Immunohistochemical expression of bcl-2 and p53 oncoproteins in colorectal adenomas and adenocarcinomas

Abstract

The immunoreactivity for bcl-2 and p53 oncoproteins was determined in 54 normal mucosa, 28 adenomas, and 43 adenocarcinoma of the large intestine. The percentage of positive immunoreactivity for bcl-2 oncoprotein was significantly higher in adenomas than in normal mucosa or adenocarcinoma (p<0.0001) while there was no difference in the percentage of positive immunoreactivity for bcl-2 oncoprotein between normal mucosa and adenocarcinoma. The percentage of positive immunoreactivity for p53 oncoprotein was significantly higher in adenocarcinoma than in normal mucosa or adenoma (p<0.0001) and the percentage of positive reactivity for p53 oncoprotein was significantly higher in adenoma than in normal mucosa (p<0.005). There was a significant inverse correlation between the rate of positive expression of bcl-2 and p53 colorectal adenocarcinoma (p<0.05).
There was no correlation between bcl-2 immunoreactivity and clinicopathologic variables of colorectal neoplasm. Positive immunoreactivity for p53 was associated with smaller tumor size (p<0.01) and higher grade of dysplasia (p<0.05) of adenoma but the immunoreactivity for p53 oncoprotein did not correlate with any one of clinicopathologic features of adenocarcinoma.
These findings suggest (1) bcl-2 oncoprotein may play a certain role in the early phases of colorectal tumorigenesis, (2) p53 oncoprotein plays an important role in malignant transformation of colorectal adenomas into adenocarcinoma but is not implicated in the process of invasion or metastasis, and (3) p53 oncoprotein may down-regulate expression of bcl-2 oncoprotein.