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 dexamethasone(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 effieiencies 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 sequence. TAT mRNA could be induced by Dex, with the maximal induction level being 2.22-folds in SMMC-7721 cells, which was significantly lower than that in HepG2 cells (15.1-fold increase, P<0.01). Dex induced the expression of LUC and CAT genes in SMMC-7721 cells as well as the HepG2 cells. Conclusion: The induction efficiency of Dex for expression of TAT mRNA is decreased in SMMC-7721 cells, which might be due to the unchanged activity of TAT.