Selection of cervical keratinocytes containing integrated HPV16 associates with episome loss and an endogenous antiviral response

Human papillomavirus infection affects the immune microenvironment and antigen presentation in penile cancer

Penile squamous cell carcinoma (PSCC) is a largely neglected condition, predominantly affecting underdeveloped regions, and is associated with risk factors such as low socioeconomic status, phimosis, and human papillomavirus (HPV) infection. Unlike other urogenital cancers, its pathophysiology and therapeutic targets remain poorly understood, particularly regarding the immune response to the tumor microenvironment. This study aims to investigate immune cell infiltration profiles, dendritic cell maturation, and lymphocyte apoptosis in both HPV-positive and HPV-negative PSCC. Clinical and histopathological data, along with peripheral blood and tumor tissue samples, were collected from 30 patients (66.6% were HPV-positive and 33.3% HPV-negative), with an additional 19 healthy donors serving as controls. Tumor-infiltrating immune cells were analyzed following enzymatic digestion of tumor tissue, enabling detailed phenotypic characterization. A simulated tumor microenvironment was created using supernatants derived from primary cultures of HPV-positive PSCC tumors. Peripheral blood mononuclear cells were isolated and differentiated into dendritic cells (Mo-DCs) for further phenotyping and lymphoproliferation assays. Lymphocytes from healthy donors and patients were exposed to tumor culture supernatants to evaluate apoptosis induced by the tumor microenvironment. Results showed that HPV-positive tumors exhibited lower T lymphocyte frequencies compared to HPV-negative tumors. Additionally, patients infected with high-risk HPV demonstrated reduced maturation rates of Mo-DCs and decreased expression of co-stimulatory molecules on these cells compared to healthy donors. Furthermore, Mo-DCs from hrHPV-positive patients showed impaired lymphoproliferation capacity relative to controls, while HPV-negative patients exhibited a trend towards reduced lymphoproliferative ability. Regarding the simulated tumor microenvironment, lymphocytes from healthy donors underwent apoptosis, contrasting with patients' lymphocytes, which showed increased viability when cultured with tumor supernatants. These results underscore the impact of HPV infection on T lymphocyte infiltration, Mo-DC maturation, and lymphocyte survival in PSCC, offering critical insights for advancing our understanding of the tumor microenvironment and guiding the development of immunotherapy strategies.

Circulating cell-free HPV DNA is a strong marker for disease severity in cervical cancer

For cervical cancer (CC), circulating cell-free HPV DNA (ccfHPV) may establish disease severity. Furthermore, HPV integration has been correlated to viral load and survival. In this study, pre-treatment plasma from 139 CC cases (50 primary surgery patients, 22 primary surgery + adjuvant oncological therapy patients, and 67 primary oncological therapy patients) was collected (2018-2020). Furthermore, plasma from 25 cervical intraepithelial neoplasia grade 3 patients and 15 healthy women (negative controls) were collected. Two next-generation sequencing (NGS) panels were used to establish ccfHPV presence and human papillomavirus type 16 (HPV16) integration status. ccfHPV was detected in four primary surgery (8.0%), eight primary surgery + adjuvant oncology (36.4%), and 54 primary oncology (80.6%) patients. For primary oncology patients with HPV16-related cancer (n = 37), more ccfHPVneg than ccfHPVpos patients had HPV16 integration (P = 0.04), and in patients with HPV16 integration (n = 13), ccfHPVpos patients had higher disease stages than ccfHPVneg patients (P = 0.05). In summary, ccfHPV presence is related to disease severity and may add to the debated Sedlis criteria used for identifying patients for adjuvant oncological therapy. However, ccfHPV detection is influenced by HPV integration status and disease stage, and these factors need to be considered in ccfHPVneg patients.

Immune microenvironment of cervical cancer and the role of IL-2 in tumor promotion

The tumor microenvironment (TME) is a heterogeneous mixture of resident and tumor cells that maintain close communication through their secretion products. The composition of the TME is dynamic and complex among the different types of cancer, where the immune cells play a relevant role in the elimination of tumor cells, however, under certain circumstances they contribute to tumor development. In cervical cancer (CC) the human papilloma virus (HPV) shapes the microenvironment in order to mediate persistent infections that favors transformation and tumor development. Interleukin-2 (IL-2) is an important TME cytokine that induces CD8+ effector T cells and NKs to eliminate tumor cells, however, IL-2 can also suppress the immune response through Treg cells. Recent studies have shown that CC cells express the IL-2 receptor (IL-2R), that are induced to proliferate at low concentrations of exogenous IL-2 through alterations in the JAK/STAT pathway. This review provides an overview of the main immune cells that make up the TME in CC, as well as the participation of IL-2 in the tumor promotion. Finally, it is proposed that the low density of IL-2 produced by immunocompetent cells is used by tumor cells through its IL-2R as a mechanism to proliferate simultaneously depleting this molecule in order to evade immune response.

TIME Is Ticking for Cervical Cancer

Cervical cancer (CC) is a major health problem among reproductive-age females and comprises a leading cause of cancer-related deaths. Human papillomavirus (HPV) is the major risk factor associated with CC incidence. However, lifestyle is also a critical factor in CC pathogenesis. Despite HPV vaccination introduction, the incidence of CC is increasing worldwide. Therefore, it becomes critical to understand the CC tumor immune microenvironment (TIME) to develop immune cell-based vaccination and immunotherapeutic approaches. The current article discusses the immune environment in the normal cervix of adult females and its role in HPV infection. The subsequent sections discuss the alteration of different immune cells comprising CC TIME and their targeting as future therapeutic approaches.

Multi-omics characterization of silent and productive HPV integration in cervical cancer

Cervical cancer (CC) that is caused by high-risk human papillomavirus (HPV) remains a significant public health problem worldwide. HPV integration sites can be silent or actively transcribed, leading to the production of viral-host fusion transcripts. Herein, we demonstrate that only productive HPV integration sites were nonrandomly distributed across both viral and host genomes, suggesting that productive integration sites are under selection and likely to contribute to CC pathophysiology. Furthermore, using large-scale, multi-omics (clinical, genomic, transcriptional, proteomic, phosphoproteomic, and single-cell) data, we demonstrate that tumors with productive HPV integration are associated with higher E6/E7 proteins and enhanced tumor aggressiveness and immunoevasion. Importantly, productive HPV integration increases from carcinoma in situ to advanced disease. This study improves our understanding of the functional consequences of HPV fusion transcripts on the biology and pathophysiology of HPV-driven CCs, suggesting that productive HPV integration should be evaluated as an indicator of high risk for progression to aggressive cancers.

Regulation of the Innate Immune Response during the Human Papillomavirus Life Cycle

High-risk human papillomaviruses (HR HPVs) are associated with multiple human cancers and comprise 5% of the human cancer burden. Although most infections are transient, persistent infections are a major risk factor for cancer development. The life cycle of HPV is intimately linked to epithelial differentiation. HPVs establish infection at a low copy number in the proliferating basal keratinocytes of the stratified epithelium. In contrast, the productive phase of the viral life cycle is activated upon epithelial differentiation, resulting in viral genome amplification, high levels of late gene expression, and the assembly of virions that are shed from the epithelial surface. Avoiding activation of an innate immune response during the course of infection plays a key role in promoting viral persistence as well as completion of the viral life cycle in differentiating epithelial cells. This review highlights the recent advances in our understanding of how HPVs manipulate the host cell environment, often in a type-specific manner, to suppress activation of an innate immune response to establish conditions supportive of viral replication.

