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

Area of Science:

• Epigenetics
• Molecular Biology
• Cancer Research

Background:

• Doxorubicin resistance in acute myelogenous leukemia (AML) is a significant clinical challenge.
• Down-regulation of the catalase gene (CAT) has been observed in resistant AML cells.
• Epigenetic modifications are increasingly recognized as key regulators of gene expression in cancer.

Purpose of the Study:

• To investigate the role of epigenetic mechanisms, specifically DNA methylation and histone modifications, in the down-regulated expression of the catalase gene (CAT) in doxorubicin-resistant AML cells (AML-2/DX100).

Main Methods:

• Bisulfite-sequencing PCR to assess DNA methylation status of the CAT gene's CpG island.
• Chromatin immunoprecipitation (ChIP) assay to evaluate histone H4 acetylation levels.
• Treatment with hydrogen peroxide (H2O2), histone deacetylase inhibitor (trichostatin A - TSA), and DNA methylation inhibitor (5-aza-2'-deoxycytidine - 5-AdC) to observe effects on CAT expression.

Main Results:

• Down-regulated CAT expression in AML-2/DX100 cells was restored by H2O2 and TSA, with only a slight increase upon 5-AdC treatment.
• Bisulfite-sequencing PCR showed no methylation of the CAT gene's CpG island in AML-2/DX100 cells.
• ChIP assays confirmed significantly decreased histone H4 acetylation in AML-2/DX100 cells compared to AML-2/WT cells, with TSA showing a greater increase than 5-AdC.
• Other peroxidase genes were overexpressed, potentially compensating for reduced H2O2-scavenging activity due to down-regulated CAT.

Conclusions:

• Histone H4 deacetylation, rather than DNA methylation, is the primary epigenetic mechanism responsible for the down-regulated CAT expression in doxorubicin-resistant AML cells.
• This epigenetic alteration contributes to the adaptation of AML cells to oxidative stress, a characteristic of drug resistance.