Changes of the cell cycle during carcinogenesis of hamster cheek pouch epithelium by 7,12-dimethylbenz[a]anthracene.

Changes of the cell cycle during carcinogenesis of hamster cheek pouch epithelium were studied and it was demonstrated that in hyperplastic and neoplastic stages, the cell cycle time decreased to approximately 2/3 and 1/3 of the normal control, respectively. A nominal growth fraction was found to exceed unity in carcinogen-treated epithelium, whether hyperplastic or neoplastic. This result seems to indicate that a considerable number of cells in which DNA synthesis is stimulated by the carcinogen fail to enter mitosis. A possible implication of repair synthesis is also discussed.