DNA methylation as a triage tool for cervical cancer screening - A meeting report

Introduction

DNA methylation is proposed as a novel biomarker able to monitor molecular events in human papillomavirus (HPV) infection pathophysiology, enabling the distinction between HPV-induced lesions with regression potential from those that may progress to HPV-related cancer.

Methods

This meeting report summarises the presentations and expert discussions during the HPV Prevention and Control Board-focused topic technical meeting on DNA methylation validation in clinician-collected and self-collected samples, novel DNA methylation markers discovery, implementation in cervical cancer screening programs, and their potential in women living with human immunodeficiency virus (HIV).

Results

Data presented in the meeting showed that HPV-positive, baseline methylation-negative women have a lower cumulative cervical cancer incidence than baseline cytology-negative women, making DNA methylation an attractive triage strategy. However, additional standardised data in different settings (low- versus high-income settings), samples (clinician-collected and self-collected), study designs (prospective, modelling, impact) and populations (immunocompetent women, women living with HIV) are needed.

Conclusion

Establishing international validation guidelines were identified as the way forward towards accurate validation and subsequent implementation in current screening programs.

Clinical Regression of High-Grade Cervical Intraepithelial Neoplasia Is Associated With Absence of FAM19A4/miR124-2 DNA Methylation (CONCERVE Study)

PURPOSE

Cervical screening can prevent cancer by detection and treatment of cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3). Screening also results in considerable overtreatment because many CIN2/3 lesions show spontaneous regression when left untreated. In this multicenter longitudinal cohort study of women with untreated CIN2/3, the prognostic value of FAM19A4/miR124-2 methylation was evaluated for clinical regression.

PATIENTS AND METHODS

Women with CIN2/3 were prospectively followed for 24 months. Surgical excision was replaced by a wait-and-see policy. FAM19A4/miR124-2 methylation was evaluated on all clinician-collected samples and self-collected samples collected at baseline. Every 6 months, human papillomavirus (HPV) testing and cytology were conducted on a clinician-collected sample, and a colposcopic examination was performed by a gynecologist to exclude progression. At the final study visit, two biopsies were taken. Clinical regression was defined as histologically confirmed absence of CIN2+ or an HPV-negative clinician-collected sample with normal cytology. Regression incidences were estimated using the Kaplan-Meier method.

RESULTS

One hundred fourteen women (median age, 30 years; range, 20-53 years) were included, 80 of whom were diagnosed with CIN2 and 34 with CIN3. During the study, 65.8% of women (75/114) did not receive surgical treatment. Women with a negative FAM19A4/miR124-2 result on the baseline clinician-collected sample showed more clinical regression (74.7%) than women with a positive methylation result (51.4%, P = .013). Regression in women with a negative FAM19A4/miR124-2 methylation test was highest when cytology was atypical squamous cells of undetermined significance/low-grade squamous intraepithelial lesion (88.4%) or HPV16 was negative (85.1%).

CONCLUSION

Most women with untreated CIN2/3 and a negative baseline FAM19A4/miR124-2 methylation test showed clinical regression. Methylation, in combination with cytology or HPV genotyping, can be used to support a wait-and-see policy in women with CIN2/3.

Posttreatment monitoring by ASCL1/LHX8 methylation analysis in women with HIV treated for cervical intraepithelial neoplasia grade 2/3

OBJECTIVE

Women with HIV (WWH) have an increased risk to develop recurrent cervical intraepithelial neoplasia grade 2/3 (rCIN2/3) after treatment compared with HIV-negative women. Therefore, appropriate posttreatment monitoring of WWH is important. This study evaluates the performance of ASCL1 and LHX8 methylation analysis as posttreatment monitoring test in WWH treated for CIN2/3, as alternative to cytology or human papillomavirus (HPV) as follow-up test.

DESIGN

Prospective observational cohort study.

METHODS

WWH treated for CIN2/3 by large loop excision of the transformation zone (LLETZ) (n  = 61) were invited for follow-up study visits at 1, 2.5 and 4 years after baseline. Baseline and follow-up cervical scrapes were tested for cytology, HPV and DNA methylation of ASCL1 and LHX8 genes. The performance of these strategies for the detection of rCIN2/3 was evaluated in the first follow-up cervical scrape.

