CHL1 and nasopharyngeal carcinoma: To determine whether the down-regulation of CHL1 in NPC was caused by hypermethylation in this promoter region, the methylation status of CHL1 was examined using MSP methylation or unmethylation specific primers in three NPC cell lines (SUNE1, CNE2 and C666), on observation both methylated and unmethylated alleles were expressed in SUNE1 and CNE2 cell lines, except in NP460 where a weak expression of methylated allele is observed (Fig. 1E).