Human papillomavirus E5 suppresses immunity via inhibition of the immunoproteasome and STING pathway

Application and Perspectives of Immunotherapy in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma poses grave challenges to clinicians and patients due to its tumour invasiveness and treatment uncertainties. Despite the substantial improvements in conventional treatment modalities such as surgery, chemotherapy and radiotherapy, the recurrence rate and mortality rate of HNSCC remain stubbornly high. Traditionally, the front-line therapy for recurrent/metastatic HNSCC has been the amalgamation of platinum-based drugs/paclitaxel, 5-fluorouracil and cetuximab, yet it only improves the prognosis of some patients, and the overall treatment situation remains severe. Immunotherapy, as an emerging luminary in the domain of cancer treatment, is committed to improving the tumour microenvironment and stimulating the immune system to perform anti-tumour functions. The continuous updates of immune checkpoint inhibitors have also obtained favourable clinical feedback and are expected to overcome the constraints of traditional therapies. This article elaborates on the trends of immunotherapy within the TME and the progress of immunotherapy, aiming to provide new ideas for treatment regimens in the new therapeutic landscape of HNSCC and offer new hope for patients.

The viral early protein 4 of human papillomavirus type 16 suppresses innate antiviral immunity

Although non-structural proteins of HPV are known to modulate interferon (IFN) responses, the specific role of HPV16 E4 in immune evasion remains poorly defined. In this study, we demonstrated that HPV16 E4 inhibited IFN and IFN-stimulated gene (ISG) expression induced by VSV, MHV, SeV, HSV1, and HPV16 infection. Plaque assays revealed that E4-expressing cells produced higher titers of VSV and HSV1, supporting its role in promoting viral replication. Dual-luciferase reporter assays and RT-qPCR analyses confirmed that HPV16 E4 attenuates IFN responses by targeting key antiviral pathways, including RIG-I/MDA5-MAVS, TLR3-TRIF, and cGAS-STING. Coimmunoprecipitation and immunoblotting assays revealed that E4 interacted with RIG-I, MDA5, MAVS, TRIF, TBK1, and IRF3, thereby inhibiting the phosphorylation of TBK1 and IRF3. Confocal microscopy and nuclear-cytoplasmic fractionation demonstrated that E4 impaired IRF3 nuclear translocation, a pivotal step in IFN signaling. E4 also suppressed the JAK-STAT pathway, resulting in reduced ISG expression. Furthermore, E4 disrupted ISGF3 complex formation by interacting with STAT2 and IRF9, thereby preventing the nuclear translocation of STAT1, STAT2, and IRF9. Collectively, these mechanisms facilitate viral replication and enable evasion of host antiviral immunity. These findings advance our understanding of HPV immune evasion strategies and suggest novel therapeutic targets for managing HPV-related diseases.

Viral oncogenesis in cancer: from mechanisms to therapeutics

The year 2024 marks the 60th anniversary of the discovery of the Epstein-Barr virus (EBV), the first virus confirmed to cause human cancer. Viral infections significantly contribute to the global cancer burden, with seven known Group 1 oncogenic viruses, including hepatitis B virus (HBV), human papillomavirus (HPV), EBV, Kaposi sarcoma-associated herpesvirus (KSHV), hepatitis C virus (HCV), human T-cell leukemia virus type 1 (HTLV-1), and human immunodeficiency virus (HIV). These oncogenic viruses induce cellular transformation and cancer development by altering various biological processes within host cells, particularly under immunosuppression or co-carcinogenic exposures. These viruses are primarily associated with hepatocellular carcinoma, gastric cancer, cervical cancer, nasopharyngeal carcinoma, Kaposi sarcoma, lymphoma, and adult T-cell leukemia/lymphoma. Understanding the mechanisms of viral oncogenesis is crucial for identifying and characterizing the early biological processes of virus-related cancers, providing new targets and strategies for treatment or prevention. This review first outlines the global epidemiology of virus-related tumors, milestone events in research, and the process by which oncogenic viruses infect target cells. It then focuses on the molecular mechanisms by which these viruses induce tumors directly or indirectly, including the regulation of oncogenes or tumor suppressor genes, induction of genomic instability, disruption of regular life cycle of cells, immune suppression, chronic inflammation, and inducing angiogenesis. Finally, current therapeutic strategies for virus-related tumors and recent advances in preclinical and clinical research are discussed.

Human papillomavirus E1 proteins inhibit RIG-I/MDA5-MAVS, TLR3-TRIF, cGAS-STING, and JAK-STAT signaling pathways to evade innate antiviral immunity

Human papillomavirus (HPV) is a major etiological agent of both malignant and benign lesions, with high-risk types, such as HPV16 and HPV18, being strongly linked to cervical cancer, while low-risk types like HPV11 are associated with benign conditions. While viral proteins such as E6 and E7 are well-established regulators of immune evasion, the role of E1 in modulating the host antiviral responses remains insufficiently characterized. This study investigates the immunomodulatory functions of HPV16 and HPV11 E1 in suppressing innate antiviral immune signaling pathways. Through a combination of RT-qPCR and luciferase reporter assays, we demonstrate that E1 suppresses the production of interferons and interferon-stimulated genes triggered by viral infections and the activation of RIG-I/MDA5-MAVS, TLR3-TRIF, cGAS-STING, and JAK-STAT pathways. Co-immunoprecipitation assays reveal that E1 interacts directly with key signaling molecules within these pathways. E1 also impairs TBK1 and IRF3 phosphorylation and obstructs the nuclear translocation of IRF3, thereby broadly suppressing IFN responses. Additionally, E1 disrupts the JAK-STAT pathway by binding STAT1, which prevents the assembly and nuclear localization of the ISGF3 complex containing STAT1, STAT2, and IRF9, thereby further diminishing antiviral response. These findings establish E1 as a pivotal regulator of immune evasion and suggest its potential as a novel therapeutic target to enhance antiviral immunity in HPV-associated diseases.

