PROM1 and head and neck squamous cell carcinoma: ALDH detoxifies intracellular aldehydes through oxidation and may have a role in the differentiation of SCs through the oxidation of retinoic acid.39 In head and neck squamous cell carcinoma (HNSC), ALDH can be used as a single marker of CSCs.40 More often, ALDH is combined with other CSC markers: ALDHhighCD44+CD24- and ALDHhighCD44+CD133+ cells may be important mediators of breast CSCs.41 Further research was conducted and the results revealed the existence of a hierarchical organization in HCC cells with tumorigenic potential as follows: CD133+ALDH+ > CD133+ALDH− > CD133−ALDH−.