Osteocalcin In Bone Metabolism And Osteotropism Of Cancer

The Biology of Osteocalcin

Osteocalcin is a noncollagenous protein. It is the most abundant matrix protein of bone and dentine (Price, 1992). It is regarded as a marker of bone turnover and metabolism, where bone resorption and formation are coupled. Osteocalcin is syn-thesised exclusively by osteoblasts and secreted into the extracellular matrix (ECM) during bone mineralisation. It is released also during osteoclastic degradation. Therefore, it is considered to be a marker of bone formation when formation and resorption of bone are uncoupled (J.P. Brown et al. 1984; Delmas et al. 1985, 1986; R.H. Christenson, 1997). Osteocalcin expression in developing chick and rat embryos coincides with the onset of mineralisation of the bone and hence it is considered to play a role in this process (Hauschka et al. 1989). Osteocalcin functions as a chemoattractant for osteoblast progenitor cells (Mundy and Poser, 1983). Also, bone resorption is poor under conditions of osteocalcin deficiency (Lian et al. 1984). These observations have supported a role for osteocalcin in bone resorption. Meta-static spread to the bone might activate bone metabolism, and therefore osteocalcin has been investigated as a potential marker of metastatic progression in certain forms of cancer, such as breast cancer and carcinoma of the prostate, which tend to show osteotropic secondary spread. Osteocalcin has turned out to be a good marker for bone turnover in osteoporosis (Delmas et al. 1983; Eastell et al. 1993). Mutations of the gla protein, a member of the osteocalcin family of proteins, have been suggested as a causal factor in the autosomal recessive Keutel syndrome, which is characterised by abnormal calcification of the cartilage (Munroe et al. 1999).

10 Ways To Fight Off Cancer

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