COX4I2 and hereditary pheochromocytoma-paraganglioma: COX4I2, as a new marker, can promote angiogenesis and epithelial–mesenchymal transition and has been widely discussed in pheochromocytoma, colorectal cancer, and respiratory diseases.[47–50] However, the specific mode of action of COX4I2 in chondrocytes remains to be elucidated.