RESULTS

Thirteen (21.3%) rCIN2/3 lesions were detected within 4 years of follow-up. In women without rCIN2/3 in follow-up, methylation levels of ASCL1 and LHX8 decreased significantly after LLETZ treatment (P  = 0.02 and 0.007, respectively). In women with rCIN2/3, methylation levels remained high after LLETZ treatment. The 4-year rCIN2/3 risk was 4.9% (95% CI: 0.6-16.5) for ASCL1/LHX8-negative women, 8.1% (95% CI: 1.7-21.9) for HPV-negative women and 7.7% (95% CI: 2.1-18.5) for cytology-negative women.

CONCLUSION

A negative ASCL1/LHX8 methylation test in follow-up is associated with a low rCIN2/3 risk and could serve as an objective test of cure and well tolerated alternative for HPV and/or cytology screening in the posttreatment monitoring of WWH.

Experiences and preferences towards collecting a urine and cervicovaginal self-sample among women attending a colposcopy clinic

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In a colposcopy referral population, the majority of women consider self-collection of a urine sample and a cervicovaginal self-sample acceptable and easy to collect in a home-based setting.

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Urine collection is worth investigating as a potential screening method to possibly improve attendance rates in cervical cancer screening.

The effectiveness of cervical cancer screening is hampered by low attendance rates. The collection of a urine sample is hypothesized to engage non-attenders in cervical cancer screening. The aim of this prospective cohort study was to evaluate experiences of women on urine collection and cervicovaginal self-sampling in a home-based setting and preferences for future cervical cancer screening. This study included 140 women, with a median age of 40 years, who were planned for a large loop excision of the transformation zone (LLETZ) procedure. All women collected a urine sample using conventional urine cups and a cervicovaginal self-sample prior to the LLETZ in a home-based setting. Following sample collection, women filled in a questionnaire. Results showed that the instructions of urine collection and cervicovaginal self-sampling were considered clear (95%, 95%CI: 88–98; 92%, 95%CI: 83–96, respectively). Women considered urine collection compared to cervicovaginal self-sampling to be more acceptable (p < 0.001), and to provide more reliable results (p < 0.001). The three highest reported preferred sampling methods for future cervical cancer screening were: urine collection (n = 39, 28%, 95%CI: 19–39), clinician-taken cervical scrape (n = 32, 23%, 95%CI: 15–34), and equal preference for urine collection, clinician-taken cervical scrape and cervicovaginal self-sampling (n = 30, 21%, 95%CI: 14–32). In conclusion, urine collection and cervicovaginal self-sampling are acceptable sampling methods, considered easy to collect in a home-based setting, and moreover, considered trustworthy. Although these results are promising, more research is required to determine if urine collection also lowers the barrier for non-attendees and, thereby, increases the attendance rates of cervical cancer screening.

A systematic review on mutation markers for bladder cancer diagnosis in urine

OBJECTIVES

To systematically summarise the available evidence on urinary bladder cancer (BC) mutation markers. Gene mutations are expected to provide novel biomarkers for urinary BC diagnosis. To date, evidence on urinary BC mutation markers has not proven sufficient to be adopted by clinical guidelines. In the present systematic review, diagnostic accuracy of urinary mutation analysis is separately assessed for primary BC diagnosis (BC detection) and for follow-up of BC patients (BC surveillance).

METHODS

A literature search (PubMed, Embase.com and Wiley/Cochrane Library) and systematic review was performed up to 31 October 2019. As studies were too heterogeneous, no quantitative analysis could be performed.

RESULTS

In total, 25 studies were summarised by qualitative analysis. For BC detection, diagnostic accuracy differed considerably for single mutation markers (sensitivity 1-85%, specificity 84-100%), and for marker panels (sensitivity 50-94%, specificity 43-97%). Similarly, for BC surveillance, diagnostic accuracy was highly variable for single mutation markers (sensitivity 0-85%, specificity 66-100%), and for marker panels (sensitivity 51-84%, specificity 66-96%).

CONCLUSION

Urinary mutation analysis showed to be a promising diagnostic tool for non-invasive BC diagnosis. Nonetheless, we observed substantial differences in diagnostic accuracy of urinary BC mutation markers among publications. To translate the data summarised in the present review to future clinical practice, heterogeneity in research design, BC population, mutation analysis technique and urinary DNA should be considered. Eventual clinical implementation of urinary BC mutation markers can only be achieved by collecting more and stronger evidence. Combining different molecular assays might overcome current shortcomings of urinary mutation analysis.

