The stem cell marker ALDH1 has been of particular interest to scientists since it has been successfully used as a marker to isolate cancer stem cells from breast
cancers. However, little is known, especially in Chinese
breast cancer patients, on whether ALDH1 enrichment is prevalent in certain subtypes of
breast cancer. In this study, we performed flow cytometry and immunohistochemistry to measure the expression of ALDH1 in 10
breast cancer cell lines and in a set of tissue microarrays consisting of 101
breast cancer tissues from the Chinese population. The 101
breast cancer tissues included 4
cancer subtypes defined on bases of their ER, PR, and HER2 statuses: triple-negative (25 cases),
luminal A (33 cases),
luminal B (16 cases) and HER2-overexpressing (HER2-OE, 27 cases). We found that ALDH1 was expressed in 25 of the 101 cases of
breast cancer tissues. When the analysis was stratified, we found that the expression of ALDH1 varied significantly among the 4 subtypes, with a higher expression in
triple-negative breast cancer (TNBC, p=0.003) than in the other 3 subtypes. In a series of
breast cancer cell lines, we also confirmed that ALDH1 activity was mainly found in TNBC cell lines compared with non-TNBC ones (15.6% ± 2.45% vs 5.5% ± 2.58%, p=0.026). These data support the concept that the expression of ALDH1 is higher in TNBC than non-TNBC, which may be clinically meaningful for a better understanding of the poor prognosis of TNBC patients.