Methylation of human papillomavirus 16, 18, 31, and 45 L2 and L1 genes and the cellular DAPK gene: Considerations for use as biomarkers of the progression of cervical neoplasia

PAX1 and SEPT9 methylation analyses in cervical exfoliated cells are highly efficient for detecting cervical (pre)cancer in hrHPV-positive women

Studies have investigated PAX1 and SEPT methylation were closely associated with cervical cancer. For this study, we verified the expressions of PAX1 and SEPT9 methylation in 236 hrHPV women cervical exfoliated cells by using quantitative methylation-specific PCR and we further explored their diagnostic value in cervical (pre)cancer detection. Our results identified that the methylation rates and levels of PAX1 and SEPT9 increased with cervical lesion severity. For a diagnosis of cervical (pre)cancer, the area under the curve (AUC) of PAX1 methylation was 0.77 (95% CI 0.71-0.83) and the AUC of SEPT9 methylation was 0.86 (95% CI 0.81∼0.90). Analyses of the PAX1 and SEPT9 methylation statuses alone or combined with commonly used tests can efficiently identify cervical (pre)cancer. In particular, SEPT9 methylation might serve as an effective and powerful biomarker for the diagnosis of cervical (pre)cancer and as an alternative triage test in HPV-based cervical (pre)cancer screening programs.Impact StatementWhat is already known on this subject? This subject showed that PAX1 and SEPT9 methylation were closely associated with cervical cancer. The methylation rates and levels of PAX1 and SEPT9 increased with cervical lesion severity and reached a peak in cervical cancer exfoliated cells. We further assessed the diagnostic performances of PAX1 and SEPT9 methylation in cervical cancer screening. In detecting cervical (pre)cancer, the sensitivity values of PAX1 and SEPT9 methylation were up to 61.18% and 82.35%, respectively, and the specificity values of PAX1 and SEPT9 methylation were up to 95.36% and 86.75%, respectively. Moreover, the ROC curve analysis showed AUC values of 0.77 for PAX1 methylation and 0.86 for SEPT9 methylation tests, which were significantly superior to other commonly used tests. These findings suggest that PAX1 and SEPT9 methylation detection may have great clinical potential in cervical cancer screening.What the results of this study add? The rates and levels of PAX1 and SEPT9 methylation increased with the severity of the cervical lesions. For a diagnosis of cervical (pre)cancer, the area under the curve (AUC) of PAX1 methylation was 0.77 (95% CI 0.71-0.83), and the sensitivity and specificity values were 61.18% and 95.36%, respectively. The AUC value of the SEPT9 methylation was 0.86 (95% CI 0.81 ∼ 0.90), and the sensitivity and specificity values were 82.35% and 86.75%, respectively. Compared with the various tests we conducted, the PAX1 methylation showed the highest specificity (95.36%), and the SEPT9 methylation demonstrated the highest accuracy(86.00%).What the implications are of these findings for clinical practice and/or further research? The methylation levels of PAX1 and SEPT9 had a certain predictive effect on the severity of cervical lesions in hrHPV-positive women. In addition, SEPT9 methylation analysis performs better than PAX1 methylation analysis and commonly used tests in cervical exfoliated cells for detecting cervical (pre)cancer in hrHPV-positive women. SEPT9 methylation analysis merits consideration as an effective and objective, alternative triage test in HPV-based cervical (pre)cancer screening programs.

Epigenetic and Transcriptomic Regulation Landscape in HPV+ Cancers: Biological and Clinical Implications

Human Papillomavirus (HPV) is an oncogenic virus that causes the highest number of viral-associated cancer cases and deaths worldwide, with more than 690,000 new cases per year and 342,000 deaths only for cervical cancer (CC). Although the incidence and mortality rates for CC are declining in countries where screening and vaccination programs have been implemented, other types of cancer in which HPV is involved, such as oropharyngeal cancer, are increasing, particularly in men. Mutational and transcriptional profiles of various HPV-associated neoplasms have been described, and accumulated evidence has shown the oncogenic capacity of E6, E7, and E5 genes of high-risk HPV. Interestingly, transcriptomic analysis has revealed that although a vast majority of the human genome is transcribed into RNAs, only 2% of transcripts are translated into proteins. The remaining transcripts lacking protein-coding potential are called non-coding RNAs. In addition to the transfer and ribosomal RNAs, there are regulatory non-coding RNAs classified according to size and structure in long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and small RNAs; such as microRNAs (miRNAs), piwi-associated RNAs (piRNAs), small nucleolar RNAs (snoRNAs) and endogenous short-interfering RNAs. Recent evidence has shown that lncRNAs, miRNAs, and circRNAs are aberrantly expressed under pathological conditions such as cancer. In addition, those transcripts are dysregulated in HPV-related neoplasms, and their expression correlates with tumor progression, metastasis, poor prognosis, and recurrence. Nuclear lncRNAs are epigenetic regulators involved in controlling gene expression at the transcriptional level through chromatin modification and remodeling. Moreover, disruption of the expression profiles of those lncRNAs affects multiple biological processes such as cell proliferation, apoptosis, and migration. This review highlights the epigenetic alterations induced by HPV, from infection to neoplastic transformation. We condense the epigenetic role of non-coding RNA alterations and their potential as biomarkers in transformation’s early stages and clinical applications. We also summarize the molecular mechanisms of action of nuclear lncRNAs to understand better their role in the epigenetic control of gene expression and how they can drive the malignant phenotype of HPV-related neoplasia. Finally, we review several chemical and epigenetic therapy options to prevent and treat HPV-associated neoplasms.

HPV16 and HPV18 Genome Structure, Expression, and Post-Transcriptional Regulation

Human papillomaviruses (HPV) are a group of small non-enveloped DNA viruses whose infection causes benign tumors or cancers. HPV16 and HPV18, the two most common high-risk HPVs, are responsible for ~70% of all HPV-related cervical cancers and head and neck cancers. The expression of the HPV genome is highly dependent on cell differentiation and is strictly regulated at the transcriptional and post-transcriptional levels. Both HPV early and late transcripts differentially expressed in the infected cells are intron-containing bicistronic or polycistronic RNAs bearing more than one open reading frame (ORF), because of usage of alternative viral promoters and two alternative viral RNA polyadenylation signals. Papillomaviruses proficiently engage alternative RNA splicing to express individual ORFs from the bicistronic or polycistronic RNA transcripts. In this review, we discuss the genome structures and the updated transcription maps of HPV16 and HPV18, and the latest research advances in understanding RNA cis-elements, intron branch point sequences, and RNA-binding proteins in the regulation of viral RNA processing. Moreover, we briefly discuss the epigenetic modifications, including DNA methylation and possible APOBEC-mediated genome editing in HPV infections and carcinogenesis.

Epigenetic approaches for cervical neoplasia screening (Review)

Human papillomavirus (HPV) infection is the leading cause of cervical cancer. The Papanicolaou cytology test is the usually employed type of screening for this infection; however, its sensibility is limited. Only a small percentage of women infected with high-risk HPV develop cervical cancer with an array of genetic and epigenetic modifications. Thus, it is necessary to develop rapid, reproducible and minimally invasive technologies for screening. DNA methylation has gained attention as an alternative method for molecular diagnosis and prognosis in HPV infection. The aim of the present review was to highlight the potential of DNA methylation in cervical neoplasia screening for clinical applications. It was observed that the methylation human and viral genes was correlated with high-grade lesions and cancer. Methylation biomarkers have shown a good capacity to discriminate between high-grade lesions with a transformative potential and cervical cancer, being able to detect these modifications at an early stage. With further research, the epigenetic profiles and subtypes of the tumors could be elaborated, which would aid in therapy selection by opening avenues in personalized precision medicine. Response to therapy could also be evaluated through such methods and the accessibility of liquid biopsies would allow a constant monitoring of the patient's status without invasive sampling techniques.

Phylogenomic Analysis of Human Papillomavirus Type 31 and Cervical Carcinogenesis: A Study of 2093 Viral Genomes

Human papillomavirus (HPV) type 31 (HPV31) is closely related to the most carcinogenic type, HPV16, but only accounts for 4% of cervical cancer cases worldwide. Viral genetic and epigenetic variations have been associated with carcinogenesis for other high-risk HPV types, but little is known about HPV31. We sequenced 2093 HPV31 viral whole genomes from two large studies, one from the U.S. and one international. In addition, we investigated CpG methylation in a subset of 175 samples. We evaluated the association of HPV31 lineages/sublineages, single nucleotide polymorphisms (SNPs) and viral methylation with cervical carcinogenesis. HPV31 A/B clade was >1.8-fold more associated with cervical intraepithelial neoplasia grade 3 and cancer (CIN3+) compared to the most common C lineage. Lineage/sublineage distribution varied by race/ethnicity and geographic region. A viral genome-wide association analysis identified SNPs within the A/B clade associated with CIN3+, including H23Y (C626T) (odds ratio = 1.60, confidence intervals = 1.17-2.19) located in the pRb CR2 binding-site within the E7 oncogene. Viral CpG methylation was higher in lineage B, compared to the other lineages, and was most elevated in CIN3+. In conclusion, these data support the increased oncogenicity of the A/B lineages and suggest variation of E7 as a contributing risk factor.