Apoptotic caspases suppress an MDA5-driven IFN response during productive replication of human papillomavirus type 31

Human papillomaviruses (HPVs) infect the basal proliferating cells of the stratified epithelium, but the productive phase of the life cycle (consisting of viral genome amplification, late gene expression, and virion assembly) is restricted to the highly differentiated suprabasal cells. While much is known regarding the mechanisms that HPVs use to block activation of an innate immune response in undifferentiated cells, little is known concerning how HPV prevents an interferon (IFN) response upon differentiation. Here, we demonstrate that high-risk HPVs hijack a natural function of apoptotic caspases to suppress an IFN response in differentiating epithelial cells. We show that caspase inhibition results in the secretion of type I and type III IFNs that can act in a paracrine manner to induce expression of interferon-stimulated genes (ISGs) and block productive replication of HPV31. Importantly, we demonstrate that the expression of IFNs is triggered by the melanoma differentiation-associated gene 5 (MDA5)-mitochondrial antiviral-signaling protein (MAVS)-TBK1 (TANK-binding kinase 1) pathway, signifying a response to double-stranded RNA (dsRNA). Additionally, we identify a role for MDA5 and MAVS in restricting productive viral replication during the normal HPV life cycle. This study identifies a mechanism by which HPV reprograms the cellular environment of differentiating cells through caspase activation, co-opting a nondeath function of proteins normally involved in apoptosis to block antiviral signaling and promote viral replication.

The Diagnostic Value of Circulating Cell-Free HPV DNA in Plasma from Cervical Cancer Patients

Circulating cell-free HPV DNA (ccfHPV DNA) may serve as a marker for cervical cancer. In this study, we used digital droplet PCR (ddPCR) to detect and quantify ccfHPV DNA in plasma from patients with HPV16- or HPV18-associated cervical cancer. Blood samples from 60 patients diagnosed with cervical cancer (FIGO IA1-IVA) at Aarhus or Odense University Hospital (June 2018 to March 2020) were collected prior to treatment, and patients were subdivided into an early stage (n = 30) and a late-stage subgroup (n = 30) according to disease stage. Furthermore, blood samples from eight women with HPV16- or 18-associated premalignant conditions (CIN3), and 15 healthy controls were collected. ddPCR was used to analyze plasma from all participants. ccfHPV DNA was detected in 19 late-stage patients (63.33%), 3 early stage patients (10.00%), and none of the CIN3 patients or controls. Quantitative evaluation showed significant correlations between ccfHPV DNA level and stage, tumor score, and tumor size. Thus, our results indicate that ccfHPV DNA may not be a useful marker for early detection of cervical cancer. However, for patients with advanced stage cervical cancer, ccfHPV DNA level represents a promising tool to establish tumor burden, making it useful for establishing treatment response and monitoring the disease.

Short- and long-range cis interactions between integrated HPV genomes and cellular chromatin dysregulate host gene expression in early cervical carcinogenesis

Development of cervical cancer is directly associated with integration of human papillomavirus (HPV) genomes into host chromosomes and subsequent modulation of HPV oncogene expression, which correlates with multi-layered epigenetic changes at the integrated HPV genomes. However, the process of integration itself and dysregulation of host gene expression at sites of integration in our model of HPV16 integrant clone natural selection has remained enigmatic. We now show, using a state-of-the-art 'HPV integrated site capture' (HISC) technique, that integration likely occurs through microhomology-mediated repair (MHMR) mechanisms via either a direct process, resulting in host sequence deletion (in our case, partially homozygously) or via a 'looping' mechanism by which flanking host regions become amplified. Furthermore, using our 'HPV16-specific Region Capture Hi-C' technique, we have determined that chromatin interactions between the integrated virus genome and host chromosomes, both at short- (<500 kbp) and long-range (>500 kbp), appear to drive local host gene dysregulation through the disruption of host:host interactions within (but not exceeding) host structures known as topologically associating domains (TADs). This mechanism of HPV-induced host gene expression modulation indicates that integration of virus genomes near to or within a 'cancer-causing gene' is not essential to influence their expression and that these modifications to genome interactions could have a major role in selection of HPV integrants at the early stage of cervical neoplastic progression.

Association between oncogenic human papillomavirus type 16 and Killian polyp

BACKGROUND

Killian polyp (KP) is a benign lesion that arises from the maxillary sinus. The etiology of KP is unknown. The aim of this study was to investigate the potential involvement of human papilloma- (HPV) and polyoma-viruses (HPyV) infections in the onset of KP.

METHODS

DNA from antral (n = 14) and nasal (n = 14) KP fractions were analyzed for HPV and HPyV sequences, genotypes, viral DNA load and physical status along with expression of viral proteins and p16 cellular protein.

RESULTS

The oncogenic HPV16 was detected in 3/14 (21.4%) antral KPs, whilst nasal KPs tested HPV-negative (0/14). The mean HPV16 DNA load was 4.65 ± 2.64 copy/104 cell. The whole HPV16 episomal genome was detected in one KP sample, whereas HPV16 DNA integration in two KPs. P16 mRNA level was lower in the KP sample carrying HPV16 episome than in KPs carrying integrated HPV16 and HPV- negative KPs (p< 0.001). None of the antral and nasal KP samples tested positive for HPyV DNA (0/28).

CONCLUSIONS

A fraction of KP tested positive for the oncogenic HPV16. HPV16 detection in the KP antral portion may be consistent with HPV16 infection derived from the maxillary sinus. HPV16 DNA integration represents a novel finding. Altogether, these data improve our knowledge on the association between KP and HPV infection, whereas it indicates that the KP onset is heterogeneous.

Virus-Host Protein-Protein Interactions between Human Papillomavirus 16 E6 A1 and D2/D3 Sub-Lineages: Variances and Similarities

High-risk strains of human papillomavirus are causative agents for cervical and other mucosal cancers, with type 16 being the most frequent. Compared to the European Prototype (EP; A1), the Asian-American (AA; D2/D3) sub-lineage seems to have increased abilities to promote carcinogenesis. Here, we studied protein-protein interactions (PPIs) between host proteins and sub-lineages of the key transforming E6 protein. We transduced human keratinocyte with EP or AA E6 genes and co-immunoprecipitated E6 proteins along with interacting cellular proteins to detect virus-host binding partners. AAE6 and EPE6 may have unique PPIs with host cellular proteins, conferring gain or loss of function and resulting in varied abilities to promote carcinogenesis. Using liquid chromatography-mass spectrometry and stringent interactor selection criteria based on the number of peptides, we identified 25 candidates: 6 unique to AAE6 and EPE6, along with 13 E6 targets common to both. A novel approach based on pathway selection discovered 171 target proteins: 90 unique AAE6 and 61 unique EPE6 along with 20 common E6 targets. Interpretations were made using databases, such as UniProt, BioGRID, and Reactome. Detected E6 targets were differentially implicated in important hallmarks of cancer: deregulating Notch signaling, energetics and hypoxia, DNA replication and repair, and immune response.

