To reveal the detailed methylation status of individual CpG sites, we analyzed the DNA sequence of the promoter region −389 to −89 bp of CYB5R2 using BGS in two NPC cell lines (TW03 and CNE2), two NPC biopsies (NPC15 and NPC27) and one normal biopsy (NNE7) (Fig. 2c). Here, CYB5R2 is linked to nasopharyngeal carcinoma.