Human papillomavirus E2 proteins suppress innate antiviral signaling pathways

Human papillomavirus (HPV) is a major cause of cancers and benign lesions. High-risk (HR) types, including HPV16 and HPV18, are strongly implicated in cervical and other malignancies, while low-risk (LR) types, such as HPV11, are predominantly associated with benign conditions. Although the immune evasion of HPV oncoproteins E6 and E7 are extensively studied, the immunomodulatory functions of the E2 protein remain poorly underexplored. This study elucidates the role of HPV11 and HPV16 E2 proteins in modulating innate immune responses, focusing on their interaction with key innate antiviral signaling pathways. We demonstrate that HPV11 and HPV16 E2 proteins effectively suppress the activation of pivotal antiviral signaling pathways, including RIG-I/MDA5-MAVS, TLR3-TRIF, cGAS-STING, and JAK-STAT. Mechanistic analyses reveal that E2 proteins interact with the core components of type I interferon (IFN)-inducing pathways, inhibiting IRF3 phosphorylation and nuclear translocation, thereby attenuating IFN expression. Additionally, E2 disrupts the JAK-STAT signaling cascade by preventing the assembly of the ISGF3 complex, comprising STAT1, STAT2, and IRF9, ultimately inhibiting the transcription of interferon-stimulated genes (ISGs). These findings underscore the broader immunosuppressive role of HPV E2 proteins, complementing the well-established immune evasion mechanisms mediated by E6 and E7. This work advances our understanding of HPV-mediated immune evasion and positions the E2 protein as a promising target for therapeutic strategies aimed at augmenting antiviral immunity in HPV-associated diseases.

E5 Oncoprotein: A Key Player in Human Papillomavirus-Positive Head and Neck Cancer Pathogenesis and Therapy Resistance

Head and neck cancer (HNC) is the sixth most prevalent type of cancer worldwide and is associated with low five-year survival rates. Alcoholism and smoking are the main risk factors associated with the development of head and neck cancer (HNC). However, Human Papillomavirus (HPV) infection has been reported as a significant risk factor, particularly for the oropharyngeal subset. In these cases, patients with HPV-positive HNC exhibit a better clinical prognosis; however, resistance to chemotherapy has been frequently reported. The carcinogenic activity of HPV is related to the viral oncoproteins E5, E6, and E7. E5 has been associated with immune evasion mechanisms and modulation of the tumor microenvironment, which appears to be linked to the virus's resistance to chemotherapeutic treatments. Here, we review the potential of HPV E5 in targeted therapy for HNC and discuss relevant data regarding the activity of this oncoprotein in head and neck carcinogenesis.

Virus-mediated immunosuppression in head and neck cancer

Head and neck cancer is the seventh most common cancer worldwide and its development is associated with viral infection. Human papillomavirus (HPV) is the major cause of oropharyngeal cancer and encodes three known oncoproteins, E5, E6, and E7. Epstein-Barr virus (EBV), which is the causative agent of most nasopharyngeal carcinoma, also employs several immunosuppressive mechanisms that contribute to the development of the disease. In this review, we synthesize and discuss several mechanisms used by these viruses to evade and escape the host immune system. In particular, we focus on the evasive tactics of HPV E5 which, we argue, is critical to establishing persistent infection and the development and progression of carcinomas. Importantly the mechanisms by which these viruses suppress immune responses may also play a key role in resistance to checkpoint blockade immunotherapies and thus impact patient outcomes.

A Single-Cell Transcriptome Atlas of Epithelial Subpopulations in HPV-Positive and HPV-Negative Head and Neck Cancers

Persistent infection with HPV causes nearly 5% of all cancers worldwide, including cervical and oropharyngeal cancers. Compared to HPV-negative (HPV-) head and neck squamous cell carcinomas (HNSCCs), HPV-positive (HPV+) HNSCCs exhibit a significantly improved treatment response; however, established treatment regimens were largely developed for HPV- disease. Effectively de-escalating therapy and optimizing treatment protocols to minimize toxicity for both HPV+ and HPV- tumors has been variably successful, in part due to the heterogeneity of cellular subpopulations. Single-cell RNA sequencing (scRNAseq) has primarily been used to define immune cell populations rather than the cell type of origin, epithelial cells. To address this, we analyzed published scRNAseq data of HPV+ and HPV- HNSCCs to distinguish epithelial tumor cell populations as a function of HPV status. We identified the transcriptome signatures, ontologies, and candidate biomarkers of newly identified epithelial subpopulations with attention to those that are shared or enriched in HPV+ or HPV- HNSCCs. We hypothesize that distinct epithelial cell populations and reprogramming in HPV- versus HPV+ HNSCC represent important components of the pro-tumor environment. These are described here as a foundation for the identification of new epithelial-cell-specific biomarkers, effectors, and candidate targets for optimizing the treatment of HNSCC.