FAM19A4/miR124-2 methylation in invasive cervical cancer: A retrospective cross-sectional worldwide study

Widespread adoption of primary human papillomavirus (HPV)-based screening has encouraged the search for a triage test which retains high sensitivity for the detection of cervical cancer and precancer, but increases specificity to avoid overtreatment. Methylation analysis of FAM19A4 and miR124-2 genes has shown promise for the triage of high-risk (hr) HPV-positive women. In our study, we assessed the consistency of FAM19A4/miR124-2 methylation analysis in the detection of cervical cancer in a series of 519 invasive cervical carcinomas (n = 314 cervical scrapes, n = 205 tissue specimens) from over 25 countries, using a quantitative methylation-specific PCR (qMSP)-based assay (QIAsure Methylation Test®). Positivity rates stratified per histotype, FIGO stage, hrHPV status, hrHPV genotype, sample type and geographical region were calculated. In total, 510 of the 519 cervical carcinomas (98.3%; 95% CI: 96.7-99.2) tested FAM19A4/miR124-2 methylation-positive. Test positivity was consistent across the different subgroups based on cervical cancer histotype, FIGO stage, hrHPV status, hrHPV genotype, sample type and geographical region. In conclusion, FAM19A4/miR124-2 methylation analysis detects nearly all cervical carcinomas, including rare histotypes and hrHPV-negative carcinomas. These results indicate that a negative FAM19A4/miR124-2 methylation assay result is likely to rule out the presence of cervical cancer.

miR-9-5p Exerts a Dual Role in Cervical Cancer and Targets Transcription Factor TWIST1

Squamous cell carcinoma (SCC) and adenocarcinoma (AC) represent the major cervical cancer histotypes. Both histotypes are caused by infection with high-risk HPV (hrHPV) and are associated with deregulated microRNA expression. Histotype-dependent expression has been observed for miR-9-5p, showing increased expression in SCC and low expression in AC. Here, we studied the regulation and functionality of miR-9-5p in cervical SCCs and ACs using cervical tissue samples and hrHPV-containing cell lines. Expression and methylation analysis of cervical tissues revealed that low levels of miR-9-5p in ACs are linked to methylation of its precursor genes, particularly miR-9-1. Stratification of tissue samples and hrHPV-containing cell lines suggested that miR-9-5p depends on both histotype and hrHPV type, with higher expression in SCCs and HPV16-positive cells. MiR-9-5p promoted cell viability and anchorage independence in cervical cancer cell lines SiHa (SCC, HPV16) and CaSki (metastasized SCC, HPV16), while it played a tumor suppressive role in HeLa (AC, HPV18). TWIST1, a transcription factor involved in epithelial-to-mesenchymal transition (EMT), was established as a novel miR-9-5p target. Our results show that miR-9-5p plays a dual role in cervical cancer in a histotype- and hrHPV type-dependent manner. MiR-9-5p mediated silencing of TWIST1 suggests two distinct mechanisms towards EMT in cervical cancer.

Abstract 2718: Longer duration of preceding high-risk HPV infection is associated with an increase of chromosomal aberrations in high-grade cervical intraepithelial neoplasia

High-grade cervical intraepithelial neoplastic (CIN2/3) lesions represent a heterogeneous disease both with respect to clinical behaviour and chromosomal aberrations detected. We hypothesized that the extent of chromosomal aberrations reflects the duration of their existence. To test this hypothesis, chromosomal profiles were determined of CIN3 lesions of women with a known 5 year history of high-risk human papillomavirus virus (hrHPV) infection, in which duration of prior hrHPV infection was considered a proxy for duration of CIN3 lesion existence. Eight women had a &lt;5 year preceding hrHPV infection (CIN3&lt;5yrPHI) and 24 had a PHI lasting ≥5 years (CIN3≥5yrPHI). For comparison, 6 CIN3 lesions adjacent to squamous cell carcinomas (CIN3-SCC), their corresponding SCCs, and 6 CIN1 lesions were included. Unsupervised hierarchical clustering analysis of the chromosomal profiles revealed two clusters. One was characterized by relatively quiet genomic profiles including all CIN1, 75% of CIN3&lt;5yrPHI and 37.5% of CIN3≥5yrPHI. Samples in the second cluster, displaying multiple aberrations, included 62.5% CIN3≥5yrPHI and all except one CIN3-SCC and all SCCs. The number of genomic aberrations increased according to lesion grade and also with longer duration of PHI. The increase in aberrations in CIN3≥5yrPHI compared to &lt;5yrPHI was highly significant (p=0.002), suggesting that CIN3≥5yrPHI represent more severe lesions. In conclusion, a longer duration of preceding hrHPV infection is associated with an increased number of chromosomal aberrations. Hence, CIN3 lesions with a longer duration of existence are more prone to have an increased short-term risk of cervical cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2718. doi:10.1158/1538-7445.AM2011-2718

