The overall objective of these studies is to evaluate the role of stimulatory and inhibitory autocrine growth factor activities in growth regulation of normal and neoplastic colonic epithelia. In addition, the effects of alterations in these pathways on tumor progression will be addressed. The use of established polyp cell lines and colon carcinoma cell lines which phenotypically range from well differentiated to poorly differentiated will allow investigation of growth factor requirements and production, growth factor receptor expression, and potential post receptor events necessary for signal transduction consequential to ligand binding. Furthermore, answers obtained from these approaches in cultured cells will be applied to primary specimens of normal colon tissue, polyp and carcinoma samples in an effort to correlate in vitro and in vivo findings. Specifically, TGF alpha and TGF beta activities will be characterized in all cell types with regard to production and response at the transcriptional and translational levels. Tools such as Northern and Southern blot analyses, radioreceptor assay, radioimmunoassay, and immunoprecipitation will be employed to examine the role of these growth factors in growth control, as well as dissect potential mechanisms by which neoplastic cells have managed to alter these mechanisms. Potential amplification of production of stimulatory molecules (TGF alpha) and/or diminution of response to inhibitory signals (TGF beta) could be hallmark events in the establishment and progression of tumor formation. The colonic epithelium is a useful model system to study such progression because normal, preneoplastic (polyp) and several stages of neoplastic tissue are available. If a role for these putative autocrine regulators is established, possible ways to block positive signals or increase responses to inhibitory signals will be examined. In these studies, specific antibodies to the growth factors or their receptors will be used. The scope of this proposal encompasses not only the identification of growth factors necessary for maintenance of normal colonic epithelia, but also the sequential alterations in normal control pathways that have contributed to colonic dysplasia and ultimately neoplasia. These studies are designed to increase our understanding of normal and neoplastic proliferation of colonic epithelia, and thus provide insight into possible ways to redirect neoplastic cells onto a normal course of growth control.
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