POU5F1 and head and neck squamous cell carcinoma: Moreover, in head and neck squamous cell carcinoma (HNSCC), EGCG treatment has been reported to downregulate the expression of stem cell markers, such as Oct4, Sox2, Nanog, and CD44 and to suppress HNSCC cells sphere forming capacity, augmenting their cisplatin (CP)-mediated chemosensitivity by inhibiting ABCC2 and ABCG2 transporter genes (Lee et al., 2013b).