In situ expression and significance of B7 costimulatory molecules within tissues of human gastric carcinoma

AIM: To explore the role and significance of costimulatory molecules B7H1, B7H2 and ICOS within tissues of human gastric carcinoma and the possible mechanisms in tumor escape. METHODS: mRNA expressions of costimulatory molecules including B7H1, B7H2,ICOS and B7-1 in tissues of human gastric carcinoma were investigated by in situ hybridization using digoxigenin-labeled oligonucleotide-probes. The tissue of chronic gastric ulcer was used as a control. All data were analyzed by SPSS statistic software. RESULTS: At the site of gastric carcinoma, mRNA expression levels of B7H1, B7H2 and ICOS were much higher than that of B7-1. Their mRNA positive expression indexes were 0.512 +/- 0.333, 0.812 +/- 0.454, 0.702 +/- 0.359 and 0.293 +/- 0.253, respectively. The positively stained cells were mainly tumor infiltrating lymphocytes (TILs), and some tumor cells. The difference between them was greatly significant P < 0.005. The mRNA expression levels of four molecules were not correlated to the pathological grade and matastasis of gastric carcinoma. CONCLUSION: ICOS-B7H1 costimulatory pathway may be predominant at the site of gastric carcinoma. B7-1mRNA might be the basis of ICOS-B7H1 interaction. ICOS-B7H interaction induces the production of IL-10 which inhibits the antitumor immune responses. Therefore, it is supposed that ICOS-B7H costimulatory pathway may be involved in the negative regulation of cell-mediated immune responses.