By comparing the effects of the carcinogen, urethane, with those of the lung toxic and tumor promoting agent, butylated hydroxytoluene, in mouse strains with different susceptibilities to adenoma formation, we will distinguish biochemical changes unique to neoplasia from those characteristic of a normal proliferative response. A single dominant gene in BALB mice which confers resistance to adenoma will be used to differentiate toxic effects of urethane from truly neoplastic ones, and will be mapped using recombinant inbred mice. We will determine by autoradiography whether this gene prevents formation of hyperplastic foci or their further progression. Transplantation studies with dissected embryonic rudiments will determine if this gene acts of epithelial or mesenchymal tissue. Lung adenoma receptors have lost their sensitivity to two known growth inhibitors - cAMP and glucocorticoids. This may be a means by which cells escape normal growth regulation, and could be an important early event in the transition from normal to neoplastic growth. Changes in these receptor proteins will be monitored in the alveolar Type 2 cells from which adenomas are derived by isolating these cells from lungs at various times after in vivo administration of urethane and/or BHT. Adenoma cAMP receptors have a decreased ability to bind the photoaffinity analog, 8-N3-cAMP, and have lost the ability for cAMP to stimulate autophosphorylation. Such changes will be looked for in isolated Type 2 cells at earlier stages of carcinogenesis. Antibodies will be prepared against the R-subunit of cAMP-dependent protein kinases, and used to determine changes in subunit concentrations and turnover rates. Preliminary studies suggest that nuclear localization of glucocorticoid receptors does not occur in the adenoma. This will be examined further both by in vivo autoradiography and subcellular fractionation in adenoma and isolated Type 2 cells. The physiological consequences of these losses of receptor sensitivity will be studied in Type 2 cells by monitoring the ability of cAMP to stimulate endogenous protein phosphorylation and the ability of glucocorticoids to induce the synthesis of specific proteins.
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