Demethylation Therapy as a Targeted Treatment for Human Papillomavirus-Associated Head and Neck Cancer

Global DNA Methylation Level in Tumour and Margin Samples in Relation to Human Papilloma Virus and Epstein-Barr Virus in Patients with Oropharyngeal and Oral Squamous Cell Carcinomas

BACKGROUND

Aberrant DNA methylation is a common epigenetic modification in cancers, including oropharyngeal squamous cell carcinoma (OPSCC) and oral squamous cell carcinoma (OSCC). Therefore, the analysis of methylation levels appears necessary to improve cancer therapy and prognosis.

METHODS

The enzyme-linked immunosorbent assay (ELISA) was used to analyse global DNA methylation levels in OPSCC and OSCC tumours and the margin samples after DNA isolation. HPV detection was conducted by hybridisation using GenoFlow HPV Array Test Kits (DiagCor Bioscience Inc., Hong Kong, China). EBV detection was performed using real-time PCR with an EBV PCR Kit (EBV/ISEX/100, GeneProof, Brno, