High-risk human papillomavirus E7 expression reduces cell-surface MHC class I molecules and increases susceptibility to natural killer cells

Therapeutic options for human papillomavirus-positive tonsil and base of tongue cancer

The incidences of human papillomavirus-positive (HPV+) tonsillar and base tongue squamous cell carcinomas (TSCC and BOTSCC) have increased in recent decades. Notably, HPV+ TSCC and BOTSCC have a significantly better prognosis than their HPV-negative counterparts when treated with current surgical options, radiotherapy, or intensified chemoradiotherapy. However, a cure is not achieved in 20% of patients with HPV+ TSCC/BOTSCC. Meanwhile, cured patients often present with severe chronic side effects. This necessitates novel tailored alternatives, such as targeted therapy, immune checkpoint inhibitors (ICIs), and treatment de-escalation, together with better follow-up. Current precision medicine therefore focuses on detecting predictive and driver cancer genes to better stratify patient treatment, provide those with poor prognostic markers targeted therapy, and select those with favorable markers for de-escalated therapy. Moreover, detecting cell-free HPV DNA (cfHPV DNA) in plasma before and after treatment has been attempted to improve follow-up. In this context, this perspective discusses the significance of optimally defining HPV+ status, which requires HPV DNA and p16INKa overexpression, using prognostic markers, such as high CD8+ T-cell counts and HPV E2 mRNA expression, tumor size, and following cfHPV DNA for patient selection for specific therapies. Clinical trials with ICI with/without chemotherapy, targeted therapy with specific inhibitors-such as phosphoinositide 3-kinase and fibroblast growth factor receptor inhibitors-or immune therapy with various HPV-based vaccines for treating recurrences have yielded promising results.

Sexually transmitted human papillomavirus and related sequelae

SUMMARYMore than 40 types of sexually transmitted human papillomavirus (HPV) infect the oropharyngeal and anogenital mucosa-high-risk types are associated with precancerous and cancerous lesions of the cervix, vagina, vulva, penis, anus, and oropharynx, and low-risk types cause non-malignant disease, such as anogenital warts. Though most HPV infections resolve spontaneously, immunodeficiencies may result in persistent infection and increased risk of HPV-related sequelae. The mechanism by which HPV results in malignant transformation is multifaceted, involving interactions with numerous cellular pathways, the host immune system, and potentially the host microbiome. Vaccination against HPV is highly efficacious in the prevention of infection and related sequelae, and there now exist several approved formulations that protect against both high- and low-risk types. Despite the advent of vaccination, early detection and treatment of cervical and anal precancerous lesions continues to be integral to secondary prevention-molecular HPV testing, cytology, and tissue biopsy allow for triaging of patients, after which appropriate treatment with close follow-up can avert cancer development.

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.

Research progress on intratumoral microorganisms in renal cancer

The human body harbors a vast array of microorganisms. Changes in the microbial ecosystem can potentially lead to diseases, including cancer. Traditionally, research has focused more on the gut microbiota and its influence on cancer. However, with the advancement of sequencing technologies, scholars have discovered that microorganisms within kidney tissues are significant components of tumor tissues. Intratumoral microorganisms may affect tumor growth and development through certain mechanisms, influence the function of immune cells, or impact the effectiveness of chemotherapy or immunotherapy in patients. This paper reviews the latest progress in the research on intratumoral microorganisms in renal cancer (RCa). It summarizes the types and distribution characteristics of these microorganisms, discusses the close association between specific viral infections (such as HPV and EBV) and RCa, and highlights the role of microorganisms in the pathogenesis of RCa. This review provides new perspectives for understanding the pathogenic mechanisms of RCa, thereby offering potential clinical applications.

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.

Association of HLA class I and II genes with cervical cancer susceptibility in a Han Chinese population

Cervical cancer (CC) is one of the leading causes of cancer-related death in females worldwide. Genome-wide association studies (GWASs) have identified CC-related susceptibility loci in HLA regions. To investigate the associations between HLA genes and cervical intraepithelial neoplasia (CIN) or cervical cancer (CC), six loci of HLA class I (HLA-A, -B, and -C) and II (HLA-DRB1, -DPB1, and -DQB1) were selected for genotyping, and the associations between these alleles or their haplotypes with CIN or CC risk or protection from disease were evaluated. In total, 2193 participants, including 909 healthy individuals in the control group, 769 patients with CC, and 515 patients with CIN2+ (CIN II and III), were enrolled in the current study. HLA genes were genotyped using the NGSgo Illumina MiSeq workflow, and the associations between these loci and CIN2+ or CC at the allele and haplotype levels were analyzed. The allele frequencies of HLA-A*33:03, B*58:01, C*03:02, DPB1*05:01, and DRB1*12:01 were lower in both the CC and CIN2+ groups than in the control group, whereas those of B*55:02, C*04:03, and DPB1*03:01 were higher in the CC group than in the control group. In the histologic CC type analysis, the differences in the frequencies of these alleles in squamous cell carcinoma (SCC) of the cervix and stage I CC showed a consistent trend. In the haplotype analysis, the frequency of A*33:03-C*03:02-B*58:01 was lower in the CC and CIN2+ groups than in the control group, and that of A*24:02-C*04:03-B*15:25 was higher in the CC group than in both the control and CIN2+ groups. These three different haplotype frequencies were also identified in the FIGO CC stage analysis. In addition, in human papilloma virus (HPV) genotype analyses, the frequencies of HLA-C*03:02 and DPB1*05:01 were significantly lower in the CC and CIN2+ groups than in the control group, and in SCC subgroup, the frequencies of HLA-DQB1*04:01 and DRB1*04:05 were higher in the HPV other genotype infection group than in the HPV16 infection group. In both HPV16 single infection and coinfection with other HPVs, the frequency of haplotype A*33:03-C*03:02-B*58:01 was lower in both CC and CIN2+ than in the control group, while the frequencies of A*11:01-C*14:02-B*51:01 and A*24:02-C*03:04-B*13:01 were higher in the CIN2+ than in CC and the control group. In the HPV16 and other HPV infection comparisons, the frequencies of DRB1*04:05-DQB1*04:01-DPB1*02:01 and DRB1*11:01-DQB1*03:01-DPB1*05:01 were lower in the HPV16 infection group than in the other HPV infection group. Our results suggest that the HLA class I and II genes may affect the risk of CIN and CC as well as the histologic CC types and FIGO stages of CC in the Han Chinese population. In addition, HLA genes were associated with HPV16 infection at both the allelic and haplotype levels.

