Immunohistochemical Evaluation of Bcl-2 Protein Expression in Gastric Adenocarcinomas

Background: bcl-2 protooncogene encodes for a 26 kD protein effective in inhibiting programmed cell death (apoptosis). Its expression has been noted in lymphomas and colonic, lung, and breast carcinomas. bcl-2 protein is believed to play a role in the gastric carcinogenic sequence where it has been demonstrated in dysplastic epithelium. To further study the role of bcl-2 protein in gastric carcinogenesis and tumor progression, an immunohistochemical study of bcl-2 expression in gastric adenocarcinomas and its relation to the histologic type, grade of differentiation, pT stage, lymph node status, and survival was performed.

Methods: Immunohistochemical staining using monoclonal bcl-2 protein antibody, clone 124, was performed on archival material.

Results: Forty-six of the sixty-four adenocarcinomas (72%) showed bcl-2 staining with immunoreactivity in 75% of the tumor or more. No specific pattern in the distribution of labeling was seen. bcl-2 reactivity was significantly associated with adenocarcinomas of the intestinal morphotype. Forty-five of 51 intestinal-type tumors (88%) were immunoreactive versus only 1 of the "diffuse" tumors (7%) (P = 0.001). Within the intestinal-type adenocarcinomas, a trend of increasing prevalence of immunoreactivity with higher histologic grades was seen. No correlation between bcl-2 expression and pT stage, lymph node status, or survival was observed.

Conclusion: bcl-2 expression in gastric adenocarcinoma appears to be associated almost exclusively with the intestinal morphotype and to some extent is more prevalent in grade 3 tumors. No correlation was noted with the pT stage, lymph node status, and survival. Inhibition of apoptosis through bcl-2 protein expression appears to be specifically associated with promotion of intestinal-type gastric adenocarcinoma but does not appear to be active and/or correlated with tumor progression.