The combination phenotype of B-cell specific Moloney murine leukaemia virus integration site 1 (BMI1) and CD44+/CD24−/low associates with poor clinicopathological features in African patients with breast cancer

Cancer stem cell theory has revolutionalised breast cancer (BC) treatment and prognosis. The role of B cell specific Moloney murine leukaemia virus integration site 1 (BMI1) cancer stem cell marker in BC is not entirely understood. Herein, we have studied the association between BMI1, its combination phenotypes with other breast cancer stem cells and BC behaviour in a cohort of African patients. Tissue microarray of BC cohort (n = 222) from Ghanaian patients was immunohistochemically stained for BMI1. The associations between BMI1, clinicopathological features, other cancer stems cell markers and outcome were analysed using Pearson's chi-square, and Kaplan Meier's log rank-test. High expression of BMI1 was observed in 85% of cases. CD44+/CD24−/low/BMI1+ phenotype was associated with unfavourable clinicopathological features including higher tumour grade (p = 0.013), larger tumour size (p = 0.048), and high clinical prognostic stage (p = 0.018). However, the CD44+CD24−/lowBMI1− was the only phenotype that showed improved BCSS. BMI1 may contribute to the inherent tumour aggressiveness of African BC. Additional functional studies are warranted to identify the underlying mechanisms and the role of stem cell network in BC development and behaviour. •Breast cancer stem cells possess features of tumour aggressiveness•The synergistic and additive effects of the combination phenotypes in enhancing tumorigenicity is not well documented•A high expression of BMI1 and its combination phenotype CD44+/CD24-/low/BMI1+ associate with unfavourable clinicopathological features•Further research into the tumourigenic potential of CD44+/CD24-/low/BMI1+ will improve our understanding in breast cancer stem cells