This is a competing renewal application for a project which was initiated in 1978. The objective of the project was to determine the molecular basis for biological differences among sub classes of colon carcinoma cells. It is ultimately intended to use these differences for new therapeutic approaches. The overall objectives of the last period of funding were to identify and characterize autocrine growth factors produced by previously identified sub-classes of colon carcinoma cell lines and to determine their responses to growth factors. Each of these objectives were accomplished. The colon carcinoma cell line bank was converted to growth in a chemically defined medium. This permitted the determination of the effects of exogenously added growth factors and combinations of growth factors on various growth assays of sub-classes of cells. TGF-alpha and gastin were identified as autocrine stimulatory factors. The expression of these autocrine factors at the mRNA and protein levels as a function of the sub- classes of carcinoma cells was determined. The response to the autocrine stimulatory and inhibitory factors (TGF-beta family) as function of sub- classes of colon carcinoma was determined. TGF-beta activity was associated with repression of c-myc oncogene and induction of extracellular matrix molecules. Having identified positive and negative autocrine factors for colon carcinoma cells, the next logical step is the characterization of how their expression is controlled by the cells and how it is affected by exogenous agents.
The specific aims of the renewal proposal are: 1. Characterize the control of TGF-alpha expression through the analysis of cis and trans elements of the TGF-alpha elements promoter, 2. Determine control of TGF-alpha expression in colon carcinoma by exogenous agents using promoter-reporter gene constructs, nuclear runoffs, Northern analysis of mRNA and protein determination, 3. Characterize the control of gastin expression in colon carcinoma using the approaches for TGF-alpha above, 4. Characterize the mechanism of TGF-beta inhibitory action in colon carcinoma.
