Kinetics of cell replication in the uterine cervix. VII. Loci of mitotic basal cells during cervical carcinogenesis.

The frequency and the topographic occurrence (i.e., loci) of vincristine-arrested mitosis in the basal-cell layer was studied during the process of cervical carcinogenesis in C57B1 mice. The total frequency of mitosis decreased (by comparison to controls) not only in cervical intraepithelial neoplasias of grades I, II and III and in invasive carcinomas, but also in the normal epithelium of carcinogen-treated animals. This confirms earlier results and suggests that the pace of replication of cells in contact with the stroma is decreased during carcinogenesis. On the other hand, the proportion of the number of mitotic basal cells occurring singly or in groups of 2, 3 or greater than or equal to 4, as well as the proportion of loci with 1, 2, 3 or greater than or equal to 4 mitoses, were similar during cervical carcinogenesis (when compared to controls). It would thus appear that the proliferation of the cervical epithelium during carcinogenesis is regulated by two factors: one that seems to diminish the total number of mitotic basal cells during carcinogenesis, and another that seems to maintain as constant the proportion of mitotic loci, both under normal conditions and throughout the development of intraepithelial neoplasias, in the uterine cervix.