Major Human Leukocyte Antigen Expression in Respiratory Papillomatosis Clinical Specimens

OBJECTIVES

Prior studies have reported low or absent major HLA class I expression on respiratory papilloma cells, conflicting with the recent clinical success of immunotherapy designed to activate HPV-specific T cells in patients with recurrent respiratory papillomatosis (RRP). We aimed to determine major human leukocyte antigen (HLA) class I expression on respiratory papilloma cells in untreated RRP clinical specimens using contemporary techniques.

METHODS

Formalin-fixed, paraffin-embedded RRP sections were subjected to signal-amplified multispectral immunofluorescence using the OPAL system to determine major and minor HLA class I expression, and digitally scanned slides were analyzed using digital pathology software. Positive and negative controls were used to optimize primary antibody conditions.

RESULTS

All samples harbored major HLA class I expression on varying proportions of papilloma cells. Considering all samples, major HLA class I expression was observed on the majority (74%) of papilloma cells. Nearly all (98%) papilloma infiltrating immune cells were positive for major HLA class I expression, serving as an internal control for each stained sample. Major HLA class I negative papilloma cells were enriched in the apical, suprabasal layers compared to the basal layers of the papillomatous epithelium, suggesting an association with the epithelial cell differentiation state. Fewer papilloma cells inconsistently expressed the minor HLA class I HLA-E across the basal and suprabasal epithelial layers.

CONCLUSION

Papilloma cells express major HLA class I molecules. Using contemporary immunofluorescent techniques with signal amplification that likely provide improved sensitivity, these results clarify the major HLA class I expression status on papilloma cells in clinical specimens.

LEVEL OF EVIDENCE

N/A.

Regulation of epithelial growth factor receptors by the oncoprotein E5 during the HPV16 differentiation-dependent life cycle

Human papillomavirus (HPV) 16 infection initiates upon viral entry into the basal cells of the epithelium. The virus manipulates signaling pathways to complete its life cycle, which depends on cellular differentiation. The virus expresses the oncoproteins E5, E6, and E7 to promote immune evasion, cell cycle progression, apoptosis inhibition, and viral replication. The least studied viral oncoprotein is E5 (16E5), which can regulate epithelial growth factor receptor (GFR) signaling pathways. GFRs such as transforming growth factor-beta receptor (TGFBR), epidermal growth factor receptor (EGFR), and keratinocyte growth factor receptor (KGFR) have essential roles in cell growth, differentiation, and proliferation. These receptors obtain their ligands from the microenvironment, and once activated, regulate cellular behavior in the epithelium. GFRs therefore represent valuable targets for the virus to establish and maintain a cellular environment supportive of infection. The ability of 16E5 to regulate proliferation and differentiation varies through the differentiating epithelium, making it necessary to adequately describe the association between 16E5 and GFRs. Here we summarize the regulation of GFR signaling pathways by 16E5, discuss the roles of stromal growth factors, and outline unresolved questions over cellular differentiation and proliferation during the HPV life cycle.

A Primer on Proteomic Characterization of Intercellular Communication in a Virus Microenvironment

Intercellular communication is fundamental to multicellular life and a core determinant of outcomes during viral infection, where the common goals of virus and host for persistence and replication are generally at odds. Hosts rely on encoded innate and adaptive immune responses to detect and clear viral pathogens, while viruses can exploit or disrupt these pathways and other intercellular communication processes to enhance their spread and promote pathogenesis. While virus-induced signaling can result in systemic changes to the host, striking alterations are observed within the cellular microenvironment directly surrounding a site of infection, termed the virus microenvironment (VME). Mechanisms employed by viruses to condition their VMEs are emerging and are critical for understanding the biology and pathologies of viral infections. Recent advances in experimental approaches, including proteomic methods, have enabled study of the VME in unprecedented detail. In this review article, we provide a primer on proteomic approaches used to study how viral infections alter intercellular communication, highlighting the ways in which these approaches have been implemented and the exciting biology they have uncovered. First, we consider the different molecules secreted by an infected cell, including proteins, either soluble or contained within extracellular vesicles, and metabolites. We further discuss the modalities of interactions facilitated by alteration at the cell surface of infected cells, including immunopeptide presentation and interactions with the extracellular matrix. Finally, we review spatial profiling approaches that have allowed distinguishing how specific subpopulations of cells within a VME respond to infection and alter their protein composition, discussing valuable insights these methods have offered.

