IDH1 and hepatocellular carcinoma: Many studies had detected the 5-hmC deficiency in various tumors which could be a feature as an important epigenetic marker for tumors.[10–13] Studies had revealed that the degree of 5-hmC deficiency was an independent unfavorable prognostic factor for malignant tumors.[14,15] Studies also had found decreased levels of 5-hmC in HCC and suggested that the shortage of TET and IDH might cause the decrease of 5-hmC.[14] Hepatitis B virus infection is the most common cause of HCC worldwide, especially in China.