Abstract 2141: TAS-115, a novel and highly potent VEGFR/MET inhibitor, shows prominent antitumor efficacy by restoring HGF-mediated hypoxia-resistant phenotype in clear cell sarcoma

Abstract

Abstract <Background> Hepatocyte growth factor (HGF) / HGF receptor (MET) signaling is considered to be involved in chemoresistance to cancer treatment. Notably, many reports have described reduced sensitivity to vascular endothelial growth factor receptor (VEGFR)-targeted inhibitors in patients with high serum HGF levels compared to those with low serum levels. This study investigated whether HGF directly influenced sensitivity to VEGFR-targeted inhibitors in human clear cell sarcoma (CCS) xenograft models using human HGF knock-in (hHGF KI) mice, and evaluated the potency of TAS-115. <Material and methods> MET signaling pathway in SU-CCS-1, a human CCS cell line, were analyzed using Western blotting analysis. To study the effects of hypoxia in SU-CCS-1 cells, culture plates were placed in airtight jars under anaerobic conditions and cell viability was assessed by ATP-based assay. In the in vivo study, SU-CCS-1 cells were subcutaneously implanted into hHGF KI mice, and compounds were orally administered once daily for 14 consecutive days. Tumor vessel density (TVD) was determined by immunohistochemistry using anti-CD31 antibody. <Results> SU-CCS-1 cells expressed MET, and exogenous HGF phosphorylated MET and its downstream factors in SU-CCS-1 cells. Exogenous HGF also significantly enhanced SU-CCS-1 cell proliferation. TAS-115 inhibited HGF-induced MET phosphorylation and SU-CCS-1 cell proliferation in a dose-dependent manner at concentrations higher than 10 nM. In contrast, pazopanib, a VEGFR-targeted multi-kinase inhibitor, could not block HGF-induced phenotypes in SU-CCS-1 cells, even at 1 μM. To evaluate the effects of HGF on the antitumor activities of TAS-115 and pazopanib against SU-CCS-1 cells, these agents were administered in hHGF KI and wild-type (WT) mice bearing subcutaneous SU-CCS-1 tumors. TAS-115 completely suppressed tumor growth and reduced TVD in SU-CCS-1 tumor tissue in both models at a dose of 200 mg/kg/d. In contrast, pazopanib suppressed tumor growth at a dose of 100 mg/kg/d in WT mice but not in hHGF KI mice. However, pazopanib significantly reduced TVD in SU-CCS-1 tumor tissue in both models. HGF is therefore suggested to impact SU-CCS-1 cells rather than mouse endothelial cells. We considered that HGF modulated cell proliferation or survival in SU-CCS-1 cells under hypoxia. Actually, hypoxic conditions induced apoptosis in SU-CCS-1 cells, and endogenous HGF dose-dependently attenuated hypoxia-related apoptosis. TAS-115 clearly restored HGF-mediated cytoprotection under hypoxia but pazopanib did not. <Conclusion> These results suggest that effects of VEGFR-targeted inhibitors are attenuated by HGF-mediated hypoxia resistance, and simultaneous inhibitors of the MET and VEGFR axes, such as TAS-115, are more effective in sarcoma patients with high serum HGF than inhibition of the VEGFR axis alone. Citation Format: Hidenori Fujita, Yukari Yamada, Miki Terasaka, Yayoi Fujioka, Naomoto Harada, Akihiro Hashimoto, Kazutaka Miyadera, Kenichi Matsuo, Kazuhiko Yonekura. TAS-115, a novel and highly potent VEGFR/MET inhibitor, shows prominent antitumor efficacy by restoring HGF-mediated hypoxia-resistant phenotype in clear cell sarcoma. [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 2141.