ALDH1A3 and head and neck squamous cell carcinoma: As shown in Fig. 1a, ALDHhigh CICs from HPV16+/p53WT HNSCC displayed a dominant ALDH isoform expression signature; ALDH1A3 was enriched in UMSCC47 and UPCI-SCC090 CICs, whereas, ALDH2 was the main isoform enriched in UD-SCC2 CICs.