Abstract
Abstract Background - Genetic and epigenetic alterations provide the selective advantage for cancer cell acquired drug resistant (ADR). A bottleneck in implementing drug combination is the challenging task of identifying combinations with acceptable risk benefit ratio. High throughput functional genomic (RNAi) screen is an ideal tool to comprehensively identify double and triple inhibitor combinations to prevent ADR. Unfortunately, most anticancer agents are antagonists (antagonists operate in the same direction as the RNAi), therefore RNAi hits with possible clinical value are the ones that disappear during the screen. Materials and Methods - We use lentiviral-borne shRNA libraries (mainly kinome collection) to transduce the different RNAis into patient-derived cancer cells. The resulting mixed cancer cell population (each lost one gene) is subject to negative screen, to identify mediators of ADR. This process was performed with approved cancer drugs, such as erlotinib, olaparib, pazopanib, etc. We developed a proprietary unique way to identify the RNAi clones that disappear/extinct, specifically in the presence of the investigated drug. RNAi clones are tracked using next generation sequencing, and quantified in treated and untreated cancer cell cultures or xenografts. The resulting drug combinations identified through this screen are tested directly on a platform of patient-derived xenografts. Results - We identified known boosters of the EGFR activity, such as DYRK1 (maintains level of EGFR protein), IKBKE (downstream survival mediator), which when reduced by their RNAi, enhance the response to erlotinib. Consequently, known inhibitors of JAK1, CDK4/6, and PI3K combined to egfr inhibitors generated more durable remissions in egfr positive cells. Remarkably, even tumors without egfr mutations were sensitive to the combinations. A similar discovery of novel combinations were found for olaparib and pazopanib. Mouse harboring patient derived xenografts tolerated combination therapy fairly well. Conclusion - Our findings demonstrate the value of clinically testing the efficacy of drug combinations empirically designed to block ADR. Animal model support our findings with acceptable toxicity. Citation Format: Izhak Haviv. Comprehensive high-throughput screen for combination therapies to block acquired resistance to targeted drugs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1190. doi:10.1158/1538-7445.AM2017-1190
Published Version
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