Human papillomavirus 16 L1 gene methylation as a potential biomarker for predicting anal intraepithelial neoplasia in men who have sex with men (MSM)

The human papillomavirus (HPV) 16 early promoter and L1 gene methylation were quantitatively measured using pyrosequencing assay in anal cells collected from men who have sex with men (MSM) to determine potential biomarkers for HPV-related anal cancer. The methylation patterns of HPV16 genes, including the early promoter (CpG 31, 37, 43, 52, and 58) and L1 genes (CpG 5600, 5606, 5609, 5615, 7136, and 7145), were analyzed in 178 anal samples. The samples were diagnosed as normal, anal intraepithelial neoplasia (AIN) 1, AIN2, and AIN3. Low methylation levels of the early promoter (< 10%) and L1 genes (< 20%) were found in all detected normal anal cells. In comparison, medium to high methylation (≥ 20–60%) in the early promoter was found in 1.5% (1/67) and 5% (2/40) of AIN1 and AIN2-3 samples, respectively. Interestingly, slightly increased L1 gene methylation levels (≥ 20–60%), especially at the HPV16 5’L1 regions CpGs 5600 and 5609, were demonstrated in AIN2-3 specimen. Moreover, a negative correlation between high HPV16 L1 gene methylation at CpGs 5600, 5609, 5615, and 7145 and a percentual CD4 count was found in AIN3 HIV positive cases. When comparing the methylation status of AIN2-3 to that of normal/AIN1 lesions, the results indicated the potential of using HPV16 L1 gene methylation as a biomarker for HPV-related cancer screening.

Emerging technologies for cervical cancer screening

Cervical cancer remains a concern worldwide, and cervical cancer screening plays an important role in reducing the burden of this disease. Although cytology is still the main strategy for cervical cancer screening, it has gradually changed to human papillomavirus testing. The specificity of human papillomavirus testing is lower than that of cytology, which leads to an increased rate of colposcopy after positive results. To decrease colposcopic examinations, an efficient triage method is needed for human papillomavirus screening. New biomarkers have been developed and evaluated for primary screening and triage of abnormal cytology or human papillomavirus-positive results. Their sensitivity and specificity were estimated and compared with those of cytology. In the present study, the following new techniques were examined: p16/Ki67 dual staining, DNA methylation, micro-ribonucleic acid, chromosomal abnormalities, Claudins and DNA ploidy. Evaluation studies of p16/Ki67 dual staining and DNA methylation were more advanced than those of other options. When p16/Ki67 dual staining was used for triage for human papillomavirus testing, the sensitivity of 2 or greater cervical intraepithelial neoplasia (CIN2+) detection was higher than that of cytology without decreased specificity. Although there are several types of DNA methylation, sensitivity and specificity were moderate for detecting CIN2+. S5 classifier is a commercialized product that consists of viral methylation, and high sensitivity with decreased specificity has been reported. Considering its combination with self-sampling, DNA methylation is a highly anticipated technique along with human papillomavirus testing for the next generation of cervical cancer screening. However, the backgrounds for cervical cancer screening differ among countries and further study is needed to identify the best available method.

Cervical cancer risk profiling: molecular biomarkers predicting the outcome of hrHPV infection

INTRODUCTION

Cervical cancer affects half a million women worldwide annually. Given the association between high-risk human papillomavirus (hrHPV) infection and carcinogenesis, hrHPV DNA testing became an essential diagnostic tool. However, hrHPV alone does not cause the disease, and, most importantly, many cervical lesions regress to normal in a year because of the host immune system. Hence, the low specificity of hrHPV DNA tests and their inability to predict the outcome of infections have triggered a further search for biomarkers.

AREAS COVERED

We evaluated the latest viral and cellular biomarkers validated for clinical use as primary screening or triage for cervical cancer and assessed their promise for prevention as well as potential use in the future. The literature search focused on effective biomarkers for different stages of the disease, aiming to determine their significance in predicting the outcome of hrHPV infections.

EXPERT OPINION

Biomarkers such as p16/Ki-67, hrHPV genotyping, hrHPV transcriptional status, and methylation patterns have demonstrated promising results. Their eventual implementation in the screening programs may support the prompt diagnosis of hrHPV infection and its progression to cancer. These biomarkers will help in making clinical management decisions on time, thus, saving the lives of hrHPV-infected women, particularly in developing countries.

Methylation in Predicting Progression of Untreated High-grade Cervical Intraepithelial Neoplasia

BACKGROUND

There is no prognostic test to ascertain whether cervical intraepithelial neoplasias (CINs) regress or progress. The majority of CINs regress in young women, and treatments increase the risk of adverse pregnancy outcomes. We investigated the ability of a DNA methylation panel (the S5 classifier) to discriminate between outcomes among young women with untreated CIN grade 2 (CIN2).

METHODS

Baseline pyrosequencing methylation and human papillomavirus (HPV) genotyping assays were performed on cervical cells from 149 women with CIN2 in a 2-year cohort study of active surveillance.

RESULTS

Twenty-five lesions progressed to CIN grade 3 or worse, 88 regressed to less than CIN grade 1, and 36 persisted as CIN1/2. When cytology, HPV16/18 and HPV16/18/31/33 genotyping, and the S5 classifier were compared to outcomes, the S5 classifier was the strongest biomarker associated with regression vs progression. The S5 classifier alone or in combination with HPV16/18/31/33 genotyping also showed significantly increased sensitivity vs cytology when comparing regression vs persistence/progression. With both the S5 classifier and cytology set at a specificity of 38.6% (95% confidence interval [CI], 28.4-49.6), the sensitivity of the S5 classifier was significantly higher (83.6%; 95% CI, 71.9-91.8) than of cytology (62.3%; 95% CI, 49.0-74.4; P = 0.005). The highest area under the curve was 0.735 (95% CI, 0.621-0.849) in comparing regression vs progression with a combination of the S5 classifier and cytology, whereas HPV genotyping did not provide additional information.

CONCLUSIONS

The S5 classifier shows high potential as a prognostic biomarker to identify progressive CIN2.

Evidence based appropriate triage strategies for implementing high risk HPV as primary technology in cervical cancer screening

Primary cervical cancer screening by HPV testing for high risk human papillomavirus (hrHPV) is expected to replace cytology-based programs in many parts of the world. Its high sensitivity and negative predictive value permit longer screening intervals up to beyond five years. However, low positive predictive value can lead to unnecessary referrals and overtreatment since most hrHPV infections are transient and will not develop disease. Therefore risk stratification is needed to effectively triage and identify women among the hrHPV positives, who are at an increased risk of cervical (pre)cancer who need further diagnostic evaluation to decide on further management. Several triage strategies like HPV16/18 genotyping, p16/Ki67 dual staining and DNA methylation markers (CADM1, MAL and miR-124-2) have been evaluated to determine suitable triage options. Triage with p16/Ki-67 dual-stain provided better long-term risk stratification than cytology with significant reduction in cumulative 5 years CIN3+ risk in p16/Ki-67 negative women. DNA methylation assays have shown higher specificity than cytology and higher sensitivity than HPV16/18 genotyping with added advantages of reproducibility and application on self-collected samples. Based on current evidence, Pap cytology with or without additional HPV16/18 genotyping remains the most recommended triage strategies for primary HPV screening. Other strategies will need more longitudinal studies to provide evidence of risk reduction in test negative results. WHO recommends Visual Inspection with Acetic Acid (VIA) for triaging HPV-positive women in LMIC settings. An optimal triage strategy that can be integrated with primary HPV screening should be able to segregate and reassure the large majority of women who are at very low risk of cervical cancer.

The use of human papillomavirus DNA methylation in cervical intraepithelial neoplasia: A systematic review and meta-analysis

BACKGROUND

Methylation of viral DNA has been proposed as a novel biomarker for triage of human papillomavirus (HPV) positive women at screening. This systematic review and meta-analysis aims to assess how methylation levels change with disease severity and to determine diagnostic test accuracy (DTA) in detecting high-grade cervical intra-epithelial neoplasia (CIN).

