The Interaction Between Human Papillomaviruses and the Stromal Microenvironment

The potential use of therapeutics and prophylactic mRNA vaccines in human papillomavirus (HPV)

Cervical cancer (CC) and other malignant malignancies are acknowledged to be primarily caused by persistent human papillomavirus (HPV) infection. Historically, vaccinations against viruses that produce neutralizing antibodies unique to the virus have been an affordable way to manage viral diseases. CC risk is decreased, but not eliminated, by HPV vaccinations. Since vaccinations have been made available globally, almost 90% of HPV infections have been successfully avoided. On the lesions and diseases that are already present, however, no discernible treatment benefit has been shown. As a result, therapeutic vaccines that elicit immune responses mediated by cells are necessary for the treatment of established infections and cancers. mRNA vaccines possess remarkable potential in combating viral diseases and malignancy as a result of their superior industrial production, safety, and efficacy. Furthermore, considering the expeditiousness of production, the mRNA vaccine exhibits promise as a therapeutic approach targeting HPV. Given that the HPV-encoded early proteins, including oncoproteins E6 and E7, are consistently present in HPV-related cancers and pre-cancerous lesions and have crucial functions in the progression and persistence of HPV-related diseases, they serve as ideal targets for therapeutic HPV vaccines. The action mechanism of HPV and HPV-related cancer mRNA vaccines, their recent advancements in clinical trials, and the potential for their therapeutic applications are highlighted in this study, which also offers a quick summary of the present state of mRNA vaccines. Lastly, we highlight a few difficulties with mRNA HPV vaccination clinical practice and provide our thoughts on further advancements in this quickly changing sector. It is expected that mRNA vaccines will soon be produced quickly for clinical HPV prevention and treatment.

Extracellular cancer‑associated fibroblasts: A novel subgroup in the cervical cancer microenvironment that exhibits tumor‑promoting roles and prognosis biomarker functions

Tumor invasion and metastasis are the processes that primarily cause adverse outcomes in patients with cervical cancer. Cancer-associated fibroblasts (CAFs), which participate in cancer progression and metastasis, are novel targets for the treatment of tumors. The present study aimed to assess the heterogeneity of CAFs in the cervical cancer microenvironment through single-cell RNA sequencing. After collecting five cervical cancer samples and obtaining the CAF-associated gene sets, the CAFs in the cervical cancer microenvironment were divided into myofibroblastic CAFs and extracellular (ec)CAFs. The ecCAFs appeared with more robust pro-tumorigenic effects than myCAFs according to enrichment analysis. Subsequently, through combining the ecCAF hub genes and bulk gene expression data for cervical cancer obtained from The Cancer Genome Atlas and Gene Ontology databases, univariate Cox regression and least absolute shrinkage and selection operator analyses were performed to establish a CAF-associated risk signature for patients with cancer. The established risk signature demonstrated a stable and strong prognostic capability in both the training and validation cohorts. Subsequently, the association between the risk signature and clinical data was evaluated, and a nomogram to facilitate clinical application was established. The risk score was demonstrated to be associated with both the tumor immune microenvironment and the therapeutic responses. Moreover, the signature also has predictive value for the prognosis of head and neck squamous cell carcinoma, and bladder urothelial carcinoma, which were also associated with human papillomavirus infection. In conclusion, the present study assessed the heterogeneity of CAFs in the cervical cancer microenvironment, and a subgroup of CAFs that may be closely associated with tumor progression was defined. Moreover, a signature based on the hub genes of ecCAFs was shown to have biomarker functionality in terms of predicting survival rates, and therefore this CAF subgroup may become a therapeutic target for cervical cancer in the future.

Molluscum Contagiosum Virus: Biology and Immune Response

Molluscum contagiosum virus is a poxvirus belonging to the Poxviridae family, which includes Orthopoxvirus, Parapoxvirus, Yantapoxvirus, Molluscipoxvirus, Smallpox virus, Cowpox virus and Monkeypox virus. MCV belongs to the genus Molluscipoxvirus and has a tropism for skin tissue. MCV infects keratinocytes and, after an incubation period of 2 weeks to 6 weeks, causes a breakdown of the skin barrier with the development of papules of variable size depending on the proper functioning of the immune response (both adaptive and acquired). MCV only infects humans and does not cause viraemia. MCV encodes for several inhibitory proteins responsible to circumvent the immune response through different signalling pathways. Individuals who can be infected with MCV are children, immunocompromised individuals such as organ transplant recipients and Human Immunodeficiency Virus (HIV)-infected individuals. Current treatments to manage MCV-induced lesions are different and include the use of immunomodulators, which, however, do not provide an effective response.

