Chemicals have been implicated as human carcinogens for more than 200 years.1 A large number of chemicals of diverse structures have now been shown to be carcinogenic in animals. Although the etiology of human neoplasia, with rare exceptions, is unknown, it has been estimated that 50% to 90% of cancer in man is caused by exposure to chemicals.2 Identification of agents as human carcinogens is difficult due in part to the long latent period in man.3 Until recently, long-term experiments in animals provided the only means for detecting the potential of chemicals to produce tumors. The bioassay of compounds by routine in vivo testing is an insurmountable task when one considers the rate at which chemicals are being added to the environment.
The need for more rapid bioassay is apparent, and the development of tissue culture techniques for the study of mammalian cells in culture has created
Evans CH, DiPaolo JA. Mammalian Cells for Carcinogen Identification. JAMA. 1973;225(6):631-632. doi:10.1001/jama.1973.03220330043014