Moreover, EMT markers (i.e. Vimentin and Slug) and CSC markers (i.e. CD44, KLF4, ALDH1 and SOX2) are used to examine the protein expression levels in human SCCHN tissue microarray; results showed that all the proteins mentioned above were overexpressed in SCCHN tissues (Fig. 5A). Here, CD44 is linked to head and neck squamous cell carcinoma.