METHODS

We performed searches in MEDLINE, EMBASE and CENTRAL from inception to October 2019. Studies were eligible if they explored HPV methylation levels in HPV positive women. Data were extracted in duplicate and requested from authors where necessary. Random-effects models and a bivariate mixed-effects binary regression model were applied to determine pooled effect estimates.

FINDINGS

44 studies with 8819 high-risk HPV positive women were eligible. The pooled estimates for positive methylation rate in HPV16 L1 gene were higher for high-grade CIN (≥CIN2/high-grade squamous intra-epithelial lesion (HSIL) (95% confidence interval (95%CI:72·7% (47·8-92·2))) vs. low-grade CIN (≤CIN1/low-grade squamous intra-epithelial lesion (LSIL) (44·4% (95%CI:16·0-74·1))). Pooled difference in mean methylation level was significantly higher in ≥CIN2/HSIL vs. ≤CIN1/LSIL for HPV16 L1 (11·3% (95%CI:6·5-16·1)). Pooled odds ratio of HPV16 L1 methylation was 5·5 (95%CI:3·5-8·5) for ≥CIN2/HSIL vs. ≤CIN1/LSIL (p < 0·0001). HPV16 L1/L2 genes performed best in predicting CIN2 or worse (pooled sensitivity 77% (95%CI:63-87), specificity 64% (95%CI:55-71), area under the curve (0·73 (95%CI:0·69-0·77)).

INTERPRETATION

Higher HPV methylation is associated with increased disease severity, whilst HPV16 L1/L2 genes demonstrated high diagnostic accuracy to detect high-grade CIN in HPV16 positive women. Direct clinical use is limited by the need for a multi-genotype and standardised assays. Next-generation multiplex HPV sequencing assays are under development and allow potential for rapid, automated and low-cost methylation testing.

FUNDING

NIHR, Genesis Research Trust, Imperial Healthcare Charity, Wellcome Trust NIHR Imperial BRC, European Union's Horizon 2020.

Methylation in host and viral genes as marker of aggressiveness in cervical lesions: Analysis in 543 unscreened women

OBJECTIVE

The present study aimed to evaluate the association between altered methylation and histologically confirmed high grade cervical intraepithelial neoplasia (hgCIN).

METHODS

Methylation levels in selected host (CADM1, MAL, DAPK1) and HPV (L1_I, L1_II, L2) genes were measured by pyrosequencing in DNA samples obtained from 543 women recruited in Curitiba (Brazil), 249 with hgCIN and 294 without cervical lesions. Association of methylation status with hgCIN was estimated by Odds Ratio (OR) with 95% confidence interval (CI).

RESULTS

The mean methylation level increased with severity of the lesion in the host and viral genes (p-trend < 0.05), with the exception of L1_II region (p-trend = 0.075). Positive association was found between methylation levels for host genes and CIN2 and CIN3 lesions respectively [CADM1: OR 4.17 (95%CI 2.03-8.56) and OR 9.54 (95%CI 4.80-18.97); MAL: OR 5.98 (95%CI 2.26-15.78) and OR 22.66 (95%CI 9.21-55.76); DAPK1: OR 3.37 (95%CI 0.93-12.13) and OR 6.74 (95%CI 1.92-23.64)]. Stronger risk estimates were found for viral genes [L1_I: OR 10.74 (95%CI 2.66-43.31) and OR 15.00 (95%CI 3.00-74.98); L1_II: OR 73.18 (95%CI 4.07-1315.94) and OR 32.50 (95%CI 3.86-273.65); L2: OR 4.73 (95%CI 1.55-14.44) and OR 10.62 (95%CI 2.60-43.39)]. The cumulative effect of the increasing number of host and viral methylated genes was associated with the risk of CIN2 and CIN3 lesions (p-trend < 0.001).

CONCLUSIONS

Our results, empowered by a wide cervical sample series with a large number of hgCIN, supported the role of methylation as marker of aggressiveness.

Eurogin roadmap 2017: Triage strategies for the management of HPV-positive women in cervical screening programs

Cervical cancer screening will rely, increasingly, on HPV testing as a primary screen. The requirement for triage tests which can delineate clinically significant infection is thus prescient. In this EUROGIN 2017 roadmap, justification behind the most evidenced triages is outlined, as are challenges for implementation. Cytology is the triage with the most follow-up data; the existence of an HR-HPV-positive, cytology-negative group presents a challenge and retesting intervals for this group (and choice of retest) require careful consideration. Furthermore, cytology relies on subjective skills and while adjunctive dual-staining with p16/Ki67 can mitigate inter-operator/-site disparities, clinician-taken samples are required. Comparatively, genotyping and methylation markers are objective and are applicable to self-taken samples, offering logistical advantages including in low and middle income settings. However, genotyping may have diminishing returns in immunised populations and type(s) included must balance absolute risk for disease to avoid low specificity. While viral and cellular methylation markers show promise, more prospective data are needed in addition to refinements in automation. Looking forward, systems that detect multiple targets concurrently such as next generation sequencing platforms will inform the development of triage tools. Additionally, multistep triage strategies may be beneficial provided they do not create complex, unmanageable pathways. Inevitably, the balance of risk to cost(s) will be key in decision making, although defining an acceptable risk will likely differ between settings. Finally, given the significant changes to cervical screening and the variety of triage strategies, appropriate education of both health care providers and the public is essential.

Identification of DAPK1 Promoter Hypermethylation as a Biomarker for Intra-Epithelial Lesion and Cervical Cancer: A Meta-Analysis of Published Studies, TCGA, and GEO Datasets

Background: Promoter hypermethylation in death-associated protein kinase 1 (DAPK1) gene has been long linked to cervical neoplasia, but the established results remained controversial. Here, we performed a meta-analysis to assess the associations of DAPK1 promoter hypermethylation with low-grade intra-epithelial lesion (HSIL), high-grade intra-epithelial lesion (HSIL), cervical cancer (CC), and clinicopathological features of CC.

Methods: Published studies with qualitative methylation data were initially searched from PubMed, Web of Science, EMBASE, and China National Knowledge Infrastructure databases (up to March 2018). Then, quantitative methylation datasets, retrieved from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, were pooled to validate the results of published studies.

Results: In a meta-analysis of 37 published studies, DAPK1 promoter hypermethylation progressively increased the risk of LSIL by 2.41-fold (P = 0.012), HSIL by 7.62-fold (P < 0.001), and CC by 23.17-fold (P < 0.001). Summary receiver operating characteristic curves suggested a potential diagnostic value of DAPK1 promoter hypermethylation in CC, with a large area-under-the-curve of 0.83, a high specificity of 97%, and a moderate sensitivity of 59%. There were significant impacts of DAPK1 promoter hypermethylation on histological type (odds ratio (OR) = 3.53, P < 0.001) and FIGO stage of CC (OR = 2.15, P = 0.003). Then, a pooled analysis of nine TCGA and GEO datasets, covering 13 CPG sites within DAPK1 promoter, identified eight CC-associated sites, six sites with diagnostic values for CC (pooled specificities: 74–90%; pooled sensitivities: 70–81%), nine loci associated with the histological type of CC, and all 13 loci with down-regulated effects on DAPK1 mRNA expression.

Conclusion: The meta-analysis suggests that DAPK1 promoter hypermethylation is significantly associated with the disease severity of cervical neoplasia. DAPK1 methylation detection exhibits a promising ability to discriminate CC from cancer-free controls.

The Progress of Methylation Regulation in Gene Expression of Cervical Cancer

Cervical cancer is one of the most common gynecological tumors in females, which is closely related to high-rate HPV infection. Methylation alteration is a type of epigenetic decoration that regulates the expression of genes without changing the DNA sequence, and it is essential for the progression of cervical cancer in pathogenesis while reflecting the prognosis and therapeutic sensitivity in clinical practice. Hydroxymethylation has been discovered in recent years, thus making 5-hmC, the more stable marker, attract more attention in the field of methylation research. As markers of methylation, 5-hmC and 5-mC together with 5-foC and 5-caC draw the outline of the reversible cycle, and 6-mA takes part in the methylation of RNA, especially mRNA. Furthermore, methylation modification participates in ncRNA regulation and histone decoration. In this review, we focus on recent advances in the understanding of methylation regulation in the process of cervical cancer, as well as HPV and CIN, to identify the significant impact on the prospect of overcoming cervical cancer.

