Over-expression of BMI1 is associated with favorable prognosis in cervical cancer

Objective: B cell-specific Moloney murine leukemia virus integration site 1 (BMI1), is a Plycomb group (PCG) protein, that is involved in the epithelial-mesenchymal transition (EMT) and induces stem cell properties, suggestive poor prognosis. In this study, we evaluated the prognostic value of BMI1 in cervical cancer. Methods: The study materials were comprised of cervical intraepithelial neoplasia (CIN, n=225), cervical cancer (n=150) and matched nonadjacent normal tissues (n=326). In order to identify BMI1 expression in the tissues, immunohistochemistry (IHC) was performed. IHC scoring was performed using digital image analysis, and the associations of BMI1 with prognosis, radiation sensitivity and human papillomavirus level were examined. Results: BMI1 compared with normal cervix and CIN lesion was highly expressed in cervical cancer. High expression of BMI1 presented better disease-free survival and overall survival than low expression according to a Kaplan-Meier survival analysis (P=0.017 and 0.035, respectively), and produced a significantly low hazard ratio for death according to a multivariate analysis (P=0.03). In CIN lesion, BMI1 was correlated with cancer stem cell (CSC) markers such as OCT4 and SOX2 (P=0.006 and 0.031, respectively), whereas in cervical cancer, no association was observed. Additionally, BMI1 expression was observed in radiation-sensitive cervical cancer, suggesting its positive prognostic indication. Conclusions: BMI1 expression is associated with favorable survival in cervical cancer, and as such, might aid the prognosis of cervical carcinoma.