PKM and Pleural effusion: To investigate PKM2 in head and neck squamous cell carcinoma (HNSCC) we chose six cell lines from different origins: SCC-9 (tongue) [31], FaDu (laryngopharynx) [32], Detroit 562 (pharynx-derived metastasis from pleural effusion) [33], HN (soft palate-derived metastasis from a cervical lymph node) [34], BHY (alveolar ridge) [34] and SCC-154 (tongue, HPV-positive) [35].