Population of ALDH1(+) cells in ovarian cancer cells. A. ALDH1 enzymatic activity in chemosensitive SKOV3 and chemoresistant SKpac16 cells as determined by the Aldefluor assay. DEAB is a specific inhibitor of ALDH1 and was used to confirm gating areas. B. A comparison of the percentage of ALDH1(+) in SKOV3 cells and chemoresistant SKpac-12, -16, and −17 cells. C. ALDH1 mRNA expression in FACS-sorted ALDH1 (+) and (−) cells. All data are representative of at least two independent experiments. (*p < 0.05).