Histone H4 deacetylation down-regulates catalase gene expression in doxorubicin-resistant AML subline

We explored if epigenetic mechanisms could be involved in the down-regulated expression of catalase gene (CAT) in the doxorubicin-resistant acute myelogenous leukemia (AML)-2/DX100 cells. Down-regulated CAT expression in AML-2/DX100 cells was completely recovered after treatment of hydrogen peroxide (H2O2) and histone deacetylase inhibitor, trichostatin A (TSA) but was increased slightly by the treatment of DNA methylation inhibitor, 5-aza-2'-deoxycytidine (5-AdC). Bisulfite-sequencing PCR revealed that a CpG island of CAT was not methylated in AML-2/DX100 cells. Chromatin immunoprecipitation assay confirmed that acetylation of histone H4 in AML-2/DX100 cells significantly decreased as compared with that in AML-2/WT cells, which was significantly increased by TSA more than 5-AdC. Meanwhile, overexpression of other up-regulated peroxidase genes appears to make compensation for decreased H2O2-scavenging activity for the down-regulated CAT expression in AML-2/DX100 cells. These results suggest that histone H4 deacetylation is responsible for the down-regulated CAT expression in AML-2/DX100 cells, which are well adapted to oxidative stress.