1-nitropyrene also caused chromosomal mutation, such as micronucleus formation, and morphological cell transformation. In contrast to the mutation spectrum of 1-nitropyrene in mammalian cells in vitro or in bacterial cells, oncogenes in 1-nitropyrene- induced tumors in rodents have primarily AT→GC mutations, as well as altered patterns of expression [13]. In general, 1-NP not only induced oxidative stress and the formation of reactive oxygen species, but also inflammatory proteins and apoptosis in mammalian cell systems and rodents. These mechanisms, together with its direct genotoxicity, could contribute to the carcinogenicity of 1-nitropyrene.