title: Down-regulation of phospho-Akt is a major molecular determinant of bortezomib-induced apoptosis in hepatocellular carcinoma cells.
abstract: Bortezomib, a proteasome inhibitor, has been clinically approved for the treatment of myeloma and lymphoma. Here, we report a differential effect of bortezomib on apoptosis in four hepatocellular carcinoma (HCC) cell lines and identify the major molecular event that determines sensitivity. Although bortezomib inhibited proteasome activity to a similar extent in all HCC cell lines, it showed differential effects on their viability: Huh-7 (IC(50) 196 nmol/L), Sk-Hep1 (IC(50) 180 nmol/L), Hep3B (IC(50) 112 nmol/L), and resistant PLC5 (IC(50) >1,000 nmol/L). Bortezomib caused cell cycle arrest at G(2)-M phase in all HCC cells tested whereas apoptotic induction was found only in sensitive cells but not in PLC5 cells. No significant bortezomib-induced NF-kappaB changes were noted in Huh-7 and PLC5. Bortezomib down-regulated phospho-Akt (P-Akt) in a dose- and time-dependent manner in all sensitive HCC cells whereas no alterations of P-Akt were found in PLC5. Down-regulation of Akt1 by small interference RNA overcame the apoptotic resistance to bortezomib in PLC5 cells, but a constitutively activated Akt1 protected Huh-7 cells from bortezomib-induced apoptosis. Furthermore, bortezomib showed suppression of tumor growth with down-regulation of P-Akt in Huh-7 tumors but not in PLC5 tumors. Down-regulation of P-Akt represents a major molecular event of bortezomib-induced apoptosis in HCC cell lines and may be a biomarker for predicting clinical response to HCC treatment. Targeting Akt signaling overcomes drug resistance to bortezomib in HCC cells, which provides a new approach for the combinational therapy of HCC.
authors.affiliation: Department of Medical Research, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei.
authors.forename: Kuen-Feng
authors.initials: KF
authors.lastname: Chen
authors.forename: Pei-Yen
authors.initials: PY
authors.lastname: Yeh
authors.forename: Kun-Huei
authors.initials: KH
authors.lastname: Yeh
authors.forename: Yen-Shen
authors.initials: YS
authors.lastname: Lu
authors.forename: Shang-Yi
authors.initials: SY
authors.lastname: Huang
authors.forename: Ann-Lii
authors.initials: AL
authors.lastname: Cheng
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D015536:Down-Regulation; D005434:Flow Cytometry; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008819:Mice, Nude; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D061988:Proteasome Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011719:Pyrazines / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D016328:NF-kappa B; D061988:Proteasome Inhibitors; D011719:Pyrazines; D000069286:Bortezomib; D051057:Proto-Oncogene Proteins c-akt