title: 7-Ketocholesterol induces P-glycoprotein through PI3K/mTOR signaling in hepatoma cells.
abstract: 7-Ketocholesterol (7-KC) is found at an elevated level in patients with cancer and chronic liver disease. The up-regulation of an efflux pump, P-glycoprotein (P-gp) leads to drug resistance. To elucidate the effect of 7-KC on P-gp, P-gp function and expression were investigated in hepatoma cell lines Huh-7 and HepG2 and in primary hepatocyte-derived HuS-E/2 cells. At a subtoxic concentration, 48-h exposure to 7-KC reduced the intracellular accumulation and cytotoxicity of P-gp substrate doxorubicin in hepatoma cells, but not in HuS-E/2 cells. In Huh-7 cells, 7-KC elevated efflux function through the activation of phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway. 7-KC activated the downstream protein synthesis initiation factor 4E-BP1 and induced P-gp expression post-transcriptionally. The stimulation of efflux was reversible and could not be prevented by N-acetyl cysteine. Total cellular ATP content remained the same, whereas the lactate production was increased and fluorescence lifetime of protein-bound NADH was shortened. These changes suggested a metabolic shift to glycolysis, but glycolytic inhibitors did not eliminate 7-KC-mediated P-gp induction. These results demonstrate that 7-KC induces P-gp through PI3K/mTOR signaling and decreased the cell-killing efficacy of doxorubicin in hepatoma cells.
authors.affiliation: National Research Institute of Chinese Medicine, No. 155-1 Li-Nong Street, Sec. 2, Taipei 112, Taiwan, ROC.
authors.forename: Sheng-Fan
authors.initials: SF
authors.lastname: Wang
authors.forename: Yueh-Ching
authors.initials: YC
authors.lastname: Chou
authors.forename: Nirmal
authors.initials: N
authors.lastname: Mazumder
authors.forename: Fu-Jen
authors.initials: FJ
authors.lastname: Kao
authors.forename: Leslie D
authors.initials: LD
authors.lastname: Nagy
authors.forename: F Peter
authors.initials: FP
authors.lastname: Guengerich
authors.forename: Cheng
authors.initials: C
authors.lastname: Huang
authors.forename: Hsin-Chen
authors.initials: HC
authors.lastname: Lee
authors.forename: Ping-Shan
authors.initials: PS
authors.lastname: Lai
authors.forename: Yune-Fang
authors.initials: YF
authors.lastname: Ueng
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D000111:Acetylcysteine / Q000494:pharmacology; D000903:Antibiotics, Antineoplastic / Q000378:metabolism / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival; D002784:Cholesterol / Q000494:pharmacology; D004317:Doxorubicin / Q000378:metabolism / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D006888:Hydroxycholesterols / Q000494:pharmacology; D007653:Ketocholesterols / Q000378:metabolism / Q000494:pharmacology*; D019344:Lactic Acid / Q000096:biosynthesis; D009840:Oligomycins / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000111:Acetylcysteine; D000903:Antibiotics, Antineoplastic; D000975:Antioxidants; D002784:Cholesterol; D004317:Doxorubicin; D006888:Hydroxycholesterols; D007653:Ketocholesterols; D019344:Lactic Acid; D009840:Oligomycins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D058570:TOR Serine-Threonine Kinases; C011724:cholest-5-en-3 beta,7 alpha-diol; C003001:7-ketocholesterol
keywords: 3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyl tetrazolium; 4E-BP1; 7-KC; 7-Ketocholesterol; 7-ketocholesterol; AKI; Akt kinase inhibitor; ERK; FBS; FLIM; GAPDH; Glycolysis; Hepatoma; LDH; MDR; MTT; NADH; P-Glycoprotein; P-glycoprotein; P-gp; PBMC; PCR; PI3K; PI3K/mTOR; ROS; RT; Rh123; eukaryotic translation initiation factor (eIF) 4E-binding protein 1; extracellular signal-regulated kinase; fetal bovine serum; fluorescence lifetime imaging; glyceraldehyde 3-phosphate dehydrogenase; lactate dehydrogenase; mTOR; mammalian target of rapamycin; multidrug resistance; p70 ribosomal protein S6 kinase; p70S6K; peripheral blood mononuclear cells; phosphatidylinositol 3-kinase; polymerase chain reaction; reactive oxygen species; reduced nicotinamide adenine dinucleotide; reverse transcription; rhodamine 123