An Exonuclease V-qPCR Assay to Analyze the State of the Human Papillomavirus 16 Genome in Cell Lines and Tissues

Integration of the human papillomavirus (HPV) genome into host cell chromosomes has been observed in a majority of HPV-positive cervical cancers and a subset of oral HPV-associated cancers. HPV integration also occurs in long-term cell culture. Screening for HPV integration can be labor intensive and yield results that are difficult to interpret. Here we describe an assay based on exonuclease V (ExoV/RecBCD) and quantitative polymerase chain reaction (qPCR) to determine if samples from cell lines and tissues contain episomal or integrated HPV. This assay can be applied to screen other small DNA viruses with episomal/linear genome configurations in their viral lifecycle and has the potential to be used in clinical settings to define viral genomic conformations associated with disease. © 2020 Wiley Periodicals LLC. Basic Protocol: Exonuclease V genomic DNA digestion and qPCR for detection of HPV16 genome configuration in cells Support Protocol: Exonuclease V analysis of HPV16 genome configuration in tissues Alternate Protocol: Determining HPV integration type or integrity of HPV episome.

Flow Cytometry Characterization of Pluripotent Transmembrane Glycoproteins on Resident Cervix Uteri Cells in Patients Screened for Cervical Cancer

The aim of this study was to characterize both by flow cytometry analysis and immunohistochemistry cervix uteri cells of nulliparous women screened for cervical intraepithelial neoplasia (CIN) in comparison to a group without CIN by using mesenchymal stem cell-like and hematopoietic lineage markers. A significant expression for CD29, CD38, HLA-I, and HLA-II was correlated positively to the CIN degree and it was more relevant in patients positive for human papilloma virus (HPV). Thus, identification and detailed characterization of pluripotent resident in uteri cells could be a promising therapeutic target.

Human Papillomavirus 16 E5 Inhibits Interferon Signaling and Supports Episomal Viral Maintenance

Human papillomaviruses (HPVs) infect keratinocytes of stratified epithelia. Long-term persistence of infection is a critical risk factor for the development of HPV-induced malignancies. Through the actions of its oncogenes, HPV evades host immune responses to facilitate its productive life cycle. In this work, we discovered a previously unknown function of the HPV16 E5 oncoprotein in the suppression of interferon (IFN) responses. This suppression is focused on keratinocyte-specific IFN-κ and is mediated through E5-induced changes in growth factor signaling pathways, as identified through phosphoproteomics analysis. The loss of E5 in keratinocytes maintaining the complete HPV16 genome results in the derepression of IFNK transcription and subsequent JAK/STAT-dependent upregulation of several IFN-stimulated genes (ISGs) at both the mRNA and protein levels. We also established a link between the loss of E5 and the subsequent loss of genome maintenance and stability, resulting in increased genome integration.IMPORTANCE Persistent human papillomavirus infections can cause a variety of significant cancers. The ability of HPV to persist depends on evasion of the host immune system. In this study, we show that the HPV16 E5 protein can suppress an important aspect of the host immune response. In addition, we find that the E5 protein is important for helping the virus avoid integration into the host genome, which is a frequent step along the pathway to cancer development.

Comparison of Human Papillomavirus Genotypes in Penile Intraepithelial Neoplasia and Associated Lesions: LCM-PCR Study of 87 Lesions in 8 Patients

Penile intraepithelial neoplasia (PeIN) is currently classified in human papillomavirus (HPV)- and non-HPV-related subtypes with variable HPV genotypes. PeINs are frequently associated with other intraepithelial lesions in the same specimen. The aim of this study was to detect and compare HPV genotypes in PeINs and associated lesions using high-precision laser capture microdissection-polymerase chain reaction and p16^INK4a immunostaining. We evaluated resected penile specimens from 8 patients and identified 33 PeINs and 54 associated lesions. The most common subtype was warty PeIN, followed by warty-basaloid and basaloid PeIN. Associated lesions were classical condylomas (17 cases), atypical classical condylomas (2 cases), flat condylomas (9 cases), atypical flat condylomas (6 cases), flat lesions with mild atypia (12 cases), and squamous hyperplasia (8 cases). After a comparison, identical HPV genotypes were found in PeIN and associated lesions in the majority of the patients (7 of 8 patients). HPV16 was the most common genotype present in both PeIN and corresponding associated lesion (50% of the patients). Nonspecific flat lesions with mild atypia, classical condylomas, and atypical condylomas were the type of associated lesions most commonly related to HPV16. Other high-risk HPV genotypes present in PeIN and associated nonspecific flat lesion with mild atypia were HPV35 and HPV39. In this study of HPV in the microenvironment of penile precancerous lesions, we identified identical high-risk HPV genotypes in PeIN and classical, flat, or atypical condylomas and, specially, in nonspecific flat lesions with mild atypia. It is possible that some of these lesions represent hitherto unrecognized precancerous lesions.

The association of integration patterns of human papilloma virus and single nucleotide polymorphisms on immune- or DNA repair-related genes in cervical cancer patients

The present study investigated the association between single nucleotide polymorphisms (SNPs) in immune- or DNA repair-related genes and the integration pattern of human papillomavirus (HPV), a promising prognostic marker in cervical cancer. The HPV integration patterns of cervical cancer patients were determined by polymerase chain reaction and in situ hybridization, and categorized as episomal (group A), single-copy or multi-copy tandem repetition integrated (group B), and undetectable HPV types (group C). After sample and SNP quality control, 166,505 SNPs in 161 samples (38, 111, and 12 patients in groups A, B, and C, respectively) were examined. None of the SNPs reached genome-wide significance, and several candidate SNPs for future study were selected, including rs10999435 on chromosome 10q22, rs1322054 on chromosome 9q32-33, and rs10902171 on chromosome 11p15. Luciferase assay identified rs1322054 as the primary functional variant to regulate gene expression in immune cell. Further studies are needed to determine the genetic background of different integration patterns of HPV in cervical cancer patients.

Type-Specific Viral Load and Physical State of HPV Type 16, 18, and 58 as Diagnostic Biomarkers for High-Grade Squamous Intraepithelial Lesions or Cervical Cancer

Purpose

High rate of false-positive tests is a major obstacle to use human papillomavirus (HPV) detection as a diagnostic tool for high-grade squamous intraepithelial lesions or cervical cancer (HSIL+). We investigated whether type-specific viral load or physical state of HPV 16, 18, and 58 are useful biomarkers for HSIL+.

Materials and Methods

Type-specific viral loads of E6 and E2 genes in cervical cells from 240, 83, and 79 HPV 16–, 18–, and 58–infected women, respectively, were determined using real-time polymerase chain reaction. Viral loads were normalized to cellular DNA (copy/cell). Total and integrated viral loads and physical state were compared between HSIL+ and controls, and diagnostic value was determined using receiver operating characteristic analysis.

