The role of bcl-2 in the progression of the colorectal adenoma-carcinoma sequence.

ABSTRACT

BACKGROUND: The bcl-2 proto-oncogene is a known inhibitor of apoptosis that may allow the accumulation and propagation of cells containing genetic alterations. METHODS: An immunohistochemical study was performed to examine the role of BCL-2 protein expression in normal colonic mucosa, adenoma, and adenocarcinoma. RESULTS: BCL-2 was present in the crypt base of normal mucosal glands, while diffuse expression of protein product was observed in 69 cases (65.1%) of adenoma and 29 cases (60%) of adenocarcinoma (p > 0.5). A diffuse expression pattern was often noted in adenomas of the tubular type, solitary lesions, small lesions (< 1 cm), and those with mild glandular dysplasia (p < 0.05, respectively). There was, however, no apparent difference as to location, Yamada type of gross appearance, and gender of patients (p > 0.05, respectively). Patterns of BCL-2 expression did not correlate with the biologic indicators of adenocarcinoma (p > 0.1, respectively). CONCLUSIONS: Our results support that bcl-2 may play an important role in the early stage of the adenoma-carcinoma sequence. Down-regulation of bcl-2 is associated with the risk of malignant transformation for colorectal adenoma.