Genome-Wide Association Analyses of HPV16 and HPV18 Seropositivity Identify Susceptibility Loci for Cervical Cancer

Infection by high-risk human papillomavirus is known to exacerbate cervical cancer development. The host immune response is crucial in disease regression. Large-scale genetic association studies for cervical cancer have identified few susceptibility variants, mainly at the human leukocyte antigen locus on chromosome 6. We hypothesized that the host immune response modifies cervical cancer risk and performed three genome-wide association analyses for HPV16, HPV18 and HPV16/18 seropositivity in 7814, 7924, and 7924 samples from the UK Biobank, followed by validation genotyping in the German Cervigen case-control series of cervical cancer and dysplasia. In GWAS analyses, we identified two loci associated with HPV16 seropositivity (6p21.32 and 15q26.2), two loci associated with HPV18 seropositivity (5q31.2 and 14q24.3), and one locus for HPV16 and/or HPV18 seropositivity (at 6p21.32). MAGMA gene-based analysis identified HLA-DQA1 and HLA-DQB1 as genome-wide significant (GWS) genes. In validation genotyping, the genome-wide significant lead variant at 6p21.32, rs9272293 associated with overall cervical disease (OR = 0.86, p = 0.004, 95% CI = 0.78-0.95, n = 3710) and HPV16 positive invasive cancer (OR = 0.73, p = 0.005, 95% CI = 0.59-0.91, n = 1431). This variant was found to be a robust eQTL for HLA-DRB1, HLA-DQB1-AS1, C4B, HLA-DRB5, HLA-DRB6, HLA-DQB1, and HLA-DPB1 in a series of cervical epithelial tissue samples. We additionally genotyped twenty-four HPV seropositivity variants below the GWS threshold out of which eleven variants were found to be associated with cervical disease in our cohort, suggesting that further seropositivity variants may determine cervical disease outcome. Our study identifies novel genomic risk loci that associate with HPV type-specific cervical cancer and dysplasia risk and provides evidence for candidate genes at one of the risk loci.

Roles of human papillomavirus in cancers: oncogenic mechanisms and clinical use

Human papillomaviruses, particularly high-risk human papillomaviruses, have been universally considered to be associated with the oncogenesis and progression of various cancers. The genome of human papillomaviruses is circular, double-stranded DNA that encodes early and late proteins. Each of the proteins is of crucial significance in infecting the epithelium of host cells persistently and supporting viral genome integrating into host cells. Notably, E6 and E7 proteins, classified as oncoproteins, trigger the incidence of cancers by fostering cell proliferation, hindering apoptosis, evading immune surveillance, promoting cell invasion, and disrupting the balance of cellular metabolism. Therefore, targeting human papillomaviruses and decoding molecular mechanisms by which human papillomaviruses drive carcinogenesis are of great necessity to better treat human papillomaviruses-related cancers. Human papillomaviruses have been applied clinically to different facets of human papillomavirus-related cancers, including prevention, screening, diagnosis, treatment, and prognosis. Several types of prophylactic vaccines have been publicly utilized worldwide and have greatly decreased the occurrence of human papillomavirus-related cancers, which have benefited numerous people. Although various therapeutic vaccines have been developed and tested clinically, none of them have been officially approved to date. Enhancing the efficacy of vaccines and searching for innovative technologies targeting human papillomaviruses remain critical challenges that warrant continuous research and attention in the future.

Viral Oncogenesis: Synergistic Role of Genome Integration and Persistence

Persistence is a strategy used by many viruses to evade eradication by the immune system, ensuring their permanence and transmission within the host and optimizing viral fitness. During persistence, viruses can trigger various phenomena, including target organ damage, mainly due to an inflammatory state induced by infection, as well as cell proliferation and/or immortalization. In addition to immune evasion and chronic inflammation, factors contributing to viral persistence include low-level viral replication, the accumulation of viral mutants, and, most importantly, maintenance of the viral genome and reliance on viral oncoprotein production. This review focuses on the process of genome integration, which may occur at different stages of infection (e.g., HBV), during the chronic phase of infection (e.g., HPV, EBV), or as an essential part of the viral life cycle, as seen in retroviruses (HIV, HTLV-1). It also explores the close relationship between integration, persistence, and oncogenesis. Several models have been proposed to describe the genome integration process, including non-homologous recombination, looping, and microhomology models. Integration can occur either randomly or at specific genomic sites, often leading to genome destabilization. In some cases, integration results in the loss of genomic regions or impairs the regulation of oncogene and/or oncosuppressor expression, contributing to tumor development.

The imprint of viral oncoproteins on the variable clinical behavior among human papilloma virus-related oropharyngeal squamous cell carcinomas

Human papilloma virus-related (HPV+) oropharyngeal squamous cell carcinomas (OPSCCs) are variable in their progression, immune landscape, treatment responses, and clinical outcomes. Their behavior is impacted not only by differences in host genomic alterations but also by diversity in levels and activity of HPV-encoded oncoproteins. Striking differences in HPV mRNA levels are found among HPV+ OPSCCs and likely derive in part from variations in the structurally diverse mix of integrated and episomal HPV genomes they often contain. Viral oncoprotein levels and function are also impacted by differential splicing of the two long polycistronic transcripts of HPV16, the HPV type within most HPV+ OPSCCs. Further variation in viral oncoprotein function arises from the distinct lineages and sub-lineages of HPV16, which encode polymorphisms in functionally important portions of oncogenes. Here we review the limited current knowledge linking HPV mRNA expression and splicing to differences in oncoprotein function that likely influence OPSCC behavior. We also summarize the evolving understanding of HPV16 physical genome state and genetic variants and their potential contributions to HPV oncoprotein levels and function. Addressing considerable remaining challenges in defining the quantitative and qualitative imprint of HPV oncoproteins on each OPSCC holds promise to guide personalization of therapy for this disease.