Results

Viral loads of HPV 16, 18, and 58 were significantly different in lesions in the same pathologic grade. High type-specific total viral loads were significantly associated with HSIL+ (odds ratio [OR], 14.065, 39.472, and 7.103 for HPV 16, 18, and 58, respectively). High integrated viral load was related to HSIL+ in women with HPV 16 (OR, 8.242), and integrated state was associated with HSIL+ in women with HPV 18 (OR, 9.443). Type-specific total viral load was significantly associated with HSIL+ (area under curve, 0.914, 0.937, and 0.971 for HPV 16, 18, and 58, respectively), indicating an excellent performance in detecting HSIL+.

Conclusion

Type-specific total viral load may be a powerful diagnostic marker for HSIL+ in HPV 16–, 18–, and 58–infected HSIL+ lesions. If demonstrated in all other high-risk HPV types, this method can lead to a paradigm shift in the strategy of equivocal cytologic abnormalities.

Detecting episomal or integrated human papillomavirus 16 DNA using an exonuclease V-qPCR-based assay

Screening for human papillomavirus (HPV) integration into host cell chromosomes typically requires large amounts of time and reagents. We developed a rapid and sensitive assay based on exonuclease V (ExoV) and quantitative polymerase chain reaction (qPCR) to determine HPV genome configurations in cell lines and tissues. We established the assay using genomic DNA from cell lines known to harbor integrated or episomal HPV16. DNA was incubated with ExoV, which is specific for linear DNA, and the DNA fraction resistant to digestion was measured by qPCR. The percent of DNA resistant to ExoV digestion was calculated relative to undigested DNA for determination of episomal or integrated HPV16. The ExoV assay was accurate, capable of distinguishing episomal from integrated HPV16 in cell lines and tissues. Future applications of the ExoV assay may include screening of HPV genome configurations in the progression of HPV-associated cancers.

Efficacy and safety of glucosaminylmuramyl dipeptide in treatment of human papillomavirus-associated diseases: a systematic review

Introduction. Human papillomavirus infection (HPV-infection) remains one of the most important health problems as it significantly reduces the quality of life and stigmatizes the patients. Also, the prevalence of cervical cancer – the most severe outcome of the HPV-infection is 5 % of the global burden of cancer. Although vaccination against human papillomavirus has been proved efficient, its availability in Russia continues to be limited. Therefore, it is important to review other methods of HPV-infection control. A number of studies have confirmed the efficacy of glucosaminylmuramyl dipeptide (GMDP) in the treatment of diseases associated with HPV-infection, but no systematic evaluation of these studies has been published in the available literature.

Aim: to analyze the data on the efficacy and safety of GMDP in the treatment of diseases and conditions associated with HPVinfection.

Materials and methods. We used the PRISMA approach. The search for the relevant publications was conducted in international scientific databases: the Scientific Electronic Library, the Google Scholar, the ScienceDirect, the Cochrane Community Library, the Pubmed/MEDLINE, and clinical research registries. For this systematic analysis, only full-text publications were used. We evaluated the reliability of evidence and the methodological quality of the studies.

Results. We used the following search queries: "glucosaminyl-muramyl dipeptide", "glucosamine L'muramyl dipeptide", "H-acetylglucosaminyl-H-acetylmuramyl dipeptide", "GMDP", "Licopid" (both in Russian and English transcriptions). Based on the results of the screening, 14 full-text publications were selected. At the final stage, review articles with secondary data were excluded; also excluded were original articles published in doubtful resources and those with an unclear status of peer reviewing. This systematic analysis includes 7 publications of acceptable methodological quality. Here, we summarize the consistent conclusions derived from these reports: the addition of therapy with GMDP to local (surgical) methods increases the efficacy of treatment and the duration of remission; destruction of condylomas is more effective when combined with the course of GMDP as compared to using the local destruction alone; GMDP enhances the production of cytokines that have a direct antiviral and antiproliferative effect in HPV-infection (interleukin-1, tumor necrosis factor alpha, gamma-interferon); GMDP causes normalization of cellular and humoral immunity (T-lymphocytes, T-cytotoxic lymphocytes, B-lymphocytes, CD3+, CD4+, CD8+, CD16+, and CD72+ lymphocytes, as well as the production of serum immunoglobulins IgA, IgG, and IgM). A high safety profile of GMDP is evidenced from the absence of reports on adverse events.

Discussion. The recommendation for the inclusion of GMDP into a comprehensive treatment for HPV-infection in addition to local interventions is a strong recommendation. The differences between the Russian and international approaches can be explained by the difference in the available resources and funding. We propose to test whether using GMDP for reducing the risk of recurrent HPV-infection is beneficial in terms of pharmacoeconomics. Conclusion. The high efficacy and safety of GMDP in the combined therapy of HPV-infection has been confirmed. Further carefully designed studies on GMDP are needed.

The APOBEC3 genes and their role in cancer: insights from human papillomavirus

The interaction between human papillomaviruses (HPV) and the apolipoprotein-B mRNA-editing catalytic polypeptide-like (APOBEC)3 (A3) genes has garnered increasing attention in recent years, with considerable efforts focused on understanding their apparent roles in both viral editing and in HPV-driven carcinogenesis. Here, we review these developments and highlight several outstanding questions in the field. We consider whether editing of the virus and mutagenesis of the host are linked or whether both are essentially separate events, coincidentally mediated by a common or distinct A3 enzymes. We discuss the viral mechanisms and cellular signalling pathways implicated in A3 induction in virally infected cells and examine which of the A3 enzymes might play the major role in HPV-associated carcinogenesis and in the development of therapeutic resistance. We consider the parallels between A3 induction in HPV-infected cells and what might be causing aberrant A3 activity in HPV-independent cancers such as those arising in the bladder, lung and breast. Finally, we discuss the implications of ongoing A3 activity in tumours under treatment and the therapeutic opportunities that this may present.

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.

Transkingdom network reveals bacterial players associated with cervical cancer gene expression program

Cervical cancer is the fourth most common cancer in women worldwide with human papillomavirus (HPV) being the main cause the disease. Chromosomal amplifications have been identified as a source of upregulation for cervical cancer driver genes but cannot fully explain increased expression of immune genes in invasive carcinoma. Insight into additional factors that may tip the balance from immune tolerance of HPV to the elimination of the virus may lead to better diagnosis markers. We investigated whether microbiota affect molecular pathways in cervical carcinogenesis by performing microbiome analysis via sequencing 16S rRNA in tumor biopsies from 121 patients. While we detected a large number of intra-tumor taxa (289 operational taxonomic units (OTUs)), we focused on the 38 most abundantly represented microbes. To search for microbes and host genes potentially involved in the interaction, we reconstructed a transkingdom network by integrating a previously discovered cervical cancer gene expression network with our bacterial co-abundance network and employed bipartite betweenness centrality. The top ranked microbes were represented by the families Bacillaceae, Halobacteriaceae, and Prevotellaceae. While we could not define the first two families to the species level, Prevotellaceae was assigned to Prevotella bivia. By co-culturing a cervical cancer cell line with P. bivia, we confirmed that three out of the ten top predicted genes in the transkingdom network (lysosomal associated membrane protein 3 (LAMP3), STAT1, TAP1), all regulators of immunological pathways, were upregulated by this microorganism. Therefore, we propose that intra-tumor microbiota may contribute to cervical carcinogenesis through the induction of immune response drivers, including the well-known cancer gene LAMP3.

