S.V. Blank

Multigene panels in Ashkenazi Jewish patients yield high rates of actionable mutations in multiple non-BRCA cancer-associated genes

OBJECTIVE To evaluate the results of multigene panel testing among Ashkenazi Jewish compared with non-Ashkenazi Jewish patients. METHODS We reviewed the medical records for all patients who underwent multigene panel testing and targeted BRCA1/2 testing at a single institution between 6/2013-1/2015. Clinical actionability for identified pathogenic mutations was characterized based on the National Comprehensive Cancer Network (NCCN) guidelines and consensus statements and expert opinion for genes not addressed by these guidelines. RESULTS Four hundred and fifty-four patients underwent multigene panel screening, including 138 Ashkenazi Jewish patients. The median patient age was fifty-two years. Three hundred and fifty-four patients (78%) had a personal history of cancer. Two hundred and fifty-one patients had breast cancer, 49, ovarian cancer, 26, uterine cancer and 20, colorectal cancer. We identified 62 mutations in 56 patients and 291 variants of uncertain significance in 196 patients. Among the 56 patients with mutations, 51 (91%) had actionable mutations. Twenty mutations were identified by multigene panels among Ashkenazi Jewish patients, 18 of which were in genes other than BRCA1/2. A review of targeted BRCA1/2 testing performed over the same study period included 103 patients and identified six mutations in BRCA1/2, all of which occurred in Ashkenazi Jewish patients. Among all Ashkenazi Jewish patients undergoing genetic testing, 25/183 (14%) had a mutation, 24/25 of which were actionable (96%) and 17/25 patients (68%) had mutations in non BRCA1/2 genes. CONCLUSIONS With the rapid acceptance of multigene panels there is a pressing need to understand how this testing will affect patient management. While traditionally many Ashkenazi Jewish patients have undergone targeted BRCA1/2 testing, our data suggest consideration of multigene panels in this population as the majority of the results are clinically actionable and often in genes other than BRCA1/2.

Abstract MIP-051: EFFICACY OF MTORC1/2 INHIBITION ON OVARIAN CANCER STEM CELLS

INTRODUCTION: Ovarian cancer is the most lethal gynecologic malignancy. Initial treatment with platinum and taxane drugs are effective, however inevitably these patients will recur and become resistant to cytotoxic therapies. Thus, new alternatives for durable treatments need to be identified. One approach is to explore the heterogeneity of epithelial ovarian cancer and identify the subpopulation of cells that are resistant to treatment. It has been hypothesized, that cancer stem cells (CSCs) can survive chemotherapy and have enhanced tumor-initiating capabilities. The AKT-PI3K-mTOR pathway is well studied and has been shown to be critical for tumor cell survival. This pathway closely regulates both mTOR complexes (mTORC1 and mTORC2). mTORC1 regulates protein synthesis and autophagy whereas mTORC2 regulates cell motility. mTORC1 and 2 ultimately affect cell proliferation, survival and angiogenesis, all inherently important in tumorgenesis. OBJECTIVES: Rapalogs are specific and potent inhibitors of mTORC1 but have no effect of mTORC2. We investigate the efficacy of dual mTORC1/2 inhibitors and its effect on the CSC population. METHODS: Carboplatin resistant ovarian cancer cell line OVCAR3 were cultured and treated with dimethyl sulfoxide (DMSO), carboplatin, or INK128, a potent dual inhibitor of mTORC1/2. Using cell surface markers CD133 and CD44, CSCs were quantified by flow cytometry. OVCAR3 spheroids were cultured as a surrogate for CSCs. Colony formation-survival assays were performed with spheroids treated with the above mentioned conditions. Analysis was performed using ArrayScan technology. Doxycyline inducible silencing cell lines derived from OVCAR3 were generated; Non-silenced (Nsi), Raptor (Sh-mTORC1) and Rictor (Sh-mTORC2). Colony formation assays using spheroids from silenced lineages were performed to evaluate growth and survival. Western blot analysis was performed to confirm silencing of targets, and to evaluate protein expression in CSCs. RESULTS: 4.87% of the untreated OVCAR3 population were CSCs. INK128 treatment of the cells confered a 2 fold increase of CD44+/CD133+ cells, presumably CSCs, P CONCLUSIONS: The PI3K/AKT/mTOR pathway appears to have a role in the biogenesis of platinum resistant ovarian cancer cells. The inhibition of mTORC1/2 delays growth of OVCAR3 cells, and may have a role in activating in stem like CSCs. However, it does not appear to selectively inhibit CD133+/CD44+ cells. These findings suggest that targeting CSCs may lead to advances in ovarian cancer treatment. Citation Format: Jing-Yi Chern MD, Melissa Frey MD, Fernanda Musa MD, Amandine Alard PhD, Stephanie V. Blank, MD, Robert Schneider, PhD. EFFICACY OF MTORC1/2 INHIBITION ON OVARIAN CANCER STEM CELLS [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr MIP-051.