ALDH1+ stem cells demonstrate more stem cell-like characteristics than CD44+/CD24–/low stem cells in different molecular subtypes of breast cancer

Background: CD44+/CD24–/low and ALDH1+ are both markers of breast cancer stem cell (BCSC), we compared the biological characteristics of CD44+/CD24–/low and ALDH1+ BCSCs in the four molecular subtypes of breast cancer.Methods: Four fresh blocks of breast cancer tissue were obtained from patients with Luminal A, Luminal B, human epidermal receptor-2 (HER2)-overexpression and triple-negative breast cancer, respectively. Flow cytometry was used to sort CD44+/CD24–/low and ALDH1+ BCSCs. The mammosphere (MS) formation experiment and NOD/SCID mouse xenograft experiment were performed to compare the self-renewal and tumorigenic abilities of CD44+/CD24–/low with those of ALDH1+ BCSCs.Results: The proportions of CD44+/CD24–/low BCSC and ALDH1+ BCSC in Luminal A, Luminal B, HER2 overexpression and triple-negative subtypes were 12.1% and 8.7%, 2.7% and 5.7%, 0.8% and 8.7%, 0.7% and 4.5%, respectively. The MS formation experiment demonstrated that ALDH1+ BCSC formed significantly more MSs than CD44+/CD24–/low BCSC in the four molecular subtypes (P<0.001). The NOD/SCID mouse xenograft experiment demonstrated that the sizes of grafted tumors formed by ALDH1+ BCSC were larger than those formed by CD44+/CD24–/low BCSC in the four molecular subtypes (P<0.05).Conclusions: In the four molecular subtypes of breast cancer, ALDH1+ BCSC demonstrated better self-renewal and tumorigenic abilities than CD44+/CD24–/low BCSC.