Human papillomavirus genome integration in squamous carcinogenesis: what have next-generation sequencing studies taught us?

Human papillomavirus (HPV) infection is associated with ∼5% of all human cancers, including a range of squamous cell carcinomas. Persistent infection by high-risk HPVs (HRHPVs) is associated with the integration of virus genomes (which are usually stably maintained as extrachromosomal episomes) into host chromosomes. Although HRHPV integration rates differ across human sites of infection, this process appears to be an important event in HPV-associated neoplastic progression, leading to deregulation of virus oncogene expression, host gene expression modulation, and further genomic instability. However, the mechanisms by which HRHPV integration occur and by which the subsequent gene expression changes take place are incompletely understood. The advent of next-generation sequencing (NGS) of both RNA and DNA has allowed powerful interrogation of the association of HRHPVs with human disease, including precise determination of the sites of integration and the genomic rearrangements at integration loci. In turn, these data have indicated that integration occurs through two main mechanisms: looping integration and direct insertion. Improved understanding of integration sites is allowing further investigation of the factors that provide a competitive advantage to some integrants during disease progression. Furthermore, advanced approaches to the generation of genome-wide samples have given novel insights into the three-dimensional interactions within the nucleus, which could act as another layer of epigenetic control of both virus and host transcription. It is hoped that further advances in NGS techniques and analysis will not only allow the examination of further unanswered questions regarding HPV infection, but also direct new approaches to treating HPV-associated human disease. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

IFN Regulatory Factors and Antiviral Innate Immunity: How Viruses Can Get Better

The interferon regulatory factor (IRF) family consists of transcriptional regulators that exert multifaceted and versatile functions in multiple biological processes. Their crucial role as central mediators in the establishment and execution of host immunity in response to pathogen-derived signals downstream pattern recognition receptors (PRRs) makes IRFs a hallmark of the host antiviral response. They function as hub molecules at the crossroad of different signaling pathways for the induction of interferon (IFN) and inflammatory cytokines, as well as of antiviral and immunomodulatory genes even in an IFN-independent manner. By regulating the development and activity of immune cells, IRFs also function as a bridge between innate and adaptive responses. As such, IRFs represent attractive and compulsive targets in viral strategies to subvert antiviral signaling. In this study, we discuss current knowledge on the wide array of strategies put in place by pathogenic viruses to evade, subvert, and/or hijack these essential components of host antiviral immunity.

Integración, carga viral y niveles de ARN mensajero de E2 de VPH 16 en la progresión de lesiones intraepiteliales cervicales

Entre las lesiones intraepiteliales escamosas cervicales (LIE) es importante distinguir aquellas asociadas con mayor riesgo de cáncer de cuello uterino. El objetivo de este trabajo fue evaluar si los niveles de expresión de E2 del VPH16 en mujeres con LIE  y con evidencia de integración viral se asocian con el grado de la lesión. Se analizaron 109 cepillados cervicales positivos para VPH 16 provenientes de 19 mujeres sin LIE, 45 mujeres con LIE de bajo grado (LIEBG) y 45 mujeres con LIE de alto grado (LIEAG). Se cuantificó el número de copias de ARNm de E2 y de los genes E2 y E6 mediante PCR en tiempo real para determinar la carga viral (E6) y la proporción E2/E6 para evaluar la integración viral. Se encontraron frecuencias similares de expresión de E2 en LEIBG y LEIAG 15/45 (33 %), la frecuencia en mujeres sin lesión fue menor 3/19 (15,8 %), todos los casos en los que se observó expresión del gen E2 tenían mezcla de ADN viral episomal e integrado. La carga viral aumentó significativamente a mayor grado de la lesión (p=0,049), mientras que la proporción E2/E6 disminuyó (p=0,049). El análisis ROC mostró una baja capacidad de los tres parámetros virales para distinguir entre lesiones de bajo y alto grado. En conclusión, aunque las lesiones con presencia de ADN viral mixto e integrado y expresión de E2 podrían estar en menor riesgo de progresión, y la carga viral y la integración se relacionaron con mayor gravedad de la lesión, su valor clínico como biomarcadores de LEIAG es limitado.

Roles of APOBEC3A and APOBEC3B in Human Papillomavirus Infection and Disease Progression

The apolipoprotein B messenger RNA-editing, enzyme-catalytic, polypeptide-like 3 (APOBEC3) family of cytidine deaminases plays an important role in the innate immune response to viral infections by editing viral genomes. However, the cytidine deaminase activity of APOBEC3 enzymes also induces somatic mutations in host genomes, which may drive cancer progression. Recent studies of human papillomavirus (HPV) infection and disease outcome highlight this duality. HPV infection is potently inhibited by one family member, APOBEC3A. Expression of APOBEC3A and APOBEC3B is highly elevated by the HPV oncoproteins E6 and E7 during persistent virus infection and disease progression. Furthermore, there is a high prevalence of APOBEC3A and APOBEC3B mutation signatures in HPV-associated cancers. These findings suggest that induction of an APOBEC3-mediated antiviral response during HPV infection may inadvertently contribute to cancer mutagenesis and virus evolution. Here, we discuss current understanding of APOBEC3A and APOBEC3B biology in HPV restriction, evolution, and associated cancer mutagenesis.

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.

Review: Anal Intraepithelial Neoplasia in HIV-Infected Men Who Have Sex with Men: Is Screening and Treatment Justified?

Anal squamous cell carcinoma (SCC) is the fourth most prevalent cancer in human immunodeficiency virus (HIV)-infected men who have sex with men (MSM). Human papillomavirus (HPV) has been detected in over 90% of anal carcinoma biopsy specimens from MSM, and is considered a necessary, but alone, insufficient factor for carcinogenesis. Anal intraepithelial neoplasia (AIN) may be precursive for SCC, and screening cytology with referral of persons with abnormality for high-resolution anoscopy-guided biopsy, and AIN treatment, has been recommended for prevention. In the absence of either randomized controlled trials or surveillance data demonstrating a reduction in anal SCC incidence, these recommendations were based on analogy with cervical cancer. HPV-mediated genetic changes associated with cervical cancer, and aneuploidy, have been documented in AIN. However, little data exist on the rate of AIN progression to SCC. The treatment of AIN is frequently prolonged and not curative, and if routinized in the care of HIV-infected MSM, would likely be recurring well into their sixth decade of life. Clinical trials demonstrating a reduction in invasive anal carcinoma incidence, as well as acceptable morbidity with repeated AIN destruction, are needed before asking our patients to commit to routine treatment.

