HDAC4 and osteosarcoma: In conclusion, different from the role of inducing osteosarcoma cell apoptosis, HDAC4‐NT of 1‐289aa has no obvious effect in chondrocytes and cartilage tissue, but HDAC4‐NT of 1‐669aa can induce chondrocyte apoptosis via the p53‐dependent ERS pathway, which may be related to the inclusion of almost all the important binding sites and PTM sites of HDAC4 in the 1‐669aa segment.