POU5F1 and cancer: CD44, aldehyde dehydrogenase 1 (ALDH1), Oct‐4, and Sox2 have been widely accepted as important and reliable surface markers for the isolation of cancer stem cells in several cancers including breast cancer.23, 24 In order to analyze whether CD44+/CD24−/low cells represented the CSC population of BCSC, the expressions of CD44 and CD24 were identified by flow cytometry.