HPV and Penile Cancer: Epidemiology, Risk Factors, and Clinical Insights

Penile cancer (PC) is a rare malignancy predominantly of squamous cell origin. Approximately 40% of penile tumors are associated with human papillomavirus (HPV) infection. Diagnosing PC remains challenging due to its rarity and variety of clinical presentations. Furthermore, the impact of HPV on the tumor immune microenvironment complicates clinical management, although recent advancements in immune checkpoint inhibitors (ICIs) have shown some efficacy in treating HPV-associated PC. Ongoing research efforts aim to develop oncologic treatments that target HPV-induced cellular modifications. Additionally, novel therapeutic vaccines and adoptive T-cell therapies targeting HPV oncoproteins represent emerging treatment modalities. Our review highlights the complex interplay between HPV and penile carcinogenesis, emphasizing its epidemiology, etiology, clinicopathological characteristics, and potential therapeutic implications.

The role of cGAS-STING signaling in the development and therapy of head and neck squamous cell carcinoma

The cGAS-STING signaling pathway plays a critical role in innate immunity and defense against viral infections by orchestrating intracellular and adaptive immune responses to DNA. In the context of head and neck squamous cell carcinoma (HNSCC), this pathway has garnered significant attention due to its potential relevance in disease development and progression. HNSCC is strongly associated with risk factors such as smoking, heavy alcohol consumption, and human papillomavirus (HPV) infection. The presence or absence of HPV in HNSCC patients has been shown to have a profound impact on patient survival and prognosis, possibly due to the distinct biological characteristics of HPV-associated tumors. This review aims to provide a comprehensive overview of the current therapeutic approaches and challenges in HNSCC management, as well as the involvement of cGAS-STING signaling and its potential in the therapy of HNSCC. In addition, by advancing the present understanding of the mechanisms underlying this pathway, Activation of cGAS-STING-dependent inflammatory signaling downstream of chromosomal instability can exert both anti-tumoral and pro-tumoral effects in a cell-intrinsic manner, suggesting individualized therapy is of great importance. However, further exploration of the cGAS-STING signaling pathway is imperative for the effective management of HNSCC.

DNA damage response and inflammatory response: Two traffic lights for HPVs on the road to transformation

Human papillomaviruses (HPVs) are non-enveloped double-stranded DNA viruses. When HPV infection persists, infected tissues can develop many HPV-related diseases such as cervical cancer and head and neck squamous cell carcinoma. To establish their persistent infection, HPVs have evolved mechanisms to manipulate the host cellular processes such as DNA damage response (DDR), which includes homologous recombination, nonhomologous end joining, and microhomology-mediated end joining. Additionally, HPVs utilize host inflammatory processes to facilitate their life cycles. Here, we bridge the concepts of DDR and inflammatory response, and discuss how HPV proteins orchestrate a sophisticated manipulation of DDR and inflammation to promote their viral replication, ultimately fostering the progression of infected cells towards oncogenic transformation to malignancy.

Allelic loss of HLA class I facilitates evasion from immune surveillance in cervical intraepithelial neoplasia

Loss of heterozygosity (LOH) has been reported to occur in HLA regions in cervical intraepithelial neoplasia (CIN) and cervical cancer. However, the details of how this is related to the progression of CIN have been unclear. In this study, we examined the human papillomavirus (HPV) antigen-presenting capacity of people with CIN and the significance of LOH of HLA class I in the progression of CIN. It was shown that differences in antigen-presenting capacity among each case depended on HLA types, not HPV genotypes. Focusing on the HLA type, there was a positive correlation between antigen-presenting capacity against HPV and the frequency of allelic loss. Furthermore, the lost HLA-B alleles had a higher HPV antigen-presenting capacity than intact alleles. In addition, frequency of LOH of HLA class I was significantly higher in advanced CIN (CIN2-3) than in cervicitis or early-stage CIN (CIN1): around half of CIN2-3 had LOH of any HLA class I. Moreover, the antigen-presenting capacity against E5, which is the HPV proteins that facilitate viral escape from this immune surveillance by suppressing HLA class I expression, had the most significant impact on the LOH in HLA-B. This study suggests that HPV evades immune surveillance mechanisms when host cells lose the capacity for antigen presentation by HLA class I molecules, resulting in long-term infection and progression to advanced lesions.

Interferon-γ-induced GBP1 is an inhibitor of human papillomavirus 18

BACKGROUND

Human papillomavirus (HPV) infection is an important factor leading to cervical cell abnormalities. 90% of cervical cancers are closely associated with persistent infection of high-risk HPV, with the highest correlation with HPV16 and 18. Currently available vaccines and antivirals have limited effectiveness and coverage. Guanylate binding protein 1 (GBP1) was induced by interferon gamma and involved in many important cellular processes such as clearance of various microbial pathogens. However, whether GBP1 can inhibit human papillomavirus infection is unclear.

RESULTS

In this study, we found that GBP1 can effectively degrade HPV18 E6, possibly through its GTPase activity or other pathways, and E6 protein degrades GBP1 through the ubiquitin-proteasome pathway to achieve immune escape.

CONCLUSION

Therefore, GBP1 is an effector of IFN-γ anti-HPV activity. Our findings provided new insights into the treatment of HPV 18 infections.

