COL1A2 and bone metastasis: Bone turnover biomarkers used in preclinical and clinical research of bone metastasis usually include serum bone-specific alkaline phosphatase (BALP), osteocalcin (OCN), and procollagen type I N propeptide, as well as pyridinoline, deoxypyridinoline, aminoterminal crosslinked telopeptide of type I collagen (NTX-I), and carboxy-terminal crosslinked telopeptides of collagen type I (CTx-I and ICTP) (11).