{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Osteonectin, also known as secreted protein acidic and rich in cysteine (SPARC) or basement-membrane protein 40 (BM-40) is a protein that in humans is encoded by the SPARC gene. Osteonectin is a glycoprotein in the bone that binds calcium. It is secreted by osteoblasts during bone formation, initiating mineralization and promoting mineral crystal formation. Fibroblasts, including periodontal fibroblasts, synthesize osteonectin. This protein is also synthesized by macrophages at sites of wound repair and platelet degranulation, so it may play an important role in wound healing. Osteonectin increases the production and activity of matrix metalloproteinases, a function important to invading cancer cells within bone. Additional functions of osteonectin beneficial to tumor cells include angiogenesis, proliferation and migration as overexpression of osteonectin is reported in many human cancers."}]}]}