Our data have shown that BMI1 is negatively correlated with some BCSC markers at both mRNA and protein levels in all BC and the ER+ subtypes; however, the association between BMI1 and BCSC markers in TNBC was limited (only CD133 and SOX10), which further supports a different role of BMI1 in relation to the molecular subtypes of BC particularly ER+ . The gene discussed is PROM1; the disease is breast cancer.