RESUMO
<p><b>OBJECTIVE</b>To detect the methylation status of TMS1 gene and its demethylation by arsenic trioxide (As₂O₃) in K562 cells.</p><p><b>METHODS</b>K562 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.</p><p><b>RESULTS</b>TMS1 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).</p><p><b>CONCLUSION</b>As₂O₃ could up-regulate TMS1 gene expression by reversing its hypermethylation and induced apoptosis by down-regulation of Bcl-2/Bax ratio in K562 cells.</p>