ALDH1A1 and cancer: In particular, low intracellular ROS levels are required to maintain stem‐like cells in both normal tissues and cancers.[35] Hypoxia has been reported to enrich CD166+ and CD133+ stem‐like cancer cell populations.[5a,c] Consistently, we also observed hypoxia stimulated the CSC markers ALDH1 and CD44V8‐10.