title: Insulin resistance contributes to multidrug resistance in HepG2 cells via activation of the PERK signaling pathway and upregulation of Bcl-2 and P-gp.
abstract: Liver tumorigenesis frequently causes insulin resistance which may be used as an independent risk factor for evaluation of survival and post-surgery relapse of liver cancer patients. In the present study, HepG2/IR, an insulin resistant HepG2 cell line, was established by exposing HepG2 cells to 0.5 µmol/l of insulin for 72 h, and comparison of HepG2/IR with the parental HepG2 cells indicated that the HepG2/IR cells showed significantly enhanced resistance to the most frequently used chemotherapeutics for solid tumors, such as cisplatin, 5-fluorouracil, vincristine and mitomycin. Flow cytometric analysis of cisplatin-treated HepG2/IR cells showed a significantly decreased hypodiploid peak and a significantly downregulated expression level of pro-apoptotic protein caspase-3 compared with the parental HepG2 cells. Our data further showed swollen endoplasmic reticulum (ER) in the cisplatin-treated HepG2/IR cells with significantly increased levels of glucose-regulated protein 78 (GRP78), phosphorylated protein kinase R-like ER kinase (p-PERK) and P-glycoprotein (P-gp). There was also an upregulated expression of anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) whereas no significant change was observed for CCAAT-enhancer-binding protein homologous protein (CHOP), which is known to be induced by ER stress and to mediate apoptosis. Our results demonstrated that insulin resistance in HepG2 cells promoted a protective unfolded protein response and upregulated the expression of ER chaperone protein GRP78, which resulted in the phosphorylation of PERK kinase to activate the PERK-mediated ER stress signal transduction pathway and the upregulation of Bcl-2 and P-gp, leading to the inhibition of the caspase-3-dependent apoptosis pathway and to the survival of liver tumor cells.
authors.affiliation: Department of Clinical Laboratory Center, The Second Hospital of Lanzhou University, Lanzhou, Gansu 730000, P.R. China.
authors.forename: Xinyue
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Clinical Laboratory Center, The Second Hospital of Lanzhou University, Lanzhou, Gansu 730000, P.R. China.
authors.forename: Linjing
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Clinical Laboratory Center, The Second Hospital of Lanzhou University, Lanzhou, Gansu 730000, P.R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: Experimental Center, Northwest University for Nationalities, Lanzhou, Gansu 730000, P.R. China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: School of Basic Medical Sciences, Lanzhou University, Lanzhou, Gansu 730000, P.R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Clinical Laboratory Center, The Second Hospital of Lanzhou University, Lanzhou, Gansu 730000, P.R. China.
authors.forename: Minghui
authors.initials: M
authors.lastname: Shen
authors.affiliation: Department of Clinical Laboratory Center, The Second Hospital of Lanzhou University, Lanzhou, Gansu 730000, P.R. China.
authors.forename: Shangdi
authors.initials: S
authors.lastname: Zhang
authors.affiliation: School of Basic Medical Sciences, Lanzhou University, Lanzhou, Gansu 730000, P.R. China.
authors.forename: Hulai
authors.initials: H
authors.lastname: Wei
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology; D002945:Cisplatin / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D000091342:Endoplasmic Reticulum Chaperone BiP; D056945:Hep G2 Cells; D006801:Humans; D007333:Insulin Resistance; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D015398:Signal Transduction; D015854:Up-Regulation; D019892:eIF-2 Kinase / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; C000595707:BCL2 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; C460640:EIF2AK3 protein, human; D019892:eIF-2 Kinase; D002945:Cisplatin