Single copy heterozygote integration of HPV 33 in chromosomal band 5p14 is found in an epithelial cell clone with selective growth advantage

Oral manifestations of human papillomavirus infections

Papillomaviruses are one of the oldest viruses known, dating back 330 million years. During this long evolution, human papillomaviruses (HPV) have developed into hijackers of human cellular and immune systems in which they replicate and remain silent. Systematic studies on oral HPV infections and their outcomes are still scarce. Oral HPV infections have been linked to sexual behaviour, but recent evidence supports their horizontal, mouth‐to‐mouth, transmission. Most HPV infections in infants are acquired vertically from the mother during the intrauterine period, during delivery, or later via saliva. The best‐known benign clinical manifestations of HPV infection are oral papilloma/condyloma and focal epithelial hyperplasia. Evidence is emerging which suggests that some oral HPV infections might persist. Persistent HPV infection is mandatory for HPV‐associated malignant transformation. However, progression of HPV‐induced lesions to malignancy requires additional cofactors. In the early 1980s, we provided the first evidence that a subset of oral cancers and other head and neck cancers might be causally linked to HPV infection. This review summarizes current knowledge on the virus itself, its transmission modes, as well as the full spectrum of oral HPV infections – from asymptomatic infections to benign, potentially malignant oral lesions, and squamous cell carcinoma.

A novel human in vitro papillomavirus type 16 positive tonsil cancer cell line with high sensitivity to radiation and cisplatin

Background

Human papillomavirus (HPV) is an established risk factor for oropharyngeal squamous cell carcinoma (OSCC). The aim was to establish cell lines from HPV-positive tonsil carcinomas to be used for treatment development.

Methods

Fresh samples from 23 HPV-positive tonsil carcinomas were cultivated in vitro. The established cell line was analyzed for viral characteristics, cell karyotype, TP53 status, and growth capabilities in nude mice. In vitro studies of sensitivities to radiation, cisplatin and cetuximab were performed.

Results

After 19 months (eight passages), one cell line, LU-HNSCC-26, was established in vitro and also grew as xenografts. The tumor was from a 48 year old non-smoking man with non-keratinizing, p16 positive tonsil OSCC, stage T2N0M0 with HPV16. It contained 19.5 (CV% 3.7) HPV16 copies/cell (passage 8). The complete HPV16 genome sequence was obtained. Episomal HPV16 was present with an E2/E7 ratio of 1.1 (CV% 2.6). In addition, HPV16 mRNA specific for the intact E2 gene was detected. The viral expression manifested 1.0 (CV% 0.1) E7 mRNA copies per HPV16 genome. The karyotype was determined and the cell line demonstrated wild type TP53. The ID50 for radiation was 0.90 Gy and the IC50 for cisplatin was 0.99 μmol/L. The cell line was inhibited to a maximum of 18% by cetuximab.

Conclusions

We established an in vitro tonsil carcinoma cell line containing episomal HPV16. This is an important step towards efficient treatment development.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5469-8) contains supplementary material, which is available to authorized users.

Oxidative stress: therapeutic approaches for cervical cancer treatment

Oxidative stress results from an imbalance between the generation and elimination of oxidant species. This condition may result in DNA, RNA and protein damage, leading to the accumulation of genetic alterations that can favor malignant transformation. Persistent infection with high-risk human papillomavirus types is associated with inflammatory responses and reactive oxygen species production. In this context, oxidative stress, chronic inflammation and high-risk human papillomavirus can act in a synergistic manner. To counteract the harmful effects of oxidant species, protective molecules, known as antioxidant defenses, are produced by cells to maintain redox homeostasis. In recent years, the use of natural antioxidants as therapeutic strategies for cancer treatment has attracted the attention of the scientific community. This review discusses specific molecules and mechanisms that can act against or together with oxidative stress, presenting alternatives for cervical cancer prevention and treatment.

DNA Oncogenic Virus-Induced Oxidative Stress, Genomic Damage, and Aberrant Epigenetic Alterations

Approximately 20% of human cancers is attributable to DNA oncogenic viruses such as human papillomavirus (HPV), hepatitis B virus (HBV), and Epstein-Barr virus (EBV). Unrepaired DNA damage is the most common and overlapping feature of these DNA oncogenic viruses and a source of genomic instability and tumour development. Sustained DNA damage results from unceasing production of reactive oxygen species and activation of inflammasome cascades that trigger genomic changes and increased propensity of epigenetic alterations. Accumulation of epigenetic alterations may interfere with genome-wide cellular signalling machineries and promote malignant transformation leading to cancer development. Untangling and understanding the underlying mechanisms that promote these detrimental effects remain the major objectives for ongoing research and hope for effective virus-induced cancer therapy. Here, we review current literature with an emphasis on how DNA damage influences HPV, HVB, and EBV replication and epigenetic alterations that are associated with carcinogenesis.

