Aims: Aldehyde dehydrogenase 1 (ALDH1) has been identified as a reliable marker of breast cancer stem cells, and its clinical significance as a prognostic indicator of breast cancer has been reported by several investigators. However, the clinical significance of ALDH1 expression in triple-negative (TN) breast cancer, a high-risk breast cancer lacking the benefit of specific therapy, remains to be solved.
Methods and results: We performed immunohistochemical analyses of 106 TN breast cancers, using paraffin-embedded sections. The basal-like phenotype was also investigated with the use of basal cytokeratin 5/6 and epidermal growth factor receptor. ALDH1 expression in carcinoma cells was found in 59% of cases and was correlated with high histological grade alone (P < 0.006), whereas ALDH1 expression in stromal cells was found in 49% of cases but was not correlated with any clinicopathological parameter. Patients with ALDH1 expression in carcinoma cells had a shorter relapse-free survival (RFS) according to the log-rank test (P = 0.015). According to Cox multivariate analysis, ALDH1 expression in carcinoma cells was an independent prognostic indicator of RFS (P = 0.025). The log-rank test revealed that stromal expression of ALDH1 had no effect on RFS.
Conclusions: ALDH1 expression in carcinoma cells is an independent prognostic factor in TN breast cancer patients.
2011 Blackwell Publishing Limited.