IDH1 and chondrosarcoma: To further confirm that it is the loss of IDH1mut rather than that of IDH1wt is responsible for the attenuated tumorigenicity of chondrosarcoma cells, we restored wild-type IDH1 expression in JJ012 and HT1080 IDH1 KO cells through the introduction of lentiviral vectors expressing Flag-tagged IDH1wt.