Viral carcinogenesis: factors inducing DNA damage and virus integration

Viruses are the causative agents of 10%-15% of human cancers worldwide. The most common outcome for virus-induced reprogramming is genomic instability, including accumulation of mutations, aberrations and DNA damage. Although each virus has its own specific mechanism for promoting carcinogenesis, the majority of DNA oncogenic viruses encode oncogenes that transform infected cells, frequently by targeting p53 and pRB. In addition, integration of viral DNA into the human genome can also play an important role in promoting tumor development for several viruses, including HBV and HPV. Because viral integration requires the breakage of both the viral and the host DNA, the integration rate is believed to be linked to the levels of DNA damage. DNA damage can be caused by both endogenous and exogenous factors, including inflammation induced by either the virus itself or by co-infections with other agents, environmental agents and other factors. Typically, cancer develops years to decades following the initial infection. A better understanding of virus-mediated carcinogenesis, the networking of pathways involved in transformation and the relevant risk factors, particularly in those cases where tumorigenesis proceeds by way of virus integration, will help to suggest prophylactic and therapeutic strategies to reduce the risk of virus-mediated cancer.

Human Papillomavirus Infection and Its Association with HIV

Human papillomavirus (HPV) can infect oral mucosa, causing asymptomatic infection or warty lesions. Several case-control studies have confirmed HPV as an independent risk factor for squamous cell carcinoma. HPV-related cancers seem to have better prognoses and different risk factors than do HPV-negative ones. HIV-infected patients are known to be at increased risk for persistent genital and anal high-risk HPV infections and intraepithelial neoplasm. Since the era of highly active antiretroviral therapy, the prevalence and persistence of warty lesions in oral mucosa have increased. Oral squamous cell carcinoma was recently added in the case definitions for common HIV-related oral mucosa lesions. The increased risk of HPV infection in HIV patients has been associated with impaired immune response to HPV, highly active antiretroviral therapy, aging of the HIV-infected patients, and direct interaction between the 2 viruses. HPV32 seems to be much more prevalent in asymptomatic HPV infections and warts among those infected with HIV than among those in the general population. Regarding HIV genes, there is evidence of an interaction between HPV and tat, rev, and vpr. HIV might play a role in HPV-associated pathogenesis by exhorting oncogenic stimuli via tat and rev or visa versa.

Episomal and integrated human papillomavirus type 16 loads and anal intraepithelial neoplasia in HIV-seropositive men

OBJECTIVES

To assess levels of episomal and integrated human papillomavirus type 16 (HPV-16) loads in HIV-seropositive men who have sex with men (MSM) in anal infection and to study the association between episomal and integrated HPV-16 loads and anal intraepithelial neoplasia (AIN).

STUDY DESIGN

A cohort study of 247 HIV-positive MSM followed each 6 months for 3 years. Overall, 135 (54.7%) men provided 665 HPV-16-positive anal samples.

METHODS

Episomal and integrated HPV-16 loads were measured with quantitative real-time PCR assays. HPV-16 integration was confirmed in samples with a HPV-16 E6/E2 of 1.5 or more with PCR sequencing to demonstrate the presence of viral-cellular junctions.

RESULTS

The HPV-16 DNA forms in anal samples were characterized as episomal only in 627 samples (94.3%), mixed in 22 samples (3.3%) and integrated only in nine samples (1.4%). HPV-16 episomal load [odds ratio (OR) = 1.5, 95% confidence interval (CI) 1.1-2.1], number of HPV types (OR = 1.4, 95% CI 1.1-1.8) and current smoking (OR = 4.8, 95% CI 1.3-18.6) were associated with high-grade AIN (AIN-2,3) after adjusting for age and CD4 cell counts. Integrated HPV-16 load was not associated with AIN-2,3 (OR = 0.7, 95% CI 0.4-1.1). Considering men with AIN-1 at baseline, four (16.7%) of the 24 men who progressed to AIN-2,3 had at least one sample with integrated HPV-16 DNA compared with three (23.1%) of 13 men who did not progress (OR = 0.7, 95% CI 0.2-3.8; P = 0.64). Integration was detected in similar proportions in samples from men without AIN, with AIN-1 or AIN-2,3.