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.

PGE2 expression by HPV6/11-induced respiratory papillomas blocks NK cell activation in patients with recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP), a rare chronic disease caused primarily by human papillomavirus types 6 and 11, consists of repeated growth of premalignant papillomas in the airway. RRP is characterized by multiple abnormalities in innate and adaptive immunity. Natural killer (NK) cells play important roles in immune surveillance and are part of the innate immune responses that help prevent tumor growth. We identified that papillomas lack classical class I MHC and retain nonclassical class I MHC expression. Moreover, in this study, we have identified and characterized the mechanism that blocks NK cell targeting of papilloma cells. Here, we show for the first time that the PGE₂ secreted by papilloma cells directly inhibits NK cells activation/degranulation principally through the PGE₂ receptor EP2, and to a lesser extent through EP4 signaling. Thus, papilloma cells have a potent mechanism to block NK cell function that likely supports papilloma cell growth.

Implications and Emerging Therapeutic Avenues of Inflammatory Response in HPV+ Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinomas (HNSCC) are a heterogeneous group of malignancies which have shown exponential incidence in the last two decades especially due to human papillomavirus (HPV) infection. The HPV family comprises more than 100 types of viruses with HPV16 and HPV18 being the most prevalent strains in HNSCC. Literature data reveal that the mutation profile as well as the response to chemotherapy and radiotherapy are distinct among HPV+ versus HPV-negative tumors. Furthermore, the presence of the virus induces activation of an immune response, in particular the recruitment of specific antiviral T lymphocytes to tumor sites. These T cells when activated produce soluble factors including cytokines and chemokines capable of modifying the local immune tumor microenvironment and impact on tumor response to the treatment. In this comprehensive review we investigated current knowledge on how the presence of an HPV can modify the inflammatory response systemically and within the tumor microenvironment's immunological responses, thereby impacting on disease prognosis and survival. We highlighted the research gaps and emerging approaches necessary to discover novel immunotherapeutic targets for HPV-associated HNSCC.

Human Papillomavirus 16 E6 Suppresses Transporter Associated with Antigen-Processing Complex in Human Tongue Keratinocyte Cells by Activating Lymphotoxin Pathway

Simple Summary

There is still limited knowledge of the critical pathogenic processes by which HPV16 induces oral carcinogenesis. Therefore, we aimed to illuminate the oncogenic role of HPV16 in the context of oral squamous cell carcinomas (OSCCs). Using human tongue keratinocyte cells, we demonstrated that HPV16 E6 promotes LTα₁β₂ and LTβR expression, thus promoting the lymphotoxin signaling pathway and leading to suppression of the transporter associated with the antigen-processing complex (TAPs; TAP1 and TAP2). Additionally, in vitro, we also demonstrated regulation of the antigenic peptide-loaded machinery in HPV-infected OSCC tissues through analysis of the transcriptomic profiles of the head and neck squamous cell carcinoma (HNSCC) cohort from the TCGA database, which was validated using fresh biopsied specimens. Thus, our study enhances the proposed functional role of HPV16 E6-associated immune-evasive properties in oral epithelial cells, revealing a possible mechanism underlying the development of HPV-mediated OSCCs.

Abstract

Infection by high-risk human papillomaviruses (hrHPVs), including HPV type 16 (HPV16), is a major risk factor for oral squamous cell carcinomas (OSCCs). However, the pathogenic mechanism by which hrHPVs promote oral carcinogenesis remains to be elucidated. Here, we demonstrated that the suppression of a transporter associated with the antigen-processing complex (TAPs; TAP1 and TAP2), which is a key molecule in the transportation of viral antigenic peptides into MHC class-I cells, is affected by the E6 protein of HPV16. Mechanistically, HPV-mediated immune evasion is principally mediated via the signal-transduction network of a lymphotoxin (LT) pathway, in particular LTα₁β₂ and LTβR. Our analysis of transcriptomic data from an HNSCC cohort from the Cancer Genome Atlas (TCGA) indicated that expression of TAP genes, particularly TAP2, was downregulated in HPV-infected cases. We further demonstrated that LTα₁β₂ and LTβR were upregulated, which was negatively correlated with TAP1 and TAP2 expression in HPV-positive clinical OSCC samples. Taken together, our findings imply that HPV16 E6 regulates the machinery of the antigenic peptide-loading system and helps to clarify the role of oncogenic viruses in the context of oral carcinoma.

Non-human primate papillomavirus E6-mediated p53 degradation reveals ancient evolutionary adaptation of carcinogenic phenotype to host niche

Non-human primates (NHPs) are infected with papillomaviruses (PVs) closely related to their human counterparts, but there are few studies on the carcinogenicity of NHP-PVs. Using an in vitro cell co-transfection assay, we systematically screened the biochemical activity of E6 proteins encoded by macaque PVs for their ability to bind and promote degradation of host p53 proteins. A host species barrier exists between HPV16 and MfPV3 with respect to E6-mediated p53 degradation that is reversed when p53 residue 129 is swapped between human and macaque hosts. Systematic investigation found that E6 proteins encoded by most macaque PV types in the high-risk species α12, but not other Alpha-PV clades or Beta-/Gamma-PV genera, can effectively promote monkey p53 degradation. Interestingly, two macaque PV types (MfPV10 and MmPV1) can simultaneously inhibit the expression of human and monkey p53 proteins, revealing complex cross-host interactions between PV oncogenes and host proteomes. Single point-mutant experiments revealed that E6 residue 47 directly interacts with p53 residue 129 for host-specific degradation. These findings suggest an ancient host niche adaptation toward a carcinogenic phenotype in high-risk primate PV ancestors. Following periods of primate host speciation, a loss-of-function mutation model could be responsible for the formation of a host species barrier to E6-mediated p53 degradation between HPVs and NHP-PVs. Our work lays a genetic and functional basis for PV carcinogenicity, which provides important insights into the origin and evolution of specific pathogens in host pathogenesis.