Assessment of viral methylation levels for high risk HPV types by newly designed consensus primers PCR and pyrosequencing

Background

Measuring viral DNA methylation in human papillomavirus (HPV) infected women showed promise for accurate detection of high-grade cervical lesions and cancer. Methylation status has been widely investigated for HPV16, sporadically for other HPV types.

Methods

Objective of this methodological study was to set up molecular methods to test the methylation levels in the twelve oncogenic HPV types by pyrosequencing, minimizing the number of HPV type-specific PCR protocols. Target CpGs were selected on the HPV L1 (two regions, L1 I and L1 II) and L2 genes.

Study samples included DNA stored at Turin, Italy, purified by cervical cells collected in Standard Transport Medium or PreservCyt from women who participated in two studies (N = 126 and 140) nested within the regional organized screening programme.

PCR consensus primers were designed by PyroMark Assay Design software to be suitable for amplification of many different oncogenic HPV types.

Results

Generation of consensus primers was successful for L1 I and II regions, unsuccessful for L2 region, for which HPV type-specific primers remained necessary. The difference between replicated tests on the same sample was ≤4% in 88%, 77% and 91% of cases when targeting the L1 I, L1 II and L2 regions, respectively. The corresponding intra-class correlation coefficients (ICC) were 0.94, 0.87 and 0.97 respectively. When comparing methylation measures based on consensus and type-specific primers, ICC was 0.97 for the L1 I region and 0.99 the for L1 II region.

Conclusions

The proposed protocols, applying consensus primers suitable to amplify the oncogenic HPV types and minimize the number of PCR reactions, represent a promising tool to quantify viral methylation in women positive for any high risk HPV type.

Impact

Potential application of these methylation protocols in screening settings can be explored to identify women with high probability of progression to high grade lesions.

Intracellular African swine fever virus DNA remains unmethylated in infected Vero cells

AIM

Sequence-specific CpG methylation of eukaryotic promoters is an important epigenetic signal for long-term gene silencing. We have now studied the methylation status of African swine fever virus (ASFV) DNA at various times after infection of Vero cells in culture.

METHODS & RESULTS

ASFV DNA was detectable throughout the infection cycle and was found unmethylated in productively infected Vero cells as documented by bisulfite sequencing of 13 viral DNA segments.

CONCLUSION

ASFV DNA does not become de novo methylated in the course of infection in selected segments spread across the entire genome. Thus DNA methylation does not interfere with ASFV genome transcription. Lack of de novo methylation has previously been observed for free intracellular viral DNA in cells permissively infected with human adenoviruses, with human papillomaviruses and others.

Expresión de EDNRB y CDX2 posibles biomarcadores en progresión al cáncer cervical

De acuerdo a la historia natural del cáncer del cuello uterino, en donde las lesiones preneoplásicas de bajo y alto grado pueden presentar fenómenos de regresión o progresión, existe gran interés en la búsqueda de biomarcadores que permita predecir la evolución de las lesiones preneoplásicas del cérvix hacia la progresión o regresión de la enfermedad. Estos biomarcadores pudieran ser de origen genético, o epigenético que alteren la expresión de los genes y que pudieran estar asociados con la carcinogénesis en diferentes tipos de tejido humano. El objetivo del estudio fue analizar la expresión del mARN de los genes SFRP1, PTPRN, CDO1, EDNRB, CDX2, EPB41L3 y HAND1 en muestras negativas para lesiones intraepiteliales cervicales (n=9), muestras con lesiones intraepiteliales de bajo grado (n=10) y alto grado (n=11). Se realizó  análisis de expresión de los genes mencionados mediante qRT-PCR y el análisis de los datos se realizó mediante la prueba no paramétrica de ANOVA. La diferencia estadística se determinó en valores p< 0,05. Para los genes EDNRB y CDX2 se observó disminución 66,7% en las muestras sin alteraciones histológicas cervicales, comparado con una disminución en la expresión del 50% en muestras con LIEBG y para el grupo de LIEAG del 36,4% para el gen EDNRB y del 27,3% para el gen CDX2 dando una diferencia estadísticamente significativa p= 0,02. Sugiriendo que EDNRB y CDX2 podrían ser útiles como posibles biomarcadores en la carcinogénesis cervical.

Methylation of the L1 gene and integration of human papillomavirus 16 and 18 in cervical carcinoma and premalignant lesions

High-risk human papillomavirus (HPV) is the primary cause of cervical carcinoma (CC). Viral integration into the host chromosomes is associated with neoplastic progression, and epigenetic changes may occur as a result. The objective of the present study was to analyze HPV L1 gene methylation and to compare the use of quantitative polymerase chain reaction (qPCR), in situ hybridization (ISH) and L1 methylation analysis as methods for detecting HPV integration. Cervical scrapes or biopsy samples positive for HPV 16 or 18, from 187 female patients with CC, squamous intraepithelial lesions (SILs) or no intraepithelial lesion (non-IL) were analyzed. Methylation of the L1 gene was determined using bisulfite modification followed by PCR, and HPV integration was subsequently analyzed. HPV 16 L1 gene methylation was revealed to increase with histological grade, with statistically significant differences observed as follows: Low-grade SIL vs. CC, P<0.0001 and non-IL vs. CC, P<0.0001. HPV 18 L1 gene methylation also increased according to histological grade, however, no statistically significant differences were observed. Methylation at CpG site 5608 of the HPV 16 L1 gene was associated with all grades of cervical lesions, whereas methylation at CpG site 5617 demonstrated the strongest association with CC (odds ratio, 42.5; 95% confidence interval, 4.7-1861; P<0.0001). The concordance rates between the various methods for the detection of the physical status of HPV 16 and HPV 18 were 96.1% for qPCR and ISH, 76.7% for qPCR and L1 gene methylation, and 84.8% for ISH and L1 gene methylation. In conclusion, methylation of the HPV 16 L1 gene increases significantly according to the grade of the cervical lesion, and methylation at CpG sites 5608 and 5617 of this gene may be used as prognostic biomarkers. ISH and L1 gene methylation have good concordance with qPCR with regards to the detection of HPV integration. Therefore, these are useful methods in determining the physical state of HPV.

Quantitative methylation analysis of human papillomavirus 16L1 gene reveals potential biomarker for cervical cancer progression

Human papillomavirus 16 is the most prevalent type found in cervical cancer worldwide, accounting for >50% of all cases. Quantitative methylation analysis of human papillomavirus 16L1 gene within 5' (CpGs 5600, 5606, 5609, 5615) and 3' (7136 and 7145) regions to determine potential biomarker for cervical cancer progression was performed in exfoliated cervical cells collected from 101 Thai women of precancerous and cancerous lesions. Intermediate to high methylation levels (>20%) were detected in HPV16 5'L1 regions especially CpG 5600 of all cancerous (100%) and 50% of CIN3 samples, whereas normal/CIN1 samples (80%) showed methylation levels <20%. Our results indicate the potential use of HPV 16L1 gene methylation at specific site as a biomarker for prognostic cervical cancer screening, however, suitable cutoff should be further evaluated in a larger sample size.

Increased methylation of human papillomavirus type 16 DNA is associated with the severity of cervical lesions in infected females from northeast China

Hypermethylation of the cytosine-phosphate-guanine (CpG) sites located at the 3'-major capsid protein L1 (3'L1) and the long control region (LCR) of the human papillomavirus (HPV) genome may be associated with the progression of cervical cancer (CC). However, the methylation status of the LCR of HPV type 16 DNA remains to be elucidated in an infected Chinese population. The aim of the present study was to investigate the association between methylation of the HPV 16 L1 gene and LCR, and the severity of cervical lesions in infected female patients. Therefore, bisulfite modification, polymerase chain reaction amplification and sequencing were used to analyze 122 HPV 16-positive clinical cervical swabs obtained from patients in northeastern China. The proportion of methylated samples at each of the 7 CpG sites within the 3'-L1/5'-LCR and 5 CpG sites within the promoter region was significantly increased in patients with CC, compared with that observed in high-grade squamous intraepithelial lesions (HSIL) and normal tissue/low-grade intraepithelial lesions (LSIL) (χ2 test, P<0.01). The mean methylation frequencies of the CpG sites 7,089 and 7,143 exhibited an area under the curve value of 0.822 [95% confidence interval (CI)=0.733-0.911] for distinguishing CC from other lesions, 0.787 (95% CI=0.700-0.874) for distinguishing normal/LSIL from HSIL and CC, and 0.763 (95% CI=0.652-0.874) for distinguishing CC from HSIL. These results suggest that the methylation of CpG sites within the HPV 16 3'-L1 and LCR region is correlated with the severity of cervical lesions. Quantification of HPV DNA methylation in the L1 gene and promoter region appears to provide a promising novel marker for distinguishing between normal tissue/LSIL, HSIL and CC in a Chinese population.

