BMI1 and breast cancer: Similarly at the mRNA level, high expression of BMI1 was negatively associated with BCSC including ALDH1A3 (P < 0.0001), CD133 (P = 0.0003), CD24 (P = 0.002) and CD44 (P = 0.0007) (Supplementary Table 4b) in the whole BC cohort.