Epigenetic identity in AML is mostly dependent on disruption of non-promoter regulatory elements and reveals potentially antagonistic effects of mutations in epigenetic modifiers [human]

Aberrant DNA methylation of gene promoters is a hallmark of AML. To define how cytosine methylation is redistributed in AML more precisely we performed base-pair resolution methylome sequencing in 119 patients. We find that leukemic DNA methylation patterning is tightly linked to somatic mutations and primarily driven by regulatory elements outside of promoters and by CpG shores as opposed to CpG islands. Active enhancers displayed much stronger focal differential methylation than promoters and were generally aberrantly hypomethylated except in IDH2 mutant and CEBPA silenced AMLs. AMLs with dominant hypermethylation feature greater epigenetic disruption of promoters. Those with dominant hypomethylation, such as DNMT3A mutated AMLs, display greater disruption of distal and intronic regions. IDH mutant AMLs manifest profound hypermethylation whereas DNMT3A mutant AMLs manifest profound hypomethylation of a different set of CpGs. In striking contrast, AMLs with co-occurring IDH1 and DNMT3A mutations exhibited epigenetic antagonism in which most CpGs affected by either mutation alone were no longer affected in the double mutant cases. These patients featured a unique gene expression profile featuring deregulated expression of RAS pathway that was not linked to DNA methylation. Overall design: Enhanced Reduced Representation Bisulfite Sequencing (ERRBS) was performed on 119 AML samples, which are a subset of those profiled using HELP in PMC3008568.