Abstract C17: Revealing targetable cancer cell vulnerabilities by in silico pathway profiling

Abstract

Abstract Successful targeted therapy of cancers relies on comprehensive understanding of vulnerabilities of the tumorigenic platform. Recent cancer genomics efforts have provided with an unprecedented opportunity to gain an unbiased insight into the functional make-up of human cancers. We have devised a computational strategy to leverage cancer genomic datasets to identify candidate pathway vulnerabilities in cancers. The core of our approach is in the delineation of molecular pathways that are activated in tumor cells as a result of secondary selection events during tumor evolution. These secondary pathways are likely to be required for tumorigenesis in the given tumor context. We applied this strategy on HER2+ breast cancers using breast cancer genomic data in the TCGA, the recently published METABRIC and the Cancer Cell Line Encyclopedia (CCLE) datasets. Although HER2+ breast cancers are treated with HER2-targeting agents in the clinic, the response is usually short-lived due to de novo and acquired resistance. We have found that HER2+ breast cancers are characterized by extensive and robust secondary upregulation of the endoplasmic reticulum (ER) quality control (ERQC) pathways, including the ER-associated degradation (ERAD) and PERK/eIF2 pathways. Our follow-up combined in silico and in vitro analyses on a panel of HER2+ and HER2- breast cancer cell lines revealed a model of HER2-driven tumorigenesis where yin-yang interplay between hyperactive HER2/mTOR signaling and the ERQC machinery regulate the ER protein homeostasis to control survival of HER2+ cells. Furthermore, we report that this delicate regulatory architecture can be exploited for therapeutic purposes, such that, combinatorial targeting of ERQC pathways to disturb the proteostatic balance synergized in selectively inducing proteotoxic cell death in therapy-refractory HER2+ cells. This study presents a computational method for identification of cancer pathway vulnerabilities, and suggests that exploiting proteotoxic ER stress may be an effective therapeutic strategy in therapy-refractory HER2+ breast cancers. Note: This abstract was not presented at the conference. Citation Format: Rashika Joshi, Kakajan Komurov. Revealing targetable cancer cell vulnerabilities by in silico pathway profiling. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr C17.