Detection of Global DNA Methylation in Cervical Intraepithelial Neoplasia and Cancerous Lesions by Pyrosequencing and Enzyme-Linked Immunosorbent Assays

BACKGROUND: Cervical cancer is one of the most significant cancer found in women worldwide especially in developing countries. Previous reports showed that global DNA hypomethylation was correlated with various types of cancer including cervical cancer. METHODS: Long interspersed nuclear element-1 (LINE1) pyrosequencing and Enzyme linked-immunosorbent assay (ELISA) assays were used for detection of global DNA methylation. The ELISA results were compared to bisulfite LINE1 pyrosequencing assay. RESULTS: Different cervical cancer cell lines (CaSki, SiHa, HeLa, ME180, MS751, C33A) showed low global methylation percentage when compared to normal white blood cells by ELISA assay (1.47%-5.09% vs 8.20%, respectively) and by LINE1 pyrosequencing (20%-45% vs 62%, respectively). Global DNA methylation levels in cervical cancer samples were lower than precancerous lesions (Normal-CIN3) by LINE1 pyrosequencing (mean, 48.8% vs 56.9%, respectively, p<0.05) and ELISA assay (mean, 3.03% vs 3.85%, respectively, p<0.05). CONCLUSION: Global DNA hypomethylation was predominantly found in cervical cancer samples detected by ELISA and LINE1 pyrosequencing assays and could be used as triage tests in cervical cancer screening. ELISA assay is a suitable method for detection of global DNA methylation in large population; however, it should be further evaluated in a large clinical samples in order to be used as screening method.