Synergistic antitumor effects of combination PI3K/mTOR and MEK inhibition (SAR245409 and pimasertib) in mucinous ovarian carcinoma cells by fluorescence resonance energy transfer imaging.

Kanako Inaba,Tetsu Yano,Yutaka Osuga,Kazuhiro Aoki,Kenbun Sone,Kei Kawana,Tomoyuki Fujii,Tomohiko Fukuda,Yuji Ikeda,Takahide Arimoto,Katsutoshi Oda,Aki Miyasaka,Tomoko Kashiyama,Chinami Makii,Osamu Wada-Hiraike

doi:10.18632/oncotarget.8807

Abstract

The aim of this study was to clarify the synergistic effects of dual inhibition of the PI3K/mTOR and MAPK pathways in ovarian mucinous carcinoma (OMC) cells, using fluorescence resonance energy transfer (FRET) imaging. We exposed 6 OMC cell lines to a PI3K/mTOR inhibitor (voxtalisib, SAR245409) and/or a MEK inhibitor (pimasertib), and evaluated synergistic effects using the Chou–Talalay method. Then, S6K (PI3K pathway) and ERK (MAPK pathway) kinase activities, and their individual proliferative or cytotoxic effects were calculated by time-lapse FRET imaging. In combination with SAR245409, pimasertib (30 nM) synergistically inhibited cell growth (combination indexes: 0.03–0.5) and induced apoptosis in all 6 OMC cell lines. FRET-imaging results demonstrated that ERK inhibition induced both anti-proliferation and apoptosis in a dose-dependent manner in both MCAS and OAW42 cells. However, S6K inhibition suppressed proliferation in a threshold manner in both cell lines, although apoptosis was only induced in OAW42 cells. These results demonstrated that combined PI3K/mTOR and MEK inhibition exhibited synergistic antitumor effects in OMC cells and that FRET imaging is useful for analyzing kinase activities in live cells and elucidating their cytostatic and cytotoxic effects.

Highlights

Ovarian cancer is a leading cause of death among patients with gynecologic malignancies [1, 2]
The aim of this study was to clarify the synergistic effects of dual inhibition of the phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MAPK) pathways in ovarian mucinous carcinoma (OMC) cells, using fluorescence resonance energy transfer (FRET) imaging
These results demonstrated that combined PI3K/mTOR and MEK inhibition exhibited synergistic antitumor effects in OMC cells and that FRET imaging is useful for analyzing kinase activities in live cells and elucidating their cytostatic and cytotoxic effects

Summary

Introduction

Ovarian cancer is a leading cause of death among patients with gynecologic malignancies [1, 2]. Co-targeting the PI3K/ mTOR and MAPK pathways synergistically inhibited the growth of various ovarian cancer cell lines [13]. We recently reported that combination treatment with a PI3K/mTOR inhibitor, SAR245409 (voxtalisib), and a MEK inhibitor, pimasertib, showed synergistic antitumor effects in 6 out of 12 endometrial cancer cell lines and that mutational statuses of KRAS, PIK3CA, and PTEN were not involved [17]. Pimasertib, alone or in combination with SAR245409, is currently being investigated in Phase I–II trials. These findings suggest that cotargeting the PI3K/mTOR and MAPK pathways might be a therapeutic option for certain OMC cells and that the synergy of dual inhibition might differ among cell lines, even within the same OMC histological types

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