ALDH1A1 and head and neck squamous cell carcinoma: It was shown that a subpopulation of HNSCC CSC-like cells is characterized by high expression of isoform 3 of the cell surface receptor CD44 (CD44v3) and aldehyde dehydrogenase-1 (ALDH1), both known to be involved in HNSCC tumor development and progression (Chen et al., 2009; Wang et al., 2009; Clay et al., 2010; Bourguignon et al., 2012).