Additionally, ARNTL promoter (cg15603424) methylation levels in NPC cell lines (CNE1, CNE2, SUNE1, HONE1, HNE1, 5-8F, 6-10B) were also significantly increased compared with that in human immortalized normal nasopharynx epithelial cell line (NP69) (Fig. 1d, Additional file 3: Figure S2; P < 0.001). This evidence concerns the gene BMAL1 and nasopharyngeal carcinoma.