HPV Integration in Head and Neck Squamous Cell Carcinomas: Cause and Consequence

Human papillomaviruses (HPVs) are a necessary cause of anogenital squamous cell carcinomas (SCC) and a subgroup of head and neck SCC, i.e., those originating in the oropharynx. The key events in high-risk HPV (HRHPV)-associated neoplastic progression include persistent infection, deregulated expression of virus early genes in basal epithelial cells, local immune suppression and the accumulation of chromosomal alterations. Evidence for these events particularly comes from studies of uterine cervical carcinogenesis; primary premalignant HRHPV-positive lesions of the head and neck mucosa are seldomly detected. Integration of virus DNA into host chromosomes is considered an important driver of carcinogenesis and observed in 40 up to 90 % of uterine cervical SCC (UCSCC) and oropharyngeal SCC (OPSCC), dependent on the integration detection method used and HRHPV type. In OPSCC, > 90 % HPV-positive tumors are infected with HPV16. Ten up to 60 % of HPV-positive tumors thus contain extrachromosomal (episomal) virus. In this chapter, causes and consequences of HPV integration are summarized from the literature, with special focus on the site of HPV integration in the cellular genome, and its effect on expression of viral oncogenes (particularly E6 and E7), on human (tumor) gene expression and on deregulation of cell proliferation, apoptosis and cell signaling pathways. Also data on DNA methylation, viral load and clinical outcome in relation to HPV integration are provided.

Mannose-Binding Lectin Does Not Act as a Biomarker for the Progression of Preinvasive Lesions of Invasive Cervical Cancer

OBJECTIVE

To evaluate serum concentrations of mannose-binding lectin (MBL) in women presenting with different human papillomavirus (HPV)-associated cervical lesions.

SUBJECTS AND METHODS

A total of 364 women, who underwent screening for cervical cancer or treatment at the Erasto Gaertner Cancer Hospital (HEG), Curitiba, Brazil, were enrolled in the study. Based on the latest cervical colposcopy-guided biopsy results, the women were divided into 4 groups: cervical intraepithelial neoplasia CIN-I (n = 54), CIN-II (n = 72), CIN-III (n = 145), and invasive cancer (n = 93). A time-resolved immunofluorometric assay was used to measure the MBL concentrations in serum. The statistical analysis was done using GraphPad Prism 6.0. Comparisons were performed by Kruskal-Wallis and Mann-Whitney tests and analyzed by χ2 test; continuous variables are presented as medians and categorical variables as frequencies.

RESULTS

The median MBL concentrations in decreasing order were as follows: invasive cancer: 1,452 ng/mL, CIN-I: 1,324 ng/mL, CIN-II: 1,104 ng/mL, and CIN-III 1,098 ng/mL. However, no statistical significance was found among the 4 groups with HPV-associated lesions (p = 0.11). Equally, the MBL levels did not show a significant association between the age of the patients and the severity of the cervical lesions (p = 0.68). No statistical significance was found in the median values of MBL or in the status of MBL deficient (<100 ng/mL) and high producers (>1,000 ng/mL) among the women in each group (p = 0.77).

CONCLUSION

In this study, there was no statistically significant difference in MBL serum levels among the groups with CIN. Hence MBL serum concentration appeared not to have influenced the progression of HPV-related preinvasive cervical lesions into invasive cancer.

The low-risk papillomaviruses

Human Papillomavirus (HPV) research has been dominated by the study of a subset of Alpha papillomaviruses that together cause almost 5% of human cancers worldwide, with the focus being on the two most prominent of these (HPV16 and 18). These viruses are referred to as 'high-risk' (hrHPV), to distinguish them from the over 200 prevalent HPV types that more commonly cause only benign epithelial lesions. The 'low-risk' (lrHPV) term used to describe this group belies their cumulative morbidity. Persistent laryngeal papillomas, which occur rarely in children and adults, require regular surgical de-bulking to allow breathing. Such infections are not curable, and despite being caused by HPV11 (a lrHPV) are associated with 1-3% risk of cancer progression if not resolved. Similarly, the ubiquitous Beta HPV types, which commonly cause asymptomatic infections at cutaneous sites, can sometimes cause debilitating papillomatosis with associated cancer risk. Recalcitrant genital warts, which affect 1 in 200 young adults in the general population, and even the ubiquitous common warts and verrucas that most of us at some time experience, cannot be reliably eradicated, with treatment strategies advancing little over the last 100 years. The review highlights molecular similarities between high and low-risk HPV types, and focuses on the different pathways that the two groups use to ensure persistent infection and adequate virus shedding from the epithelial surface. Understanding the normal patterns of viral gene expression that underlie lesion formation, and which also prevent loss of the infected basal cells in established lesions, are particularly important when considering new treatment options. Finally, the common requirement for deregulated viral gene expression and genome persistence in development of cancers, unites both high and low-risk HPV types, and when considered alongside viral protein functions, provides us with a working understanding of the mechanisms that underlie HPV-associated pathology.

Molecular mechanisms of HPV mediated neoplastic progression

Human Papillomavirus is the major etiological agent in the development of cervical cancer but not a sufficient cause. Despite significant research, the underlying mechanisms of progression from a low-grade squamous intraepithelial lesion to high grade squamous intraepithelial lesion are yet to be understood. Deregulation of viral gene expression and host genomic instability play a central role in virus-mediated carcinogenesis. Key events such as viral integration and epigenetic modifications may lead to the deregulation of viral and host gene expression. This review has summarized the available literature to describe the possible mechanism and role of viral integration in mediating carcinogenesis. HPV integration begins with DNA damage or double strand break induced either by oxidative stress or HPV proteins and the subsequent steps are driven by the DNA damage responses. Inflammation and oxidative stress could be considered as cofactors in stimulating viral integration and deregulation of cellular and viral oncogenes during the progression of cervical carcinoma. All these events together with the host and viral genetic and epigenetic modifications in neoplastic progression have also been reviewed which may be relevant in identifying a new preventive therapeutic strategy. In the absence of therapeutic intervention for HPV-infected individuals, future research focus should be directed towards preventing and reversing of HPV integration. DNA damage response, knocking out integrated HPV sequences, siRNA approach, modulating the selection mechanism of cells harboring integrated genomes and epigenetic modifiers are the possible therapeutic targets.

The human papillomavirus E7 oncoprotein as a regulator of transcription

High-risk human papillomaviruses (HPVs) encode oncoproteins which manipulate gene expression patterns in the host keratinocytes to facilitate viral replication, regulate viral transcription, and promote immune evasion and persistence. In some cases, oncoprotein-induced changes in host cell behavior can cause progression to cancer, but a complete picture of the functions of the viral oncoproteins in the productive HPV life cycle remains elusive. E7 is the HPV-encoded factor most responsible for maintaining cell cycle competence in differentiating keratinocytes. Through interactions with dozens of host factors, E7 has an enormous impact on host gene expression patterns. In this review, we will examine the role of E7 specifically as a regulator of transcription. We will discuss mechanisms of regulation of cell cycle-related genes by E7 as well as genes involved in immune regulation, growth factor signaling, DNA damage responses, microRNAs, and others pathways. We will also discuss some unanswered questions about how transcriptional regulation by E7 impacts the biology of HPV in both benign and malignant conditions.

