[Interferon-alpha upregulates thymidine phosphorylase expression via JAK-STAT transcriptional activation and mRNA stabilization in human hepatocellular carcinoma SMMC-7721 cells].

Objective: To examine how the thymidine phosphorylase (TP) gene expression is upregulated by interferon-alpha (IFN-alpha) in human hepatocellular carcinoma SMMC-7721 cells.
Methods: TP mRNA levels were determined by RT-PCR. Whether the JAK-STAT cascade mediates IFN-alpha-induced TP mRNA expression was studied by pretreatment with Janus Kinase (JAK) inhibitor, AG-490. Effects of IFN-alpha on TP mRNA stability were detected with additional actinomycin D.
Results: The expression of TP mRNA was induced by IFN-alpha in a dose- and time-dependent manner in SMMC-7721 (human hepatocellular carcinoma) cells. TP mRNA levels rose at 8 h, reached the peak value at 12 h, and remained at a high level up to 72 h in SMMC-7721 cells treated with IFN-alpha 10000 U/ml. IFN-alpha at a dose of 5000 or 10000 U/ml up-regulated TP expression about 3 fold compared with that of non-treated cells (P < 0.05). Induction of TP mRNA expression by IFN-alpha was significantly inhibited in SMMC-7721 cells by pretreatment with AG-490, in comparison with that treated with IFN-alpha alone. Pretreatment of SMMC-7721 cells with IFN-alpha 10000 U/ml for 24 h caused a substantial stabilization of TP mRNA, with a half-live of 35.8 h, compared with 8.5 hr in the control SMMC-7721 cells.
Conclusion: IFN-alpha at certain doses upregulates TP mRNA expression via both JAK-STAT transcriptional activation and post-transcriptional mRNA stabilization in human hepatocellular carcinoma SMMC-7721 cells.