ALDH1A1 and head and neck squamous cell carcinoma: We found that the protein expression of AGR2 in HNSCC was significantly correlated with Survivin (P < 0.01, r = 0.2466), Cyclin D1 (P < 0.001, r = 0.4425), ALDH1 (P < 0.001, r = 0.5508), Sox2 (P < 0.001, r = 0.4573), Oct4 (P < 0.001, r = 0.5606), and Slug (P < 0.001, r = 0.5214) (Supplementary Figs. S3, Supplementary Table 2).