Figure 2. Melatonin reverses DDP chemoresistance by inhibiting β-catenin nuclear translocation. (A, B) Protein expression of β-catenin, DKK1, c-Myc and CylincD1 in the CNE2 and CNE2/DDP (A), 5-8F and 5-8F/DDP cell lines (B) treated with melatonin (2 mM) for 48 hr, as determined by western blot. (C) mRNA expression of Wnt/β-catenin downstream genes (AXIN2, SOX9, CD44 and CCND2) in CNE2 and CNE2/DDP, 5-8F and 5-8F/DDP cell lines treated with melatonin (2 mM) for 48 hr, as determined by qPCR. (D, E) Representative images of immunofluorescent staining for β-catenin in CNE2 and CNE2/DDP (D), 5-8F and 5-8F/DDP (E) treated with or without melatonin (2 mM) for 48 hr. (F) Relative luciferase activity of NPC cells transfected with the TOP/FOPFlash vector and pRL-TK vector. Data presented are the mean ± SD; **P < 0.01 compared with control using Student t-test.