Abstract 4711: Evaluation of effect of autophagy inhibition by SAR405, a selective Vps34 inhibitor, on proliferation of pleural mesothelioma cells

Abstract

Abstract Pleural mesothelioma is a poor prognostic malignancy because the efficacy of therapies remains limited; thus, there is an urgent need to elucidate the pathophysiology leading to newer treatment modalities. Macroautophagy (hereafter referred to as autophagy) is an intracellular degradation system in which cytoplasmic components are degraded by the lysosome. Autophagy plays pivotal roles in various physiological processes, including adaptation to starvation, preimplantation embryonic development, elimination of intracellular pathogens, and regulation of innate and adaptive immunity. In cancer cells, autophagy may have the potential to function protectively for the cells and, alternatively, to work suppressively. It can promote tumor growth in established cancers through autophagy-mediated intracellular recycling, providing substrates for metabolism and maintain that the functional pool of mitochondria. On the other hand, it may lead to a cytotoxic effect called autophagy-dependent cell death. Several reports have demonstrated that autophagy has cytoprotective effects on pleural mesothelioma cell lines. In this study, we assessed effects of inhibition of autophagy using SAR405, which specifically inhibits Vps34 in an early step of autophagy, on pleural mesothelioma cells. Additionally, we investigated whether SAR405 could enhance the growth suppression induced by cisplatin in these cells. Mesothelioma cell lines, including NCI-H28 (H28), NCI-H2452 (H2452), and MSTO-211H (211H), were cultured with 0.1-50 μM SAR405 or 1.0-5.0 μM cisplatin for cell viability analysis using water-soluble tetrazolium salt-8, and cell cycle analysis. For the assessment of autophagy, a plasmid, pMRX-IP-GFP-LC3-RFP-LC3ΔG, was stably transfected into mesothelioma cells. Transfected cells generate GFP-LC3-RFP-LC3ΔG, and it is cleaved into GFP-LC3 and RFP-LC3ΔG by inherent ATG4. GFP-LC3 levels are decreased by autophagy activation, while RFP-LC3ΔG serves as an internal control. SAR405 dose-dependently suppressed cell viability, accompanied by a significantly increase in the proportions of cells in the G2/M phase. The IC50 of SAR405 at 72 hours was 11.5 μM for H28, 16.7 μM for H2452, and 14.9 μM for 211H. SAR405 inhibited autophagy 24 hours after treatment at 2.5 μM for H28 and 211H, and at 5.0 μM for H2452. Furthermore, cisplatin induced autophagy at 5.0 μM for H28, 0.5 μM for H2452, 1.0 μM for 211H. The combination of 2.5-10 µM SAR405 and 0.5-5.0 µM cisplatin exhibited additive or synergistic effects on cell growth inhibition in all plural mesothelioma cell lines. In conclusion, Vps34 inhibition by SAR405 suppressed cell growth in pleural mesothelioma cells, accompanied by autophagy inhibition. The combination of SAR405 and cisplatin resulted in a synergistic inhibition of cell proliferation. Citation Format: Yoshiki Kuwabara, Kosuke Sakai, Shigeru Ishi, Shin Yokosuka, Masatoshi Abe, Tomoyuki Takahashi, Yuichiro Kawano, Hiroaki Nishimura, Maiko Toda-Sasaki, Yumiko Kobayashi-Ogawa, Satoshi Kikuchi, Yusuke Hirata, Hiroyuki Kyoyama, Gaku Moriyama, Nobuyuki Koyama, Kazutsugu Uematsu. Evaluation of effect of autophagy inhibition by SAR405, a selective Vps34 inhibitor, on proliferation of pleural mesothelioma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4711.