ABSTRACT
Carcinogenesis represents the unwarranted appearance or increased incidence of abnormal cell proliferation occurring in an age-matched low-risk group whose propensity for development of cancer is statistically lower. Mutagenesis refers to the ability of a virus or chemical agent to induce changes in the genetic sequence of mammalian or bacterial cells, thus altering the phenotypic expression of cell characteristics. As with the chemical activation of procarcinogens to proximate and ultimate carcinogens, the bioactivation of chemicals also results in the formation of free radicals and reactive oxygen species (ROS)—that is, chemical species that cause oxidative damage to biomolecules, including nucleic acids (DNA), proteins, and lipids. The ability of free radicals and ROS to elicit DNA mutations and cause dysregulated cell signaling contributes to the multistage carcinogenesis pathway. The process of carcinogenesis is divided into three experimentally defined stages: tumor initiation, tumor promotion, and tumor progression.
