Expression of bcl-2 Protein in Colorectal Adenoma and Adenocarcinoma and its Relationship with p53 and Apoptosis

Kim, Ae Ree; Cho, Seong Jin; Won, Nam Hee; Chae, Yang Seok

Abstract

Either increased cellular proliferation or decreased death might result in an expansion of their numbers in the oncogenic process. Cellular apoptosis represents an autonomous suicide pathway that helps to restrict the cell number. However bcl-2 and mutant p53 inhibit programmed cell death. To determine whether the bcl-2 gene is activated during colorectal tumorigenesis and whether it has any relationship with p53 and apoptosis, we studied the expression of bcl-2 and p53 in the normal colonic mucosa, in the adenomatous polyps and in the adenocarcinomas using the immunohistochemical method. Also we evaluated the status of apoptosis using the in situ end labeling method. The bcl-2 immunoreactivity was restricted to the basal epithelial cells of all normal colonic mucosa and they were expressed in all adenomas and 86% of adenocarcinomas, especially in the superficial lesion of some tumors. Mutations of p53 were not found in the normal colonic mucosa, but they were present in dysplastic cells of adenomas (52%) and in cancer cells of the adenocarcinomas (47%). Apoptosis was confined to the tips of the normal colonic mucosa. It was more easily detected in the p53-positive adenomas than in the p53-negative adenomas (p=0.010). In the adenocarcinomas, the findings of apoptotic process are not related with p53 mutation (p=0.3) and bcl-2 expression (p=0.187). p53 and bcl-2 are probably one step of several apoptotic processes in the adenocarcinomas.