[Up-regulation of thymidine phosphorylase and anti-angiogenesis by interferon alpha in human hepatocellular carcinoma cell line and xenograft]

Abstract

Objective: To further study the impact of interferon-alpha (IFN-alpha) on thymidine phosphorylase (TP) expression and angiogenesis.

Methods: Human hepatocellular carcinoma cells of the line SMMC-7721 were cultured and added with IFN-alpha of different doses: 0 (as control group), 1000, 5000 and 10,000 U/ml. Twenty-four hours later RT-PCR was used to detect the TP mRNA expression. Boyden chamber method was used to examine the endothelial cells migration. Suspension of SMMC-7721 cells was inoculated subcutaneously into 30 male BALB/c-nu/nu mice, the mice were randomly divided into 5 equal groups to be subcutaneously injected with IFN-alpha of different doses: 0 (as control group), 1.0 x 10(6), 3.0 x 10(6), 9.0 x 10(6), and 1.5 x 10(7) U.kg(-1).d(-1) for 3 weeks. The eating behavior, activity, body weight, and tumor size were observed. The rats were killed 2 days after the drug injection was stopped. The subcutaneous tumors were taken out to undergo histological examination and TP protein expression by ELISA. The microvessel density (MVD) was detected using anti-CD34 monoclonal antibody.

Results: The TP mRNA expression of the SMMC-7721 cells induced by IFN-alpha of the doses of 5000 U/ml and 10,000 U/ml significantly increased in comparison with the un-treated SMMC-7721 cells (0 U/ml, P < 0.05). The endothelial cell migration significantly increased in the IFN-alpha 1000 U/ml group compared with the control group (P < 0.001), and then decreased along with the increase of IFN-alpha dose; there were no significant differences in the epithelial migration among the groups of 0, 5000, and 10,000 U/ml IFN-alpha doses (all P > 0.05). The TP protein expression levels of the tumor in the rats treated with IFN-alpha of the doses of 9.0 x 10(6), and 1.5 x 10(7) U.kg(-1).d(-1) were 48 ng/mg +/- 24 ng/mg and 60 ng/mg +/- 6 ng/mg respectively, 1.9 and 2.4 times that of the control group (both P < 0.01). The MVD of the tumors was 6.0 +/- 1.8 in the 9.0 x 10(6) U.kg(-1).d(-1) IFN-alpha group, significantly higher than that of the control group (P < 0.01); and was 4.0 +/- 1.5 in the 1.5 x 10(7) U.kg(-1).d(-1) group, significantly lower than that of the 9.0 x 10(6) U.kg(-1).d(-1) group (P < 0.05) and not significantly different from that of the control group. The tumor inhibiting rate of the 1.5 x 10(7) U.kg(-1).d(-1) IFN-alpha group was 68%, significantly higher than that of the untreated group (P < 0.05).

Conclusion: IFN-alpha of certain doses up-regulate the TP expression, and inhibit the angiogenesis induced by TP as well.