Abstract 4664: Co-targeting HGF-cMET signaling with MEK inhibitors in metastatic uveal melanoma

Abstract

Abstract Metastatic uveal melanoma (UM) patients usually die within one year, emphasizing an urgent need to develop new treatment strategies. Mitogen-activated protein kinase kinase (MEK) inhibitors improve survival in cutaneous melanoma patients but have limited efficacy in UM patients. Our previous work show that HGF-cMET signaling provides resistance to MEK inhibitors in metastatic UM cells. In this study, we further investigated the mechanisms of HGF-driven resistance to MEK inhibitors in metastatic UM cells. Cellular signaling pathway analysis was carried out to determine the role of downstream Bcl2 family members in overcoming trametinib-mediated apoptosis by HGF in metastatic UM cells. A new class of clinical grade cMET antibody and inhibitor were tested for their capacity to revert the resistance to trametinib mediated by HGF and tumor microenvironment. Selective inhibitors were utilized to determine the PI3K isoform dependency of metastatic UM cells in HGF-mediated protection against trametinib in metastatic UM cells. We demonstrate that the expression of two BH3-only family proteins, Bim-EL and Bmf, is upregulated in trametinib treated cells, but returns to basal levels upon HGF treatment in these cells. Targeting HGF-cMET signaling with LY2875358, a neutralizing and internalizing anti-cMET bivalent antibody, and LY2801653, a dual cMET/RON inhibitor overcomes resistance to trametinib provided by exogenous HGF and by conditioned medium from primary hepatic stellate cells. PI3Kβ-sparing inhibitor GDC0032 effectively blocks HGF-induced AKT phosphorylation and HGF-mediated resistance in trametinib treated cells in growth assays. In conclusion, our data suggest that HGF promotes resistance to MEK inhibitors through modulating Bim-EL and Bmf expression in UM cells. Our data also support the notion that selectively blocking PI3K isoform activities or cMET signaling may delay the onset of resistance to MEK inhibitors provided by tumor microenvironment in metastatic uveal melanoma. Citation Format: Hanyin Cheng, Ken Kageyama, Timothy Purwin, Connie Liao, Mizue Terai, Takami Sato, Andrew Aplin. Co-targeting HGF-cMET signaling with MEK inhibitors in metastatic uveal melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4664.