Figure 5. Effects of melatonin and DDP combination on malignant properties of nasopharyngeal carcinoma (NPC) cells. (A–D) The cell viability of the CNE2 (A), 5-8F (B), HONE1 (C) and SUNE1 (D) cells incubated with melatonin (72 hr) (green line) alone and DDP alone (blue line) or melatonin with DDP combination (red line) was determined by CCK-8 assay. (E, F) Images (E) and quantification (F) clonogenic colony formation assays of the indicated cells treated with melatonin for 2 weeks. All of the experiments were performed at least three times. Data presented are the mean ± SD; **P < 0.01, *P < 0.05 compared with control using Student t-test.