CONCLUSION

High episomal HPV-16 load but not HPV-16 integration load measured by real-time PCR was associated with AIN-2,3.

Molecular markers implicating early malignant events in cervical carcinogenesis

BACKGROUND

Human papillomavirus can induce a stepwise progression of precursor lesions to carcinoma. Sensitive and specific molecular markers are needed to identify the cervical lesions (CIN) at risk for this progression. hTERT activation could be one indicator of a point of no return in malignant progression.

METHODS

The UT-DEC-1 cell line is an in vitro model for the study of human papillomavirus-induced progression. Using molecular mining, nine potential genes interlinking hTERT and viral oncogene expression with the phenotypical features of CIN2 were identified. After preliminary testing with real-time PCR, five genes were selected for further analysis: hTERT, DKC1, Bcl-2, S100A8, and S100A9. These proteins were also tested in a series of 120 CIN lesions using immunohistochemistry.

RESULTS

Analysis of the mRNA expression of these genes at different cell passages revealed three time points with significant changes. hTERT, Bcl-2, and S100A9 were also overexpressed in CIN lesions, and the expression pattern changed during the progression toward CIN3 lesions.

CONCLUSIONS

These identified time points that were combined with the mRNA overexpression of target genes matched events previously shown to be important in the progression toward malignancy: (a) the viral integration into the cell genome and episome loss; (b) the selection of cells with an acquired growth advantage and ability to maintain telomerase activity; and (c) the final stage of malignancy with permanently upregulated telomerase.

IMPACT

hTERT, Bcl-2, and S100A9 together might compose a potential prognostic marker panel for the assessment of CIN lesions. These results, however, need further validation in prospective clinical settings. (c)2010 AACR.

Mechanism of genomic instability in cells infected with the high-risk human papillomaviruses

In HPV–related cancers, the “high-risk” human papillomaviruses (HPVs) are frequently found integrated into the cellular genome. The integrated subgenomic HPV fragments express viral oncoproteins and carry an origin of DNA replication that is capable of initiating bidirectional DNA re-replication in the presence of HPV replication proteins E1 and E2, which ultimately leads to rearrangements within the locus of the integrated viral DNA. The current study indicates that the E1- and E2-dependent DNA replication from the integrated HPV origin follows the “onion skin”–type replication mode and generates a heterogeneous population of replication intermediates. These include linear, branched, open circular, and supercoiled plasmids, as identified by two-dimensional neutral-neutral gel-electrophoresis. We used immunofluorescence analysis to show that the DNA repair/recombination centers are assembled at the sites of the integrated HPV replication. These centers recruit viral and cellular replication proteins, the MRE complex, Ku70/80, ATM, Chk2, and, to some extent, ATRIP and Chk1 (S317). In addition, the synthesis of histone γH2AX, which is a hallmark of DNA double strand breaks, is induced, and Chk2 is activated by phosphorylation in the HPV–replicating cells. These changes suggest that the integrated HPV replication intermediates are processed by the activated cellular DNA repair/recombination machinery, which results in cross-chromosomal translocations as detected by metaphase FISH. We also confirmed that the replicating HPV episomes that expressed the physiological levels of viral replication proteins could induce genomic instability in the cells with integrated HPV. We conclude that the HPV replication origin within the host chromosome is one of the key factors that triggers the development of HPV–associated cancers. It could be used as a starting point for the “onion skin”–type of DNA replication whenever the HPV plasmid exists in the same cell, which endangers the host genomic integrity during the initial integration and after the de novo infection.

High-risk human papillomavirus infection can cause several types of cancers. During the normal virus life cycle, these viruses maintain their genomes as multicopy nuclear plasmids in infected cells. However, in cancer cells, the viral plasmids are lost, which leaves one of the HPV genomes to be integrated into the genome of the host cell. We suggest that the viral integration and the coexistence of episomal and integrated HPV genomes in the same cell play key roles in early events that lead to the formation of HPV–dependent cancer cells. We show that HPV replication proteins expressed at the physiological level from the viral extrachromosomal genome are capable of replicating episomal and integrated HPV simultaneously. Unscheduled replication of the integrated HPV induces a variety of changes in the host genome, such as excision, repair, recombination, and amplification, which also involve the flanking cellular DNA. As a result, genomic modifications occur, which could have a role in reprogramming the HPV–infected cells that leads to the development of cancer. We believe that the mechanism described in this study may reflect the underlying processes that take place in the genome of the HPV–infected cells and may also play a role in the formation of other types of cancers.

