IDH1 and central nervous system cancer: IDH1 is a critical enzyme of TCA cycle that catalyzes the conversion of isocitrate to alpha-ketoglutarate.28 And IDH1/2 genes are mutated in some cancers, including gliomas, osteosarcoma, and AML.29 The present study revealed the overexpression of IDH1 in osteosarcoma and high IDH1 protein level was correlated with poor prognosis of osteosarcoma patients.