Human Papillomavirus-Associated Tumor Extracellular Vesicles in HPV+ Tumor Microenvironments

Most infections with human papillomaviruses (HPVs) are self-resolving and asymptomatic. However, some infections can lead to the development of cancer at different mucosal sites, such as the cervix and the head and neck. Head and neck cancers (HNCs) are dichotomized into HPV-positive (HPV+) or HPV-negative (HPV-) based on their respective etiologies. Notably, the tumor microenvironment (TME) of the HPV+ subtype has an immune landscape characterized with increased immune infiltration, higher levels of T cell activation, and higher levels of immunoregulatory stimuli compared to their HPV- counterparts. Both enveloped and nonenveloped viruses hijack the extracellular vesicle (EV) biogenesis pathway to deploy a "trojan horse" strategy with a pseudoviral envelope to enhance infectivity and evade inflammation. EVs derived from HPV-infected tumor cells could allow for the stealth transport of viral cargo to neighboring nonmalignant cellular populations or infiltrating immune cells within the TME. Furthermore, viral cargo or altered cellular cargo from HPV-associated tumor EVs (HPV-TEVs) could alter the functional state or biological responses of the recipient cellular populations, which could shape the distinctive HPV+ TME. This review will cover the impact of EVs released from HPV-infected cells on HPV-induced carcinogenesis, their role in shaping the distinctive HPV+ tumor microenvironment, and current efforts to develop a painless EV-based liquid biopsy for HPV+ cancers.

Exosomes from cervical cancer cells facilitate pro-angiogenic endothelial reconditioning through transfer of Hedgehog-GLI signaling components

BACKGROUND

Angiogenic switch is a hallmark feature of transition from low-grade to high-grade cervical intraepithelial neoplasia (CIN) in cervical cancer progression. Therefore, early events leading to locally-advanced cervical metastatic lesions demand a greater understanding of the underlying mechanisms. Recent leads indicate the role of tumor-derived exosomes in altering the functions of endothelial cells in cervical cancer, which needs further investigation.

METHODS

Exosomes isolated from cervical cancer cell lines were assessed for their angiogenic effect on the human umbilical vein endothelial cells (HUVEC) using tube formation and wound healing assay. The exosomal uptake by HUVEC cells was monitored using PKH-67 labelling followed by fluorescence microscopy. Alterations in Hh-GLI signaling components, PTCH1 and GLI1, in HUVEC were measured by immunoblotting. Changes in angiogenesis-related transcripts of vascular endothelial growth factor VEGF-A, VEGF-B, VEGFR2 and angiopoietin-1, angiopoietin-2, osteopontin were measured in exosome-treated HUVEC and in the exosomal RNA by RT-PCR.

RESULTS

Enhanced tube formation, with an increased number of nodes and branching was observed in HUVEC's treated with exosomes derived from different cervical cancer cell lines. HPV-positive (SiHa and HeLa) cells' exosomes were more angiogenic. Exosome-treated HUVEC showed increased migration rate. PKH-67 labelled exosomes were found internalized in HUVEC. A high level of PTCH1 protein was detected in the exosome-treated endothelial cells. Subsequent RT-PCR analysis showed increased transcripts of Hh-GLI downstream target genes VEGF-A, VEGFR2, angiopoietin-2, and decreased expression of VEGF-B, and angiopoietin-1, suggestive of active Hh-GLI signaling. These effects were more pronounced in HUVEC's treated with exosomes of HPV-positive cells. However, these effects were independent of tumor-derived VEGF-A as exosomal cargo lacked VEGF-A transcripts or proteins.

CONCLUSION

Overall, the data showed cervical cancer exosomes promote pro-angiogenic response in endothelial cells via upregulation of Hh-GLI signaling and modulate downstream angiogenesis-related target genes. The study provides a novel exosome-mediated mechanism potentially favoring cervical angiogenesis and thus identifies the exosomes as potential pharmacological targets against locally-advanced metastatic cervical lesions.

