Bcl-2 expression and frequency of apoptosis correlate with morphogenesis of colorectal neoplasia.

AIM To investigate whether the expression of apoptosis and cell proliferation related proteins is related to the macroscopic form of colorectal neoplasia. METHODS The extent of apoptosis, using the 3' end DNA labelling method, and the immunohistochemical expression of cell proliferation (Ki-67) and apoptosis related proteins (Bcl-2, Bak, and p53) were investigated in 64 colorectal adenomas and 22 early carcinomas extending no further than the upper submucosal region. The specimens were classified into three types of macroscopic form (polypoid, flat, and depressed). RESULTS The Ki-67 labelling index and the Bak score did not differ significantly among each macroscopic form. In contrast, the apoptotic index and the Bcl-2 score changed significantly according to the macroscopic forms. Compared with polypoid and flat tumours, depressed tumours had a significantly lower apoptotic index (2.84, 2.28, and 1.44, respectively) and a significantly lower Bcl-2 score (3.18, 2.70, and 1.64, respectively). The proliferation/apoptosis ratio was significantly lower in polypoid tumours than in the other two macroscopic forms. The Bcl-2 score became significantly lower as the tumours flattened or took on a depressed form. Immunohistochemical p53 overexpression did not correlate with the macroscopic forms. CONCLUSIONS These results suggest that differences in both Bcl-2 expression and apoptosis may play an important role in the morphogenesis of colorectal neoplasia.