ARE MG-63 AND HOS TE85 HUMAN OSTEOSARCOMA CELL-LINES REPRESENTATIVE MODELS OF THE OSTEOBLASTIC PHENOTYPE

The aim of this study was to perform a systematic comparison of two widely used osteosarcoma cell lines and ascertain their relevance as experimental models for investigating osteoblast function. We have therefore compared growth, differentiated cell function, integrin expression and adhesive profiles of MG-63, HOS TE85, and human bone derived cells. Both osteosarcoma cell lines proliferated more rapidly than osteoblast-like cells with HOS cells exhibiting the shortest doubling time. HOS cells expressed higher levels of alkaline phosphatase than MG-63 cells under basal conditions but only MG-63 cells showed the increased enzyme activity following 1,25-dihydroxyvitamin D-3 (1,25(OH)(2)D-3) administration, which is characteristic of bone derived cells. Osteocalcin was not detected in supernatants from any cells under basal conditions but levels produced by MG-63 cells on addition of 1,25(OH)(2)D-3 were comparable with those of osteoblast-like cells. alpha 1, alpha 2, alpha 3, alpha 5, alpha V, and beta 1 integrin subunits were detected on all cells and there was no staining for alpha L, alpha M, beta 2, and beta 3. alpha 3 and beta 1 were the major subunits detected on MG-63, HOS, and bone derived cells but relative concentrations of other or subunits were dependent on cell type; alpha 4 and alpha 6 subunits could only be detected on osteosarcoma cell lines. Short term, serum-free cell adhesion assays showed that the three cell types adhered in a saturable manner to collagen I, fibronectin, and laminin. Maximal adhesion of osteosarcoma cell lines and human bone derived cells was observed after 2 hours and similar extracellular matrix protein coating concentrations were required by the three cell types to achieve optimum binding: maximal adhesion to collagen I and fibronectin occurred at 0.1-0.5 mu g/cm(2) and maximal adhesion to laminin occurred at 5-10 mu g/cm(2). These studies indicate that both osteosarcoma cell lines provide appropriate models for studying integrin subunit expression and cell adhesion. In addition, MG-63 cells are also suitable for investigating regulation and production of osteocalcin by human osteoblast-like cells. Proliferation and alkaline phosphatase activity exhibited by both MG-63 and HOS TE85 cells were not very representative of bone cell cultures and therefore neither cell line is ideally suited to studying these aspects of osteoblast function.