While the TET family is directly responsible for 5-hmC generation, the co-factor α-ketoglutarate (α-KG) is absolutely required 5-mC to 5-hmC conversion,6α-KG is mainly produced by isocitrate dehydrogenases (IDHs).17 To determine whether IDH and /or TET-family enzymes are responsible for 5-hmC loss in HCC, we examined IDH and TET-family genes expressions in HCC tumor tissues (cohort 1, n=108) using quantitative real-time polymerase chain reaction (qRT-PCR). The gene discussed is IDH2; the disease is hepatocellular carcinoma.