Fig. 3

Promoter methylation differences in cervical cytology and cervical carcinoma cell lines. a Methylation (%) of total genomic DNA in three grades of cervical cytology, i.e., NILM (N = 33), LSIL (N = 70), and HSIL (N = 67), was compared by CpG positions among four genes (ADCY8, CDH8, ZNF582, and MGMT). Pairwise comparisons of methylation for each CpG position between cytological grades (NILM vs. LSIL, LSIL vs. HSIL, and NILM vs. HSIL) revealed significantly higher levels for HSIL vs. LSIL and LSIL vs. NILM at multiple positions for ADCY8, CDH8, and ZNF582. For MGMT, methylation levels were not significantly different among cytological grades. Methylation levels for each CpG position increased concurrently with cytological grade for ADCY8, CDH8, and ZNF582 by Spearman’s ρ (p < 0.001). *p < 0.05 by the Wilcoxon rank-sum test. b SiHa, HeLa, and Ca Ski cell lines with genome-integrated HPV demonstrated promoter hypermethylation of ADCY8, CDH8, and ZNF582 genes. For HPV-negative cell lines, DoTc2 and C33-A revealed an inconsistent pattern of hypermethylation in the studied genes. Using SiHa methylation (%) as a reference (o), cell lines with significantly different levels are indicated by an asterisk. *p < 0.05 by the Wilcoxon rank-sum test. NS not statistically significant. Cell lines were analyzed for CpG methylation in duplicate collections