Molecular tests potentially improving HPV screening and genotyping for cervical cancer prevention

INTRODUCTION

Human papillomavirus (HPV)-related cancers can be averted by type-specific vaccination (primary prevention) and/or through detection and ablation of precancerous cervical lesions (secondary prevention). This review presents current challenges to cervical cancer screening programs, focusing on recent molecular advances in HPV testing and potential improvements on risk stratification. Areas covered: High-risk (HR)-HPV DNA detection has been progressively incorporated into cervix cancer prevention programs based on its increased sensitivity. Advances in next-generation sequencing (NGS) are being rapidly applied to HPV typing. However, current HPV DNA tests lack specificity for identification of cervical precancer (CIN3). HPV typing methods were reviewed based on published literature, with a focus on these applications for screening and risk stratification in the emerging complex clinical scenario post-vaccine introduction. In addition, the potential for NGS technologies to increase specificity is discussed in regards to reflex testing of specimens for emerging biomarkers for cervix precancer/cancer. Expert commentary: Integrative multi-disciplinary molecular tests accurately triaging exfoliated cervical specimens will improve cervical cancer prevention programs while simplifying healthcare procedures in HPV-infected women. Hence, the concept of a 'liquid-biopsy' (i.e., 'molecular' Pap test) highly specific for early identification of cervical precancerous lesions is of critical importance in the years to come.

Virtues and Weaknesses of DNA Methylation as a Test for Cervical Cancer Prevention

Epigenetics is the study of heritable and non-heritable genetic coding that is additive to information contained within classical DNA base pair sequences. Differential methylation has a fundamental role in the development and outcome of malignancies, chronic and degenerative diseases and aging. DNA methylation can be measured accurately and easily via various molecular methods and has become a key technology for research and healthcare delivery, with immediate roles in the elucidation of disease natural history, diagnostics and drug discovery. This review focuses on cancers of the lower genital tract, for which the most epigenetic information exists. DNA methylation has been proposed as a triage for women infected with human papillomavirus (HPV) and may eventually directly complement or replace HPV screening as a one-step molecular diagnostic and prognostic test. Methylation of human genes is strongly associated with cervical intraepithelial neoplasia (CIN) and cancer. Of the more than 100 human methylation biomarker genes tested so far in cervical tissue, close to 20 have been reported in different studies, and approximately 10 have been repeatedly shown to have elevated methylation in cervical cancers and high-grade CIN (CIN2 and CIN3), most prominently CADM1, EPB41L3, FAM19A4, MAL, miR-124, PAX1 and SOX1. Obtaining consistent performance data from the literature is quite difficult because most methylation studies used a variety of different assay methodologies and had incomplete and/or biased clinical specimen sets, varying assay thresholds and disparate target gene regions. There have been relatively few validation studies of DNA methylation biomarkers in large population-based screening studies, but an encouraging development more recently is the execution of well-designed studies to test the true performance of the markers in real-world settings. Methylation of HPV genes, especially HPV16, HPV18, HPV31, HPV33 and HPV45, in disease progression has been a major focus of research. Elevated methylation of the HPV16 L1 and L2 open reading frames, in particular, is associated with CIN2, CIN3 and invasive cancer. Essentially all cancers have high levels of methylation for human genes and for driver HPV types, which suggests that quantitative methylation tests may have utility in predicting CIN2 and CIN3 that are likely to progress. It is still early in the process of development of methylation biomarkers, but already they are showing strong promise as a universal and systematic approach to molecular triage, applicable to all cancers, not just cancer of the cervix. DNA methylation testing is better than HPV genotyping triage and is competitive with or complementary to other approaches such as cytology and p16 staining. Genome-wide studies are underway to systematically expand methylation classifier panels and find the best combinations of biomarkers. Methylation testing is likely to show big improvements in performance in the next 5 years.

Human Papillomavirus Type 16 L2 DNA Methylation in Exfoliated Cervical Cells From College-Age Women

OBJECTIVES

The Carolina Women's Care Study (CWCS) at the University of South Carolina followed 467 young women with the goal of identifying biomarkers of human papillomavirus (HPV) persistence. In this study, we analyzed the methylation of HPV16 DNA.

METHODS

The aims of this study were to determine the methylation status of the HPV16 L2 gene in DNA isolated from exfoliated cervical cells collected longitudinally as part of the CWCS and to determine the prevalence of polymorphisms (single nucleotide polymorphisms [SNPs]) in folate metabolizing enzymes and DNA repair enzymes known to affect DNA methylation in blood-derived genomic DNA from CWCS participants. For methylation studies, DNA samples were bisulfite converted and amplified with the EpiTect Whole Bisulfitome kit. Polymerase chain reaction was performed for amplicons containing 5 CpG sites in L2. Pyrosequencing was carried out using EpigenDx and analyzed with PyroMark Software. Taqman genotyping assays were performed to determine selected SNP alleles in the CWCS cohort.

RESULTS AND CONCLUSIONS

Methylation data were obtained for 82 samples from 27 participants. Of these, 22 participants were positive for HPV16 for 3 or more visits (≥12 months). Methylation in L2 was detectable, but methylation levels varied and were not associated with HPV16 persistence. No linearity of methylation levels over time was observed in participants for whom longitudinal data could be analyzed. Analysis of 9 selected SNPs did not reveal an association with persistence. We conclude that at early stages of infection methylation of HPV16 L2 DNA in Pap test samples is not a predictive biomarker of HPV persistence.

Human papillomaviruses in epigenetic regulations

Human Papillomaviruses (HPVs) are double-stranded DNA viruses, that infect epithelial cells and are etiologically involved in the development of human cancer. Today, over 200 types of human papillomaviruses are known. They are divided into low-risk and high-risk HPVs depending on their potential to induce carcinogenesis, driven by two major viral oncoproteins, E6 and E7. By interacting with cellular partners, these proteins are involved in interdependent viral and cell cycles in stratified differentiating epithelium, and concomitantly induce epigenetic changes in infected cells and those undergoing malignant transformation. E6 and E7 oncoproteins interact with and/or modulate expression of many proteins involved in epigenetic regulation, including DNA methyltransferases, histone-modifying enzymes and subunits of chromatin remodeling complexes, thereby influencing host cell transcription program. Furthermore, HPV oncoproteins modulate expression of cellular micro RNAs. Most of these epigenetic actions in a complex dynamic interplay participate in the maintenance of persistent infection, cell transformation, and development of invasive cancer by a considerable deregulation of tumor suppressor and oncogenes. In this study, we have undertaken to discuss a number of studies concerning epigenetic regulations in HPV-dependent cells and to focus on those that have biological relevance to cancer progression.

Triage of high-risk HPV positive women in cervical cancer screening

INTRODUCTION

High-risk human papillomavirus (hrHPV) testing is expected to replace cytology as primary screening method for cervical cancer screening in an increasing number of countries. The high sensitivity of hrHPV testing is combined with a limited specificity which makes triaging of hrHPV positive women necessary. As an ideal triage method does not yet exist, an optimal triage strategy for hrHPV positive women based on current knowledge should be obtained. The aim of this article is to present an overview of available options for triage of hrHPV positive women, with their strengths and limitations and possible future opportunities.

AREAS COVERED

Current knowledge on morphological biomarkers, molecular biomarkers and combined triage strategies will be discussed to give an overview of the state-of-the-art on triaging hrHPV positive women. The literature search was limited to studies on triage strategies for hrHPV positive women. Expert commentary: Experience with morphology-based biomarkers makes these a valuable triage method. However, they lack the ability of differentiating productive from transforming infections. Molecular biomarkers are objective, highly reproducible, can be used in high throughput testing, and show promising results. With more extensive knowledge on these molecular markers, cervical cancer screening may transform to a full molecular screening in the future.

