EVIDENCE FOR FUNCTIONAL PLATELET-DERIVED GROWTH-FACTOR RECEPTORS ON MG-63 HUMAN OSTEO-SARCOMA CELLS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (7) , 2966-2970
Abstract
The specific interaction of platelet-derived growth factor (PDGF) with the human osteosarcoma cell line MG-63 was studied. Scatchard analysis of 125I-PDGF binding to MG-63 cells indicated there were 32,000 specific PDGF-binding sites per cell with a Kd of 2.4 .times. 10-11 M. Unlabeled PDGF blocked the specific binding of labled PDGF to MG-63 cells at concentrations > 1 ng/ml. When assayed for phosphorylation of MG-63 membrane vesicles, PDGF was shown to stimulate a dose-dependent phosphorylation of a protein (phosphoprotein with a MW of 185,000) which was stable in 1 M NaOH. In the absence of PDGF, a prominent alkali-stable phosphoprotein with a MW of 116,000 was noted. PDGF also stimulated a dose-dependent increase in [3H]aminoisobutyric acid uptake, [3H]thymidine incorporation and cell proliferation. When tested for secretion of PDGF-like factors, the mitogenic activity of MG-63-conditioned serum-free medium was not blocked by anti-PDGF antiserum. Concentrated MG-63 conditioned medium did not compete with 125I-PDGF for specific receptor sites on diploid fibroblasts. Therefore, MG-63 osteosarcoma cells have functinal PDGF receptors and do not secrete PDGF-like mitogens.

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