The dynamic DNA methylomes of double-stranded DNA viruses associated with human cancer

The natural history of cancers associated with virus exposure is intriguing, since only a minority of human tissues infected with these viruses inevitably progress to cancer. However, the molecular reasons why the infection is controlled or instead progresses to subsequent stages of tumorigenesis are largely unknown. In this article, we provide the first complete DNA methylomes of double-stranded DNA viruses associated with human cancer that might provide important clues to help us understand the described process. Using bisulfite genomic sequencing of multiple clones, we have obtained the DNA methylation status of every CpG dinucleotide in the genome of the Human Papilloma Viruses 16 and 18 and Human Hepatitis B Virus, and in all the transcription start sites of the Epstein-Barr Virus. These viruses are associated with infectious diseases (such as hepatitis B and infectious mononucleosis) and the development of human tumors (cervical, hepatic, and nasopharyngeal cancers, and lymphoma), and are responsible for 1 million deaths worldwide every year. The DNA methylomes presented provide evidence of the dynamic nature of the epigenome in contrast to the genome. We observed that the DNA methylome of these viruses evolves from an unmethylated to a highly methylated genome in association with the progression of the disease, from asymptomatic healthy carriers, through chronically infected tissues and pre-malignant lesions, to the full-blown invasive tumor. The observed DNA methylation changes have a major functional impact on the biological behavior of the viruses.

Telomerase suppression by chromosome 6 in a human papillomavirus type 16-immortalized keratinocyte cell line and in a cervical cancer cell line

BACKGROUND

High-risk human papillomavirus (HPV) types play a major role in the development of cervical cancer in vivo and can induce immortalization of primary human keratinocytes in vitro. Activation of the telomere-lengthening enzyme telomerase constitutes a key event in both processes. Because losses of alleles from chromosome 6 and increased telomerase activity have been observed in high-grade premalignant cervical lesions, we analyzed whether human chromosome 6 harbors a putative telomerase repressor locus that may be involved in HPV-mediated immortalization.

METHODS

Microcell-mediated chromosome transfer was used to introduce chromosomes 6 and 11 to the in vitro generated HPV type 16 (HPV16)-immortalized keratinocyte cell line FK16A and to the in vivo derived HPV16-containing cervical cancer cell line SIHA: Hybrid clones were analyzed for growth characteristics, telomerase activity, human telomerase reverse transcriptase (hTERT) and HPV16 E6 expression, and telomere length. FK16A hybrid clones were also transduced with an hTERT-containing retrovirus to examine the effect of ectopic hTERT expression on growth. Statistical tests were two-sided.

RESULTS

Introduction of human chromosome 6 but not of chromosome 11 to both cell lines yielded hybrid cells that demonstrated crisis-like features (i.e., enlarged and flattened morphology, vacuolation, and multinucleation) and underwent growth arrest after a marked lag period. In the chromosome 6 hybrid clones analyzed, telomerase activity and hTERT messenger RNA (mRNA) expression were statistically significantly reduced compared with those in the chromosome 11 hybrid clones (for telomerase activity, P =.004 for the FK16A hybrids and P =.039 for the SiHa hybrids; for hTERT mRNA expression, P =.003 for the FK16A hybrids). The observed growth arrest was associated with telomeric shortening. Ectopic expression of hTERT in FK16A cells could prevent the telomeric shortening-based growth arrest induced by chromosome 6.

CONCLUSIONS

Chromosome 6 may harbor a repressor of hTERT transcription, the loss of which may be involved in HPV-mediated immortalization.

[Human papillomavirus and the development of cervical cancer: concept of carcinogenesis]

Infection with high risk human papillomavirus (hrHPV) plays a central aetiological role in cervical cancer. Still, cervical carcinogenesis is a multistep process which requires other events in addition to hrHPV infection. Recent data have resulted in the following concept of cervical carcinogenesis: hrHPV infects normal squamous epithelium. In most cases this will not lead to a lesion or at worst give rise to a regressing low grade cervical intraepithelial neoplasia (CIN). Both phenomena involve viral clearance. Only persistent hrHPV infections will lead to a high grade CIN lesion, a subset of which may undergo malignant transformation. At the transition of CIN 2 to CIN 3 deregulated expression of the viral oncogenes E6 and E7 takes place, resulting in genetic instability. Subsequently, activation of the telomere-lengthening enzyme, telomerase occurs, at the result of which cells obtain an infinite replication capacity. Ultimately, successive allele losses occur at different chromosomal locations which, followed by a clonal outgrowth result in an invasive carcinoma.

