Recently, a high level of CD44v3 isoform together with aldehyde dehydrogenase-1 (ALDH1) (CD44v3highALDH1high) have also been detected in the subpopulation of cancer stem cells (CSCs) of Human Head and Neck Squamous Cell Carcinoma (HNSCC) cell line [30,31]. Here, ALDH1A1 is linked to head and neck squamous cell carcinoma.