A Review on Inosine Pranobex Immunotherapy for Cervical HPV-Positive Patients

The purpose of this review was to examine and summarize data for inosine pranobex (IP) immunotherapy in cervical HPV-positive patients. Persistent or recurring cervical human papillomavirus (HPV) infection is a major cause of cervical cancer. Self-clearance and blocking of cervical HPV infection depend on the status of the host immune system. Immunotherapy helps accelerate elimination of the infection. Host immunity is involved in the development of HPV infection. Several mechanisms of interaction between the virus and the immune system have been revealed; however, the mechanisms have not been completely elucidated. A properly functioning immune system impedes HPV progress and helps clear the pathogen from the body. IP has antiviral efficacy because it modulates both cellular and humoral immunities. IP has been on the market since 1971. Nevertheless, it has seldom been administered to treat cervical HPV infections. In this review, Google Scholar, PubMed/MEDLINE, Scopus, Cochrane Library, and Research Gate were searched for the period 1971–2021. Prospective controlled trials, observational and retrospective studies, and meta-analysis and reviews on immunotherapy against HPV cervical infection were explored. Prior studies showed strong clinical efficacy of combined and standalone IP therapy in reversing HPV-induced changes in the cervix, preventing disease progression, and clearing the pathogen. IP treatment enhanced host antiviral activity against HPV, delayed or stopped cervical oncogenesis, and rapidly removed HPV from the body.

Epigallocatechin-3-gallate Can Prevent Type 2 Human Papillomavirus E7 from Suppressing Interferon-Stimulated Genes

Human papillomavirus (HPV) in high-risk groups is known to suppress the type I interferon (IFN) signaling pathway leading to the transcription of interferon-stimulated genes (ISGs), which have many antiviral functions. However, the effects of HPV on the action of various ISGs in low-risk groups are not fully understood. We aimed to investigate whether antiviral ISGs are expressed in transfected keratinocytes with type 2 HPV (HPV-2) E7. The mRNA and protein expressions of ISGs and type I IFN signaling pathway components were evaluated by quantitative real-time polymerase chain reaction, western blot, immunofluorescence, and/or immunohistochemistry. Compared with normal skin, mRNA expression of all ISGs in HPV-2 positive cutaneous warts was significantly decreased (p < 0.05). In comparison with empty vector transfection, E7 transfection significantly down-regulated the mRNA and protein expressions of ISGs and type I IFN signaling pathway components, which were significantly up-regulated by E7 siRNA transfection (p < 0.05). Interestingly, epigallocatechin-3-gallate (EGCG) pretreatment up-regulated the mRNA and protein expressions of ISGs and type I IFN signaling pathway components, which were significantly down-regulated by E7 transfection (p < 0.05). Our results demonstrate that EGCG is a potential candidate for cutaneous wart prevention.

Does involucrin have a role in verruca vulgaris? A clinical and immunohistochemical study

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Ex Vivo Culture Models to Indicate Therapy Response in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is characterized by a poor 5 year survival and varying response rates to both standard-of-care and new treatments. Despite advances in medicine and treatment methods, mortality rates have hardly decreased in recent decades. Reliable patient-derived tumor models offer the chance to predict therapy response in a personalized setting, thereby improving treatment efficacy by identifying the most appropriate treatment regimen for each patient. Furthermore, ex vivo tumor models enable testing of novel therapies before introduction in clinical practice. A literature search was performed to identify relevant literature describing three-dimensional ex vivo culture models of HNSCC to examine sensitivity to chemotherapy, radiotherapy, immunotherapy and targeted therapy. We provide a comprehensive overview of the currently used three-dimensional ex vivo culture models for HNSCC with their advantages and limitations, including culture success percentage and comparison to the original tumor. Furthermore, we evaluate the potential of these models to predict patient therapy response.

