IDH2 and TET2 mutations are mutually exclusive in AML (Figueroa et al., 2010, Gaidzik et al., 2012), and it has been reported that expression of mutant IDH or administration of 2HG can inhibit TET2 in vitro and in vivo, resulting in decreased production of 5hmC (Figueroa et al., 2010, Sasaki et al., 2012a, Xu et al., 2011) and reduced DNA demethylation (Pastor et al., 2013). The gene discussed is IDH1; the disease is acute myeloid leukemia.