The E-cadherin gene is silenced by CpG methylation in human hepatocellular carcinomas

5-Aza-2'-deoxycytidine-induced T-cadherin expression in HepG2-derived tumors and its inhibitory effects on tumor growth in nude mice

AIM: To observe 5-Aza-2'-deoxycytidine (5-Aza-CdR)-induced T-cadherin gene expression in HepG2 cells and to determine its inhibitory effects on proliferation of HepG2-derived tumor cells in nude mice.

METHODS: The HepG2-derived tumor model in nude mice was established by subcutaneous inoculation. Twenty-one Nude mice were randomly divided into two groups: the experiment group (n = 11) and control group (n = 10). Experiment group nude mice were intraperitoneally injected with 5-Aza-CdR while control group nude mice were only given equivalent volume of PBS. The mice were killed at week 4. Tumor growth in nude mice was observed, and the T-cadherin mRNA and protein expressions of the tumors were detected using reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry.

RESULTS: At the end of the fourth week, the T-cadherin mRNA expression in the tumors of the experiment group was significantly higher than that the control group (t = 6.613, P < 0.05). Immunohistochemistry further showed that the protein expression of T-cadherin was almost not detected in the HepG2-derived tumor cells of the control group w while the T-cadherin expression was detected on the membranes of the HepG2-derived tumor cells of the experiment group. After 4 weeks' treatment with 5-Aza-CdR, the average volume of HepG2-derived tumors in the experiment group was significantly smaller than that in the control group (t = 2.337, P = 0.025).

CONCLUSION: 5-Aza-CdR induces HepG2 cells to re-express T-cadherin and inhibits growth of HepG2-derived tumors in nude mice. Its mechanism may be that demethylation of the methylated T-cadherin promoter induced by 5-Aza-CdR restores T-cadherin reexpression and thus inhibits the growth of the HepG2-derived tumors in nude mice.