Involvement of Egr-1 in HGF-induced elevation of the human 5alpha-R1 gene in human hepatocellular carcinoma cells.
Steroid 5alpha-reductase 1 (5alpha-R1), a key enzyme in the conversion of steroids into their respective 5alpha-reduced derivatives, plays a key role in some hormone-dependent tumours and is abundant in the liver, although it is also widely distributed throughout the body. HGF (hepatocyte growth factor) is a pleiotropic cytokine/growth factor involved in the progression of hepatocellular carcinoma. In the present paper, we report the stimulatory effect of HGF on human 5alpha-R1 transcription in hepatocellular carcinoma cells. Pre-treatment with actinomycin D or cycloheximide blocked the up-regulation of 5alpha-R1 mRNA expression by HGF, indicating that the increased level of 5alpha-R1 mRNA expression is regulated by transcriptional activation and was dependent on de novo protein synthesis. Functional analysis of the 5'-flanking region of the 5alpha-R1 gene by transfection analysis showed that the -79 to -50 region functioned as the HGF-responsive region. Mutagenesis and electrophoretic mobility-shift assays demonstrated that induction of 5a-R1 by HGF is mediated by an Egr-1 (early growth-response gene 1)-binding site at -60/-54. In addition, overexpression of Egr-1 was sufficient to transactivate 5alpha-R1 promoter activity, and knockdown of Egr-1 with gene-specific small interfering RNA resulted in inhibition of HGF-induced up-regulation of endogenous 5alpha-R1 expression. These data provide the first evidence that HGF stimulates 5alpha-R1 expression through up-regulation of the transcription factor Egr-1, thus suggesting the possibility that regulation of steroid metabolism by HGF represents a mechanism for high risk of hepatocellular carcinogenesis in males.
Rui
Caixia
C
Beijing Institute of Radiation Medicine, 27 Taiping Road, Beijing 100850, P.R. China.
Li
Changyan
C
Xu
Wangxiang
W
Zhan
Yiqun
Y
Li
Yonghui
Y
Yang
Xiaoming
X
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000235:genetics* / Q000378:metabolism*; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D051766:Early Growth Response Protein 1 / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects* / Q000235:genetics; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D015533:Transcriptional Activation / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects
C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017228:Hepatocyte Growth Factor; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase; C476566:steroid-5alpha-reductase type 1