Lost sensibility of tyrosine aminotransferase to dexamethasone in human hepatoma cell line SMMC-7721 / 第二军医大学学报

ABSTRACT

Objective:To investigate the mechanism responsible for lost sensibility of tyrosine aminotransferase(TAT)to dexam- ethasone(Dex)in human hepatoma cell line SMMC-7721 through examining the cDNA sequence of TAT and the status of glucocorticoid receptor(GR)pathway.Methods:The TAT cDNA fragment containing the full length of coding sequence was amplified by reverse transcription-polymerase chain reaction(RT-PCR)and was sequenced.The expression of TAT mRNA was determined by real-time quantitative PCR to observe the influence of Dex on expression of TAT mRNA in SMMC-7721 cells.The experiement with HepG2 cells was performed as the control.Reporter genes(GRE-tk-LUC and GRE-MMTV-CAT)were transiently transfected into SMMC-7721 cells by electroporation.The induction efficiencies of LUC and CAT genes expression by Dex were examined and compared between SMMC-7721 cells and HepG2 cells.Results:The results showed that there was a same-sense mutation(Gln576Gln)in TAT cDNA se- quence.TAT mRNA could be induced by Dex,with the maximal induction level being 2.22-folds in SMMC-7721 cells,which was signifi- cantly lower than that in HepG2 cells(15.1-fold increase,P