Growth factors and their receptors play a critical role in stimulating either normal or abnormal cell growth. For example, although PDGF and EGF stimulate normal connective tissue cell growth, overexpression often causes cellular transformation. Also many human tumors overexpress the EGF-receptor, or its homologue neu. Amplification of the neu gene in human mammary adenocarcinomas is an indicator of poor prognosis. Furthermore, genetic alteration of the EGF- or CSF-1-M-receptors has generated truncated forms with transforming potential respectively the erb- B and fms oncogenes. The goal of the present project is to characterize potential overexpression or genetic alterations of the PDGF-receptor of human childhood connective tissue tumors, sarcomas. Such tumors, which are uncommon in adults, are prime candidates for study because their normal counterparts, connective tissue cells, display the PDGF-receptor and display a mitogenic response to the ligand. Epithelial cells lack the receptor . Functional, immunologic and molecular approaches will be used to define receptor alterations in tumor specimens. Overexpression of the PDGF-receptor protein in human sarcoma samples will be defined using PDGF binding, PDGF stimulate tyrosine kinase actively and Western blot analysis utilizing specific anti-peptide antisera. PDGF-receptor RNA will be quantified by Northern gels and gene amplification quantified by Southern analysis. Expression of truncated forms of the PDGF-receptor mRNA will be characterized by nuclease protection experiments and by cDNA cloning and sequencing analysis of certain PDGF-receptor transcripts. Similar changes will be characterized at a protein level using eptiope specific antisera. The present experiments should define alterations of PDGF-receptor structure or expression in human sarcomas which are associated with loss of growth control. Such changes may prove to be an important clinical prognostic variable in these difficult cases.
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