STINGing Defenses: Unmasking the Mechanisms of DNA Oncovirus-Mediated Immune Escape

DNA oncoviruses represent an intriguing subject due to their involvement in oncogenesis. These viruses have evolved mechanisms to manipulate the host immune response, facilitating their persistence and actively contributing to carcinogenic processes. This paper describes the complex interactions between DNA oncoviruses and the innate immune system, with a particular emphasis on the cGAS-STING pathway. Exploring these interactions highlights that DNA oncoviruses strategically target and subvert this pathway, exploiting its vulnerabilities for their own survival and proliferation within the host. Understanding these interactions lays the foundation for identifying potential therapeutic interventions. Herein, we sought to contribute to the ongoing efforts in advancing our understanding of the innate immune system in oncoviral pathogenesis.

Molecular aspects of cervical cancer: a pathogenesis update

Cervical cancer (CC) is a significant health problem, especially in low-income countries. Functional studies on the human papillomavirus have generated essential advances in the knowledge of CC. However, many unanswered questions remain. This mini-review discusses the latest results on CC pathogenesis, HPV oncogenesis, and molecular changes identified through next-generation technologies. Interestingly, the percentage of samples with HPV genome integrations correlates with the degree of the cervical lesions, suggesting a role in the development of CC. Also, new functions have been described for the viral oncoproteins E5, E6, and E7, resulting in the acquisition and maintenance of cancer hallmarks, including proliferation, immune response evasion, apoptosis, and genomic instability. Remarkably, E5 oncoprotein affects signaling pathways involved in the expression of interferon-induced genes and EGFR-induced proliferation, while E6 and E7 oncoproteins regulate the DNA damage repair and cell cycle continuity pathways. Furthermore, next-generation technologies provide vast amounts of information, increasing our knowledge of changes in the genome, transcriptome, proteome, metabolome, and epigenome in CC. These studies have identified novel molecular traits associated with disease susceptibility, degree of progression, treatment response, and survival as potential biomarkers and therapeutic targets.

Insights into the mechanisms and structure of breakage-fusion-bridge cycles in cervical cancer using long-read sequencing

Cervical cancer is caused by human papillomavirus (HPV) infection, has few approved targeted therapeutics, and is the most common cause of cancer death in low-resource countries. We characterized 19 cervical and four head and neck cancer cell lines using long-read DNA and RNA sequencing and identified the HPV types, HPV integration sites, chromosomal alterations, and cancer driver mutations. Structural variation analysis revealed telomeric deletions associated with DNA inversions resulting from breakage-fusion-bridge (BFB) cycles. BFB is a common mechanism of chromosomal alterations in cancer, and our study applies long-read sequencing to this important chromosomal rearrangement type. Analysis of the inversion sites revealed staggered ends consistent with exonuclease digestion of the DNA after breakage. Some BFB events are complex, involving inter- or intra-chromosomal insertions or rearrangements. None of the BFB breakpoints had telomere sequences added to resolve the dicentric chromosomes, and only one BFB breakpoint showed chromothripsis. Five cell lines have a chromosomal region 11q BFB event, with YAP1-BIRC3-BIRC2 amplification. Indeed, YAP1 amplification is associated with a 10-year-earlier age of diagnosis of cervical cancer and is three times more common in African American women. This suggests that individuals with cervical cancer and YAP1-BIRC3-BIRC2 amplification, especially those of African ancestry, might benefit from targeted therapy. In summary, we uncovered valuable insights into the mechanisms and consequences of BFB cycles in cervical cancer using long-read sequencing.

Human Papilloma Virus Positive Oropharyngeal Squamous Cell Carcinoma and the Immune System: Pathogenesis, Immunotherapy and Future Perspectives

Oropharyngeal squamous cell carcinoma (OPSCC), a subset of head and neck squamous cell carcinoma (HNSCC), involves the palatine tonsils, soft palate, base of tongue, and uvula, with the ability to spread to adjacent subsites. Personalized treatment strategies for Human Papillomavirus-associated squamous cell carcinoma of the oropharynx (HPV+OPSCC) are yet to be established. In this article, we summarise our current understanding of the pathogenesis of HPV+OPSCC, the intrinsic role of the immune system, current ICI clinical trials, and the potential role of small molecule immunotherapy in HPV+OPSCC.

Computational and AI-driven 3D structural analysis of human papillomavirus (HPV) oncoproteins E5, E6, and E7 reveal significant divergence of HPV E5 between low-risk and high-risk genotypes

There are over 220 identified genotypes of Human papillomavirus (HPV), and the HPV genome encodes 3 major oncogenes, E5, E6, and E7. Conservation and divergence in protein sequence and function between low-risk versus high-risk oncogenic HPV genotypes has not been fully characterized. Here, we used modern computational and structural folding algorithms to perform a comparative analysis of HPV E5, E6, and E7 between multiple low risk and high risk genotypes. We first identified significantly greater sequence divergence in E5 between low- and high-risk genotypes compared to E6 and E7. Next, we used AlphaFold to model the structure of papillomavirus proteins and complexes with high confidence, including some with no established consensus structure. We observed that HPV E5, but not E6 or E7, had a dramatically different 3D structure between low-risk and high-risk genotypes. To our knowledge, this is the first comparative analysis of HPV proteins using Alphafold artificial intelligence (AI) system. The marked differences in E5 sequence and structure in high-risk HPVs may contribute in important and underappreciated ways to the development of HPV-associated cancers.

