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.
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.
Ou
Da-Liang
DL
Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
Shen
Ying-Chun
YC
Liang
Ja-Der
JD
Liou
Jun-Yang
JY
Yu
Sung-Liang
SL
Fan
Hsiang-Hsuan
HH
Wang
Da-Sheng
DS
Lu
Yen-Shen
YS
Hsu
Chiun
C
Cheng
Ann-Lii
AL
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
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