engleski

CpG methylation of HPV 16 and HPV 18 in cervical samples with different cytological diagnosis

Infection with human papillomavirus (HPV) is the central cause of cervical cancer. There are at least 15 high-risk (HR) HPV types that are significantly associated with progression of cervical intraepithelial neoplasia (CIN) to cervical cancer. High-risk human papillomavirus types 16, 18, 31, 33, 35, 45, 52 and 58 are commonly found in cervical cancer worldwide. HPV types 16 and 18 are the two most common types in invasive cervical cancer worldwide with a relative contribution of 71%. In Croatia, HPV 16 and HPV 18 are at the first and the fourth place, respectively, among HR HPV types in cervical samples with different cytological diagnosis. The infection with HPV is widespread and little is known about the secondary factors associated with progression from subclinical infection to cancer. Methylation of CpG sites in HPV 16 and HPV 18 genomes that represses transcription of HPV genes is one of the factors that are possibly relevant in carcinogenic progression. Therefore, in this study, we focused on HPV 16 and HPV 18 positive cervical samples and analyzed CpG methylation of HPV 16 and HPV 18 genomes. Furthermore, CpG methylation will be analysed in cell lines containing either HPV 16 (CaSki, SiHa) either HPV 18 (HeLa). Methylation specific PCR (MSP) with primers specific for methylated and unmethylated forms of the L1 gene of HPV 18 was used to amplify bisulfite converted DNA. Bisulfite sequencing was used to identify a number and a position of methylated cytosines inside three regions (L1 and 5’ LCR, enhancer and promoter) of HPV 16 genome that include 19 CpG sites. Preliminary data showed the highest methylation rate among carcinoma lesions, in comparison of CIN 1-3 or asymptomatic samples. Correlation and possible significance between CpG methylation of HPV 16 and HPV 18 genes and the cytological diagnosis will be presented.

human papillomavirus (HPV); DNA methylation; cervical cancer

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