Immune escape of head and neck cancer mediated by the impaired MHC-I antigen presentation pathway

Tumor immune evasion is a hallmark of Head and Neck Cancers. The advent of immune checkpoint inhibitors (ICIs) in the first-line setting has transformed the management of these tumors. Unfortunately, the response rate of Head and Neck Squamous Cell Carcinomas (HNSCC) to ICIs is below 15%, regardless of the human papillomavirus (HPV) status, which might be partially related with impaired antigen presentation machinery (APM). Mechanistically, HNSCC cells are usually defective in the expression of MHC-I associated APM, while this transcriptional pathway is critical for the activation of tumor-killing effector T-cells. To specifically illuminate the phenomenon and seek for therapeutic strategies, this review summarizes the most recently identified role of genetic and functional dysregulation of the MHC-I pathway, specifically through changes at the genetic, epigenetic, post-transcriptional, and post-translational levels, which substantially contributes to HNSCC immune escape and ICI resistance. Several treatment modalities can be potentially exploited to restore APM signaling in tumors, which improves anti-tumor immunity through the activation of interferons, vaccines or rimantadine against HPV and the inhibition of EGFR, SHP-2, PI3K and MEK. Additionally, the combinatorial use of radiotherapy or cytotoxic agents with ICIs can synergize to potentiate APM signaling. Future directions would include further dissection of MHC-I related APM signaling in HNSCC and whether reversing this inhibition in combination with ICIs would elicit a more robust immune response leading to improved response rates in HNSCC. Therapeutic approaches to restore the MHC-I antigen presentation machinery in Head and Neck Cancer. (Red color texts represent the according strategies and the outcomes).

Rescue of NLRC5 expression restores antigen processing machinery in head and neck cancer cells lacking functional STAT1 and p53

The antigen processing machinery (APM) components needed for a tumor cell to present an antigen to a T cell are expressed at low levels in solid tumors, constituting an important mechanism of immune escape. More than most other solid tumors, head and neck squamous cell carcinoma (HNSCC) cells tend to have low APM expression, rendering them insensitive to immune checkpoint blockade and most other forms of immunotherapy. In HNSCC, this APM deficiency is largely driven by high levels of EGFR and SHP2, leading to low expression and activation of STAT1; however, recent studies suggest that p53, which is often mutated in HNSCCs, may also play a role. In the current study, we aimed to investigate the extent to which STAT1 and p53 individually regulate APM component expression in HNSCC cells. We found that in cells lacking functional p53, APM expression could still be induced by interferon-gamma or DNA-damaging chemotherapy (cisplatin) as long as STAT1 expression remained intact; when both transcription factors were knocked down, APM component expression was abolished. When we bypassed these deficient pathways by rescuing the expression of NLRC5, APM expression was also restored. These results suggest that dual loss of functional STAT1 and p53 may render HNSCC cells incapable of processing and presenting antigens, but rescue of downstream NLRC5 expression may be an attractive strategy for restoring sensitivity to T cell-based immunotherapy.

Bioinformatics analysis of immune characteristics in tumors with alternative carcinogenesis pathways induced by human papillomaviruses

BACKGROUND

Human papillomaviruses (HPVs) induce a subset of head and neck squamous cell carcinomas (HNSCC) and anogenital cancers, particularly cervical cancer (CC). The major viral proteins that contribute to tumorigenesis are the E6 and E7 oncoproteins, whose expression is usually enhanced after the integration of viral DNA into the host genome. Recently, an alternative tumorigenesis pathway has been suggested in approximately half of HNSCC and CC cases associated with HPV infection. This pathway is characterized by extrachromosomal HPV persistence and increased expression of the viral E2, E4, and E5 genes. The E6, E7, E5, and E2 proteins have been shown to modify the expression of numerous cellular immune-related genes. The antitumor immune response is a critical factor in the prognosis of HPV-driven cancers, and its characterization may contribute to the prediction and personalization of the increasingly used cancer immunotherapy.

METHODS

We analyzed the immune characteristics of HPV-dependent tumors and their association with carcinogenesis types. Transcriptomic HNSCC and CC datasets from The Cancer Genome Atlas were used for this analysis.

RESULTS

Clustering with immune-related genes resulted in two clusters of HPV16-positive squamous cell carcinomas in both tumor types: cluster 1 had higher activation of immune responses, including stimulation of the antigen processing and presentation pathway, which was associated with higher immune cell infiltration and better overall survival, and cluster 2 was characterized by keratinization. In CC, the distribution of tumor samples into clusters 1 and 2 did not depend on the level of E2/E5 expression, but in HNSCC, most E2/E5-high tumors were localized in cluster 1 and E2/E5-low tumors in cluster 2. Further analysis did not reveal any association between the E2/E5 levels and the expression of immune-related genes.

CONCLUSIONS

Our results suggest that while the detection of immune responses associated with preserved expression of genes encoding components of antigen processing and presentation machinery in HPV-driven tumors may be markers of better prognosis and an important factor in therapy selection, the type of carcinogenesis does not seem to play a decisive role in the induction of antitumor immunity.