The Interaction Between Human Papillomaviruses and the Stromal Microenvironment

Human papillomaviruses (HPVs) are small, double-stranded DNA viruses that replicate in stratified squamous epithelia and cause a variety of malignancies. Current efforts in HPV biology are focused on understanding the virus-host interactions that enable HPV to persist for years or decades in the tissue. The importance of interactions between tumor cells and the stromal microenvironment has become increasingly apparent in recent years, but how stromal interactions impact the normal, benign life cycle of HPVs, or progression of lesions to cancer is less understood. Furthermore, how productively replicating HPV impacts cells in the stromal environment is also unclear. Here we bring together some of the relevant literature on keratinocyte-stromal interactions and their impacts on HPV biology, focusing on stromal fibroblasts, immune cells, and endothelial cells. We discuss how HPV oncogenes in infected cells manipulate other cells in their environment, and, conversely, how neighboring cells may impact the efficiency or course of HPV infection.

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.

Identification of host transcriptional networks showing concentration-dependent regulation by HPV16 E6 and E7 proteins in basal cervical squamous epithelial cells

Development of cervical squamous cell carcinoma requires increased expression of the major high-risk human-papillomavirus (HPV) oncogenes E6 and E7 in basal cervical epithelial cells. We used a systems biology approach to identify host transcriptional networks in such cells and study the concentration-dependent changes produced by HPV16-E6 and -E7 oncoproteins. We investigated sample sets derived from the W12 model of cervical neoplastic progression, for which high quality phenotype/genotype data were available. We defined a gene co-expression matrix containing a small number of highly-connected hub nodes that controlled large numbers of downstream genes (regulons), indicating the scale-free nature of host gene co-expression in W12. We identified a small number of ‘master regulators’ for which downstream effector genes were significantly associated with protein levels of HPV16 E6 (n = 7) or HPV16 E7 (n = 5). We validated our data by depleting E6/E7 in relevant cells and by functional analysis of selected genes in vitro. We conclude that the network of transcriptional interactions in HPV16-infected basal-type cervical epithelium is regulated in a concentration-dependent manner by E6/E7, via a limited number of central master-regulators. These effects are likely to be significant in cervical carcinogenesis, where there is competitive selection of cells with elevated expression of virus oncoproteins.

Human Papillomavirus Laboratory Testing: the Changing Paradigm

High-risk human papillomaviruses (HPVs) cause essentially all cervical cancers, most anal and oropharyngeal cancers, and some vaginal, vulvar, and penile cancers. Improved understanding of the pathogenesis of infection and the availability of newer tests are changing the approach to screening and diagnosis. Molecular tests to detect DNA from the most common high-risk HPVs are FDA approved for use in conjunction with cytology in cervical cancer screening programs. More-specific tests that detect RNA from high-risk HPV types are now also available. The use of molecular tests as the primary screening tests is being adopted in some areas. Genotyping to identify HPV16 and -18 has a recommended role in triaging patients for colposcopy who are high-risk HPV positive but have normal cytology. There are currently no recommended screening methods for anal, vulvar, vaginal, penile, or oropharyngeal HPV infections. HPV testing has limited utility in patients at high risk for anal cancer, but p16 immunohistochemistry is recommended to clarify lesions in tissue biopsy specimens that show moderate dysplasia or precancer mimics. HPV testing is recommended for oropharyngeal squamous cell tumors as a prognostic indicator. Ongoing research will help to improve the content of future guidelines for screening and diagnostic testing.

The Genomics, Epigenomics, and Transcriptomics of HPV-Associated Oropharyngeal Cancer--Understanding the Basis of a Rapidly Evolving Disease

Human papillomavirus (HPV) has been shown to represent a major independent risk factor for head and neck squamous cell cancer, in particular for oropharyngeal carcinoma. This type of cancer is rapidly evolving in the Western world, with rising trends particularly in the young, and represents a distinct epidemiological, clinical, and molecular entity. It is the aim of this review to give a detailed description of genomic, epigenomic, transcriptomic, and posttranscriptional changes that underlie the phenotype of this deadly disease. The review will also link these changes and examine what is known about the interactions between the host genome and viral genome, and investigate changes specific for the viral genome. These data are then integrated into an updated model of HPV-induced head and neck carcinogenesis.

Interplay between NF-κB/interferon signaling and the genome replication of HPV

HPV infection can persist within the infected epithelium for years. The viral persistence is primarily attributed to the ability of the virus to maintain its genome as nuclear episomes in the basal cells. Recent studies have revealed that HPV induces DNA damage response to facilitate productive amplification of the viral genome. DNA damage response comprises a part of the cellular defense mechanism against viral infection and its activation can result in induction of innate immune responses. The activation of NF-κB and interferon (IFN) signals has been shown to suppress the genome replication of HPV while the viral proteins inhibit NF-κB/IFN signaling. This review intends to focus on illustrating the interplay between NFκB/IFN signaling and HPV genome replication in the HPV life cycle.

Recent Insights into the Control of Human Papillomavirus (HPV) Genome Stability, Loss, and Degradation

Most human papillomavirus (HPV) antiviral strategies have focused upon inhibiting viral DNA replication, but it is increasingly apparent that viral DNA levels can be chemically controlled by approaches that promote its instability. HPVs and other DNA viruses have a tenuous relationship with their hosts. They must replicate and hide from the DNA damage response (DDR) and innate immune systems, which serve to protect cells from foreign or “non-self” DNA, and yet they draft these same systems to support their life cycles. DNA binding antiviral agents promoting massive viral DNA instability and elimination are reviewed. Mechanistic studies of these agents have identified genetic antiviral enhancers and repressors, antiviral sensitizers, and host cell elements that protect and stabilize HPV genomes. Viral DNA degradation appears to be an important means of controlling HPV DNA levels in some cases, but the underlying mechanisms remain poorly understood. These findings may prove useful not only for understanding viral DNA persistence but only in devising future antiviral strategies.

Establishment and characterization of a human papillomavirus type 16-positive tonsillar carcinoma xenograft in BALB/c nude mice

BACKGROUND

Among head and neck cancers, human papillomavirus type 16 (HPV16) is associated with tonsillar carcinomas. Despite this, no HPV16-positive tonsillar cancer cell line has been established in nude mice.

METHODS

Fresh tonsillar carcinoma biopsies were obtained from 23 patients and implanted subcutaneously into nude mice (BALB/c, nu/nu).

RESULTS

After 7 months, one xenograft was established. The primary tumor harbored 2.7 copies (95% confidence interval = 2.4-2.9) of HPV16/cell and displayed 99.9% (7904/7906) nucleotide identity to HPV16 (EU118173.1). The xenograft showed increased methylation in two E2-binding sites of the HPV16 genome. Both episomal and integrated HPV16 were detected in the original tumor and in 14 xenografts from the second passage. From this passage, a viral load of 6.4 copies/cell (range = 4.6-9.6) and 3.7 (range = 1.0-5.5) E7-mRNA transcripts/HPV16-genome were detected.

