Cancer stem cell marker Bmi-1 expression is associated with basal-like phenotype and poor survival in breast cancer

The purpose of present study was to examine the expression of cancer stem cell marker Bmi-1 in breast cancer tissue and to evaluate the clinical implication of Bmi-1 expression for these patients.

A total of 171 breast cancer patients who received surgical treatment in our hospital were enrolled in this study. Bmi-1 expression in breast cancer tissue was assayed by immunohistochemistry. Statistical analyses were applied to test the relationship between expression of Bmi-1 and clinicopathologic features and patient survival. The relationship between Bmi-1 and the basal-like phenotype of breast cancer also was analyzed in this study.

Positive Bmi-1 expression was detected in 89 of 171 (52%) invasive breast cancers patients. The Bmi-1 status was significantly correlated to histological grade III (p = 0.001) and basal-like phenotype (p < 0.001). The 5 year overall survival of the patients with Bmi-1-positive and -negative cancers were 78 and 91.9%, respectively (p = 0.03). Histological grade (p = 0.046) and Bmi-1 status (p = 0.012) were detected as the independent prognostic factors in the Cox regression test.

Bmi-1 status is an independent prognostic factor, which also is associated with tumor histological grade and basal-like phenotype. The high proportions of positive Bmi-1 expression in basal-like breast cancer may be related to the high aggressiveness behavior of this subtype of breast cancer.