Telomerase activity exclusively in cervical carcinomas and a subset of cervical intraepithelial neoplasia grade III lesions: strong association with elevated messenger RNA levels of its catalytic subunit and high-risk human papillomavirus DNA

In this study, we investigated telomerase activity and human telomerase reverse transcriptase (hTERT) mRNA expression in relation to high-risk human papillomavirus (HPV) DNA presence in the spectrum of cervical premalignant lesions. Reconstruction experiments revealed that telomerase activity determined by the telomeric repeat amplification protocol assay and hTERT mRNA by reverse transcriptase-PCR could be detected in down to 100 and 1 SiHa cervical cancer cells, respectively. Telomeric repeat amplification protocol analysis on cervical tissue specimens revealed that none of the histomorphologically normal cervical samples (n = 8) and cervical intraepithelial neoplasia (CIN) grade I (n = 10) and grade II (n = 8) lesions had detectable telomerase activity. However, telomerase activity was shown in 40% of CIN grade III lesions (n = 15) and 96% of squamous cell carcinomas (n = 24). Despite the fact that hTERT mRNA was found at much higher frequencies, semiquantitative reverse transcriptase-PCR revealed that elevated hTERT mRNA levels were strongly correlated with detectable telomerase activity. Furthermore, telomerase activity and elevated hTERT mRNA levels were only detected in cases that contained high-risk HPV DNA. In contrast, low or undetectable hTERT mRNA levels were demonstrated in both high-risk HPV positive and negative cases. These data indicate that telomerase activity detectable with the assay used and concomitant elevated levels of hTERT mRNA reflect a rather late step in the CIN to squamous cell carcinoma sequence, which follows infection with high-risk HPV.

Hemidesmosome formation is initiated by the beta4 integrin subunit, requires complex formation of beta4 and HD1/plectin, and involves a direct interaction between beta4 and the bullous pemphigoid antigen 180

Hemidesmosomes (HDs) are stable anchoring structures that mediate the link between the intermediate filament cytoskeleton and the cell substratum. We investigated the contribution of various segments of the beta4 integrin cytoplasmic domain in the formation of HDs in transient transfection studies using immortalized keratinocytes derived from an epidermolysis bullosa patient deficient in beta4 expression. We found that the expression of wild-type beta4 restored the ability of the beta4-deficient cells to form HDs and that distinct domains in the NH2- and COOH-terminal regions of the beta4 cytoplasmic domain are required for the localization of HD1/plectin and the bullous pemphigoid antigens 180 (BP180) and 230 (BP230) in these HDs. The tyrosine activation motif located in the connecting segment (CS) of the beta4 cytoplasmic domain was dispensable for HD formation, although it may be involved in the efficient localization of BP180. Using the yeast two-hybrid system, we could demonstrate a direct interaction between beta4 and BP180 which involves sequences within the COOH-terminal part of the CS and the third fibronectin type III (FNIII) repeat. Immunoprecipitation studies using COS-7 cells transfected with cDNAs for alpha6 and beta4 and a mutant BP180 which lacks the collagenous extracellular domain confirmed the interaction of beta4 with BP180. Nevertheless, beta4 mutants which contained the BP180-binding region, but lacked sequences required for the localization of HD1/plectin, failed to localize BP180 in HDs. Additional yeast two- hybrid assays indicated that the 85 COOH-terminal residues of beta4 can interact with the first NH2-terminal pair of FNIII repeats and the CS, suggesting that the cytoplasmic domain of beta4 is folded back upon itself. Unfolding of the cytoplasmic domain may be part of a mechanism by which the interaction of beta4 with other hemidesmosomal components, e.g., BP180, is regulated.

