[Silence mechanism of WT1 gene in leukemic cell line U937]

This study was aimed to investigate the methylation status of WT1 gene in leukemia cell lines and its relation with expression of WT1 gene. The WT1 gene was silenced by DNA methylation or histone deacetylation, and the expression of WT1 gene was induced by using HDAC inhibitor and/or demethylation agent of DNA. Some leukemia cell lines (U937, HL-60, K562, KG1) were detected by RT-PCR, MS-PCR, restriction analysis, and DNA sequencing. U937 leukemic cells without WT1 mRNA expression were incubated with HDAC inhibitor Trichostatin A (TSA) and/or demethylation agent decitabine. The results showed that the U937 cells did not express WT1 gene, but HL-60, K562 and KG1 cells highly expressed WT1 gene; WT1 gene was unmethylated in HL-60 cells, but methylated in K562 and U937 cells. WT1 expression could be reactivated by co-incubation with TSA and decitabine, but not was observed by using single drug. It is concluded that WT1 promoter is methylated in some leukemia cells, however, the methylation can not affect its expression. DNA methylation and deacetylation of histones are synergistic to inhibit the expression of WT1 in leukemic U937 cells, the combination of TSA with decitabine can induce expression of WT1 gene.