PROGNOSTIC-SIGNIFICANCE OF P53 OVEREXPRESSION AND MUTATION IN COLORECTAL ADENOCARCINOMAS

The p53 tumour-suppressor gene is found altered in the majority of col orectal cancers. Lesions include allelic loss, mutation of the gene an d overexpression of the p53 protein. All of these lesions have been an alysed for prognostic significance, and whereas both mutation and alle lic loss have been shown to be reasonably useful markers of prognosis, the utility of overexpression of the p53 protein is more ambiguous. G iven that many authors use p53 overexpression as a marker for point mu tation this issue is of some importance. We have therefore examined 10 0 colorectal carcinomas for mutation of the p53 gent, as well as overe xpression of the p53 protein. Results show that whereas mutation of th e p53 gene is associated with p53 overexpression, the degree of associ ation depends, at least in part, upon the particular antibody used. Mo reover, although mutation of the p53 gene does provide prognostic info rmation, overexpression of the p53 protein, as detected with two antib odies, does not. These results suggest that immunohistochemistry is no t a suitable alternative to direct detection of mutations in assessing prognosis in colorectal cancer patients.