HISTOCHEMICAL-STUDIES OF PROGRESSIVE P53 MUTATIONS DURING COLONIC CARCINOGENESIS IN SPRAGUE-DAWLEY RATS INDUCED BY N-METHYL-N-NITRO-NITROSOGUANIDINE OR AZOXYMETHANE

We studied the increasing expression of the p53 tumor suppressor gene in Sprague-Dawley rats, chemically induced to develop colon cancer. p5 3 expression was evaluated histochemically at various stages of tumor progression (during a period of 40 weeks) that can be followed by colo nic hyperproliferation labeled by H-3-thymidine incorporation. We foun d that high level nuclear expression of p53 protein correlates with pr ogression of malignancy in carcinogen-induced animals, whereas cytopla smic staining is related to the onset and early development of maligna ncy.