The clinicopathological significance of Bmi-1 expression in pathogenesis and progression of gastric carcinomas.

BACKGROUND Oncogenic Bmi-1 (B-lymphoma Moloney murine leukemia virus insertion region-1) belongs to the Polycomb-group (PcG) family of proteins and plays an important role in the regulation of proliferation, senescence, cell cycle and apoptosis, chromosome stability, activation of gene transcription. METHODS To clarify the roles of Bmi-1 in tumourigenesis and progression of gastric carcinomas, it was examined by immunohistochemistry (IHC) and real-time RT-PCR in gastric carcinomas, dysplasia, intestinal metaplasia (IM), and gastritis with a comparison of its expression with clinicopathological parameters of carcinomas. RESULTS There was gradually increased Bmi-1 protein expression from gastritis, IM, dyplasia to carcinoma (p<0.001). Bmi-1 expression was positively linked to tumor size, depth of invasion, lymph node metastasis and worse prognosis of carcinomas (p<0.001), but not to age or sex of carcinoma patients (p>0.05). There was higher Bmi-1 protein expression in intestinal-type carcinomas than diffuse-type ones (p<0.001). At mRNA level, Bmi-1 protein expression was increased from gastritis, IM, dysplasia and carcinoma (p<0.001). Bmi-1 overexpression was observed in gastric carcinoma with larger diameter, deeper invasion, lymph node metastasis, and intestinal-type carcinoma (p<0.05). CONCLUSION These findings indicate that up-regulated Bmi-1 expression is positively linked to pathogenesis, growth, invasion, metastasis and differentiation of gastric carcinomas. It was considered as a promising marker to indicate the aggressive behaviors and prognosis of gastric carcinomas.