Non-random allelic losses at 3p, 11p and 13q during HPV-mediated immortalization and concomitant loss of terminal differentiation of human keratinocytes

To obtain a comprehensive overview of chromosomal alterations that may underlie human papillomavirus (HPV)-mediated immortalization, 4 foreskin keratinocyte cell lines generated by transfection with either HPV 16 (cell lines FK16A and FK16B) or HPV 18 (FK18A and FK18B) were subjected to chromosomal analysis using comparative genomic hybridization (CGH). Three cell lines were analyzed both in the mortal state during their extended lifespan and in the subsequent immortal state. From cell line FK18A, only immortal cells were tested. Chromosomal imbalances increased in number through the process of immortalization. Subsequent loss of heterozygosity (LOH) analysis, using a panel of 21 microsatellite markers selected on the basis of CGH losses, revealed no clonal LOHs in cells at the mortal stage. However, in the immortal descendants 67% of underrepresentations detected by CGH were expressed as clonal LOH at the respective loci. Clonal LOHs at 3p, 11p and 13q were detected in 2 cell lines each and were thus considered non-random. Immortal cells of 1 cell line (FK18B) revealed LOH at all 3 loci. Moreover, all immortal cell lines displaying allelic losses at one or more of these loci shared a severely dysplastic phenotype after organotypic culturing, as shown previously. Therefore, loss-of-function mutations of genes at these loci, eventually in combination, are potentially involved in the process of HPV-mediated immortalization that is attended by a loss of terminal differentiation. Since chromosomal changes at these loci are also found in HPV-associated carcinomas in vivo, the HPV-transfected cell lines seem to provide a valuable model system for studying HPV-mediated carcinogenesis.

Non-random allelic losses at 3p, 11p and 13q during HPV-mediated immortalization and concomitant loss of terminal differentiation of human keratinocytes

To obtain a comprehensive overview of chromosomal alterations that may underlie human papillomavirus (HPV)-mediated immortalization, 4 foreskin keratinocyte cell lines generated by transfection with either HPV 16 (cell lines FK16A and FK16B) or HPV 18 (FK18A and FK18B) were subjected to chromosomal analysis using comparative genomic hybridization (CGH). Three cell lines were analyzed both in the mortal state during their extended lifespan and in the subsequent immortal state. From cell line FK18A, only immortal cells were tested. Chromosomal imbalances increased in number through the process of immortalization. Subsequent loss of heterozygosity (LOH) analysis, using a panel of 21 microsatellite markers selected on the basis of CGH losses, revealed no clonal LOHs in cells at the mortal stage. However, in the immortal descendants 67% of underrepresentations detected by CGH were expressed as clonal LOH at the respective loci. Clonal LOHs at 3p, 11p and 13q were detected in 2 cell lines each and were thus considered non-random. Immortal cells of 1 cell line (FK18B) revealed LOH at all 3 loci. Moreover, all immortal cell lines displaying allelic losses at one or more of these loci shared a severely dysplastic phenotype after organotypic culturing, as shown previously. Therefore, loss-of-function mutations of genes at these loci, eventually in combination, are potentially involved in the process of HPV-mediated immortalization that is attended by a loss of terminal differentiation. Since chromosomal changes at these loci are also found in HPV-associated carcinomas in vivo, the HPV-transfected cell lines seem to provide a valuable model system for studying HPV-mediated carcinogenesis.

Viral E6-E7 transcription in the basal layer of organotypic cultures without apparent p21cip1 protein precedes immortalization of human papillomavirus type 16- and 18-transfected human keratinocytes

Organotypic cultures of human keratinocytes provide a useful model system to study human papillomavirus (HPV)-host cell interactions. In this study, we analyzed organotypic cultures of two HPV type 16 (HPV16) (FK16A and FK16B)- and two HPV18 (FK18A and FK18B)-transfected keratinocyte cell lines through the process of immortalization in vitro. For FK16A and FK18B cells, passages of both mortal cells in their extended life span and subsequent immortal stages were studied. Mortal cells of FK16A and FK18B showed a morphology reminiscent of mild to moderate dysplasia, whereas in their immortal descendants, severely dysplastic features were observed. Immortal FK18A cells were mildly to moderately dysplastic, while FK16B cells were severely dysplastic. The increasing degrees of dysplasia were associated with a decreasing expression of differentiation markers cytokeratin 10 and profilaggrin. All raft cultures expressed E6-E7 mRNAs in the basal layer, while the amount of viral transcripts in the suprabasal cells was in general proportional to the degree of dysplasia. In all cases, E6-E7 transcription and dysplastic features were highly correlated with cellular proliferation, as assessed by Ki-67 (MIB-1) antigen expression. Moreover, high levels of E6-E7 transcription and expression of p21cip1 protein in the basal layer seemed to be mutually exclusive. We conclude that expression of E6-E7 in the basal cells associated with increased proliferation in the absence of detectable p21cip1 protein is apparently necessary but not sufficient for immortalization, or for the loss of terminal differentiation, for which yet to be discovered additional events are required. The model system described in this study provides a valuable tool to analyze alterations in viral transcription regulation during HPV-mediated cell transformation.

