Correlations of BMI-1 expression and telomerase activity in ovarian cancer tissues.

AIM To investigate the correlation between oncoprotein Bmi-1 and telomerase activity in ovarian cancer tissues. METHODS SP immunohistochemistry was adopted to detect the expression of Bmi-1 protein in tissues of 47 ovarian epithelial cancer cases. Modified telomeric repeat amplification protocol (TRAP, silver staining technique) was used to detect the telomerase activity. RESULTS While in 80.85% (38/47) of ovarian epithelial cancer cases Bmi-1 protein was overexpressed, 46.81% (22/47) had very strong expression level. Bmi-1 expression levels in ovarian carcinoma tissue differ depending on tissue grade (higher for G3 cancer cases- 93.10% than for grade G2 cases - 61.11%) and the stage of the disease (lower for phase II and phase III cases - 66.67% than for phase IV cases- 92.31%). In ovarian epithelial cancer tissues, 87.23% (41/47) demonstrated positive telomerase activity in contrast to zero activity in normal tissues. Majority (90.24%) of specimens with positive telomerase activity possessed high Bmi-1 expression levels. Spearman correlation analysis indicated that expression of Bmi-1 protein was positively correlated with the elevated telomerase activity. CONCLUSIONS Bmi-1 protein is highly expressed in ovarian epithelial cancer tissues, and its expression level correlates with histological grade and clinical phase of the patients. Elevation of Bmi-1 expression is closely correlated to the increased telomerase activity.