SPARC (secreted protein acidic and rich in cysteine), also known as osteonectin and BM40, is a secreted matricellular glycoprotein . SPARC is produced by fibroblasts, capillary endothelial cells, platelets and macrophages, especially in areas of tissue morphogenesis and remodeling.SPARC is involved in tissue renewal, tissue remodeling, and embryonic development and work by exerting counter-adhesive and antiproliferative effects that lead to changes in cell shape, disruption of cell adhesion, and inhibition of the cell cycle. SPARC is abundantly expressed in bone where it promotes osteoblast differentiation and inhibits adipogenesis. SPARC is highly expressed in many tumor types undergoing an endothelial to mesenchymal transistion; its expression, however, mainly decreases the likelihood of metastasis and confers sensitivity to chemotherapy and radiation.SPARC has also been linked with obesity and diabetes.