IDH1 and hepatocellular carcinoma: IDH1/2 are frequently mutated in cancers, but not in HCC, and the gain-of-function IDH1/2-mutantenzymes lead to the accumulation of the oncometabolite D-2-hydroxyglutarate, resulting in aberrant DNA and histone methylation by competitively inhibiting enzymes such as TET and JMJD.67