Virological characteristics of cervical cancers carrying pure episomal form of HPV16 genome.

Many studies on integration have reported conflicting results regarding the role of HPV integration in cervical cancer. We hypothesized that high viral load and disruption of E2 gene associated with integration of HPV were not the only pathway leading to cancer development. This study analysed the viral load and integration status of HPV16, measured the HPV16 E6/E7 mRNA transcript levels, delineated the E2 and LCR sequence variation, and determined the methylation status of two E2 binding sites. The results showed that viral load was not associated with the physical status of HPV genome. Levels of the three E6/E7 mRNA transcripts in invasive cervical cancers containing purely episomal viral genome were found to be similar to those containing integrated viral genome, suggesting that cancers containing episomal viral genome were also mediated by an up-regulated E6/E7 mRNA expression, and more importantly, did not depend on integration and disruption of the E2 gene. The alternative mechanism that up-regulated the expression of E6 and E7 in invasive cancers harbouring episomal viral genome was likely to be a consequence of methylation of the two E2 binding sites located at the promoter region of HPV16. These observations are in line with the hypothesis that HPV integration was not the only mechanism leading to the development of cervical cancer.

Cheung JL ，Cheung TH ，Yu MY ，Chan PK ... -  《-》

Viral E6 is overexpressed via high viral load in invasive cervical cancer with episomal HPV16.

Hong D ，Liu J ，Hu Y ，Lu X ，Li B ，Li Y ，Hu D ，Lu W ，Xie X ，Cheng X ... -  《BMC CANCER》

HPV prevalence, E6 sequence variation and physical state of HPV16 isolates from patients with cervical cancer in Sichuan, China.

Qiu AD ，Wu EQ ，Yu XH ，Jiang CL ，Jin YH ，Wu YG ，Chen Y ，Chen Y ，Shan YM ，Zhang GN ，Fan Y ，Zha X ，Kong W ... -  《GYNECOLOGIC ONCOLOGY》

Methylation status of HPV16 E2-binding sites classifies subtypes of HPV-associated oropharyngeal cancers.

The human papillomavirus (HPV) E2 protein is a transcriptional repressor of the oncogenes E6/E7 and loss of E2 function is considered a key step in carcinogenesis. Integration of HPV into the host genome may disrupt the E2 gene. Furthermore, methylation of CpG dinucleotides in E2-binding sites (E2BSs) in the HPV upstream regulatory region may interfere with transcriptional repression of E6 and E7 by E2. The authors hypothesized that the CpG methylation status of E2BS identifies subtypes of HPV type 16 (HPV16)-associated oropharyngeal squamous cell cancers (OPSCC) in association with E2 gene integrity and viral integration. Methylation of 10 CpG dinucleotides within the upstream regulatory region, encompassing E2BSs 1, 2, 3, and 4, was quantitatively analyzed by bisulfite pyrosequencing in 57 HPV16-associated OPSCC cases. E2 status was analyzed by gene amplification and quantitative real-time reverse transcriptase-polymerase chain reaction. Viral integration was determined by integration-specific polymerase chain reaction methods. Three subgroups with differential methylation at E2BS3 and E2BS 4 were identified: 1) complete methylation (>80%) associated with the presence of integrated HPV genomes with an intact E2 gene; 2) intermediate methylation levels (20%-80%) with predominantly episomal HPV genomes with intact E2; and 3) no methylation (<20%) with a disrupted E2 gene. Patients with high methylation levels tended to have a worse 5-year overall survival compared with patients with intermediate methylation (hazard ratio, 3.23; 95% confidence interval, 1.13-9.24 [P = .06]). Methylation of E2BS3 and E2BS4 in OPSCC is associated with E2 integrity and viral physical status. It might explain deregulated viral oncogene expression in the presence of E2. The prognostic significance of E2BS methylation for patients with HPV-associated OPSCC needs to be analyzed further.

Reuschenbach M ，Huebbers CU ，Prigge ES ，Bermejo JL ，Kalteis MS ，Preuss SF ，Seuthe IM ，Kolligs J ，Speel EJ ，Olthof N ，Kremer B ，Wagner S ，Klussmann JP ，Vinokurova S ，von Knebel Doeberitz M ... -  《-》

Physical status and expression of HPV genes in cervical cancers.

Park JS ，Hwang ES ，Park SN ，Ahn HK ，Um SJ ，Kim CJ ，Kim SJ ，Namkoong SE ... -  《GYNECOLOGIC ONCOLOGY》