Immunohistochemical estimation of in-situ cell cycle time in neoplastic epithelial cells in human large intestine: a new cell proliferation index

In-situ cell cycle time (in-situ Tc) of epithelial cells could be estimated by using a formula; in-situ Tc = cell proliferation rate divided by mitosis rate, on a scale of Tm (cell cycle time in M phase) arbitrary unit (AU), In order to see the nature of in-situ Tc in the adenoma-carcinoma sequence in the human large intestine, the in-situ Tc in 27 cases of adenoma and 71 cases of adenocarcinoma with adenoma components in the human large intestine was estimated by using this formula, counting proliferating cells and mitotic cells in the immunohistochemistry of Ki-67 antigen. C12 antigen was examined as an oncogenic progression indicator in the adenoma-carcinoma sequence. The in-situ Tc tended to shorten in adenoma in accordance with the histological grading of atypia but not in adenoma component. No significant differences in the in-situ Tc was recognized as a whole among adenomas, adenoma components and adenocarcinomas in the mucosa, whereas the in-situ Tc of adenoma components with moderate to severe atypia was significantly longer than that of adenocarcinomas in the mucosa (p = 0.05). The in-situ Tc lengthened in adenocarcinomas invading the submucosa and shortened in adenocarcinomas invading the proper muscular layer. The cases expressing the C12 antigen increased in order of adenoma, adenoma component and adenocarcinoma. The cases expressing the C12 antigen indicated short in situ Tc in the adenomas and adenocarcinomas but not in the adenoma components. Thus, the estimated in-situ Tc is a useful index of the oncogenetic progression, which is different from that detected by the C12 antigen.