""""""""The transforming growth factor-betas (TGF-betas), which include TGF-betas 1, 2 and 3 in mammals, are a family of multifunctional growth modulators that control an array of functions in animal cells from virtually every lineage. The TGF-betas are able to act as both positive and negative regulators of cell growth, differentiation and transformation depending on the cell type, growth conditions and presence or absence of other peptide growth factors. The TGF-beta response system has been implicated as a tumor suppressor pathway in several organ sytems."""""""" """"""""The most recent efforts have continued to investigate the role of TGF-beta in mouse models of chemically-induced lung tumorigenesis. Expression of the TGF-beta ligands (TGF-betas 1, 2 and 3) and TGF-beta type I and type II receptors (TGF-beta RI and RII) was examined in TGF-beta 1 wildtype (+/+) and TGF-beta 1 heterozygous (+/-) mice. Although the heterozygous mice were shown to be grossly normal, increased cell turnover was demonstrated in the liver and lung. Treatment of these mice with the chemical carcinogen diethylnitrosamine resulted in enhanced tumorigenesis in the liver and lung compared to the TGF-beta 1 wildtype littermates. Immunostaining and in situ hybridization for TGF-beta 1, TGF-beta RI and TGF-beta RII proteins and mRNAs, respectively, showed similar expression in lung adenomas of mice of both TGF-beta 1 genotypes. Tumors in the heterozygous mice did not lose the remaining wild-type TGF-beta 1 allele, indicating that the TGF-beta 1 ligand is a new form of tumor suppressor that shows haploid insufficiency in its ability to protect against tumorigenesis. Future efforts will be aimed at investigating the effects of the TGF-beta 1 genotype on TGF-beta 1 target genes."""""""" """"""""In addition to examining mouse models, we have investigated the regulation of production of proteases, protease inhibitors and extracellular matrix proteins by TGF-beta 1 in human lung cancer cells. To investigate the relationship between plasminogen activator (PA), plasminogen activator inhibitor-1 (PAI-1) and the extracellular matrix in malignant and normal lung epithelial cells and to determine whether malignant lung epithelial cells may be more invasive than normal lung epithelial cells because of differences in expression of these proteins in response to TGF-beta, the regulation of PA, PAI-1, fibronectin, laminin and thrombospondin by TGF-beta 1 in human non-small cell lung cancer (NSCLC) cells was examined and compared with normal human bronchial epithelial (NHBE) cells. TGF-beta 1 caused a persistent increase in expression of the mRNAs for both PA and PAI-1 in NSCLC cells, with the increase in PAI-1 mRNA beginning several hours before that of PA mRNA. By immunoprecipitation analysis, it was shown that TGF-beta 1 also induced a corresponding increase in the amount of PAI-1 protein in these NSCLC cells as well. In contrast, while TGF-beta 1 also increased expression of PAI-1 mRNA in NHBE cells, expression of PA mRNA decreased simultaneously. Treatment of NSCLC cells with TGF-beta 1 resulted in a persistent increase in expression of the mRNAs for fibronectin, laminin and thrombospondin; expression of fibronectin protein also increased after treatment with TGF-beta 1 in these cells. When NHBE cells were similarly cultured in the presence of TGF-_1, expression of fibronectin mRNA also increased in a persistent manner; however, only an early transient increase in the level of the mRNAs for laminin and thrombospondin was detected in these cells. These data show that there is differential regulation of the genes for PA and PAI-1 and the extracellular matrix protein fibronectin in response to TGF-beta 1 not only when NSCLC and NHBE cells are compared, but also when different NSCLC cells are compared with each other. Future efforts will be directed at additional proteases and extracellular matrix proteins to more precisely eulucidate the role of TGF-beta in lung cancer."""""""" The significance of this project is to determine the role of TGF-beta in lung cancer and identify other important negative growth factors that regulate gene expression and cellular proliferation of lung cells. These negative growth factors that slow lung cancer growth may identify targets for development of new chemopreventative agents.
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