Immunohistochemical Study on p53 in Microwave-fixed Paraffin Sections of Colorectal Tumors

Expression of p 53, a tumor suppressor gene product, was studied immunohistologically in microwave (MW)-fixed paraffin sections of 98 colorectal carcinomas and 44 adenomas. Using a monoclonal antibody (PAb 1801), nuclear p53 was successfully detected in 62 (62.2%) out of 98 carcinoma cases, while no staining for p53 was demonstrated in the adjacent normal mucosa. There was no correlation between the incidence of p53 expression in colorectal carcinomas and clinicopathologic features such as tumor size or depth of invasion. In colorectal adenomas, only 4 (9%) out of 44 adenomas were found to express p53. This expression of p53, however, was restricted to only a few glands within tubular or tubulo-villous adenomas with moderate dysplasia. Thus, the expression of p53 protein was characteristic of carcinomas and seemed to reflect the disturbance of the regulation mechanism for cell proliferation. The present study demonstrated the usefulness of MW fixation for the preservation of p53. Furthermore, the immunohistochemical detection of p53 in MW-fixed paraffin sec-tions is expected to provide valuable information on the mechanism of' carcinogenesis in colorectal epithelium.