Abstract 5371: A pooled apoptome shRNA screen to identify pathways that enhance NVP-BEZ235-induced apoptosis

Abstract

Abstract NVP-BEZ235 is a dual inhibitor of class 1 phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) catalytic activity. It induces cell death in a subset of breast cancer cell lines characterized by amplification of human epidermal growth factor receptor 2 (HER2/ErbB2) and/or activating PIK3CA mutations, but not in cell lines with loss of function of the PTEN tumor suppressor protein or KRAS mutations. In order to better understand the molecular mechanisms leading to cell death, to identify potential biomarkers of activity and to reveal pathways that may even enhance NVP-BEZ235 induced lethality, a pooled short hairpin RNA (shRNA) screen using a lentiviral-based shRNA library targeting the apoptome was performed in NVP-BEZ235-sensitive MDA-MB453 and HCC1954 breast cancer cells. This strategy led to the identification of shRNAs that sensitized cells to NVP-BEZ235-induced apoptosis. Top sensitizers included pro-survival BCL2 family members, BCL2L1 and MCL1. Validation studies were carried out with single shRNAs targeting BCL2L1 and MCL1 as well as drug combination studies of NVP-BEZ235 with ABT-263 or ABT-747, both BCL2 homology domain 3 (BH3)-only protein mimetics. Cell death assays and biochemical readouts including PARP cleavage support the use of BCL2 family inhibitors to enhance NVP-BEZ235-induced cell death in HER2 amplified/PIK3CA mutated breast cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5371. doi:10.1158/1538-7445.AM2011-5371