Genomic instability of the host cell induced by the human papillomavirus replication machinery

Development of invasive cervical cancer upon infection by 'high-risk' human papillomavirus (HPV) in humans is a stepwise process in which some of the initially episomal 'high-risk' type of HPVs (HR-HPVs) integrate randomly into the host cell genome. We show that HPV replication proteins E1 and E2 are capable of inducing overamplification of the genomic locus where HPV origin has been integrated. Clonal analysis of the cells in which the replication from integrated HPV origin was induced showed excision, rearrangement and de novo integration of the HPV containing and flanking cellular sequences. These data suggest that papillomavirus replication machinery is capable of inducing genomic changes of the host cell that may facilitate the formation of the HPV-dependent cancer cell.

Early integration of high copy HPV16 detectable in women with normal and low grade cervical cytology and histology

BACKGROUND

Integration of human papillomavirus (HPV) DNA has been considered a late event in cervical carcinogenesis. However, integrated forms of HPV were recently detected in cancer precursor lesions using a new real time polymerase chain reaction (PCR) to detect the deletions at the 3362-3443 region of HPV16 E2 OBJECTIVE: To study the frequency of HPV16 DNA integration in cervical lesions and compare the sensitivity of an additional upstream region of the E2 ORF (2962-3138) in detecting HPV integration.

METHODS

Using the TaqMan based PCR, HPV16 positive DNA samples were analysed in 164 cervical scrapings from women participating in a multicentre screening trial. Biopsy confirmation was available in 62 cases.

RESULTS

Primers targeting the 3362-3443 region detected the majority of E2 deletions. In only 23% of the samples was the E2 upstream region equal or better target than the 3362-3443 region. Mixed (episomal/integrated) pattern was the most prevalent physical state of HPV16, also present in PAP smears with normal morphology. Pure integrated form was most prevalent in HSIL and cancer lesions, but also detectable in low grade abnormalities (NSIL, ASC-US, LSIL). Women with only integrated HPV16 were almost 10 years older than those with episomal HPV16. Viral load of integrated HPV16 was related to cytological abnormality (p = 0.003) but not to histology.

CONCLUSIONS

Integrated HPV16 is present in low grade cervical lesions, mostly mixed with the episomal form. Women with the pure integrated form of HPV16 are older than those with the other forms.

Detection of human papillomavirus from archival tissues in cervical cancer patients in Mauritius

BACKGROUND

Around half a million new cases of cervical cancer are diagnosed worldwide each year, accounting for almost 300,000 deaths. Development of cervical cancer can be multi-factorial, but high-risk human papillomaviruses (HPV) have been associated with the aetiology of cervical cancer. It is believed that HPV DNA integrates into the host DNA causing abnormal cell growth with cells becoming carcinogenic and spreading metastatically. In Mauritius, cervical cancer account for 65% of gynaecological cancers and 3.4% of the cervical cancers are diagnosed at the stage of carcinoma in situ.

OBJECTIVES

To determine the prevalence of HPV in histological samples from patients with cervical cancer in Mauritius.

STUDY DESIGN

DNA from archival cervical samples from a cohort of 65 patients suffering from cervical cancer and controls from Mauritius were tested for the presence of HPV using MY09/11 and GP5+/6+ primer sets.

RESULTS

In a cohort of 65 patients from Mauritius, diagnosed with cervical cancer in the year 2000, 19% of cervical histology sections were found to be positive for the presence of high-grade HPV, exclusively HPV18 using MY09 and MY11 primers. Only 15% of the Mauritian population is over 50 years of age, whereas 66% (35) of the diagnosed cases of cervical cancer were seen in patients above 50 years with 50% (5) affected with HPV. These findings suggest that for an infection with HPV to develop into cancer may take years if not decades. Differences were noted using two different primer sets, MY09/11 and GP5+/6+. The latter produce a much smaller amplicon (150bp) compared to the former ( approximately 450bp). Seven additional positive cases were detected with the GP5+/6+ primer set, resulting in an apparent prevalence of 32% as compared to the 19% seen with the MY09/11 primer set. This may indicate that some degradation of the target DNA has occurred during processing and storage of histological samples.

