The broad goal of this research is to define the roles of polypeptide growth factors, including platelet-derived growth factor (PDGF) and brain-derived growth factor (BDGF) in the regulation of growth of normal and transformed cells. This proposal has four aims: 1) To define the autocrine role of PDGF-like molecules (p28 v-sis and c-sis gene product) in the growth of cells transformed by infection with simian sarcoma virus (SSV) and by transfection with a cDNA clone of the c-sis gene. Differences in expression of these PDGF-like molecules will be examined in cells with varying degrees of tumorigenicity. Intracellular PDGF-like molecules will be measured with enzyme-linked immunosorbent assay. Intracellular biosynthesis and processing will be studied by Northern gel analysis of transcripts, metabolic labeling, subcellular fractionation, and electron microscopy. 2) To define the differences in biosynthesis, processing, and turnover of the PDGF receptor in SSV- and c-sis-transformed cells and in normal cells. The bio-synthesis, processing, and turnover of the PDGF receptor will be analyzed by immunoprecipitation of metabolically labeled cells. PDGF- receptor negative cells derived from transformed cells will be selected to test the obligatory role of the receptor in transformation of these transformed cells. 3) To study the cell biology of BDGF in neuroblastoma cells. The biosynthesis and secretion will be studied by immunoprecipitation of metabolically labeled cells using anti-BDGF antibodies. The effects of anti-BDGF antibodies on the growth of neuroblastoma cells in culture and in athymic nude mice will be examined. 4) To isolated and characterize the BDGF receptor from bovine uterus and to study the biochemistry (protein tyrosine kinase activity) and biological properties. Isolation of a significant quantity of the receptor will permit preparation of antibodies to the receptor and studies of biosynthesis and turnover of the receptor in normal and transformed cells, including neuroblastoma cells. These studies should provide insight into the roles of PDGF and BDGF in the regulation of normal cell growth and may help understand the alteration of this growth regulation that leads to some forms of cancer.
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