SNAI2 and head and neck squamous cell carcinoma: Although, a significant correlation between immunohistochemical Slug staining intensity or the frequency of the stained cells among tumor cells and Slug gene expression was not possible to state, both the % of Slug positive cells in cancer cell nests as well as the Slug staining intensity were higher in HNSCC cases with upregulated Slug gene expression than in the cases with Slug gene expression level at the normal control mucosa (Supplementary Figure S2).