Two mechanisms have been reported that dysfunction of IDH and/or TET enzymes, two key factors in 5-hmC generation, that would lead to greatly decreased 5-hmC levels in human tumors: loss-of-function mutations target TET2 and IDH1/2 mutations that result in TET activity inhibition via α-KG reduction and 2-hydroxyglutarate accumulation.17, 29, 30 HCC harbors no IDH1 mutations,31 recent studies found IDH2 protein decreased in HCC.9 Herein, we demonstrated IDH1 and IDH2 had similar RNA expressions in both HCC and peritumoral liver tissues. The gene discussed is IDH1; the disease is hepatocellular carcinoma.