Importance of the Immune Microenvironment in the Spontaneous Regression of Cervical Squamous Intraepithelial Lesions (cSIL) and Implications for Immunotherapy

Cervical high-grade squamous intraepithelial lesions (cHSILs) develop as a result of a persistent high-risk human papilloma virus (hrHPV) infection. The natural course of cHSIL is hard to predict, depending on a multitude of viral, clinical, and immunological factors. Local immunity is pivotal in the pathogenesis, spontaneous regression, and progression of cervical dysplasia; however, the underlying mechanisms are unknown. The aim of this review is to outline the changes in the immune microenvironment in spontaneous regression, persistence, and responses to (immuno)therapy. In lesion persistence and progression, the immune microenvironment of cHSIL is characterized by a lack of intraepithelial CD3+, CD4+, and CD8+ T cell infiltrates and Langerhans cells compared to the normal epithelium and by an increased number of CD25+FoxP3+ regulatory T cells (Tregs) and CD163+ M2 macrophages. Spontaneous regression is characterized by low numbers of Tregs, more intraepithelial CD8+ T cells, and a high CD4+/CD25+ T cell ratio. A ‘hot’ immune microenvironment appears to be essential for spontaneous regression of cHSIL. Moreover, immunotherapy, such as imiquimod and therapeutic HPV vaccination, may enhance a preexisting pro-inflammatory immune environment contributing to lesion regression. The preexisting immune composition may reflect the potential for lesion regression, leading to a possible immune biomarker for immunotherapy in cHSILs.

HPV infection alters vaginal microbiome through down-regulating host mucosal innate peptides used by Lactobacilli as amino acid sources

Despite the high prevalence of both cervico-vaginal human papillomavirus (HPV) infection and bacterial vaginosis (BV) worldwide, their causal relationship remains unclear. While BV has been presumed to be a risk factor for HPV acquisition and related carcinogenesis for a long time, here, supported by both a large retrospective follow-up study (n = 6,085) and extensive in vivo data using the K14-HPV16 transgenic mouse model, we report a novel blueprint in which the opposite association also exists. Mechanistically, by interacting with several core members (NEMO, CK1 and β-TrCP) of both NF-κB and Wnt/β-catenin signaling pathways, we show that HPV E7 oncoprotein greatly inhibits host defense peptide expression. Physiologically secreted by the squamous mucosa lining the lower female genital tract, we demonstrate that some of these latter are fundamental factors governing host-microbial interactions. More specifically, several innate molecules down-regulated in case of HPV infection are hydrolyzed, internalized and used by the predominant Lactobacillus species as amino acid source sustaining their growth/survival. Collectively, this study reveals a new viral immune evasion strategy which, by its persistent/negative impact on lactic acid bacteria, ultimately causes the dysbiosis of vaginal microbiota.

HPV-associated oropharyngeal cancer: epidemiology, molecular biology and clinical management

Human papillomavirus (HPV)-positive (HPV⁺) oropharyngeal squamous cell carcinoma (OPSCC) has one of the most rapidly increasing incidences of any cancer in high-income countries. The most recent (8th) edition of the UICC/AJCC staging system separates HPV⁺ OPSCC from its HPV-negative (HPV⁻) counterpart to account for the improved prognosis seen in the former. Indeed, owing to its improved prognosis and greater prevalence in younger individuals, numerous ongoing trials are examining the potential for treatment de-intensification as a means to improve quality of life while maintaining acceptable survival outcomes. In addition, owing to the distinct biology of HPV⁺ OPSCCs, targeted therapies and immunotherapies have become an area of particular interest. Importantly, OPSCC is often detected at an advanced stage owing to a lack of symptoms in the early stages; therefore, a need exists to identify and validate possible diagnostic biomarkers to aid in earlier detection. In this Review, we provide a summary of the epidemiology, molecular biology and clinical management of HPV⁺ OPSCC in an effort to highlight important advances in the field. Ultimately, a need exists for improved understanding of the molecular basis and clinical course of this disease to guide efforts towards early detection and precision care, and to improve patient outcomes.

The incidence of human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (OPSCC) is increasing rapidly in most developed countries. In this Review, the authors provide an overview of the epidemiology, molecular biology and treatment of HPV-positive OPSCC, including discussions of the role of treatment de-escalation and emerging novel therapies.

The incidence of human papillomavirus-associated oropharyngeal cancer (HPV⁺ OPSCC) is expected to continue to rise over the coming decades until the benefits of gender-neutral prophylactic HPV vaccination begin to become manifest.

The incidence of HPV⁺ OPSCC appears to be highest in high-income countries, although more epidemiological data are needed from low- and middle-income countries, in which HPV vaccination coverage remains low.

The substantially better prognosis of patients with HPV⁺ OPSCC compared to those with HPV^– OPSCC has been recognized in the American Joint Committee on Cancer TNM8 staging guidelines, which recommend stratification by HPV status to improve staging.

The molecular biology and genomic features of HPV⁺ OPSCC are similar to those of other HPV-associated malignancies, with HPV oncogenes (E6 and E7) acting as key drivers of pathogenesis.

Treatment de-intensification is being pursued in clinical trials, although identifying the ~15% of patients with HPV⁺ OPSCC who have recurrent disease, and who therefore require more intensive treatment, remains a key challenge.

Prognostic Markers and Driver Genes and Options for Targeted Therapy in Human-Papillomavirus-Positive Tonsillar and Base-of-Tongue Squamous Cell Carcinoma

The incidence of Human-papillomavirus-positive (HPV⁺) tonsillar and base-of-tongue squamous cell carcinoma (TSCC and BOTSCC, respectively) is increasing epidemically, but they have better prognosis than equivalent HPV-negative (HPV⁻) cancers, with roughly 80% vs. 50% 3-year disease-free survival, respectively. The majority of HPV⁺ TSCC and BOTSCC patients therefore most likely do not require the intensified chemoradiotherapy given today to head and neck cancer patients and would with de-escalated therapy avoid several severe side effects. Moreover, for those with poor prognosis, survival has not improved, so better-tailored alternatives are urgently needed. In line with refined personalized medicine, recent studies have focused on identifying predictive markers and driver cancer genes useful for better stratifying patient treatment as well as for targeted therapy. This review presents some of these endeavors and briefly describes some recent experimental progress and some clinical trials with targeted therapy.

