OBJECTIVETo detect the methylation status of TMS1 gene and its demethylation by arsenic trioxide (As₂O₃) in K562 cells.

METHODSK562 cells were treated with different concentrations of As₂O₃ for 48 hours. Methylation-specific PCR (MSP) was used to determine the methylation status of TMS1. RT-PCR and Western blot were used to detect the levels of TMS1 mRNA and protein. TMS1 associated apoptosis proteins Bcl-2/Bax were also analyzed by Western blot. Apoptosis were evaluated by flow cytometry using Annexin V/propium iodide (PI) double staining.

RESULTSTMS1 gene was completely methylated in K562 cells and the levels of TMS1 mRNA and protein were low (0.01±0.01, 0.09±0.02), which could be reversed (mRNA: 0.72±0.04; protein: 1.30±0.06; P<0.01) by 2 μmol/L As2O3 via overt demethylation of TMS1 gene. Apoptosis in experiment group (12.24±1.06) was significantly higher than that in control group (2.05±0.16, P<0.05). In experiment group, the down-expression of antiapoptotic protein Bcl-2 and up-expression of pro-apoptotic protein Bax led to an obvious decline ratio of Bcl-2/Bax (0.56±0.12), as compared to the control group (1.94±0.14, P<0.01).

CONCLUSIONAs₂O₃ could up-regulate TMS1 gene expression by reversing its hypermethylation and induced apoptosis by down-regulation of Bcl-2/Bax ratio in K562 cells.

Apoptosis ; drug effects ; Arsenicals ; pharmacology ; CARD Signaling Adaptor Proteins ; Cytoskeletal Proteins ; metabolism ; DNA Methylation ; drug effects ; Down-Regulation ; Gene Expression Regulation, Leukemic ; Humans ; K562 Cells ; Oxides ; pharmacology ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; bcl-2-Associated X Protein ; metabolism