CD44 and head and neck squamous cell carcinoma: CD44+ HNSCC cells exhibited CSC characteristics and down-regulated HLA-A2, HLA class II, and TAP2, as well as high levels of immune modulatory cytokines such interleukin-8 (IL-8) and granulocyte colony-stimulating factor (G-CSF), indicating antigen presentation and processing dysfunction (Chikamatsu et al., 2011).