title: PDGF induces c-myc mRNA expression in MG-63 human osteosarcoma cells but does not stimulate cell replication.
abstract: The platelet-derived growth factor (PDGF) modulated growth response of the MG-63 human osteosarcoma cell line, which neither expresses c-sis mRNA nor secretes a PDGF analogue, was characterized. Scatchard analysis demonstrated that the MG-63 cells have 23,000 receptors per cell with a Kd of 5 X 10(-11) M. The receptor became phosphorylated, in a PDGF concentration-dependent manner, when 32P-orthophosphate-labeled cells were treated with PDGF for 3 h at 4 degrees C. The phosphorylated receptor was identified by autoradiography and gel electrophoresis after isolation of the 32P-labeled receptor using a solid-phase monoclonal antibody directed against phosphotyrosine. Binding of the receptor to the antibody was inhibited by 5 mM phenyl phosphate, further suggesting that PDGF stimulated tyrosine-specific receptor autophosphorylation. In addition, treatment of MG-63 cells with PDGF for 3 h at 37 degrees C induced a 7.5-fold increase in c-myc mRNA accumulation as analyzed on Northern gels. However, MG-63 cells grew equally well in either serum-(which contains PDGF) or plasma-(which does not) supplemented medium. Furthermore, PDGF did not stimulate DNA synthesis in growth arrested MG-63 cells, nor did it potentiate DNA synthesis modulated by somatomedin C. Thus MG-63 cells are a naturally occurring cell variant in which PDGF stimulates c-myc expression but does not modulate mitogenesis.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004261:DNA Replication / Q000187:drug effects; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008938:Mitosis; D009857:Oncogenes; D012516:Osteosarcoma / Q000235:genetics*; D010766:Phosphorylation; D019000:Phosphotyrosine; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
chemical_list: D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D019000:Phosphotyrosine; D014443:Tyrosine; D007334:Insulin-Like Growth Factor I; D017479:Receptors, Platelet-Derived Growth Factor