Abstract 2366: The tyrosine phosphatase, SHP-2, participates in regulating PD-L1 expression in non-small cell lung cancer

Abstract

Abstract Immune checkpoint inhibitors, specifically those which target T cell surface receptor Programmed Cell Death-1 (PD-1) and its ligand, Programmed cell death ligand-1 (PD-L1), have demonstrated clinical benefit in patients with non-small cell lung cancer (NSCLC). Currently, tumor expression of PD-L1 serves as the FDA-approved companion diagnostic for response to anti-PD-1/PD-L1 therapy. However, a fraction of patients who express PD-L1 exhibit a response to treatment, and in some cases, patient tumors that do not express PD-L1 demonstrate response to therapy, making this a poor predictive biomarker. Further, the mechanism by which PD-L1 expression is controlled remains under-studied. In this study, we seek to determine the impact of the protein tyrosine phosphatase, SHP-2, on PD-L1 expression through Jak/STAT- mediated signaling in NSCLC cell lines. SHP-2 can harbor activating mutations which prevent auto-inhibition of the catalytic phosphatase domain, and that may be pro-tumorigenic in some tumors. To understand the impact of SHP-2 activity on PD-L1 expression, we first assessed activation of STAT3 in NSCLC tumor cells after treatment with IFNγ and other mitogens. We then transfected NSCLC cells with wildtype and hyperactive SHP-2 mutants or ablated SHP-2 with siRNA specific for SHP-2 and measured both STAT3 and PD-L1 expression. Cell lines A549 and H661 exhibit low endogenous expression of both SHP-2 and PD-L1, and thus were chosen for transfection with hyperactive SHP-2 mutants (E76K and G503V), which also altered PD-L1 expression by western blot analysis. Quantitative real-time PCR (qPCR) and western blot analysis revealed that siRNA ablation of SHP-2 led to increased PD-L1 expression in the H460 cell line. Cells transfected with the SHP-2 activating mutants will also be assessed alteration of cell proliferation. Finally, using data obtained from The Cancer Genome Atlas project, STAT3 and PD-L1 expression levels are being evaluated in NSCLC tumor samples in which SHP-2 is mutated (E76K or G503V). With these data, we expect to gain a more complete understanding of the role of SHP-2 within the tumor microenvironment and the extent to which it controls PD-L1 expression, leading to new drug targets or combinations of drugs and better predictive biomarkers of response to PD-1 and PD-L1 inhibitors. Citation Format: Keller Toral, Brent Harris, Jarrod Creameans, Penni Black. The tyrosine phosphatase, SHP-2, participates in regulating PD-L1 expression in non-small cell lung cancer [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 2366.