5-aza-2'-deoxycytidine (DAC) treatment downregulates the HPV E6 and E7 oncogene expression and blocks neoplastic growth of HPV-associated cancer cells

High-risk human papillomaviruses (hr HPVs) may cause various human cancers and associated premalignant lesions. Transformation of the host cells is triggered by overexpression of the viral oncogenes E6 and E7 that deregulate the cell cycle and induce chromosomal instability. This process is accompanied by hypermethylation of distinct CpG sites resulting in silencing of tumor suppressor genes, inhibition of the viral E2 mediated control of E6 and E7 transcription as well as deregulated expression of host cell microRNAs. Therefore, we hypothesized that treatment with demethylating agents might restore those regulatory mechanisms. Here we show that treatment with 5-aza-2′-deoxycytidine (DAC) strongly decreases the expression of E6 and E7 in a panel of HPV-transformed cervical cancer and head and neck squamous cell carcinoma cell lines. Reduction of E6 and E7 further resulted in increased target protein levels including p53 and p21 reducing the proliferation rates and colony formation abilities of the treated cell lines. Moreover, DAC treatment led to enhanced expression of tumor the suppressive miRNA-375 that targets and degrades E6 and E7 transcripts. Therefore, we suggest that DAC treatment of HPV-associated cancers and respective precursor lesions may constitute a targeted approach to subvert HPV oncogene functions that deserves testing in clinical trials.

Genome-wide association studies and epigenome-wide association studies go together in cancer control

Completion of the human genome a decade ago laid the foundation for: using genetic information in assessing risk to identify individuals and populations that are likely to develop cancer, and designing treatments based on a person's genetic profiling (precision medicine). Genome-wide association studies (GWAS) completed during the past few years have identified risk-associated single nucleotide polymorphisms that can be used as screening tools in epidemiologic studies of a variety of tumor types. This led to the conduct of epigenome-wide association studies (EWAS). This article discusses the current status, challenges and research opportunities in GWAS and EWAS. Information gained from GWAS and EWAS has potential applications in cancer control and treatment.

Identification of key genes associated with cervical cancer by comprehensive analysis of transcriptome microarray and methylation microarray

Cervical cancer is the second most commonly diagnosed type of cancer and the third leading cause of cancer-associated mortality in women. The current study aimed to determine the genes associated with cervical cancer development. Microarray data (GSE55940 and GSE46306) were downloaded from Gene Expression Omnibus. Overlapping genes between the differentially expressed genes (DEGs) in GSE55940 (identified by Limma package) and the differentially methylated genes were screened. Gene Ontology (GO) enrichment analysis was subsequently performed for these genes using the ToppGene database. In GSE55940, 91 downregulated and 151 upregulated DEGs were identified. In GSE46306, 561 overlapping differentially methylated genes were obtained through the differential methylation analysis at the CpG site level, CpG island level and gene level. A total of 5 overlapping genes [dipeptidyl peptidase 4 (DPP4); endothelin 3 (EDN3); fibroblast growth factor 14 (FGF14); tachykinin, precursor 1 (TAC1); and wingless-type MMTV integration site family, member 16 (WNT16)] between the 561 overlapping differentially methylated genes and the 242 DEGs were identified, which were downregulated and hypermethylated simultaneously in cervical cancer samples. Enriched GO terms were receptor binding (involving DPP4, EDN3, FGF14, TAC1 and WNT16), ameboidal-type cell migration (DPP4, EDN3 and TAC1), mitogen-activated protein kinase cascade (FGF14, EDN3 and WNT16) and cell proliferation (EDN3, WNT16, DPP4 and TAC1). These results indicate that DPP4, EDN3, FGF14, TAC1 and WNT16 may be involved in the pathogenesis of cervical cancer.

Human papillomaviruses: research priorities for the next decade

Human papillomaviruses are the causative agents of cervical, anal as well as many oropharyngeal cancers. While prophylactic vaccines have been developed, uptake is low in the US and other Western countries, and access is limited in less developed countries. A number of areas are emerging as critical for future study. These include investigation of the mechanisms regulating infection and progression to cancer at both cervical and oropharyngeal sites as these appear to be distinct. HPV-induced cancers also may be susceptible to immune therapy, revealing opportunities for treating advanced cervical disease and reducing the morbidity of treatments for oropharyngeal cancers. We believe these areas are critical focal points for HPV cancer research in the next decade.

A Novel Recombinant Anti-CD22 Immunokinase Delivers Proapoptotic Activity of Death-Associated Protein Kinase (DAPK) and Mediates Cytotoxicity in Neoplastic B Cells

The serine/threonine death-associated protein kinases (DAPK) provide pro-death signals in response to (oncogenic) cellular stresses. Lost DAPK expression due to (epi)genetic silencing is found in a broad spectrum of cancers. Within B-cell lymphomas, deficiency of the prototypic family member DAPK1 represents a predisposing or early tumorigenic lesion and high-frequency promoter methylation marks more aggressive diseases. On the basis of protein studies and meta-analyzed gene expression profiling data, we show here that within the low-level context of B-lymphocytic DAPK, particularly CLL cells have lost DAPK1 expression. To target this potential vulnerability, we conceptualized B-cell-specific cytotoxic reconstitution of the DAPK1 tumor suppressor in the format of an immunokinase. After rounds of selections for its most potent cytolytic moiety and optimal ligand part, a DK1KD-SGIII fusion protein containing a constitutive DAPK1 mutant, DK1KD, linked to the scFv SGIII against the B-cell-exclusive endocytic glyco-receptor CD22 was created. Its high purity and large-scale recombinant production provided a stable, selectively binding, and efficiently internalizing construct with preserved robust catalytic activity. DK1KD-SGIII specifically and efficiently killed CD22-positive cells of lymphoma lines and primary CLL samples, sparing healthy donor- or CLL patient-derived non-B cells. The mode of cell death was predominantly PARP-mediated and caspase-dependent conventional apoptosis as well as triggering of an autophagic program. The notoriously high apoptotic threshold of CLL could be overcome by DK1KD-SGIII in vitro also in cases with poor prognostic features, such as therapy resistance. The manufacturing feasibility of the novel CD22-targeting DAPK immunokinase and its selective antileukemic efficiency encourage intensified studies towards specific clinical application. Mol Cancer Ther; 15(5); 971-84. ©2016 AACR.

Predicting DNA Methylation State of CpG Dinucleotide Using Genome Topological Features and Deep Networks

The hypo- or hyper-methylation of the human genome is one of the epigenetic features of leukemia. However, experimental approaches have only determined the methylation state of a small portion of the human genome. We developed deep learning based (stacked denoising autoencoders, or SdAs) software named “DeepMethyl” to predict the methylation state of DNA CpG dinucleotides using features inferred from three-dimensional genome topology (based on Hi-C) and DNA sequence patterns. We used the experimental data from immortalised myelogenous leukemia (K562) and healthy lymphoblastoid (GM12878) cell lines to train the learning models and assess prediction performance. We have tested various SdA architectures with different configurations of hidden layer(s) and amount of pre-training data and compared the performance of deep networks relative to support vector machines (SVMs). Using the methylation states of sequentially neighboring regions as one of the learning features, an SdA achieved a blind test accuracy of 89.7% for GM12878 and 88.6% for K562. When the methylation states of sequentially neighboring regions are unknown, the accuracies are 84.82% for GM12878 and 72.01% for K562. We also analyzed the contribution of genome topological features inferred from Hi-C. DeepMethyl can be accessed at http://dna.cs.usm.edu/deepmethyl/.

Determination of malignant potential of cervical intraepithelial neoplasia

Basic diagnostic procedures in cervical cancer screening are able to set the diagnosis but they do not provide any information about the biological nature and behavior of lesions. The causal link of HPV infection and cervical cancer and discoveries of complex interactions between host and HPV genome opened new possibilities in molecular diagnostics. HPV DNA analysis, determination of viral load, detection of E6 and E7 mRNA transcripts, identifying of methylation profiles, genomic changes, miRNAs, and telomerase activity should be the right choice for exact diagnostics and prediction of behavior of premalignant lesions of the cervix. These findings set a completely new light not only in diagnostic but also in management and treatment of cervical dysplasia and cervical cancer.

DAPK1 Promoter Methylation and Cervical Cancer Risk: A Systematic Review and a Meta-Analysis

Objective

The Death-Associated Protein Kinase 1 (DAPK1) gene has been frequently investigated in cervical cancer (CC). The aim of the present study was to carry out a systematic review and a meta-analysis in order to evaluate DAPK1 promoter methylation as an epigenetic marker for CC risk.

Methods

A systematic literature search was carried out. The Cochrane software package Review Manager 5.2 was used. The fixed-effects or random-effects models, according to heterogeneity across studies, were used to calculate odds ratios (ORs) and 95% Confidence Intervals (CIs). Furthermore, subgroup analyses were conducted by histological type, assays used to evaluate DAPK1 promoter methylation, and control sample source.

