PURPOSE: NNK [4-(methylnitrosamino)-1-(3-pyridyle)-1-butanone] is anicotine-derived nitrosaminoketone contained in tobacco smoke used as a powerful chemical carcinogen for rodent experimental models of pulmonary carcinogenesis. To clarify its carcinogenetic mechanisms, we examined the expression status of 22,625 mouse genes. METHODS: The affymetrix GeneChip mouse expression 430 A arrays have been used in CD1-induced mouse lung tumor. The affected genes were analyzed by Ingenuity pathway analysis to investigate functional network and gene ontology.