The endogenous IDHWT and IDHMUT chondrosarcoma cell lines harbour additional genetic alterations (unpublished data), including CDKN2A loss, and were derived from patients with high-grade (II and III) and differentiated tumours, meaning that these cell lines are representative models for the role of IDH mutations in more advanced tumour stages. This evidence concerns the gene IDH2 and chondrosarcoma.