Results

A total of 20 papers, published between 2001 and 2014, on 1929 samples, were included in the meta-analysis. DAPK1 promoter methylation was associated with an increased CC risk based on the random effects model (OR: 21.20; 95%CI = 11.14–40.35). Omitting the most heterogeneous study, the between study heterogeneity decreased and the association increased (OR: 24.13; 95% CI = 15.83–36.78). The association was also confirmed in all the subgroups analyses.

Conclusions

A significant strong association between DAPK1 promoter methylation and CC was shown and confirmed independently by histological tumor type, method used to evaluate methylation and source of control samples. Methylation markers may have value in early detection of CC precursor lesions, provide added reassurances of safety for women who are candidates for less frequent screens, and predict outcomes of women infected with human papilloma virus.

Methylated Host Cell Gene Promoters and Human Papillomavirus Type 16 and 18 Predicting Cervical Lesions and Cancer

Change in the host and/or human papillomavirus (HPV) DNA methylation profile is probably one of the main factors responsible for the malignant progression of cervical lesions to cancer. To investigate those changes we studied 173 cervical samples with different grades of cervical lesion, from normal to cervical cancer. The methylation status of nine cellular gene promoters, CCNA1, CDH1, C13ORF18, DAPK1, HIC1, RARβ2, hTERT1, hTERT2 and TWIST1, was investigated by Methylation Specific Polymerase Chain Reaction (MSP). The methylation of HPV18 L1-gene was also investigated by MSP, while the methylated cytosines within four regions, L1, 5’LCR, enhancer, and promoter of the HPV16 genome covering 19 CpG sites were evaluated by bisulfite sequencing. Statistically significant methylation biomarkers distinguishing between cervical precursor lesions from normal cervix were primarily C13ORF18 and secondly CCNA1, and those distinguishing cervical cancer from normal or cervical precursor lesions were CCNA1, C13ORF18, hTERT1, hTERT2 and TWIST1. In addition, the methylation analysis of individual CpG sites of the HPV16 genome in different sample groups, notably the 7455 and 7694 sites, proved to be more important than the overall methylation frequency. The majority of HPV18 positive samples contained both methylated and unmethylated L1 gene, and samples with L1-gene methylated forms alone had better prognosis when correlated with the host cell gene promoters’ methylation profiles. In conclusion, both cellular and viral methylation biomarkers should be used for monitoring cervical lesion progression to prevent invasive cervical cancer.

HPV16 CpG methyl-haplotypes are associated with cervix precancer and cancer in the Guanacaste natural history study

OBJECTIVE

To evaluate HPV16 CpG methylation and methyl-haplotypes and their association with cervix precancer and cancer utilizing massively parallel single molecule next-generation sequencing (NGS).

METHODS

A nested case-control study of HPV16 positive women was performed in a prospective cohort from Guanacaste, Costa Rica designed to study the natural history of HPV and cervical neoplasia. Controls encompassed 31 women with transient infections; there were 44 cases, including 31 women with CIN3 and 13 with cervical cancer. DNA samples from exfoliated cervical cells were treated with bisulfite and four regions (E6, E2, L2 and L1) were amplified with barcoded primers and tested by NGS. CpG methylation was quantified using a bioinformatics pipeline.

RESULTS

Median methylation levels were significantly different between the CIN3+ cases versus controls in the E2, L2, and L1 regions. Methyl-haplotypes, specifically in 5 CpG sites included in the targeted L2 region, with the pattern "--+-+" had the highest Area Under the Curve value (AUC=88.40%) observed for CIN3 vs.

CONTROLS

The most significant CpG site, L2 4277, determined by bisulfite NGS had an AUC=78.62%.

CONCLUSIONS

This study demonstrates that NGS of bisulfite treated HPV DNA is a useful and efficient technique to survey methylation patterns in HPV16. This procedure provides quantitative information on both individual CpG sites and methyl-haplotypes that identify women with elevated present or subsequent risk for HPV16 CIN3 and cancer.

Methylation of viral and host genes and severity of cervical lesions associated with human papillomavirus type 16

Methylation of human papillomavirus (HPV) and host genes may predict cervical cancer risk. We examined the methylation status of selected sites in HPV16 and human genes in DNA extracted from exfoliated cervical cell samples of 244 women harboring HPV16-positive cancer or cervical intraepithelial neoplasia (CIN) or negative for intraepithelial lesions or malignancy (NILM). We quantified the methylation of CpG sites in the HPV16 L1 gene (CpG 6367 and 6389) and in the human genes EPB41L3 (CpG 438, 427, 425) and LMX1 (CpG 260, 262, 266, 274) following bisulfite treatment and pyrosequencing. Receiver operating characteristic (ROC) curves were used to analyze the diagnostic utility of methylation level for the different sites and for a joint predictor score. Methylation in all sites significantly increased with lesion severity (p < 0.0001). Area under the curve (AUC) was highest among the CIN2/3 vs. cancer ranging from 0.786 to 0.853 among the different sites. Site-specific methylation levels strongly discriminated CIN2/3 from NILM/CIN1 and cancer from CIN2/3 (range of odds ratios [OR]: 3.69-12.76, range of lower 95% confidence bounds: 1.03-4.01). When methylation levels were mutually adjusted for each other EPB41L3 was the only independent predictor of CIN2/3 vs. NILM/CIN1 contrasts (OR = 9.94, 95%CI: 2.46-40.27). High methylation levels of viral and host genes are common among precancerous and cancer lesions and can serve as independent risk biomarkers. Methylation of host genes LMX1 and EPB41L3 and of the viral HPV16 L1 sites has the potential to distinguish among precancerous lesions and to distinguish the latter from invasive disease.

HPV16 methyl-haplotypes determined by a novel next-generation sequencing method are associated with cervical precancer

We have developed and evaluated a next-generation bisulfite sequencing (NGS) assay to distinguish HPV16 cervical precancer (CIN2-3; N=59) from HPV16-positive transient infections (N=40). Cervical DNA was isolated and treated with bisulfite and HPV16 methylation was quantified by (i) amplification with barcoded primers and massively parallel single molecule sequencing and (ii) site-specific pyrosequencing. Assays were evaluated for agreement using intraclass correlation coefficients (ICC). Odds ratios (OR) for high methylation vs. low methylation were calculated. Single site pyrosequencing and NGS data were correlated (ICC=0.61) and both indicated hypermethylation was associated with precancer (ORs of 2-37). Concordant NGS and pyrosequencing results yieled ORs that were stronger when compared with using either assay separately. Within the L1 region, the ORs for CIN2-3 were 14.3 and 22.4 using pyrosequencing and NGS assays, respectively; when both methods agreed the OR was 153. NGS assays provide methylation haplotypes, termed methyl-haplotypes from single molecule reads: cases had increased methyl-haplotypes with ≥1 methylated CpG site(s) per fragment compared with controls, particularly in L1 (p=3.0×10(-8)). The maximum discrimination of cases from controls for a L1 methyl-haplotype had an AUC of 0.89 corresponding to a sensitivity of 92.5% and a specificity of 73.1%. The strengthening of the OR when the two assays were concordant suggests the true association of CpG methylation with precancer is stronger than with either assay. As cervical cancer prevention moves to DNA testing methods, DNA based biomarkers, such as HPV methylation could serve as a reflex strategy to identify women at high risk for cervix cancer.

Mapping of HPV transcripts in four human cervical lesions using RNAseq suggests quantitative rearrangements during carcinogenic progression

Two classes of Human papillomaviruses (HPV) infect the anogenital track: high risk viruses that are associated with risk of cervical cancer and low risk types that drive development of benign lesions, such as condylomas. In the present study, we established quantitative transcriptional maps of the viral genome in clinical lesions associated with high risk HPV16 or low risk HPV6b. Marked qualitative and quantitative changes in the HPV16 transcriptome were associated with progression from low to high grade lesions. Specific transcripts encoding essential regulatory proteins such as E7, E2, E1^E4 and E5 were identified. We also identified intrinsic differences between the HPV6b-associated condyloma transcript map and that of the HPV16-associated low grade CIN specifically regarding promoter usage. Characterization and quantification of HPV transcripts in patient samples thus establish the impact of viral transcriptional regulation on the status of HPV-associated lesions and may therefore help in defining new biologically-relevant prognosis markers.

