Abstract LB-338: SHP2 inhibition enhances sensitivity to MEK inhibitors in multiple resistant cancer models

Abstract

Abstract Targeting tumors with kinase inhibitors induces complex adaptive programs that enable the persistence of a fraction of the original cell population, facilitating the eventual outgrowth of inhibitor-resistant tumor clones. Most tumors developing resistance to MEK inhibitors upregulate and/or activation of at least one of several different receptor tyrosine kinases (RTKs), which drive resistance. Notably, different RTKs or RTK combinations are upregulated in different cancer cells, even those from the same histotype. SHP2 (encoded by PTPN11) is required for RAS/ERK pathway activation downstream of most RTKs, suggesting that it might provide a common targetable resistance node in multiple resistant cancer cell lines. We show that the addition of a newly identified SHP2 inhibitor, SHP099, to MEK therapy enhances cell killing and impedes the emergence of drug-resistant cell populations in diverse cancer models in vitro and in vivo. These effects occurred in a wide range of malignancies, including KRAS mutant pancreas, lung cancer, triple negative breast cancer, and serous ovarian cancer cell lines, as well as in PDX and GEMM models. SHP099 effects were overcome by expressing an SHP2 mutant that loses drug binding but retain catalytic activity and regulation, demonstrating that on target effects of the inhibitor. Mechanistic studies across multiple cellular cancer models suggest that SHP2 inhibition by SHP099 prevents the compensatory RAS and ERK1/2 reactivation in response to MEK therapy and impedes the engagement of the ERK1/2 transcriptional programs (i.e., MYC, ETV1, FOSL1, etc.) and signaling outputs that characterize the drug-tolerant state. Combining full doses of MEK inhibitors and SHP099 causes significant toxicity in mice, but non-toxic, efficacious dosing regimens can be achieved. Our findings suggest that SHP099, in combination with MEK inhibition is a promising therapeutic strategy for enhancing the effectiveness of targeted therapies. Citation Format: Carmine Fedele, Kwan Ho Tang, Hao Ran, Wei Wei, Brian Diskin, George Miller, Benjamin G. Neel. SHP2 inhibition enhances sensitivity to MEK inhibitors in multiple resistant cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-338.