Prevalence of Epstein-Barr virus in oral squamous cell carcinomas, premalignant lesions and normal mucosa--a study using the polymerase chain reaction

Epstein-Barr virus (EBV) prevalence was assessed in 12 clinically normal oral mucosas, nine premalignant lesions, 36 oral squamous cell carcinomas (OSCCs) and a human papillomavirus (HPV) 16 positive cell line, derived from an OSCC studied. The polymerase chain reaction (PCR) with two pairs of primers with different sensitivities was used. With primers specific for the BamHIW repeat, EBV was found in 100% of OSCCs, in 77.8% of premalignant lesions and in 8.3% of clinically normal oral mucosas (P = 0.0001). Using primers specific for the single copy BNLF-1 gene, EBV was detected in 50% of OSCC and in none of the premalignant lesions. No statistically significant associations could be established among EBV presence and clinico-pathological data of OSCC. The cell line derived from an HPV/EBV-positive carcinoma did not reveal EBV DNA. The higher prevalence of EBV in OSCCs and premalignant lesions may be due to increased EBV shedding, possibly due to associated immunodepression in these patients, rather than its clonal presence in the neoplastic cells.

Transition of human papillomavirus type 16 and 18 transfected human foreskin keratinocytes towards immortality: activation of telomerase and allele losses at 3p, 10p, 11q and/or 18q

This study aimed at resolving cellular genetic alterations in the process of in vitro immortalization of human keratinocytes by human papillomavirus (HPV) types 16 and 18. Four cell lines of primary human foreskin keratinocytes transfected with HPV 16 and HPV 18, respectively, were analysed during the transition from the mortal to immortal state. All cell lines showed strong telomerase activity at the immortal state, whereas no or only weak telomerase activity was detected in mortal precursor cells. This was consistent with telomere stabilization or restoration only observed in immortal cells. HPV physical state and copy number appeared constant during immortalization and HPV E6/E7 transcripts were present throughout. Immortalization was associated with clonal allele losses at 3p combined with either 11q or 18q or at 10p, dependent on the cell line. Moreover, a correlation was evident between the onset of telomerase activity and allele loss at 3p or 10p. All immortalized cells retained the capability to differentiate after growth in the presence of physiological calcium and serum. Moreover, one of the immortal cell lines displayed terminal differentiation after organotypic culturing on collagen rafts. The data suggest that (a) several pathways exist for HPV mediated immortalization that may involve genes residing at 3p, 10p, 11q and/or 18q; (b) 3p and 10p may encode genes involved in telomerase regulation; and (c) immortalization in vitro can be correlated with a spectrum of morphological changes varying from mild to severe dysplasia.

Age-dependence of human papillomavirus DNA presence in oral squamous cell carcinomas

The aetiology of oral cancer is thought to be multifactorial. Apart from the two known major risk factors (tobacco and alcohol), a viral aetiology has been proposed, with special reference to human papillomavirus (HPV). 35 cases of oral squamous cell carcinoma (OSCC), seen at the Departments of Oral & Maxillofacial Surgery and Oral Pathology and Otolaryngology of the Free University of Amsterdam, were analysed as well as 12 biopsies of clinically and histologically normal gingival mucosa collected from healthy individuals after tooth extractions, using the polymerase chain reaction (PCR) and two different sets of primers that are able to detect a broad spectrum of HPV types. An overall HPV positivity of 54.3% in OSCC was found, the majority of positive cases (78.9%) harbouring HPV type 16. In contrast, no positivity for HPV was detected in the clinically normal oral mucosal samples analysed. Furthermore, a significant association between HPV presence and age was found: patients older than 60 years showed a lower prevalence of the virus (29.4%) compared with patients below this age (77.8%) (P < 0.05). The results from the present study suggest an association between HPV and OSCC, particularly in patients under the seventh decade.

