Introduction: B-cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) is a member of polycomb group, which participates in axial patterning, hematopoiesis, cell cycle regulation, and senescence. Recently, overexpression of Bmi-1 has been reported in various human cancers and proved to be associated with poor survival. The aim of this study was to investigate the expression of Bmi-1 protein in human uterine cervical cancer (UCC) and explore its associations with clinicopathological factors and prognosis.

Methods: Western blot was used to detect the expression of Bmi-1 in 4 human cervical cancer cell lines (Hela, SiHa, CasKi, and C33A) and a normal cervical epithelial cell line. In addition, 152 UCC and 30 adjacent normal cervical paraffin-embedded samples were collected to detect Bmi-1 expression by immunohistochemistry.

Results: Western blot analysis showed Bmi-1 was overexpressed in 4 human UCC cell lines but not in the normal cervical epithelial cell line. Moreover, immunohistochemical staining revealed Bmi-1 was overexpressed in 63.2% UCC tissues (Bmi-1 ++ or +++), and the overexpression of Bmi-1 protein was significantly correlated with tumor size (P = 0.046), clinical stage (P = 0.021), and regional lymph nodes metastasis (P = 0.010). Survival analysis showed a significant difference between Bmi-1 protein overexpression and poor survival (P = 0.021). Cox proportional hazards risk analysis indicated that Bmi-1 protein overexpression was an independent prognostic factor for overall survival.

Conclusions: B-cell-specific Moloney murine leukemia virus integration site 1 is overexpressed in UCC and correlated with adverse clinical characteristics and poor prognosis, which suggests that the Bmi-1 might participate in the development and progression of UCC and have clinical potential not only as a useful predictor of aggressive phenotype but also a promising prognostic predictor.