ALDH and CD44 are associated with tumorigenesis and CSC properties in ovarian cancer when used as individual CSC markers.30,31 In the present study, we isolated the CSC subset of ascites-derived tumour cells and cell lines with the aid of both ALDH and CD44 markers, which are overexpressed in this tumour cell population, and validated the ALDH+CD44+ subset as an ovarian CSC subpopulation for the first time to our knowledge. This evidence concerns the gene CD44 and ovarian cancer.