OBJECTIVETo study methylation of Id4 gene and demethylation effect of arsenic trioxide (ATO) in Raji cells.

METHODSHuman Burkitt's Raji lymphoma cells were cultared and treated with ATO at different concentrations and different time points. Methylated degree of Id4 gene was detected by methylation specificity polymerase chain reaction (MS-PCR), Id4 mRNA expression in Raji cell by reverse transcription polymerase chain reaction (RT-PCR), the growth of cell by MTT assay, and cell apoptosis and cycle distribution by Flow Cytometry (FCM).

RESULTS(1) The Id4 gene exhaustive methylation in control group, and hypermethylation in experimental group were reversed by ATO in a dose-dependent manner. (2) Id4 mRNA expression in Raji cells treated with ATO for 48 h increased gradually with ATO concentration increasing in experimental group. (3) Raji cell growth inhibited rates after different concentrations of ATO treatment for 24, 48, 72 h were 12.15% ∼ 92.17% in the experimental group (P < 0.05). (4) Apoptosis peak emerged after ATO treatment for 48 hours in experimental group, while a much lower apoptosis in control group. (5) After ATO treatment for 48 h in experiment group, the cells were arrested at G(0)/G(1) phase in a dose-dependent manner.

CONCLUSIONId4 gene presents exhaustive methylation in Raji cells. ATO can reverse the hypermethylation of Id4 gene and recover the expression of Id4 mRNA. Hypermethylation of Id4 gene is one of the reasons of Raji cells malignant proliferations.