Characterization of a Human Osteosarcoma Cell Line (Saos-2) with Osteoblastic Properties

Abstract This study examines the osteoblastic properties of the established human osteosarcoma cell line Saos-2. Saos-2 cells inoculated into diffusion chambers, which were implanted i.p. into nude mice, produced mineralized matrix in 4 of 6 chambers at 8 weeks. In 5 of 6 chambers there was a strong positive alkaline phosphatase reaction. In culture the alkaline phosphatase levels increased with time and cell density, reaching very high levels at confluence: 4–7 µmol/mg protein/min. The cells show a sensitive adenylate cyclase response to parathyroid hormone, 50% effective dose = 2.8 nm, which increases with cell density and is further raised by dexamethasone treatment. They also exhibit typical binding of 1-25-dihydroxyvitamin D 3 to 3.2S receptor protein with an apparent K d of 0.21 nm; the numbers of sites per cell were 3,300 at 50,000 cells/cm 2 and 1,800 at 280,000 cells/cm 2 . The presence of osteonectin was visualized with a monoclonal antibody which revealed a reticular pattern on the cell surface. Osteonectin was also detected in the medium by Western blots, migrating at around M r 40,000 in nonreduced gels and M r 44,000 in reduced gels. The Saos-2 cells thus possess several osteoblastic features and could be useful as a permanent line of human osteoblast-like cells and as a source of bone-related molecules.