Loss of expression of the cancer stem cell marker aldehyde dehydrogenase 1 correlates with advanced-stage colorectal cancer

BACKGROUND: Colorectal cancer (CRC) progression is mediated by cancer stem cells (CSCs). We sought to determine if the expression of the CSC marker aldehyde dehydrogenase 1 (ALDH1) in CRC tumors varies by American Joint Committee on Cancer stage or correlates to clinical outcomes. METHODS: Primary and metastatic CRC samples from 96 patients were immunostained with antibodies to ALDH1 and imaged to evaluate marker expression. The percentage of ALDH1 ⁺ cells was correlated to clinical outcomes. RESULTS: ALDH1 was overexpressed in CRC tumors compared with nonneoplastic tissue. Marker expression was highest in nonmetastatic tumors. The loss of expression was associated with advanced stage and metastatic disease. No significant correlation was found between ALDH1 expression and metastasis, recurrence, or survival. CONCLUSIONS: ALDH1 was highly expressed in nonmetastatic CRC, but expression was lost with advancing stage. ALDH1 could be an effective therapeutic target in early CRC but not late-stage disease. No correlation was found between ALDH1 and disease prognosis.