CYP1A1 GENE REGULATION AND HUMAN CANCER

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A major goal of our laboratory has been the elucidation of the role of the human cytochrome P450, CYP1A1, in lung carcinogenesis. The protein product of the CYP1A1 gene and its associated catalytic activities, including aryl (or aromatic) hydrocarbon hydroxylase (AHH), are known to be intimately associated with the metabolic activation of many of the procarcinogenic polycyclic aromatic hydrocarbons (PAHs) found in cigarette smoke and other environmental pollutants to highly reactive intermediates. Elevated levels of AHH activity have been implicated in numerous studies as a significant risk factor in the etiology of lung cancer. Our investigations have been focused upon elucidating the mechanisms by which CYP1A1 gene expression is regulated and to establish a functional relationship between deviations from normal patterns of expression and lung cancer. A. Our studies of the regulation of expression of the human CYP1A1 gene using oligonucleotide directed mutagenesis and reporter gene expression in non-small cell lung cancer derived cell lines reveal that transcriptional activation of the gene is mediated through two widely separated DNA regulatory elements. This activation appears to be synergistic, as each element contributes roughly only 30% to the overall expression of the gene. These data are supported by gel mobility shift analyses of protein/DNA interactions at each site under control and inducing conditions. This work represents the first effort at characterization of the regulatory elements of the human CYP1A1 gene and the determination of the role for each in the regulation of expression of the gene in the adult lung. B. Interindividual variability in CYP1A1 gene expression may arise as a result of genetic differences within the genes encoding CYP1A1 transcriptional regulatory proteins. We have identified at least two restriction fragment length polymorphisms (RFLPs) within the gene encoding the major transcriptional activator of the CYP1A1 gene, the aromatic hydrocarbon (Ah) receptor. DNA from age, race, and sex matched control and histologically confirmed lung cancer patients is presently under examination to determine the frequency of these newly acquired genetic markers within the two populations. The significance of these projects is the elucidation of the interactive role of genetically determined factors and chemical carcinogens in pulmonary carcinogenesis. The results will have diagnostic and prevention applications.