RAD001) vs. mTOR complex 1/2 inhibition (PP242) as single agents and with Carboplatin (CPP) in a preclinical model of serous ovarian cancer (OVCA). Methods: In vitro: OVCAR3 and SKOV3 cell lines were exposed to the following treatment conditions: RAD001 or PP242 as single agents, vehicle, CPP alone, and RAD001 or PP242 followed by CPP. Colony forming assays (CFAs) were performed and quantified. mRNA levels of AKT, downstream targets of mTOR and the DNA repair response (ATR, ATM, BRCA1/2) were quantified by qRTPCR. Immunoblots characterized the protein expression of key components of mTOR and DNA repair pathways. Non-parametric analyses were used to compare results across groups on SPSS. In vivo: OVCAR3 cells expressing F-Luciferase were injected IP into SCID-BG mice. 15 wks post-injection, mice were exposed to the treatment conditions described above for 4 weeks. Tumor growth and response to treatment were assessed using bioluminescence imaging (IVIS). Results were analyzed on Living Image and Prism6. Results: In vitro: OVCAR3 and SKOV3 cells are highly sensitive to mTOR inhibition. CFAs showed significantly decreased colony counts and diameter in groups exposed to either PP242 or RAD001 vs. control, an effect that was potentiated by CPP (Fig 1). qRTPCR revealed a significant decrease in 4EBP1 mRNA with mTOR inhibition (p<0.0001), but no change in other biomarkers. Although treatment with both mTOR inhibitors resulted in decreased expression of p-S6 by immunoblots, treatment with the dual inhibitor (PP242) caused a decrease in p-AKT, p-4EBP1, total and p-CHK1, and total and p-BRCA1. The levels of these proteins were not changed by addition of CPP despite the significant effect observed in the functional assay (CFA). In vivo: Treatment with CPP + PP242 was associated with a longer median survival than other treatment groups (Table 1). A decrease in tumor burden was seen on IVIS and tumor flux (photons/sec) at the end of treatment was significantly lower in mice treated with CPP+PP242 compared to other groups (p<0.0001). Conclusions: Our preclinical model supports the concurrent use of dual mTOR inhibitors and platinum chemotherapy in the treatment of OVCA. mTOR complex 1/2 inhibition impairs the DNA repair response and correlates with improved survival in a murine model. Citation Format: Fernanda Musa, Amandine Alard, Gizelka David-West, Iulia Giuroiu, Stephanie Blank, Bhavana Pothuri, John P. Curtin, Robert Schneider. mTOR complex inhibition as a novel therapeutic strategy in high-grade papillary serous ovarian cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4525. doi:10.1158/1538-7445.AM2014-4525