Background: Cancer stem cells (CSCs) may play crucial roles in tumour progression. Aldehyde dehydrogenase 1 (ALDH1), CD44 and CD24 have been established as CSC markers in breast cancer. However, populations recognised as positive for these markers do not always correspond to each other. Moreover, only a few studies have immunohistochemically demonstrated these markers in clinical samples, and how their expressions relate to patient outcomes remains unknown. We investigated how CSC expressions change in a tumour during disease progression and the correspondence among these markers within a lesion.
Methods: Pairs of primary and metastatic tumours from 15 patients were immunohistochemically examined. Two patients had Stage IV while the others had no metastatic disease at the time of surgery. Recurrent tumours were obtained from the lungs (1 case), liver (1), gastrointestinal tract (2), bone (1), local skin nodules (7) and contralateral lymph nodes (3).
Results: 33% of primary and metastatic lesions were positive for ALDH1 (>5% defined as positive). As to subtype, 60% of triple negative but only 22% of luminal type tumours were positive for ALDH1. ALDH1 expressions of primary and metastatic lesions tended to correspond (11 of 15 cases), regardless of the proportions of positive cells. Two cases became positive and the other two lost ALDH1 expression. Disease free survivals were 3 to 115 months and there was no ALDH1 expression trend for either primary or metastatic lesions. In a preliminary examination with several cases, the expression patterns of CD44+/24- were very different from those of ALDH1-positive cells.
Conclusion: Populations of cells positive for CSC markers rarely differ between primary and metastatic lesions. We are now further examining the correspondence between ALDH1 and CD44 positivity within single tumours employing a double-staining method.