Apoptosis and expression of apoptosis-related proteins Bid and Bcl-xL in human small intestinal adenocarcinoma

AIM: To examine whether apoptosis and expression of apoptosis-related proteins Bid and Bcl-xL are involved in the pathogenesis of small intestinal adenocarcinoma.

METHODS: Forty-two tissue samples, including 7 from human small intestinal adenocarcinoma (of the jejunum and ileum) and 35 from normal small intestine (the jejunum), were examined in our study. Apoptotic index (AI) was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. The expression of Bid and Bcl-xL proteins was detected by immunohistochemistry (IHC).

RESULTS: A significantly higher level of enterocyte apoptosis was observed in normal small intestine tissue compared with small intestinal adenocarcinoma (mean AI, 15.78% vs 0.29%, t = 6.51, P < 0.01). The positive rate of Bid expression in normal small intestine tissue (moderate/strong immunoreactivity in the cytoplasm of villus epithelial cells) was significantly higher (77.14% vs 28.57%, P < 0.05) than that in small intestinal adenocarcinoma, while the positive rate of Bcl-xL expression was significantly lower (34.29% vs 86.71%, P < 0.05) in normal small intestine tissue than in adenocarcinoma. The percentage of samples having a Bid/Bcl-xL ratio ≥ 1 was significantly lower in small intestinal adenocarcinoma compared to normal small intestinal tissue (14.29% vs 80.00%, P < 0.01). A positive correlation was noted between AI and Bid expression level (r = 0.368, P < 0.05), but not between AI and Bcl-xL expression level (r = 0.017, P > 0.05).

CONCLUSION: Decreased apoptosis, Bid expression and Bid/Bcl-xL ratio may play a role in the carcinogenesis of human small intestine adenocarcinoma.