The human papillomavirus oncoproteins: a review of the host pathways targeted on the road to transformation

Persistent infection with high-risk human papillomaviruses (HR-HPVs) is the causal factor in over 99 % of cervical cancer cases, and a significant proportion of oropharyngeal and anogenital cancers. The key drivers of HPV-mediated transformation are the oncoproteins E5, E6 and E7. Together, they act to prolong cell-cycle progression, delay differentiation and inhibit apoptosis in the host keratinocyte cell in order to generate an environment permissive for viral replication. The oncoproteins also have key roles in mediating evasion of the host immune response, enabling infection to persist. Moreover, prolonged infection within the cellular environment established by the HR-HPV oncoproteins can lead to the acquisition of host genetic mutations, eventually culminating in transformation to malignancy. In this review, we outline the many ways in which the HR-HPV oncoproteins manipulate the host cellular environment, focusing on how these activities can contribute to carcinogenesis.

The immune response in HPV+ oropharyngeal cancer

Although human papillomavirus (HPV)⁺ oropharyngeal cancers often present with metastasis, most patients have excellent long-term survival. The reason underlying such an apparent contradiction remains unclear, but we have recently demonstrated that the improved survival of HPV⁺ oropharyngeal cancer patients has an immunological component, as the levels of tumor-infiltrating lymphocytes (TILs) can be used to stratify HPV⁺ patients into high-risk and low-risk groups.

Immunology of HPV-mediated cervical cancer: current understanding

Human papilloma virus (HPV) has emerged as a primary cause of cervical cancer worldwide. HPV is a relatively small (55 nm in diameter) and non-enveloped virus containing approximately 8 kb long double stranded circular DNA genome. To date, 228 genotypes of HPV have been identified. Although all HPV infections do not lead to the development of malignancy of cervix, only persistent infection of high-risk types of HPV (mainly with HPV16 and HPV18) results in the disease. In addition, the immunity of the patients also acts as a key determinant in the carcinogenesis. Since, no HPV type specific medication is available for the patient suffering with cervical cancer, hence, a deep understanding of the disease etiology may be vital for developing an effective strategy for its prevention and management. From the immunological perspectives, the entire mechanisms of disease progression still remain unclear despite continuous efforts. In the present review, the recent developments in immunology of HPV-mediated cervix carcinoma were discussed. At the end, the prevention of disease using HPV type specific recombinant vaccines was also highlighted.

PD-L1 Expression and a High Tumor Infiltrate of CD8+ Lymphocytes Predict Outcome in Patients with Oropharyngeal Squamous Cells Carcinoma

Carcinogenesis of human papillomavirus (HPV)-related (+) oropharyngeal squamous cell carcinoma (OPSCC) differs from HPV-negative (–) OPSCC. HPV-related immune-escape-mechanism could be responsible for the development and progression of HPV+ tumors and an immunophenotype different from HPV– OPSCC is expected. The purpose of this study was to analyze the expression of programmed cell death protein 1 ligand 1 (PD-L1) and its prognostic relevance in relation to CD8+ tumor infiltrating lymphocytes (TILs) and the major histocompatibility complex (MHC) I expression in OPSCC. We quantified PD-L1 expression on tumor cells (TC) and macrophages and MHC I expression in association to CD8⁺ TILs by immunohistochemistry on tissue microarray derived from 171 HPV+/-OPSCC. HPV-status was determined by p16^INK4a immunohistochemistry/HPV-DNA detection. Presence of CD8⁺ TILs, PD-L1 expression on TC, and a more frequent loss of MHC I in HPV+ compared to HPV- OPSCC was detected. A high amount of CD8⁺ TILs in the whole cohort and in HPV+ OPSCC and PD-L1 expression on TC in HPV- OPSCC was associated with favorable overall survival. There was a trend for an improved outcome according to PD-L1 expression (macrophages) in HPV+ OPSCC without reaching statistical significance. CD8⁺ TILs and PD-L1-expression have prognostic impact in OPSCC and might present useful biomarkers for predicting clinical outcome and personalized therapy concepts.

Mechanisms of Natural Killer Cell Evasion Through Viral Adaptation

The continuous interactions between host and pathogens during their coevolution have shaped both the immune system and the countermeasures used by pathogens. Natural killer (NK) cells are innate lymphocytes that are considered central players in the antiviral response. Not only do they express a variety of inhibitory and activating receptors to discriminate and eliminate target cells but they can also produce immunoregulatory cytokines to alert the immune system. Reciprocally, several unrelated viruses including cytomegalovirus, human immunodeficiency virus, influenza virus, and dengue virus have evolved a multitude of mechanisms to evade NK cell function, such as the targeting of pathways for NK cell receptors and their ligands, apoptosis, and cytokine-mediated signaling. The studies discussed in this article provide further insights into the antiviral function of NK cells and the pathways involved, their constituent proteins, and ways in which they could be manipulated for host benefit.

Protecting Tumors by Preventing Human Papilloma Virus Antigen Presentation: Insights from Emerging Bioinformatics Algorithms

Recent developments in bioinformatics technologies have led to advances in our understanding of how oncogenic viruses such as the human papilloma virus drive cancer progression and evade the host immune system. Here, we focus our review on understanding how these emerging bioinformatics technologies influence our understanding of how human papilloma virus (HPV) drives immune escape in cancers of the head and neck, and how these new informatics approaches may be generally applicable to other virally driven cancers. Indeed, these tools enable researchers to put existing data from genome wide association studies, in which high risk alleles have been identified, in the context of our current understanding of cellular processes regulating neoantigen presentation. In the future, these new bioinformatics approaches are highly likely to influence precision medicine-based decision making for the use of immunotherapies in virally driven cancers.

The Impact of Intratumoral and Gastrointestinal Microbiota on Systemic Cancer Therapy

The human microbiome is a complex aggregate of microorganisms, and their genomes exert a number of influences crucial to the metabolic, immunologic, hormonal, and homeostatic function of the host. Recent work, both in preclinical mouse models and human studies, has shed light on the impact of gut and tumor microbiota on responses to systemic anticancer therapeutics. In light of this, strategies to target the microbiome to improve therapeutic responses are underway, including efforts to target gut and intratumoral microbes. Here, we discuss mechanisms by which microbiota may impact systemic and antitumor immunity, in addition to outstanding questions in the field. A deeper understanding of these is critical as we devise putative strategies to target the microbiome.