Human papillomaviruses: Knowns, mysteries, and unchartered territories

There has been an explosion in the number of papillomaviruses that have been identified and fully sequenced. Yet only a minute fraction of these has been studied in any detail. Most of our molecular research efforts have focused on the E6 and E7 proteins of "high-risk," cancer-associated human papillomaviruses (HPVs). Interactions of the high-risk HPV E6 and E7 proteins with their respective cellular targets, the p53 and the retinoblastoma tumor suppressors, have been investigated in minute detail. Some have thus questioned if research on papillomaviruses remains an exciting and worthwhile area of investigation. However, fundamentally new insights on the biological activities and cellular targets of the high-risk HPV E6 and E7 proteins have been discovered and previously unstudied HPVs have been newly associated with human diseases. HPV infections continue to be an important cause of human morbidity and mortality and since there are no antivirals to combat HPV infections, research on HPVs should remain attractive to new investigators and biomedical funding agencies, alike.

Human papillomavirus associated cervical lesion: pathogenesis and therapeutic interventions

Human papillomavirus (HPV) is the most prevalent sexually transmitted virus globally. Persistent high-risk HPV infection can result in cervical precancerous lesions and cervical cancer, with 70% of cervical cancer cases associated with high-risk types HPV16 and 18. HPV infection imposes a significant financial and psychological burden. Therefore, studying methods to eradicate HPV infection and halt the progression of precancerous lesions remains crucial. This review comprehensively explores the mechanisms underlying HPV-related cervical lesions, including the viral life cycle, immune factors, epithelial cell malignant transformation, and host and environmental contributing factors. Additionally, we provide a comprehensive overview of treatment methods for HPV-related cervical precancerous lesions and cervical cancer. Our focus is on immunotherapy, encompassing HPV therapeutic vaccines, immune checkpoint inhibitors, and advanced adoptive T cell therapy. Furthermore, we summarize the commonly employed drugs and other nonsurgical treatments currently utilized in clinical practice for managing HPV infection and associated cervical lesions. Gene editing technology is currently undergoing clinical research and, although not yet employed officially in clinical treatment of cervical lesions, numerous preclinical studies have substantiated its efficacy. Therefore, it holds promise as a precise treatment strategy for HPV-related cervical lesions.

The High-Risk Human Papillomavirus Type Influences the Tissue Microenvironment in Cervical Intraepithelial Neoplasia Grade 2

High-risk, cancer-causing human papillomavirus (HPV) types are associated with cervical precancer and cancer. A high proportion of high-risk HPV precancer lesions undergo immune-mediated regression. The purpose of this study was to determine if the tissue microenvironment of HPV16 and 18 (HPV16/18) cervical intraepithelial neoplasia grade 2 lesions differed from other high-risk types (HPV 'other'). Consistent with other studies, we found that progression to higher-grade disease was more frequent in HPV16/18 lesions when compared with HPV 'other' lesions. HPV16/18 lesions were significantly more likely to be indoleamine 2,3,-dioxygenase 1 (IDO1)-positive and were associated with reduced CD8 and FoxP3 T cells in the lesion. In the stroma, reduced Tbet- and CD32-positive cells and increased Blimp1-positive cells were significantly associated with HPV16/18 lesions when compared with HPV 'other' types. On analysis of the IDO1-positive tissues, lesional IDO1 was associated with significantly decreased numbers of CD4-, CD8-, and FoxP3-positive cells in the stroma compared with IDO1-negative tissues. These data suggest that IDO1 expression may impair infiltration of CD4, CD8, and FoxP3 cells into the stroma beneath the precancer lesion. Increased expression of IDO1 may contribute to immune avoidance and an increased frequency of disease progression in HPV16- and 18-positive lesions.

Insights into the Mechanisms and Structure of Breakage-Fusion-Bridge Cycles in Cervical Cancer using Long-Read Sequencing

Cervical cancer is caused by human papillomavirus (HPV) infection, has few approved targeted therapeutics, and is the most common cause of cancer death in low-resource countries. We characterized 19 cervical and four head and neck cell lines using long-read DNA and RNA sequencing and identified the HPV types, HPV integration sites, chromosomal alterations, and cancer driver mutations. Structural variation analysis revealed telomeric deletions associated with DNA inversions resulting from breakage-fusion-bridge (BFB) cycles. BFB is a common mechanism of chromosomal alterations in cancer, and this is one of the first analyses of these events using long-read sequencing. Analysis of the inversion sites revealed staggered ends consistent with exonuclease digestion of the DNA after breakage. Some BFB events are complex, involving inter- or intra-chromosomal insertions or rearrangements. None of the BFB breakpoints had telomere sequences added to resolve the dicentric chromosomes and only one BFB breakpoint showed chromothripsis. Five cell lines have a Chr11q BFB event, with YAP1/BIRC2/BIRC3 gene amplification. Indeed, YAP1 amplification is associated with a 10-year earlier age of diagnosis of cervical cancer and is three times more common in African American women. This suggests that cervical cancer patients with YAP1/BIRC2/BIRC3-amplification, especially those of African American ancestry, might benefit from targeted therapy. In summary, we uncovered new insights into the mechanisms and consequences of BFB cycles in cervical cancer using long-read sequencing.