Abstract 5837: Acquired resistance to anticancer drug of high glucose-exposed HepG2

Abstract

Abstract Reports show that diabetic patients with cancer tend to show resistance to anticancer drug treatment and have poor prognosis compared to non-diabetic patients. We observed that HepG2-HG, which is a derivative of the hepatocellular carcinoma cell line HepG2 exposed continuously to high glucose, shows high resistance to etoposide. In this study, we aimed to understand the involvement of excretion transporter and apoptosis regulatory factor in anti-cancer drug resistance in HepG2-HG. HepG2 was cultured in minimum essential medium (MEM) (with 5.5 mM glucose), and HepG2-HG was cultured in MEM supplemented with up to 25 mM glucose. Sensitivity to anticancer drugs was evaluated by the SRB assay. mRNA expression was assessed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) on Rotor-Gene Q using the KAPA SYBR FAST qPCR kit. Proteins extracted using the Ultra-RIPA kit were electrophoresed, transferred to a membrane by the iBlot 2 gel transfer device, reacted with antibodies, and evaluated for expression using enhanced chemiluminescence (ECL) prime reagent. IC50 values of etoposide in HepG2 and HepG2-HG were 0.59 µM and 17.5 µM, respectively. Comparison of the expression of the excretion transporter showed that the expression of p-glycoprotein (p-gp) was markedly enhanced in HepG2-HG compared to that in HepG2. Continuous contact of HepG2-HG with high glucose induced the expression of the glucose transporter GLUT1, which may provide a survival mechanism for cancer cells via escape from hypoxia-induced apoptosis. Furthermore, the expression of phospho-p70S6K was high in HepG2-HG, suggesting an increase in the activity of the mammalian target of rapamycin (mTOR). Therefore, we suggest that increased p-gp expression and mTOR activity in HepG2-HG provided resistance to etoposide by decreasing intracellular drug levels and suppressing the apoptotic mechanism. Estimation of the contribution of both mechanisms to etoposide resistance of HepG2-HG requires further examination. Citation Format: Shuichi Kishimoto, Shoji Fukushima. Acquired resistance to anticancer drug of high glucose-exposed HepG2 [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 5837.