Modulating the microbiome to improve therapeutic response in cancer

Although novel therapies, including immunotherapy, have dramatically improved outcomes for many patients with cancer, overall outcomes are heterogeneous and existing biomarkers do not reliably predict response. To date, predictors of response to cancer therapy have largely focused on tumour-intrinsic features; however, there is growing evidence that other host factors (eg, host genomics and the microbiome) can substantially affect therapeutic response. The microbiome, which refers to microbiota within a host and their collective genomes, is becoming increasingly recognised for its influence on host immunity, as well as therapeutic responses to cancer treatment. Importantly, microbiota can be modified via several different strategies, affording new angles in cancer treatment to improve outcomes. In this Review, we examine the evidence on the role of the microbiome in cancer and therapeutic response, factors that influence and shape host microbiota, strategies to modulate the microbiome, and present key unanswered questions to be addressed in ongoing and future research.

Microparticles produced by human papillomavirus type 16 E7-expressing cells impair antigen presenting cell function and the cytotoxic T cell response

High-risk, cancer-causing human papillomaviruses (HPV) cause infections of the epidermis that may progress to cancer, including cervical cancer. Viral persistence, contributed to by viral evasion of the host immune response, is associated with the likelihood of cancer developing. Langerhans cells (LCs) are the only professional antigen presenting cells located in the epidermis, therefore may influence the antiviral immune response. Microparticles, or microvesicles, are small membrane particles shed by cells that can exert effects on other cells at both a local and systemic level. We found increased numbers of microparticles were shed from human or mouse keratinocytes expressing the HPV16 E7 oncoprotein, compared with control keratinocytes. Co-culture of LCs with microparticles from E7-expressing cells suppressed the cytotoxic T cell response. We attributed this, at least in part, to the reduction in surface of CD40 and intracellular pro-inflammatory cytokine IL-12 p40 subunit that we measured in the LCs. The evidence provided here shows that co-culture of E7-microparticles with LCs inhibits antigen-specific cytotoxicity. This is an important finding, suggesting that microparticles from HPV-infected cells could suppress the T cell response by regulating LCs, potentially contributing to persistence of HPV infection and cancer.

Synthetic siRNA targeting human papillomavirus 16 E6: a perspective on in vitro nanotherapeutic approaches

High-risk human papillomaviruses infect skin and mucosa, causing approximately 5% of cancers worldwide. In the search for targeted nanotherapeutic approaches, siRNAs against the viral E6 transcript have been molecules of interest but have not yet seen successful translation into the clinic. By reviewing the past approximately 15 years of in vitro literature, we identify the need for siRNA validation protocols which concurrently evaluate ranges of key treatment parameters as well as characterize downstream process restoration in a methodical, quantitative manner and demonstrate their implementation using our own data. We also reflect on the future need for more appropriate cell culture models to represent patient lesions as well as the application of personalized approaches to identify optimal treatment strategies.

Analysis of Class I Major Histocompatibility Complex Gene Transcription in Human Tumors Caused by Human Papillomavirus Infection

Oncoproteins from high-risk human papillomaviruses (HPV) downregulate the transcription of the class I major histocompatibility complex (MHC-I) antigen presentation apparatus in tissue culture model systems. This could allow infected or transformed cells to evade the adaptive immune response. Using data from over 800 human cervical and head & neck tumors from The Cancer Genome Atlas (TCGA), we determined the impact of HPV status on the mRNA expression of all six MHC-I heavy chain genes, and the β2 microglobulin light chain. Unexpectedly, these genes were all expressed at high levels in HPV positive (HPV+) cancers compared with normal control tissues. Indeed, many of these genes were expressed at significantly enhanced levels in HPV+ tumors. Similarly, the transcript levels of several other components of the MHC-I peptide-loading complex were also high in HPV+ cancers. The coordinated expression of high mRNA levels of the MHC-I antigen presentation apparatus could be a consequence of the higher intratumoral levels of interferon γ in HPV+ carcinomas, which correlate with signatures of increased infiltration by T- and NK-cells. These data, which were obtained from both cervical and oral tumors in large human cohorts, indicates that HPV oncoproteins do not efficiently suppress the transcription of the antigen presentation apparatus in human tumors.

Human papillomavirus-driven immune deviation: challenge and novel opportunity for immunotherapy

It is now recognized that the immune system can be a key component of restraint and control during the neoplastic process. Human papillomavirus (HPV)-associated cancers of the anogenital tract and oropharynx represent a significant clinical problem but there is a clear opportunity for immune targeting of the viral oncogene expression that drives cancer development. However, high-risk HPV infection of the target epithelium and the expression of the E6/E7 oncogenes can lead to early compromise of the innate immune system (loss of antigen-presenting cells) facilitating viral persistence and increased risk of cancer. In these circumstances, a succession of interacting and self-reinforcing events mediated through modulation of different immune receptors, chemokine and cytokine responses (CCL20; CCL2; CCR2; IL-6; CCR7; IL-12) further promote the generation of an immune suppressive microenvironment [increased levels of Tregs, Th17, myeloid-derived suppressor cells (MDSCs) and PD-L1]. The overexpression of E6/E7 expression also compromises the ability to repair cellular DNA, leading to genomic instability, with the acquisition of genetic changes providing for the selection of advantaged cancer cells including additional strategies for immune escape. Therapeutic vaccines targeting the HPV oncogenes have shown some encouraging success in some recent early-phase clinical trials tested in patients with HPV-associated high-grade anogenital lesions. A significant hurdle to success in more advanced disease will be the local and systemic immune suppressive factors. Interventions targeting the different immunosuppressive components can provide opportunity to release existing or generate new and effective antitumour immunity. Treatments that alter the protumour inflammatory environment including toll-like receptor stimulation, inhibition of IL-6-related pathways, immune-checkpoint inhibition, direct modulation of MDSCs, Tregs and macrophages could all be useful in combination with therapeutic HPV vaccination. Future progress in delivering successful immunotherapy will depend on the configuration of treatment protocols in an insightful and timely combination.

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.