EB virus-induced ATR activation accelerates nasopharyngeal carcinoma growth via M2-type macrophages polarization

Chronic inflammation induced by persistent viruses infection plays an essential role in tumor progression, which influenced on the interaction between the tumor cells and the tumor microenvironment. Our earlier study showed that ATR, a key kinase participant in single-stranded DNA damage response (DDR), was obviously activated by Epstein-Barr virus (EBV) in nasopharyngeal carcinoma (NPC). However, how EBV-induced ATR activation promotes NPC by influencing inflammatory microenvironment, such as tumor-associated macrophages (TAMs), remains elusive. In this study, we showed that EBV could promote the expression of p-ATR and M2-type TAMs transformation in clinical NPC specimens. The expression of p-ATR and M2-type TAMs were closely correlated each other and involved in TNM stage, lymph node metastasis and poor prognosis of the patients. In addition, the expression levels of CD68⁺CD206⁺, Arg1, VEGF, and CCL22 were increased in EB⁺ CNE1 cells, and decreased when ATR was inhibited. In the nude mice, EBV-induced ATR activation promoted subcutaneous transplanted tumor growth, higher expression of Ki67 and lung metastasis via M2-type TAMs recruitment. Experimental data also showed that the polarization of M2, the declined tumor necrosis factor-α (TNF-α) and increased transforming growth factor-β (TGF-β) were associated with ATR. Meanwhile, ATR activation could promote PPAR-δ and inhibited c-Jun and p-JNK expression, then downregulate JNK pathway. Collectively, our current study demonstrated the EBV infection could activate the ATR pathway to accelerate the transition of TAMs to M2, suggesting ATR knockdown could be a potential effective treatment strategy for EBV-positive NPC.

In Vitro Organotypic Systems to Model Tumor Microenvironment in Human Papillomavirus (HPV)-Related Cancers

Despite the well-known role of chronic human papillomavirus (HPV) infections in causing tumors (i.e., all cervical cancers and other human malignancies from the mucosal squamous epithelia, including anogenital and oropharyngeal cavity), its persistence is not sufficient for cancer development. Other co-factors contribute to the carcinogenesis process. Recently, the critical role of the underlying stroma during the HPV life cycle and HPV-induced disease have been investigated. The tumor stroma is a key component of the tumor microenvironment (TME), which is a specialized entity. The TME is dynamic, interactive, and constantly changing—able to trigger, support, and drive tumor initiation, progression, and metastasis. In previous years, in vitro organotypic raft cultures and in vivo genetically engineered mouse models have provided researchers with important information on the interactions between HPVs and the epithelium. Further development for an in-depth understanding of the interaction between HPV-infected tissue and the surrounding microenvironment is strongly required. In this review, we critically describe the HPV-related cancers modeled in vitro from the simplified ‘raft culture’ to complex three-dimensional (3D) organotypic models, focusing on HPV-associated cervical cancer disease platforms. In addition, we review the latest knowledge in the field of in vitro culture systems of HPV-associated malignancies of other mucosal squamous epithelia (anogenital and oropharynx), as well as rare cutaneous non-melanoma associated cancer.

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.

Venn-diaNet : venn diagram based network propagation analysis framework for comparing multiple biological experiments

BACKGROUND

The main research topic in this paper is how to compare multiple biological experiments using transcriptome data, where each experiment is measured and designed to compare control and treated samples. Comparison of multiple biological experiments is usually performed in terms of the number of DEGs in an arbitrary combination of biological experiments. This process is usually facilitated with Venn diagram but there are several issues when Venn diagram is used to compare and analyze multiple experiments in terms of DEGs. First, current Venn diagram tools do not provide systematic analysis to prioritize genes. Because that current tools generally do not fully focus to prioritize genes, genes that are located in the segments in the Venn diagram (especially, intersection) is usually difficult to rank. Second, elucidating the phenotypic difference only with the lists of DEGs and expression values is challenging when the experimental designs have the combination of treatments. Experiment designs that aim to find the synergistic effect of the combination of treatments are very difficult to find without an informative system.

RESULTS

We introduce Venn-diaNet, a Venn diagram based analysis framework that uses network propagation upon protein-protein interaction network to prioritizes genes from experiments that have multiple DEG lists. We suggest that the two issues can be effectively handled by ranking or prioritizing genes with segments of a Venn diagram. The user can easily compare multiple DEG lists with gene rankings, which is easy to understand and also can be coupled with additional analysis for their purposes. Our system provides a web-based interface to select seed genes in any of areas in a Venn diagram and then perform network propagation analysis to measure the influence of the selected seed genes in terms of ranked list of DEGs.

CONCLUSIONS

We suggest that our system can logically guide to select seed genes without additional prior knowledge that makes us free from the seed selection of network propagation issues. We showed that Venn-diaNet can reproduce the research findings reported in the original papers that have experiments that compare two, three and eight experiments. Venn-diaNet is freely available at: http://biohealth.snu.ac.kr/software/venndianet.

