Previous studies have reported that breast cancer stem cells may be closely associated with tumor metastasis, recurrence, and even the failure of chemotherapy and radiotherapy. The aim of the present study was to investigate whether important cell signaling pathways associated with drug resistance are activated in stem-like acetaldehyde dehydrogenase (ALDH)hi cluster of differentiation (CD)44+ cells, and to analyze the association between ALDHhiCD44+ cells and specific pathological features. ALDHhiCD44+ cells and non-stem-like ALDHlowCD44+ cells were separated from MDA-MB-231 cells by fluorescence-activated cell sorting, and the mRNA expression levels of Notch1 and β-catenin were estimated by performing quantitative polymerase chain reaction in the stem-like and non-stem-like cells. Line correlation analysis was used to evaluate the correlation between an immunohistochemical panel of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) and Ki-67, and ALDHhiCD44+ cells from patients with invasive breast carcinoma. The mRNA levels of Notch1 and β-catenin were significantly higher in the ALDHhiCD44+ cells compared with those in the ALDHlowCD44+ cells (P<0.05); furthermore, the present study determined a high correlation (P<0.05) between the ALDHhiCD44+ cells and Ki-67 expression (P=0.007), but no correlation (P≥0.05) with ER (P=0.065), PR (P=0.107) and HER2 (P=0.050). Overall, these data clearly indicate that ALDHhiCD44+ cells may serve as novel diagnostic and prognostic factors in breast cancer.
Keywords: breast cancer; immunohistochemical; signaling pathway; stem-like cell.