Human papillomavirus molecular biology and disease association

Human papillomaviruses (HPVs) have evolved over millions of years to propagate themselves in a range of different animal species including humans. Viruses that have co‐evolved slowly in this way typically cause chronic inapparent infections, with virion production in the absence of apparent disease. This is the case for many Beta and Gamma HPV types. The Alpha papillomavirus types have however evolved immunoevasion strategies that allow them to cause persistent visible papillomas. These viruses activate the cell cycle as the infected epithelial cell differentiates in order to create a replication competent environment that allows viral genome amplification and packaging into infectious particles. This is mediated by the viral E6, E7, and E5 proteins. High‐risk E6 and E7 proteins differ from their low‐risk counterparts however in being able to drive cell cycle entry in the upper epithelial layers and also to stimulate cell proliferation in the basal and parabasal layers. Deregulated expression of these cell cycle regulators underlies neoplasia and the eventual progression to cancer in individuals who cannot resolve high‐risk HPV infection. Most work to date has focused on the study of high‐risk HPV types such as HPV 16 and 18, which has led to an understanding of the molecular pathways subverted by these viruses. Such approaches will lead to the development of better strategies for disease treatment, including targeted antivirals and immunotherapeutics. Priorities are now focused toward understanding HPV neoplasias at sites other than the cervix (e.g. tonsils, other transformation zones) and toward understanding the mechanisms by which low‐risk HPV types can sometimes give rise to papillomatosis and under certain situations even cancers. Copyright © 2015 John Wiley & Sons, Ltd.

Classic and nonclassic HLA class I expression in penile cancer and relation to HPV status and clinical outcome

PURPOSE

Loss of expression of HLA class I is a mechanism of immune evasion in various cancers that is often associated with a worse patient outcome. We analyzed HLA expression in a large cohort with penile cancer in relation to clinical outcome.

MATERIALS AND METHODS

We used penile cancer tissue blocks from 168 patients who underwent surgical resection between 2000 and 2009 to construct tissue microarrays. Immunohistochemical staining was done with antibodies directed against classic and nonclassic HLA molecules. HLA expression was scored semiquantitatively, divided into 3 expression groups and correlated with clinicopathological variables, including HPV and survival. Survival analysis was performed using the Kaplan-Meier method and Cox proportional hazards models.

RESULTS

Complete and partial loss of total classic HLA class I was observed in 32% and 50% of cases, and up-regulation of HLA-E and G in 16% and 13%, respectively. When corrected for relevant clinical parameters, partial HLA-A loss was significantly associated with decreased survival overall (HR 2.3, 95% CI 1.1-4.6) and in HPV negative patients alone (HR 3.4, 95% CI 1.4-8.4). Abnormal HLA-B/C, E or G expression levels were not associated with survival.

CONCLUSIONS

To our knowledge this is the first study to describe a link between HLA expression and the clinical outcome of penile cancer. HLA down-regulation occurs frequently and partial loss of HLA-A is an independent predictor of poor survival in HPV negative patients. Complete understanding of the mechanisms and relevance of HLA down-regulation and immune evasion in regard to the clinical outcome will contribute to the future design of immunotherapy interventions.

NK cells and virus-related cancers

Natural killer (NK) cells become activated during viral infections and can play roles in such infections by attacking virus-infected cells or by regulating adaptive immune responses. Experimental models suggest that NK cells may also have the capacity to restrain virus-induced cancers. Here, we discuss the seven viruses linked to human cancers and the evidence of NK cell involvement in these systems.

HLA class I and II expression in oropharyngeal squamous cell carcinoma in relation to tumor HPV status and clinical outcome

HPV-DNA positive (HPVDNA+) oropharyngeal squamous cell carcinoma (OSCC) has better clinical outcome than HPV-DNA negative (HPVDNA-) OSCC. Current treatment may be unnecessarily extensive for most HPV+ OSCC, but before de-escalation, additional markers are needed together with HPV status to better predict treatment response. Here the influence of HLA class I/HLA class II expression was explored. Pre-treatment biopsies, from 439/484 OSCC patients diagnosed 2000-2009 and treated curatively, were analyzed for HLA I and II expression, p16(INK4a) and HPV DNA. Absent/weak as compared to high HLA class I intensity correlated to a very favorable disease-free survival (DFS), disease-specific survival (DSS) and overall survival (OS) in HPVDNA+ OSCC, both in univariate and multivariate analysis, while HLA class II had no impact. Notably, HPVDNA+ OSCC with absent/weak HLA class I responded equally well when treated with induction-chemo-radiotherapy (CRT) or radiotherapy (RT) alone. In patients with HPVDNA- OSCC, high HLA class I/class II expression correlated in general to a better clinical outcome. p16(INK4a) overexpression correlated to a better clinical outcome in HPVDNA+ OSCC. Absence of HLA class I intensity in HPVDNA+ OSCC suggests a very high survival independent of treatment and could possibly be used clinically to select patients for randomized trials de-escalating therapy.

Human papillomavirus, high-grade intraepithelial neoplasia and killer immunoglogulin-like receptors: a Western Australian cohort study

Background

Human papillomavirus (HPV) is the causative agent in cervical cancer and HPV genotypes 16 and 18 cause the majority of these cancers. Natural killer (NK) cells destroy virally infected and tumour cells via killer immunoglobulin-like receptors (KIR) that recognize decreased MHC class I expression. These NK cells may contribute to clearance of HPV infected and/or dysplastic cells, however since KIR controls NK cell activity, KIR gene variation may determine outcome of infection.

Methods

KIR gene frequencies were compared between 147 patients with a history of high-grade cervical intraepithelial neoplasia (CIN) and a control population of 187, to determine if any KIR genes are associated with high-grade CIN. In addition a comparison was also made between cases of high grade CIN derived from 30 patients infected with HPV 16/18 and 29 patients infected with non-16/18 HPV to determine if KIR variation contributes to the disproportional carcinogenesis derived from HPV 16/18 infection.

Results

High-grade CIN was weakly associated with the absence of KIR2DL2 and KIR2DS2 (p = 0.046 and 0.049 respectively, OR 0.6; 95% CI 0.4 – 0.9) but this association was lost after correction for multi-gene statistical analysis. No difference in KIR gene frequencies was found between high-grade CIN caused by HPV 16/18 and non-16/18.

Conclusion

No strong association between KIR genes, high-grade CIN and HPV genotype was found in the Western Australian population.

An RNA aptamer provides a novel approach for the induction of apoptosis by targeting the HPV16 E7 oncoprotein

BACKGROUND

Human papillomavirus 16 (HPV16) is a high-risk DNA tumour virus, which is a major causative agent of cervical cancer. Cellular transformation is associated with deregulated expression of the E6 and E7 oncogenes. E7 has been shown to bind a number of cellular proteins, including the cell cycle control protein pRb. In this study, RNA aptamers (small, single-stranded oligonucleotides selected for high-affinity binding) to HPV16 E7 were employed as molecular tools to further investigate these protein-protein interactions.