Integrated human papillomavirus type 16 and loss of heterozygosity at 11q22 and 18q21 in an oral carcinoma and its derivative cell line

A human papillomavirus (HPV) type 16 containing oral squamous cell carcinoma cell line 93VU147T at early passage was demonstrated to match its primary tumor with regard to HPV status and loss of heterozygosity at loci potentially involved in HPV-mediated carcinogenesis. DNA in situ hybridization of the cell line and the primary tumor revealed the presence of HPV 16 DNA clonally associated with the neoplastic cells. One- and two-dimensional Southern blot hybridization suggested HPV 16 to be integrated in the host genome at over hundred copies/cell. An identical restriction enzyme profile was observed for the tumor and the cell line. Viral DNA integration was confirmed by fluorescence in situ hybridization on metaphase spreads of the cell line, which revealed six stained loci comprising one at 15q14-15 and five at cytogenetically unidentifiable chromosomes. In addition, the tumor and the cell line displayed mRNA expression of the E6/E7 region encoding the viral oncoproteins, as determined by reverse transcription-PCR. Northern blot analysis of the cell line revealed three major and three minor transcripts harboring E6/E7 sequences. Both the primary tumor and cell line showed loss of heterozygosity at the 11q22 (D11S35) and 18q21 (DCC) loci. These data support a role for HPV 16 in the development of a subset of oral cancers, presumably in concert with loss of function of tumor suppressor genes at 11q and 18q.

Analysis of p53 status in tonsillar carcinomas associated with human papillomavirus

Tonsillar squamous cell carcinomas (a total of 14) were examined both for the presence of human papillomavirus (HPV) DNA and for p53 alterations. General primer-mediated HPV polymerase chain reaction (GP-PCR) revealed the presence of HPV DNA in 12/14 cases. Subsequent typing by HPV type-specific PCR and sequence or hybridization analysis of GP-PCR products revealed DNA from HPV 16 in seven cases, from HPV 33 in two cases, and from HPV 7, HPV 16/33 and HPV 33/59 each in a single case. p53 immunohistochemistry performed on nine HPV containing tonsillar carcinomas using polyclonal serum CM-1 showed elevated p53 levels in four cases. These included 3/5 HPV 16 containing carcinomas and the HPV 33/59 containing carcinoma. Analysis of p53 mutations using denaturing gradient gel electrophoresis (DGGE) of GC-clamped PCR products of exons 5 to 8 showed p53 gene alterations in 3/13 cases, including 2/11 HPV positive cases and 1/2 HPV negative cases. The alterations included a silent point mutation within exon 8 of an HPV 16 containing carcinoma, a 1 bp deletion within exon 8 of an HPV 33 containing carcinoma, and a missense mutation within exon 7 of one of the HPV negative carcinomas. There was evident discrepancy between p53 immunohistochemistry and gene analysis. Four HPV containing cases showing elevated p53 levels did not reveal the presence of exon 5 to 8 alterations affecting the amino acid code, suggesting the presence of mutations occurring in other exons or non-mutational p53 stabilization. The data indicate that HPV and elevated p53 can coexist in tonsillar carcinomas and that despite the low frequency of p53 mutations the presence of HPV is not exclusively related to the absence of mutated p53.

Three sensitive methods for the detection of cytomegalovirus in lung tissue of patients with interstitial pneumonitis

Interstitial pneumonia after allogeneic bone marrow transplantation is frequently associated with human cytomegalovirus (HCMV) infection. However, in a considerable proportion of the cases, no infectious agent can be determined and the interstitial pneumonia is then classified as idiopathic. Hypothetically, idiopathic interstitial pneumonia could be caused by HCMV present in such small amounts or such conformation that the virus cannot be detected by routine histopathologic analysis or viral culture techniques. To check this hypothesis, three sensitive methods for HCMV detection (in situ hybridization, the polymerase chain reaction for HCMV-DNA detection, and immunohistochemistry for the detection of HCMV immediate early antigens) have been applied on lung tissue sections of bone marrow transplant patients who died with interstitial pneumonia. Three categories were distinguished: (1) patients with HCMV-related interstitial pneumonia (n = 5); (2) patients with idiopathic interstitial pneumonia (n = 10); and (3) patients with HCMV interstitial pneumonia who had been treated with antiviral therapy (n = 2). In the first category, all three techniques yielded clearly positive results, whereas these techniques indicated that one of the patients of the second category had HCMV-related pneumonia. In the third category no positive signals could be obtained. The presented data indicate that a direct involvement of HCMV in idiopathic interstitial pneumonia is unlikely. However, a PCR performed for Epstein-Barr virus (EBV) was positive in two patients with idiopathic interstitial pneumonia. These data indicate that the introduction of new sensitive techniques such as in situ hybridization, immunohistochemistry, and the polymerase chain reaction revives the interest for HCMV and other causative infectious agents in idiopathic interstitial pneumonia.