mIDH -associated DNA hypermethylation in acute myeloid leukemia reflects differentiation blockage rather than inhibition of TET-mediated demethylation.

Isocitrate dehydrogenases 1 and 2 ( IDH1/2 ) are recurrently mutated in acute myeloid leukemia (AML), but their mechanistic role in leukemogenesis is poorly understood. The inhibition of TET enzymes by D-2-hydroxyglutarate (D-2-HG), which is produced by mutant IDH1/2 ( mIDH1/2 ), has been suggested to promote epigenetic deregulation during tumorigenesis. In addition, mIDH also induces a differentiation block in various cell culture and mouse models. Here we analyze the genomic methylation patterns of AML patients with mIDH using Infinium 450K data from a large AML cohort and found that mIDH is associated with pronounced DNA hypermethylation at tens of thousands of CpGs. Interestingly, however, myeloid leukemia cells overexpressing mIDH , cells that were cultured in the presence of D-2-HG or TET2 mutant AML patients did not show similar methylation changes. In further analyses, we also characterized the methylation landscapes of myeloid progenitor cells and analyzed their relationship to mIDH -associated hypermethylation. Our findings identify the differentiation state of myeloid cells, rather than inhibition of TET-mediated DNA demethylation, as a major factor of mIDH -associated hypermethylation in AML. Furthermore, our results are also important for understanding the mode of action of currently developed mIDH inhibitors.
Competing Interests: Conflict of interest: The authors declare no conflict of interest.