ABCC5 and head and neck squamous cell carcinoma: pointed out that the axis of forkhead box protein M1 (FOXM1) and MDR1/MRP5 is a newly defined drug efflux mechanism in HNSCC cell lines (CNE1, CNE2, and EC109) (50, 51); however, the FOXM1/MPR5 or FOXM1/MDR1 axis has not yet been clarified in HNC cells.