Distinct DNA methylation profiles between adenocarcinoma and squamous cell carcinoma of human uterine cervix.

Alterations in DNA methylation offer unique prospects as tumor markers. The big limitation in cervical cancer research is that it is too hard to obtain the pure normal tissue from a cervical cancer mass. So, we first profile type-specific DNA methylation of major two types of human uterine cervical cancer, adenocarcinoma (ACA) and squamous cell carcinoma (SCC), to establish a precise source of marker research. To assess the DNA methylation status of promoter regions in human uterine cervical ACAs and SCCs, fresh frozen tissues were obtained from bulky tumor masses to minimize the contamination from normal tissues and two array platforms using digestion with methylation-sensitive restriction-enzyme HpaII, ligation, and PCR were performed: an array of 11,994 (approximately 1.5 kb) PCR products from 10,445 promoter regions, and an array of 355,264 oligonucleotides for 18,212 HpaII fragments in 12,617 promoter regions. Loci near 21 genes showed significant differences between six ACA and four SCC from the analysis of two array data. Real-time PCR-based validation was performed on 13 loci using other nearby candidate methylation targets in the same promoter. Methylation patterns of 11 of 13 linked loci concurred with the microarray results. Four loci were further studied using tissues from additional patients (23 ACA and 24 SCC). Hypermethylation of loci in PAK6 and NOGOR most strongly correlated with ACA. Therefore, we have identified the 21 genes with differential methylation pattern between ACA and SCC and, furthermore, we found that PAK6 and NOGOR could be useful markers of ACA to be distinct from SCC.