Suppression of Stromal Interferon Signaling by Human Papillomavirus 16

Human papillomaviruses (HPVs) infect squamous epithelia and cause several important cancers. Immune evasion is critical for viral persistence. Fibroblasts in the stromal microenvironment provide growth signals and cytokines that are required for proper epithelial differentiation, maintenance, and immune responses and are critical in the development of many cancers. In this study, we examined the role of epithelial-stromal interactions in the HPV16 life cycle using organotypic (raft) cultures as a model. Rafts were created using uninfected human foreskin keratinocytes (HFKs) and HFKs containing either wild-type HPV16 or HPV16 with a stop mutation to prevent the expression of the viral oncogene E5. Microarray analysis revealed significant changes in gene expression patterns in the stroma in response to HPV16, some of which were E5 dependent. Interferon (IFN)-stimulated genes (ISGs) and extracellular matrix remodeling genes were suppressed, the most prominent pathways affected. STAT1, IFNAR1, IRF3, and IRF7 were knocked down in stromal fibroblasts using lentiviral short hairpin RNA (shRNA) transduction. HPV late gene expression and viral copy number in the epithelium were increased when the stromal IFN pathway was disrupted, indicating that the stroma helps control the late phase of the HPV life cycle in the epithelium. Increased late gene expression correlated with increased late keratinocyte differentiation but not decreased IFN signaling in the epithelium. These studies show HPV16 has a paracrine effect on stromal innate immunity, reveal a new role for E5 as a stromal innate immune suppressor, and suggest that stromal IFN signaling may influence keratinocyte differentiation.IMPORTANCE The persistence of high-risk human papillomavirus (HPV) infections is the key risk factor for developing HPV-associated cancers. The ability of HPV to evade host immunity is a critical component of its ability to persist. The environment surrounding a tumor is increasingly understood to be critical in cancer development, including immune evasion. Our studies show that HPV can suppress the expression of immune-related genes in neighboring fibroblasts in a three-dimensional (3D) model of human epithelium. This finding is significant, because it indicates that HPV can control innate immunity not only in the infected cell but also in the microenvironment. In addition, the ability of HPV to regulate stromal gene expression depends in part on the viral oncogene E5, revealing a new function for this protein as an immune evasion factor.

The role of the innate and adaptive immune response in HPV-associated oropharyngeal squamous cell carcinoma

Human papilloma virus (HPV) has been implicated in the development of oropharyngeal squamous cell carcinoma (OPSCC) and is directly attributed to its increasing incidence. The immune microenvironment surrounding HPV‐associated OPSCC tumors is complex and plays a critical role in the carcinogenic process. The neoplastic mechanism includes cells of the innate immunity such as macrophages, and dendritic cells as well as cells of the adaptive immune process such as CD8+ T‐cells. The intricate interactions between these two arms of the immune system allow for a pro‐inflammatory and pro‐tumorigenic environment. Intensive efforts are underway to gain a greater understanding of the mechanisms involved in the immune system's role in tumor development. This study seeks to summarize the current knowledge pertaining to role of the innate and adaptive immune response in HPV‐associated OPSCC.

Level of Evidence

3a

Activities of stromal and immune cells in HPV-related cancers

The immune system is composed of immune as well as non-immune cells. As this system is a well-established component of human papillomavirus- (HPV)-related carcinogenesis, high risk human papillomavirus (hrHPV) prevents its routes and mechanisms in order to cause the persistence of infection. Among these mechanisms are those originated from stromal cells, which include the cancer-associated fibroblasts (CAFs), the myeloid-derived suppressor cells (MDSCs) and the host infected cells themselves, i.e. the keratinocytes. These types of cells play central role since they modulate immune cells activities to create a prosperous milieu for cancer development, and the knowledge how such interactions occur are essential for prognostic assessment and development of preventive and therapeutic approaches. Nevertheless, the precise mechanisms are not completely understood, and this lack of knowledge precluded the development of entirely efficient immunotherapeutic strategies for HPV-associated tumors. As a result, an intense work for attaining how host immune response works, and developing of effective therapies has been applied in the last decade. Based on this, this review aims to discuss the major mechanisms of immune and non-immune cells modulated by hrHPV and the potential and existing immunotherapies involving such mechanisms in HPV-related cancers. It is noticed that the combination of immunotherapies has been demonstrated to be essential for obtaining better results, especially because the possibility of increasing the modulating capacity of the HPV-tumor microenvironment has been shown to be central in strengthening the host immune system.

