SMAD1 and chondrosarcoma: First, p-SMAD3 and p-SMAD1/5 accumulated in nuclei of chondrosarcoma cells, whereas PEG10 was abundantly expressed in enchondroma cells, indicating that expression of PEG10 and activated R-SMADs were mutually exclusive between these benign and malignant cartilage tumours (Fig. 6a).