OBJECTIVETo investigate the expression differences of apoptosis-inducing factor (AIF) and caspase-3 among colorectal carcinoma, adenoma and normal mucosa, and to identify the relationship between AIF and caspase-3 expression in colorectal adenoma-carcinoma sequence.

METHODSFormalin-fixed paraffin embedded colorectal tissues from 174 cases, including 84 adenomas, 72 carcinomas, and 18 normal mucosa, were examined for expression of AIF and caspase-3 by streptavidin-peroxidase (SP) immunohistochemistry.

RESULTSThe positive rates of AIF and caspase-3 in colorectal adenoma were higher than those in normal mucosa (P <0.05). The positive rate of AIF in adenoma showed no significant difference compared to colorectal carcinoma (P >0.05). However, caspase-3 expression in adenomas was significantly higher than that in carcinoma (P <0.05). The positive rate of AIF in tubular adenoma was significantly higher than that in villous adenoma (P <0.05), while the positive expression rate of caspase-3 in the two types of adenoma showed no significant difference (P >0.05). AIF expression had no prominent correlation with the caspase-3 expression (P >0.05).

CONCLUSIONSThe dysregulation of caspase-independent pathway of apoptosis may be an early event in the development of colorectal carcinogenesis, while the dysregulation of the caspase-dependent pathway of apoptosis may be one of contributing factors of colorectal carcinogenesis. The caspase-independent pathway of apoptosis and the caspase-dependent pathway of apoptosis are two relatively independent pathways in colorectal carcinogenesis.