Genes regulating apoptosis: an immunohistochemical study of BCL-2 and P53 expression in colorectal adenomas and carcinomas

ABSTRACT

Evidence is accumulating for the failure of apoptosis as an important factor in the evolution of colorectal cancer and its poor response to adjuvant therapy. The proto-oncogene Bcl-2 is a known inhibitor of apoptosis that may allow the accumulation and propagation of cells containing genetic alterations. Inactivation of P[53] the tumour suppressor gene are common in human colorectal cancer.This study aimed at evaluating the expression of Bcl-2 and P[53] proteins in colorectal adenomas versus carcinomas for better understanding of their role in the process of colorectal carcinogenesis and correlate their expression with the clinicopathologic features of these tumours. So we analyzed the expression of these markers in 11 colorectal adenomas and 14 carcinomas with the adjacent normal mucosa. Staining patterns were assessed semiquantitatively and correlated with each other and with age, sex, tumour size, site, tumour differentiation and Dukes' classification. A higher proportion of adenomas [54.5%] than carcinomas [36.4%] expressed BCL-2, Bcl-2 expression was more frequent in well differentiated carcinomas than moderately and poorly differentiated carcinomas. A lower proportion of adenomas [35.7%] than carcinomas [64.3%] expressed P[53] A total of [18.2%] of adenomas and [13.3%] of carcinomas expressed both markers. We suggested that Bcl-2 provides a survival advantage in the proliferative compartment of normal crypts of colorectal neoplasms, however, its expression is lost during the evolution from adenomas to carcinomas, whereas P[53] expression is increased. Although P[53] expression doesn't delineate aggressive behaviour and tumour progression in colorectal cancer, Bcl-2 provides a favorable marker for good differentiation in these tumours