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 most recent efforts have investigated the regulation of protease, protease inhibitor and extracellular matrix proteins by TGF-beta in established lung cancer and normal lung cell lines. We have shown that TGF-beta 1 is able to autoregulate both its mRNA and protein in some non-small cell lung cancer (NSCLC) cells as well as in normal human bronchial epithelial (NHBE) cells. We have also shown that TGF-beta 1 causes an increase in plasminogen activator (PA) in NSCLC cells, a protein which participates in the processing of plasminogen to plasmin. TGF-beta 1 also causes an increase in the level of plasminogen activator-inhibitor (PAI) in NSCLC cells, a protein which inhibits PA. While TGF-beta 1 also causes an increase in PAI in NHBE cells, TGF-beta 1 produces a decrease in PA in these cells. We also showed that TGF-beta 1 causes a persistent increase in extracellular matrix proteins in NSCLC cells, while it causes only a transient increase in these proteins in NHBE cells. A new project has been initiated to identify potential mutations in the TGF-beta receptor genes that may be linked to tumorigenesis and microsatellite instability. Several SCLC cell lines were examined for TGF-beta type II receptor by amplification of a 73 base-pair region of the TGF-beta type II receptor using PCR technology. 87% of the SCLC cells were shown to have a frameshift mutation in the TGF-beta type II receptor. Another new project that has been initiated involves the use of the TGF-beta ligands and receptors as potential biomarkers for lung cancer in human lung biopsy specimens and animal carcinogenesis model systems. Immunohistochemistry using specific antibodies to the TGVF-beta ligands and receptors was used to localize expression of these proteins in the A/J mouse model system after treatment with urethane. We have also cloned novel genes that are stimulated by the TGF-betas and are identifying and characterizing these genes and determining whether these gene products can slow the growth of lung cancer cells. It will be investigated whether expression of the TGF-betas and these new genes can be stimulated by chemopreventative agents such as retinoic acid and new RAR- and RXR-specific compounds so that growth of lung cancer cells can be slowed by increased expression of the TGF-betas. 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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