Characterization of HPV DNA methylation of contiguous CpG sites by bisulfite treatment and massively parallel sequencing-the FRAGMENT approach

Invasive cervix cancer (ICC) is the third most common malignant tumor in women and human papillomavirus 16 (HPV16) causes more than 50% of ICC. DNA methylation is a covalent modification predominantly occurring at CpG dinucleotides and increased methylation across the HPV16 genome is strongly associated with ICC development. Next generation (Next Gen) sequencing has been proposed as a novel approach to determine DNA methylation. However, utilization of this method to survey CpG methylation in the HPV16 genome is not well described. Moreover, it provides additional information on methylation “haplotypes.” In the current study, we chose 12 random samples, amplified multiple segments in the HPV16 bisulfite treated genome with specific barcodes, inspected the methylation ratio at 31 CpG sites for all samples using Illumina sequencing, and compared the results with quantitative pyrosequencing. Most of the CpG sites were highly consistent between the two approaches (overall correlation, r = 0.92), thus verifying that Next Gen sequencing is an accurate and convenient method to survey HPV16 methylation and thus can be used in clinical samples for risk assessment. Moreover, the CpG methylation patterns (methylation haplotypes) in single molecules identified an excess of complete-and non-methylated molecules and a substantial amount of partial-methylated ones, thus indicating a complex dynamic for the mechanisms of HPV16 CpG methylation. In summary, the advantages of Next Gen sequencing compared to pyrosequencing for HPV genome methylation analyses include higher throughput, increased resolution, and improved efficiency of time and resources.

Clinical implications of (epi)genetic changes in HPV-induced cervical precancerous lesions

Infection of cervical epithelium with high-risk human papilloma virus (hrHPV) might result in productive or transforming cervical intraepithelial neoplasia (CIN) lesions, the morphology of which can overlap. In transforming CIN lesions, aberrations in host cell genes accumulate over time, which is necessary for the ultimate progression to cancer. On the basis of (epi)genetic changes, early and advanced transforming CIN lesions can be distinguished. This paves the way for new molecular tools for cervical screening, diagnosis and management of cervical cancer precursor lesions.

Human Papillomavirus 16, 18, 31 and 45 viral load, integration and methylation status stratified by cervical disease stage

Background

Persistent infection with oncogenic Human Papillomavirus (HPV) is associated with the development of cervical cancer with each genotype differing in their relative contribution to the prevalence of cervical disease. HPV DNA testing offers improved sensitivity over cytology testing alone but is accompanied by a generally low specificity. Potential molecular markers of cervical disease include type-specific viral load (VL), integration of HPV DNA into the host genome and methylation of the HPV genome. The aim of this study was to evaluate the relationship between HPV type-specific viral load, integration and methylation status and cervical disease stage in samples harboring HPV16, HPV18, HPV31 or HPV45.

Methods

Samples singly infected with HPV16 (n = 226), HPV18 (n = 32), HPV31 (n = 75) or HPV45 (n = 29) were selected from a cohort of 4,719 women attending cervical screening in England. Viral load and integration status were determined by real-time PCR while 3’L1-URR methylation status was determined by pyrosequencing or sequencing of multiple clones derived from each sample.

Results

Viral load could differentiate between normal and abnormal cytology with a sensitivity of 75% and a specificity of 80% (odds ratio [OR] 12.4, 95% CI 6.2–26.1; p < 0.001) with some variation between genotypes. Viral integration was poorly associated with cervical disease. Few samples had fully integrated genomes and these could be found throughout the course of disease. Overall, integration status could distinguish between normal and abnormal cytology with a sensitivity of 72% and a specificity of 50% (OR 2.6, 95% CI 1.0–6.8; p = 0.054). Methylation levels were able to differentiate normal and low grade cytology from high grade cytology with a sensitivity of 64% and a specificity of 82% (OR 8.2, 95% CI 3.8–18.0; p < 0.001). However, methylation varied widely between genotypes with HPV18 and HPV45 exhibiting a broader degree and higher magnitude of methylated CpG sites than HPV16 and HPV31.

Conclusions

This study lends support for HPV viral load and CpG methylation status, but not integration status, to be considered as potential biomarkers of cervical disease.

Cancer diagnostic classifiers based on quantitative DNA methylation

Epigenetic change is part of the carcinogenic process and a deep reservoir for biomarker discovery. Reversible methylation of cytosines is noteworthy because it can be measured accurately and easily by various molecular methods and DNA methylation patterns are linked to important tumourigenic pathways. Clinically relevant methylation changes are known in common human cancers such as cervix, prostate, breast, colon, bladder, stomach and lung. Differential methylation may have a central role in the development and outcome of most if not all human malignancies. The advent of deep sequencing holds great promise for epigenomics, with bioinformatics tools ready to reveal large numbers of new targets for prognosis and therapeutic intervention. This review focuses on two selected cancers, namely cervix and prostate, which illustrate the more general themes of epigenetic diagnostics in cancer. Also discussed is differential methylation of specific human and viral DNA targets and laboratory methods for measuring methylation biomarkers.

Credentialing of DNA methylation assays for human genes as diagnostic biomarkers of cervical intraepithelial neoplasia in high-risk HPV positive women

Objective

Testing for high risk human papillomavirus (HR-HPV) is increasing; however due to limitations in specificity there remains a need for better triage tests. Research efforts have focused recently on methylation of human genes which show promise as diagnostic classifiers.

Methods

Methylation of 26 genes: APC, CADM1, CCND2, CDH13, CDKN2A, CTNNB1, DAPK1, DPYS, EDNRB, EPB41L3, ESR1, GSTP1, HIN1, JAM3, LMX1, MAL, MDR1, PAX1, PTGS2, RARB, RASSF1, SLIT2, SOX1, SPARC, TERT and TWIST1 was measured by pyrosequencing in cytology specimens from a pilot set of women with normal or cervical intraepithelial neoplasia grade 3 (CIN3) histology. Six genes were selected for testing in Predictors 1, a colposcopy referral study comprising 799 women. The three genes EPB41L3, DPYS and MAL were further tested in a second colposcopy referral study, Predictors 2, comprising 884 women.

Results

The six genes selected from the pilot: EPB41L3, EDNRB, LMX1, DPYS, MAL and CADM1 showed significantly elevated methylation in CIN2 and CIN3 (CIN2/3) versus ≤CIN1 in Predictors 1 (p < 0.01). Highest methylation was observed in cancer tissues. EPB41L3 methylation was the best single classifier of CIN2/3 in both HR-HPV positive (p < 0.0001) and negative samples (p = 0.02). Logistic regression modeling showed that other genes did not add significantly to EPB41L3 and in Predictors 2, its classifier value was validated with AUC 0.69 (95% CI 0.65–0.73).

Conclusion

Several methylated genes show promise for detecting CIN2/3 of which EPB41L3 seems the best. Methylated human gene biomarkers used in combination may be clinically useful for triage of women with HR-HPV infections.

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Methylation of 26 human genes assessed by pyrosequencing in 40 cytology specimens

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Several methylated genes show promise for detecting CIN2/3.

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EBP41L3 shows reproducible biomarker potential in high risk HPV positive women.

Overexpression of Cancer-Associated Genes via Epigenetic Derepression Mechanisms in Gynecologic Cancer

Like other cancers, most gynecologic cancers are caused by aberrant expression of cancer-related genes. Epigenetics is one of the most important gene expression mechanisms, which contribute to cancer development and progression by regulating cancer-related genes. Since the discovery of differential gene expression patterns in cancer cells when compared with normal cells, extensive efforts have been made to explore the origins of abnormal gene expression in cancer. Epigenetics, the study of inheritable changes in gene expression that do not alter DNA sequence is a key area of this research. DNA methylation and histone modification are well-known epigenetic mechanisms, while microRNAs and alternative splicing have recently been identified as important regulators of epigenetic mechanisms. These mechanisms not only affect specific target gene expression but also regulate the functioning of other epigenetic mechanisms. Moreover, these diverse epigenetic regulations occur simultaneously. Epigenetic regulation of gene expression is extraordinarily complicated and all epigenetic mechanisms to be studied at once to determine the exact gene regulation mechanisms. Traditionally, the contribution of epigenetics to cancer is thought to be mediated through the inactivation of tumor suppressor genes expression. But recently, it is arising that some oncogenes or cancer-promoting genes (CPGs) are overexpressed in diverse type of cancers through epigenetic derepression mechanism, such as DNA and histone demethylation. Epigenetic derepression arises from diverse epigenetic changes, and all of these mechanisms actively interact with each other to increase oncogenes or CPGs expression in cancer cell. Oncogenes or CPGs overexpressed through epigenetic derepression can initiate cancer development, and accumulation of these abnormal epigenetic changes makes cancer more aggressive and treatment resistance. This review discusses epigenetic mechanisms involved in the overexpression of oncogenes or CPGs via epigenetic derepression in gynecologic cancers. Therefore, improved understanding of these epigenetic mechanisms will provide new targets for gynecologic cancer treatment.