CONCLUSION

Using primer sets MY09/11 and GP5+/6+, only HPV type 18 was found in the Mauritian cohort with a prevalence of 32%.

Progression from productive infection to integration and oncogenic transformation in human papillomavirus type 59-immortalized foreskin keratinocytes

Studies of changes in the virus and host cell upon progression from human papillomavirus (HPV) episomal infection to integration are critical to understanding HPV-related malignant transformation. However, there exist only a few in vitro models of both productive HPV infection and neoplastic progression on the same host background. We recently described a unique foreskin keratinocyte cell line (ERIN 59) that contains HPV 59 (a close relative of HPV 18). Early passages of ERIN 59 cells (passages 9-13) contained approximately 50 copies of episomes/cell, were feeder cell-dependent, and could be induced to differentiate and produce infectious virus in a simple culture system. We now report that late passage cells (passages greater than 50) were morphologically different from early passage cells, were feeder cell independent, and did not differentiate or produce virus. These late passage cells contained HPV in an integrated form. An integration-derived oncogene transcript was expressed in late passage cells. The E2 open reading frame was interrupted in this transcript at nucleotide 3351. Despite a lower viral genome copy number in late passage ERIN 59 cells, expression of E6/E7 oncogene transcripts was similar to early passage cells. We conclude that ERIN 59 cells are a valuable cell line representing a model of progression from HPV 59 episomal infection and virus production to HPV 59 integration and associated oncogenic transformation on the same host background.

Systematic review of genomic integration sites of human papillomavirus genomes in epithelial dysplasia and invasive cancer of the female lower genital tract

Cancers of the anogenital tract as well as some head and neck cancers are caused by persistent infections with high-risk type human papillomaviruses (HPVs). Two viral oncogenes, E6 and E7, induce severe chromosomal instability associated with centrosome aberrations, anaphase bridges, chromosome lagging, and breaking. This occurs early in preneoplastic lesions, when the viral genome still persists in an episomal state. In most invasive cancers and also in a few high-grade dysplastic lesions, however, integration of high-risk HPV genomes into the host genome is observed. Integration seems to be a direct consequence of chromosomal instability and an important molecular event in the progression of preneoplastic lesions. Disruption or deregulation of defined critical cellular gene functions by insertional mutagenesis by integrated HPV genome fragments has been hypothesized as one major promoting factor in the pathogenesis of HPV-associated cancers. This hypothesis was based on the detection of HPV integration events in the area of tumor-relevant genes in few cases. Here, we reviewed >190 reported integration loci with respect to changes in the viral structure and the targeted genomic locus. This analysis confirms that HPV integration sites are randomly distributed over the whole genome with a clear predilection for genomic fragile sites. No evidence for targeted disruption or functional alteration of critical cellular genes by the integrated viral sequences could be found.

HPV infections and tonsillar carcinoma

Since human papillomavirus (HPV) was first linked to laryngeal/oral carcinomas in 1983, several studies have confirmed its causal role in a subgroup of upper aerodigestive tract tumours. Of the non-genital cancers, tonsillar carcinomas (TCs) have the strongest association with HPV. By the end of 2002, 432 TCs had been analysed for HPV DNA. Overall detection rate was 51%, with HPV-16 being the most prevalent (84%). The original proposal that HPV-33 would be the most frequent HPV in TCs has not been confirmed, being present in only 4.6% of cases. HPV copy numbers are similar to those found in genital carcinomas (10-300 copies/cell), although HPV is mainly episomal in TC. The importance of this observation is unclear, although a role for subepithelial proliferative lymphatic tissue has been speculated. Patients with HPV-16 positive tumours have better overall and disease specific survival than HPV negative patients. They are also younger and the association with conventional risk factors-smoking and drinking-is less significant than in HPV negative patients. Thus, recent data suggest a distinct pattern for HPV-16 positive TCs.

Genetic alterations in cancer as a result of breakage at fragile sites

The organization and replication of DNA render fragile sites (FSs) prone to breakage, recombination as well as becoming preferential targets for mutagens-carcinogens and integration of oncogenic viruses. For many years, attempts to link FSs and cancer generated mostly circumstantial evidence. The discoveries that chromosome translocations, amplification of proto-oncogenes, deletion of tumor suppressor genes, and integration of oncogenic viruses all result from the specific breakage of genomic DNA at FSs, however, have provided compelling support for such a link, further suggesting a causative role for FSs in cancer.