Prolonged treatment with DNMT inhibitors induces distinct effects in promoters and gene-bodies

Area of Science:

• Epigenetics
• Cancer Biology
• Hematology

Background:

• Demethylating drugs 5-azacytidine (AZA) and decitabine (DAC) are effective treatments for Myelodysplastic Syndromes (MDS).
• The precise mechanisms by which low-dose AZA and DAC impact the methylome are not fully understood.
• Previous research focused on high-dose effects or specific gene promoter methylation.

Purpose of the Study:

• To characterize genome-wide DNA methylation changes induced by prolonged low-dose AZA and DAC treatment in a leukemic cell model.
• To investigate the effect of nano-molar drug concentrations on the methylome.
• To determine the relationship between DNA demethylation, gene expression, and CpG island (CGI) methylation.

Main Methods:

• Genome-wide analysis of DNA methylation patterns.
• Prolonged continuous treatment of SKM-1 leukemic cells with nano-molar concentrations of AZA and DAC for one month.
• Correlation analysis between CGI methylation and gene expression.

Main Results:

• Continuous low-dose AZA and DAC treatment for one month halved hypermethylated probes in leukemic cells.
• Identified 803 candidate regions with significant demethylation.
• Demethylation preferentially occurred at promoter CGIs, while gene-body CGIs showed resistance.
• The correlation between promoter CGI methylation and gene expression was lost post-treatment.

Conclusions:

• Low-dose demethylating agents can induce significant genome-wide DNA demethylation, particularly at promoter regions.
• Demethylation at promoters is not always sufficient to alter gene expression, suggesting other regulatory mechanisms maintain cellular states.
• These findings provide insights into the epigenetic effects of low-dose hypomethylating therapy in hematologic malignancies.