SOX2 and head and neck squamous cell carcinoma: Concordantly with our protein data, a strong correlation between the mRNA levels of NANOG and SOX2 was specifically observed in N+ patients from the TCGA HNSCC cohort (Spearman coefficient 0.21, p = 0.001), but not in the N0 patients (Spearman coefficient 0.12, p = 0.104).