title: Induction of Bim expression contributes to the antitumor synergy between sorafenib and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase inhibitor CI-1040 in hepatocellular carcinoma.
abstract: OBJECTIVE
  Sorafenib has proved survival benefit for patients with advanced hepatocellular carcinoma (HCC). This study explored whether the efficacy of sorafenib can be improved by adding the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor CI-1040 to vertically block the Raf/MEK/ERK pathway.
  
  
  METHODS
  The growth inhibitory effects of sorafenib and CI-1040 were tested in HCC cell lines (Huh-7 and Hep3B) and human umbilical vascular endothelial cells (HUVEC). The potential synergistic growth inhibitory effects were measured by median effect analysis. Apoptosis was measured by flow cytometry. The effects on ERK phosphorylation and levels of apoptosis regulatory proteins were measured by Western blotting. The in vivo antitumor activity of sorafenib and CI-1040 were tested in xenograft HCC models.
  
  
  RESULTS
  Combination of sorafenib and CI-1040 synergistically inhibited ERK phosphorylation and cell growth and induced apoptosis in both HCC cells and HUVECs. Increased expression of Bim protein, which correlated with the extent of ERK inhibition, was found in both HCC cells and HUVECs. Knockdown of Bim expression by small interfering RNA partially abrogated the synergistic proapoptotic effects of sorafenib and CI-1040. Combination therapy inhibited tumor growth significantly better than either single agent in the xenograft models.
  
  
  CONCLUSIONS
  The antitumor effects of sorafenib in HCC can be improved by vertical blockade of Raf/MEK/ERK signaling with CI-1040.
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Da-Liang
authors.initials: DL
authors.lastname: Ou
authors.forename: Ying-Chun
authors.initials: YC
authors.lastname: Shen
authors.forename: Ja-Der
authors.initials: JD
authors.lastname: Liang
authors.forename: Jun-Yang
authors.initials: JY
authors.lastname: Liou
authors.forename: Sung-Liang
authors.initials: SL
authors.lastname: Yu
authors.forename: Hsiang-Hsuan
authors.initials: HH
authors.lastname: Fan
authors.forename: Da-Sheng
authors.initials: DS
authors.lastname: Wang
authors.forename: Yen-Shen
authors.initials: YS
authors.lastname: Lu
authors.forename: Chiun
authors.initials: C
authors.lastname: Hsu
authors.forename: Ann-Lii
authors.initials: AL
authors.lastname: Cheng
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D000072224:Bcl-2-Like Protein 11; D001549:Benzamides / Q000494:pharmacology*; D001557:Benzenesulfonates / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D002470:Cell Survival / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D042783:Endothelial Cells / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D011725:Pyridines / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077157:Sorafenib; D014407:Tumor Cells, Cultured; D048490:raf Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C120227:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D001549:Benzamides; D001557:Benzenesulfonates; D008565:Membrane Proteins; D010671:Phenylurea Compounds; D011518:Proto-Oncogene Proteins; D011725:Pyridines; D034741:RNA, Small Interfering; D009536:Niacinamide; D000077157:Sorafenib; D048490:raf Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases