COL2A1 and osteosarcoma: Its overexpression induces suppression of SMAD3, resulting in inhibition of cell proliferation, migration, and invasion in osteosarcoma cells (Gu et al., 2020), and in downregulation of COL2A1 and Aggrecan and upregulation of ADAMTS in chondrocytes, which may be involved in the development of osteoarthritis (Li et al., 2015).