CONCLUSION

This xenograft represents the first established HPV16-positive tonsillar tumor in nude mice and could provide an experimental system of HPV16-positive tonsillar cancers.

Activation of NF-κB by human papillomavirus 16 E1 limits E1-dependent viral replication through degradation of E1

NF-κB is a family of transcription factors that regulate gene expression involved in many processes, such as the inflammatory response and cancer progression. Little is known about associations of NF-κB with the human papillomavirus (HPV) life cycle. We have developed a tissue culture system to conditionally induce E1-dependent replication of the human papillomavirus 16 (HPV16) genome in human cervical keratinocytes and found that expression of HPV16 E1, a viral helicase, results in reduction of IκBα and subsequent activation of NF-κB in a manner dependent on helicase activity. Exogenous expression of a degradation-resistant mutant of IκBα, which inhibits the activation of NF-κB, enhanced E1-dependent replication of the viral genome. Wortmannin, a broad inhibitor of phosphoinositide 3-kinases (PI3Ks), and, to a lesser extent, VE-822, an ATR kinase inhibitor, but not KU55933, an ATM kinase inhibitor, suppressed the activation of NF-κB and augmented E1-dependent replication of the HPV16 genome. Interestingly, the enhancement of E1-dependent replication of the viral genome was associated with increased stability of E1 in the presence of wortmannin as well as the IκBα mutant. Collectively, we propose that expression of E1 induces NF-κB activation at least in part through the ATR-dependent DNA damage response and that NF-κB in turn limits E1-dependent replication of HPV16 through degradation of E1, so that E1 and NF-κB may constitute a negative feedback loop.

IMPORTANCE

A major risk factor in human papillomavirus (HPV)-associated cancers is persistent infection with high-risk HPVs. To eradicate viruses from infected tissue, it is important to understand molecular mechanisms underlying the establishment and maintenance of persistent infection. In this study, we obtained evidence that human papillomavirus 16 (HPV16) E1, a viral DNA helicase essential for amplification of the viral genomes, induces NF-κB activation and that this limits E1-dependent genome replication of HPV16. These results suggest that NF-κB mediates a negative feedback loop to regulate HPV replication and that this feedback loop could be associated with control of the viral copy numbers. We could thus show for the first time that NF-κB activity is involved in the establishment and maintenance of persistent HPV infection.

CCCTC-binding factor recruitment to the early region of the human papillomavirus 18 genome regulates viral oncogene expression

Host cell differentiation-dependent regulation of human papillomavirus (HPV) gene expression is required for productive infection. The host cell CCCTC-binding factor (CTCF) functions in genome-wide chromatin organization and gene regulation. We have identified a conserved CTCF binding site in the E2 open reading frame of high-risk HPV types. Using organotypic raft cultures of primary human keratinocytes containing high-risk HPV18 genomes, we show that CTCF recruitment to this conserved site regulates viral gene expression in differentiating epithelia. Mutation of the CTCF binding site increases the expression of the viral oncoproteins E6 and E7 and promotes host cell proliferation. Loss of CTCF binding results in a reduction of a specific alternatively spliced transcript expressed from the early gene region concomitant with an increase in the abundance of unspliced early transcripts. We conclude that high-risk HPV types have evolved to recruit CTCF to the early gene region to control the balance and complexity of splicing events that regulate viral oncoprotein expression.

IMPORTANCE

The establishment and maintenance of HPV infection in undifferentiated basal cells of the squamous epithelia requires the activation of a subset of viral genes, termed early genes. The differentiation of infected cells initiates the expression of the late viral transcripts, allowing completion of the virus life cycle. This tightly controlled balance of differentiation-dependent viral gene expression allows the virus to stimulate cellular proliferation to support viral genome replication with minimal activation of the host immune response, promoting virus productivity. Alternative splicing of viral mRNAs further increases the complexity of viral gene expression. In this study, we show that the essential host cell protein CTCF, which functions in genome-wide chromatin organization and gene regulation, is recruited to the HPV genome and plays an essential role in the regulation of early viral gene expression and transcript processing. These data highlight a novel virus-host interaction important for HPV pathogenicity.

Pathogenesis of human papillomavirus-associated mucosal disease

Human papillomaviruses (HPVs) are a necessary cause of carcinoma of the cervix and other mucosal epithelia. Key events in high-risk HPV (HRHPV)-associated neoplastic progression include persistent infection, deregulated expression of virus early genes in basal epithelial cells and genomic instability causing secondary host genomic imbalances. There are multiple mechanisms by which deregulated virus early gene expression may be achieved. Integration of virus DNA into host chromosomes is observed in the majority of cervical squamous cell carcinomas (SCCs), although in ∼15% of cases the virus remains extrachromosomal (episomal). Interestingly, not all integration events provide a growth advantage to basal cervical epithelial cells or lead to increased levels of the virus oncogenes E6 and E7, when compared with episome-containing basal cells. The factors that provide a competitive advantage to some integrants, but not others, are complex and include virus and host contributions. Gene expression from integrated and episomal HRHPV is regulated through host epigenetic mechanisms affecting the virus long control region (LCR), which appear to be of functional importance. New approaches to treating HRHPV-associated mucosal neoplasia include knockout of integrated HRHPV DNA, depletion of virus transcripts and inhibition of virus early gene transcription through targeting or use of epigenetic modifiers. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Interferon treatment of human keratinocytes harboring extrachromosomal, persistent HPV-16 plasmid genomes induces de novo viral integration

Interferons (IFNs) have been used to treat epithelial lesions caused by human papillomavirus (HPV) persistence. Here, we exposed primary human keratinocytes (HFKs) immortalized by persistently replicating HPV-16 plasmid genomes to increasing levels of IFN-γ. While untreated HFKs retained replicating HPV-16 plasmids for up to 60-120 population doublings, IFN led to rapid HPV-16 plasmid loss. However, treated cultures eventually gave rise to outgrowth of clones harboring integrated HPV-16 genomes expressing viral E6 and E7 oncogenes from chimeric virus-cell mRNAs similar to those in cervical and head and neck cancers. Surprisingly, every HPV-16 integrant that arose after IFN exposure stemmed from an independent integration event into a different cellular gene locus, even within parallel cultures started from small cell inocula and cultured separately for ≥ 25 doublings to permit the rise and expansion of spontaneous integrants. While IFN treatment conferred a growth advantage upon preexisting integrants added to mixed control cultures, our results indicate that IFN exposure directly or indirectly induces HPV-16 integration, rather than only selects preexisting, spontaneous integrants that appear to be much less frequent. We estimate that IFN exposure increased integration rates by ≥ 100-fold. IFN-induced HPV-16 integration involved a wide range of chromosomal loci with less apparent selection for recurrent insertions near genes involved in cancer-related pathways. We conclude that IFNs and other potential treatments targeting high-risk HPV persistence that disrupt viral genome replication may promote increased high-risk HPV integration as a step in cancer progression. Therapies against high-risk HPV persistence thus need to be evaluated for their integration-inducing potential.

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.