METHODOLOGY/PRINCIPAL FINDINGS

This study is focused on one aptamer (termed A2). Transfection of this molecule into HPV16-transformed cells resulted in inhibition of cell proliferation (shown using real-time cell electronic sensing and MTT assays) due to the induction of apoptosis (as demonstrated by Annexin V/propidium iodide staining). GST-pull down and bead binding assays were used to demonstrate that the binding of A2 required N-terminal residues of E7 known to be involved in interaction with the cell cycle control protein, pRb. Using a similar approach, A2 was shown to disrupt the interaction between E7 and pRb in vitro. Furthermore, transfection of HPV16-transformed cells with A2 appeared to result in the loss of E7 and rise in pRb levels, as observed by immunoblotting.

CONCLUSIONS/SIGNIFICANCE

This paper includes the first characterisation of the effects of an E7 RNA aptamer in a cell line derived from a cervical carcinoma. Transfection of cells with A2 was correlated with the loss of E7 and the induction of apoptosis. Aptamers specific for a number of cellular and viral proteins have been documented previously; one aptamer (Macugen) is approved for clinical use and several others are in clinical trials. In addition to its role as a molecular tool, A2 could have further applications in the future.

The immune response to papillomavirus during infection persistence and regression

Human papillomavirus (HPV) infections cause a significant global health burden, predominantly due to HPV-associated cancers. HPV infects only the epidermal cells of cutaneous and mucosal skin, without penetration into the dermal tissues. Infections may persist for months or years, contributed by an array of viral immune evasion mechanisms. However in the majority of cases immunity-based regression of HPV lesions does eventually occur. The role of the innate immune response to HPV in persistence and regression of HPV infection is not well understood. Although an initial inflammatory infiltrate may contribute to disease regression, sustained inflammation at the HPV-induced lesions, characterized by macrophage and neutrophil infiltration, has been observed in persistence. Pathogen-associated molecular patterns (PAMPs) are important in innate recognition. The double stranded DNA and an L1 and L2 capsid components of the HPV virion are potential PAMPs that can trigger signaling through cellular pattern recognition receptors, including toll-like receptors (TLR). TLR expression is increased in regressing HPV disease but is reduced in persistent lesions, suggesting a role for TLR in HPV regression. With regard to the adaptive immune response, a key indicator of regression in humans is infiltration of the lesion with both CD4 and CD8 T cells. In individuals with persistent lesions, CD8 T cell and immune suppressive regulatory T cells (Tregs) infiltrate the infection site. There is no association between persistence or regression and the presence of serum antibodies to the viral capsid antigens of HPV. There is still much to be learned about the immunological events that trigger regression of HPV disease. Understanding the viral and host factors that influence persistence and regression is important for the development of better immunotherapeutic treatments for HPV-associated disease.

Interaction of epithelial biomarkers, local immune response and condom use in cervical intraepithelial neoplasia 2-3 regression

OBJECTIVE

Cervical intraepithelial neoplasia grades 2-3 (CIN2-3) are usually treated by cone excision, although only 30% progress to cancer and 6-50% regress spontaneously. Biomarkers predicting CIN2-3 regression would be of great clinical value and could reduce unnecessary cone excision and associated complications. The aim of this study was to investigate whether punch-biopsy derived immunohistochemical biomarkers, local immune response, CIN lesion size and condom use are independently correlated to regression of CIN2-3.

METHODS

A prospective population-based cohort study of 162 women aged 25-40, with first-time onset diagnosis of CIN2-3 in colposcopy-directed biopsies was carried out. The median biopsy-cone interval was 16 weeks. Regression was defined as CIN1 or less in the cone biopsy.

RESULTS

The regression rate was 21% (34/162). pRb>30% in the lower epithelial half was the strongest predictor for regression (30% regression, p<0.0001). If additionally a CIN-lesion was smaller than 2.5mm and CD4+ lymphoid cells in the subepithelial stroma ≤ 195 per 1.04 mm basal membrane, the regression rate was 53%. In CIN-lesions>2.5mm and CD4+-stroma ≤195, consistent condom use increased the regression rate from 13% to 67% (p=0.003). If pRb was ≤30%, the regression rate was low (6%).

CONCLUSION

Biomarkers and CIN lesion length can predict CIN2-3 regression, and might be helpful to identify patients who can increase the regression rate of CIN lesions by consistent condom use.

Susceptibility to cervical cancer: an overview

Cervical cancer is the second most common cancer in females worldwide. It is well-established that Human Papillomavirus (HPV) infections play a critical role in the development of cervical cancer. However, a large number of women infected with oncogenic HPV types will never develop cervical cancer. Thus, there are several external environment and genetic factors involved in the progression of a precancerous lesion to invasive cancer. In this review article, we addressed possible susceptible phenotypes to cervical cancer, focusing on host genome and HPV DNA variability, multiple HPV infections, co-infection with other agents, circulating HPV DNA and lifestyle.

Human papillomavirus entry into NK cells requires CD16 expression and triggers cytotoxic activity and cytokine secretion

Human papillomavirus (HPV) infections account for more than 50% of infection-linked cancers in women worldwide. The immune system controls, at least partially, viral infection and around 90% of HPV-infected women clear the virus within two years. However, it remains unclear which immune cells are implicated in this process and no study has evaluated the direct interaction between HPVs and NK cells, a key player in host resistance to viruses and tumors. We demonstrated an NK-cell infiltration in HPV-associated preneoplastic cervical lesions. Since HPVs cannot grow in vitro, virus-like particles (VLPs) were used as a model for studying the NK-cell response against the virus. Interestingly, NK cells displayed higher cytotoxic activity and cytokine production (TNF-α and IFN-γ) in the presence of HPV-VLPs. Using flow cytometry and microscopy, we observed that NK-cell stimulation was linked to rapid VLP entry into these cells by macropinocytosis. Using CD16(+) and CD16(-) NK-cell lines and a CD16-blocking antibody, we demonstrated that CD16 is necessary for HPV-VLP internalization, as well as for degranulation and cytokine production. Thus, we show for the first time that NK cells interact with HPVs and can participate in the immune response against HPV-induced lesions.

