These studies try to identify critical target genes and alterations in biochemical pathways which are involved in cell transformation. Biological endpoints being examined include DNA adduct formation, gene expression, and oncogene activation. Activation of the K-ras proto-oncogene appears to be one step in the development of mouse lung tumors. In order to identify other factors involved in tumor progression, epithelial cell lines are being developed from these murine tumors. The expression of growth factors, proto-oncogenes, and proteases are being characterized in these cell lines and in solid tumors. Preliminary data indicates that gene expression in these murine tumors is similar to that observed in human lung tumors. Quantitative PCR analysis of messenger RNA will be employed using cell lines or benign and malignant tumors to identify specific genes whose expression or suppression may be involved in the progression from benign to malignant to a fully metastatic phenotype. The role of M genes in tumorigenesis in inbred mouse strains with differing susceptibilities to formation of liver and lung tumors is being investigated. Activation of ras genes by point mutations in spontaneous liver and lung tumors from the parental C3H and C57 strains and the B6C3F1 progeny is being identified by sequencing, slot blotting and RFLP analysis following PCR amplification of ras gene fragments in DNA isolated from the tumors Persistence of 0 degree- MG DNA adducts in lung and in isolated lung cells following treatment with the tobacco specific carcinogen NNK (4-(methyl-nitros-amino)-1-(3-- pyridyl)-1-butafione is also being compared using the susceptible A/J and the resistant C57 mouse strains. The nude mouse tumorigenicity assay is being employed to try to detect other transforming genes in tumors lacking activated ra genes. Activation of oncogenes by methylene chloride, a chemical with widespread industrial use and potential human exposure, is being investigated in order to identify the mechanism whereby this chemical induces liver and lung tumors in B6C3F1 mice. Methylene chloride induced lung tumors are also being screened for other genetic damage such as allele loss during carcinogenesis.
