Curcuminoids Activate TET Enzymes and Increase DNA Hydroxymethylation and Active Demethylation in Leukemia Cells

Curcuminoids demonstrate diverse pharmacological activity as antioxidant, neuroprotective, antitumor, and anti-inflammatory drugs. Dimethoxycurcumin (DMC) is a metabolically stable analog of curcumin, and both drugs modify the activity of several epigenetic enzymes that affect DNA methylation and histone modifications. 5-hydroxymethylcytosine (5hmC) is an epigenetic mark involved in active demethylation and in gene expression regulation. The effect of curcuminoids on the activity and expression of TET enzymes involved in 5hmC oxidation and active demethylation in leukemia cells is unclear. In this study, we investigated the impact of curcumin and DMC on the activity and expression of the three isoforms of TET enzymes. We also studied their effect on global 5hmC and performed a genome-wide analysis of 5hmC distribution at the single CpG level using oxidative bisulfite sequencing, which can differentiate between 5hmC and 5-methylcytosine. Both curcumin and DMC increased the activity and the mRNA expression of the three isoforms of TET. Concordantly, they also increased the global 5hmC level in leukemia cells. Single CpG analysis showed that both drugs induced a 5hmC increase and active demethylation at gene promoters, CpG islands and shores, exons, introns, and intergenic regions. Curcumin induced a promoter 5hmC increase in 194 genes and promoter-active demethylation in 154 genes. On the other hand, DMC induced a promoter 5hmC increase in 173 genes and promoter-active demethylation in 171 genes. Our study identifies curcuminoids as active demethylators through the activation of TET enzymes and provides a rationale for testing their combination with DNA hypomethylating agents in leukemia animal models.