[Expression and clinical significance of Bmi-1 protein in bladder cancer]

At present, the molecular mechanisms of development and progression of bladder cancer are still poorly understood. This study was to explore the expression and significance of Bmi-1 in bladder cancer, and analyze its correlations to clinicopathologic features and prognosis of bladder cancer.

The expression of Bmi-1 protein in 137 specimens of bladder cancer and 30 specimens of normal bladder tissues was detected by SP immunohistochemistry, and its correlations to clinicopathologic features and prognosis of the patients were analyzed.

The positive rate of Bmi-1 protein was significantly higher in bladder cancer than in normal bladder tissues (54.3% vs. 16.7%, P<0.05). The positive rate of Bmi-1 protein was 20.6% in grade G1 bladder cancer, 54.3% in grade G2 bladder cancer, and 78.8% in grade G3 bladder cancer, with significant difference (P<0.05). It was significantly lower in superficial bladder cancer than in invasive bladder cancer (32.5% vs. 81.5%,P<0.05). The expression intensity of Bmi-1 was related to tumor size, classification, TNM stage and prognosis (P<0.05), but not to tumor number and tumor recurrence (P>0.05). The patients were followed up for 44-86 months, with a median of 66 months. The 5-year survival rate was significantly higher in superficial bladder cancer patients than in invasive bladder cancer patients (89.6% vs. 39.2%, P<0.05), and higher in Bmi-1-negative patients than in Bmi-1-positive patients (78.5% vs. 50.8%,P<0.05).

Bmi-1 protein is highly expressed in bladder cancer. Detecting Bmi-1 protein is helpful for diagnosis and prognostic evaluation of bladder cancer.