MEKK1 induces c-Jun complexes that act as negative regulators for cell survival and proliferation of HCC cells.
c-Jun has a variety of functions including proliferation, differentiation and death. c-Jun is specifically phosphorylated by c-Jun N-terminal kinase (JNK) which is regulated by Ras-MEKK1-MKK4/7 pathway. Previous studies showed that c-Jun protein plays a positive role in cell proliferation of normal hepatocytes and was detected in hepatocellular carcinoma (HCC) tissues. However, the function of c-Jun in HCC cells has not been examined. The aim of this study was to investigate whether the MEKK1-JNK signaling pathway and c-Jun may be involved in the survival and proliferation of HCC. Surprisingly, an active not dominant negative form of MEKK1 (CA-MEKK1) remarkably inhibited the colony formation of HCC cells. Gel retardation assays indicated that CA-MEKK1 induces c-Jun DNA binding, and luciferase assays exhibited that CA-MEKK1 enhances the transactivating activity of c-Jun in HCC cells. These results suggested that the inhibitory effect of CA-MEKK1 on colony formation is likely to be mediated by c-Jun. As expected, when wild-type c-Jun was transfected, the colony formation was significantly reduced. Especially in HuH7 cells, c-Jun transfected cells failed to make any colonies. Our data suggested that c-Jun activation can induce negative effect on survival and proliferation of HCC cells.
Komoda
Fumitake
F
Department of Medicine and Clinical Oncology (K1), Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuou-ku, Chiba 260-8670, Japan.
Shino
Yuji
Y
Hirano
Tatsuya
T
Okutomi
Yoshiyuki
Y
Okamoto
Hideki
H
Hayashi
Yukio
Y
Suyama
Takahito
T
Ebara
Masaaki
M
Saisho
Hiromitsu
H
Shirasawa
Hiroshi
H
D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D002455:Cell Division / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D004273:DNA, Neoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008113:Liver Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D048728:MAP Kinase Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000096:biosynthesis / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D018808:Transcription Factor AP-1; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human