Regulation of immune responses to HPV infection and during HPV-directed immunotherapy

The recent development of vaccines prophylactic against human papillomavirus (HPV) infection has the potential to reduce the incidence of cervical cancer globally by up to 70% over the next 40 years, if universal immunization is adopted. As these prophylactic vaccines do not alter the natural history of established HPV infection, immunotherapies to treat persistent HPV infection and associated precancers would be of benefit to assist with cervical cancer control. Efforts to develop immuno-therapeutic vaccines have been hampered by the relative non-immunogenicity of HPV infection, by immunoregulatory processes in skin, and by subversion of immune response induction and immune effector functions by papillomavirus proteins. This review describes HPV-specific immune responses induced by viral proteins, their regulation by host and viral factors, and highlights some conclusions from our own recent research.

Human papillomavirus 16 E5 modulates the expression of host microRNAs

Human papillomavirus (HPV) infection is a prerequisite of developing cervical cancer, approximately half of which are associated with HPV type 16. HPV 16 encodes three oncogenes, E5, E6, and E7, of which E5 is the least studied so far. Its roles in regulating replication and pathogenesis of HPV are not fully understood. Here we utilize high-throughput screening to coordinately investigate the effect of E5 on the expression of host protein-coding and microRNA genes. MicroRNAs form a class of 22nt long noncoding RNAs with regulatory activity. Among the altered cellular microRNAs we focus on the alteration in the expression of miR-146a, miR-203 and miR-324-5p and their target genes in a time interval of 96 hours of E5 induction. Our results indicate that HPV infection and subsequent transformation take place through complex regulatory patterns of gene expression in the host cells, part of which are regulated by the E5 protein.

Identification of key amino acid residues that determine the ability of high risk HPV16-E7 to dysregulate major histocompatibility complex class I expression

High risk human Papillomavirus (HPV) types are the major causative agents of cervical cancer. Reduced expression of major histocompatibility complex class I (MHC I) on HPV-infected cells might be responsible for insufficient T cell response and contribute to HPV-associated malignancy. The viral gene product required for subversion of MHC I synthesis is the E7 oncoprotein. Although it has been suggested that high and low risk HPVs diverge in their ability to dysregulate MHC I expression, it is not known what sequence determinants of HPV-E7 are responsible for this important functional difference. To investigate this, we analyzed the capability to affect MHC I of a set of chimeric E7 variants containing sequence elements from either high risk HPV16 or low risk HPV11. HPV16-E7, but not HPV11-E7, causes significant diminution of mRNA synthesis and surface presentation of MHC I, which depend on histone deacetylase activity. Our experiments demonstrate that the C-terminal region within the zinc finger domain of HPV-E7 is responsible for the contrasting effects of HPV11- and HPV16-E7 on MHC I. By using different loss- and gain-of-function mutants of HPV11- and HPV16-E7, we identify for the first time a residue variation at position 88 that is highly critical for HPV16-E7-mediated suppression of MHC I. Furthermore, our studies suggest that residues at position 78, 80, and 88 build a minimal functional unit within HPV16-E7 required for binding and histone deacetylase recruitment to the MHC I promoter. Taken together, our data provide new insights into how high risk HPV16-E7 dysregulates MHC I for immune evasion.

RNA interference of human papillomavirus type 16 E7 increases HLA class I antigen expression in HaCaT-E7 cells

BACKGROUND

High-risk human papillomaviruses (HPVs) are the major causative agents of cervical cancer. The E7 protein of high-risk HPV disturbs cell cycle control and down-regulates components of the antigen presentation pathway, suggesting an ideal target for development of the immunotherapy in HPV-positive cervical cancers. We previously reported that HPV16 E7 could down-regulate cell-surface HLA class I antigen accompanying decreased expression of transporter associated with antigen processing 1 (TAP-1). The purpose of this study was to determine whether knockdown of HPV16 E7 could up-regulate surface HLA class I antigen expression in HPV16 E7 expressing HaCaT cells (HaCaT-E7).

METHODS

An E7-specific small interfering RNA (siRNA) was transfected into the HaCaT-E7 cells, and the expression of HPV16 E7 was measured by real-time reverse transcriptase polymerase chain reaction and Western blot. With the use of flow cytometry analysis, the levels of cell surface HLA class I antigen and intracellular TAP-1 expression were detected.

RESULTS

It was found that transfection of HPV16 E7-siRNA reduced HPV16 E7 expression as measured on messenger RNA and protein levels. The flow cytometry analysis showed that, compared with mock transfection, a statistically significant increase of approximately 75% in surface HLA class I levels was observed in HaCaT-E7 cells at 72 hours after transfection of E7 siRNA. Moreover, he knockdown of E7 in HaCaT-E7 cells could result in an increase of intracellular TAP-1 expression, which is essential for the expression of HLA class I at cell surface.

CONCLUSIONS

Our study showed that the knockdown of HPV16 E7 could increase cell surface HLA class I antigen expression in HaCaT-E7 cells. In addition, for HPV-positive human cervical cancer, our observations indicate that the HPV E7 gene is a target of choice.

Local immune response in the microenvironment of CIN2-3 with and without spontaneous regression

Fifteen to thirty percent of cases with histologically confirmed CIN2-3 in cervical biopsies regress spontaneously (ie, show CIN1 or less in the follow-up cervical cone). The balance between immune-reactive cells from the host and high-risk human papillomavirus (hrHPV) genotypes may provide a biological explanation for this phenomenon. We retrospectively studied 55 cases of CIN2-3 in a cervical biopsy with subsequent cervical cone to assess whether hrHPV genotypes (by AMPLICOR and Linear Array tests) CD4, CD8, CD25, CD138 and Foxp3 cells (by quantitative immunohistochemistry) in the cervical biopsies can predict regression (defined as CIN1 or less in the follow-up cone biopsy). Eighteen percent of the CIN2-3 cases regressed (median biopsy-cervical cone time interval: 12.0 weeks, range: 5.0-34.1 weeks). HPV-16 correlated with low CD8+ and high CD25+. None of the regressing CIN2-3 lesions contained HPV-16. The regressing CIN2-3 lesions had lower numbers of stromal CD138+ and higher numbers of stromal CD8+cells; higher stromal and intra-epithelial ratios of CD4+/CD25+ cells; higher ratios of CD8+/CD25+ cells and lower ratios of CD8+/CD4+, CD138+/Foxp3+ and CD25+/Foxp3+ cells in the stroma. With multivariate survival analysis, stromal CD8+ cell numbers, CD4+/CD25+ cell ratios and CD138+ cell numbers are found to be independent regression predictors. In conclusion, in non-HPV-16 CIN2-3 lesions, assessing stromal immune cells can be a useful prognostic indicator of regression or persistence.