Mechanisms involved in ceramide-induced cell cycle arrest in human hepatocarcinoma cells.
OBJECTIVE
To investigate the effect of ceramide on the cell cycle in human hepatocarcinoma Bel7402 cells. Possible molecular mechanisms were explored.


METHODS
[3- (4, 5)-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay, plasmid transfection, reporter assay, FACS and Western blotting analyses were employed to investigate the effect and the related molecular mechanisms of C2-ceramide on the cell cycle of Bel7402 cells.


RESULTS
C2-ceramide was found to inhibit the growth of Bel7402 cells by inducing cell cycle arrest. During the process, the expression of p21 protein increased, while that of cyclinD1, phospho-ERK1/2 and c-myc decreased. Furthermore, the level of CDK7 was downregulated, while the transcriptional activity of PPARgamma was upregulated. Addition of GW9662, which is a PPARgamma specific antagonist, could reserve the modulation action on CDK7.


CONCLUSIONS
Our results support the hypothesis that cell cycle arrest induced by C2-ceramide may be mediated via accumulation of p21 and reduction of cyclinD1 and CDK7, at least partly, through PPARgamma activation. The ERK signaling pathway was involved in this process.
Wang
Jing
J
Research Center for Eco-Environmental Sciences, The Chinese Academy of Sciences, Haidian District, Beijing 100085, China. wangjing@rcees.ac.cn
Lv
Xiao-Wen
XW
Shi
Jie-Ping
JP
Hu
Xiao-Song
XS
D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D047495:PPAR gamma / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000095043:Cyclin-Dependent Kinase-Activating Kinase
D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; C064769:N-acetylsphingosine; D047495:PPAR gamma; D019938:Cyclin D1; D018844:Cyclin-Dependent Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D013110:Sphingosine; D000095043:Cyclin-Dependent Kinase-Activating Kinase; C000722416:CDK7 protein, human