Methylation-specific digital karyotyping of HPV16E6E7-expressing human keratinocytes identifies novel methylation events in cervical carcinogenesis


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Abstract

Transformation of epithelial cells by high-risk human papillomavirus (hrHPV) types can lead to anogenital carcinomas, particularly cervical cancer, and oropharyngeal cancers. This process is associated with DNA methylation alterations, often affecting tumour suppressor gene expression. This study aimed to comprehensively unravel genome-wide DNA methylation events linked to a transforming hrHPV-infection, which is driven by deregulated expression of the viral oncogenes E6 and E7 in dividing cells. Primary human keratinocytes transduced withHPV16E6E7and their untransduced counterparts were subjected to methylation-specific digital karyotyping (MSDK) to screen for genome-wide DNA-methylation changes at different stages of HPV-induced transformation. Integration of the obtained methylation profiles with genome-wide gene expression patterns of cervical carcinomas identified 34 genes with increased methylation in HPV-transformed cells and reduced expression in cervical carcinomas. For 12 genes (CLIC3,CREB3L1,FAM19A4,LFNG,LHX1,MRC2,NKX2-8,NPTX-1,PHACTR3,PRDM14,SOSTandTNFSF13) specific methylation in HPV-containing cell lines was confirmed by semi-quantitative methylation-specific PCR. Subsequent analysis ofFAM19A4,LHX1,NKX2-8,NPTX-1,PHACTR3andPRDM14in cervical tissue specimens showed increasing methylation levels for all genes with disease progression. All six genes were frequently methylated in cervical carcinomas, with highest frequencies (up to 100%) seen forFAM19A4,PHACTR3andPRDM14. Analysis of hrHPV-positive cervical scrapes revealed significantly increased methylation levels of the latter three genes in women with high-grade cervical disease compared to controls. In conclusion, MSDK analysis ofHPV16-transduced keratinocytes at different stages of HPV-induced transformation resulted in the identification of novel DNA methylation events, involvingFAM19A4,LHX1,NKX2-8,PHACTR3andPRDM14genes in cervical carcinogenesis. These genes may provide promising triage markers to assess the presence of (pre)cancerous cervical lesions in hrHPV-positive women. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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