P53 PROTEIN OVEREXPRESSION IN COLORECTAL TUMORS FROM PATIENTS WITH FAMILIAL ADENOMATOUS POLYPOSIS - IS IT AN EARLY OR LATE EVENT

Objectives: Tumor development is a multistep process associated with m ultiple genetic alterations. Familial adenomatous polyposis (FAP) is a classical paradigm to study genetic alterations in the development of colorectal neoplasms. In this study, we investigated the timing of p5 3 overex pression by immunohistochemistry in colorectal carcinogenesis in FAP patients and in sporadic adenomas and adenocarcinomas. Methods : We examined 40 microadenomas, 114 tubular adenomas, and three adenoc arcinomas from five FAP patients and 30 sporadic adenomas and 14 spora dic adenocarcinomas. Results: p53 overexpression was observed in 43 of 114 adenomas with mild and moderate dysplasia and in three of three a denocarcinomas and in none of 40 microadenomas from FAP patients. In s poradic tumors, six of 30 adenomas with moderate to severe dysplasia a nd 11 of 14 carcinomas showed p53 overexpression. Uninvolved colonic m ucosa in FAP patients, control patients, and patients with sporadic tu mors did not stain for p53, Conclusions: These results indicate that p 53 overexpression occurs early in the development of colorectal adenom as in FAP, whereas it is a late event in the development of sporadic t umors.