Human papillomavirus type 16 E5-mediated upregulation of Met in human keratinocytes

Human papillomaviruses (HPVs) cause benign lesions that can lead to malignancy. How cellular changes induced by viral oncogenes contribute to the progeny virion production is not always clear. Stromally-derived growth factors and their receptors are critical for development of malignancy, but their impact on the pre-malignant HPV life cycle is unknown. We show that HPV16 increases levels of Met, a growth factor receptor critical for tumor cell invasion, motility, and cancer metastasis. The viral oncogene E5 is primarily responsible for Met upregulation, with E6 playing a minor role. Met induction by E5 requires the epidermal growth factor receptor, which is also increased by E5 at the mRNA level. E5-induced Met contributes motility of HPV-containing cells. Finally, Met signaling is necessary for viral gene expression, particularly in the differentiation-dependent phase of the viral life cycle. These studies show a new role for E5 in epithelial-stromal interactions, with implications for cancer development.

Induction of Interferon Kappa in Human Papillomavirus 16 Infection by Transforming Growth Factor Beta-Induced Promoter Demethylation

Persistent high-risk human papillomavirus (HPV) infection is the major causal factor in cervical and other anogenital cancers. Because there are currently no therapeutics capable of preventing neoplastic progression of HPV infections, understanding the mechanisms of HPV-mediated persistence, including immune evasion, is a major research priority. The multifunctional growth factor transforming growth factor beta (TGFβ) has been shown to inhibit expression of early viral transcripts from cells harboring integrated HPV genomes or cells infected with retroviruses expressing HPV oncoproteins. However, the mechanism of TGFβ-induced inhibition has not been fully defined. In this study, we have observed a previously uncharacterized ability of TGFβ to repress the differentiation-induced upregulation of late HPV16 gene expression. In addition, interferon kappa (IFN-κ), a keratinocyte-specific, constitutively expressed cytokine suppressed by differentiation, can be transcriptionally induced by TGFβ1. TGFβ-mediated IFN-κ transcription only occurs in cells containing HPV16, and this is due to TGFβ1-mediated reversal of HPV-induced methylation of the IFN-κ promoter through active DNA demethylation mediated by thymine DNA glycosylase (TDG). This novel interaction between growth factor and innate immune signaling may shed light on the mechanisms of HPV persistence and how the virus manipulates both immune and growth factor signaling to promote its life cycle.IMPORTANCE Persistent infection by high-risk HPVs is the primary risk factor for development of HPV-induced cancers. Persistence involves viral evasion of the immune response, including the IFN response. HPV is also known to suppress TGFβ signaling, which inhibits viral gene expression. Here, we show that the TGFβ and IFN pathways are interrelated in the context of HPV16 infection through the upregulation of IFN-κ by TGFβ. The ability of TGFβ to induce IFN-κ promoter demethylation and transcriptional activation provides a new explanation for why HPV has evolved mechanisms to inhibit TGFβ in infected cells.

Human Papillomavirus and the Stroma: Bidirectional Crosstalk during the Virus Life Cycle and Carcinogenesis

Human papillomaviruses (HPVs) are double-stranded DNA (dsDNA) tumor viruses that are causally associated with human cancers of the anogenital tract, skin, and oral cavity. Despite the availability of prophylactic vaccines, HPVs remain a major global health issue due to inadequate vaccine availability and vaccination coverage. The HPV life cycle is established and completed in the terminally differentiating stratified epithelia, and decades of research using in vitro organotypic raft cultures and in vivo genetically engineered mouse models have contributed to our understanding of the interactions between HPVs and the epithelium. More recently, important and emerging roles for the underlying stroma, or microenvironment, during the HPV life cycle and HPV-induced disease have become clear. This review discusses the current understanding of the bidirectional communication and relationship between HPV-infected epithelia and the surrounding microenvironment. As is the case with other human cancers, evidence suggests that the stroma functions as a significant partner in tumorigenesis and helps facilitate the oncogenic potential of HPVs in the stratified epithelium.