[Investigation on the mechanisms of p15INK4B gene demethylation by valproate in Molt-4 cells].

Objective: To study the antitumour effects of sodium valproate (VPA) on the proliferation, differentiation and cell cycle of Molt-4 cell and to investigate its demethylation mechanisms.

Methods: After Molt-4 cells trated with VPA at different concentrations, cell viability and growth curve were assessed by MTT assay. Cell cycle changes were analyzed by flow cytometry. The expression level of p15, DNA methyltransferase 1 (DNMT-1), DNMT3A and 3B mRNA were detected by RT-PCR and the methylation level was detected by hn-MSPCR.

Results: VPA significantly inhibited the proliferation of Molt-4 cells. After 48 h culture with 5.0 mmol/L VPA, the percentages of Molt-4 cells in G(0)/G(1) phase was (66.87 ± 3.31)% and in S phase was (8.47 ± 2.56)%, while in control group, the cells in G(0)/G(1) phase increased and in S phase decreased significantly. The p15 gene in Molt-4 cells failed to express due to its hypermethylation. The expression level of p15 gene mRNA increased significantly after exposure to VPA for 48 h. As compared with control group, the expression of DNMT-1 was down-regulated in a dose-dependent manner. The expression level of DNMT3B decreased at 10.0 mmol/L concentration.

Conclusion: VPA has a demethylation effect on p15 INK4B gene by inhibiting the DNMT-1 and DNMT3B gene activities to recover p15 gene activity, which arrests Molt-4 cell in G(0)/G(1) phase.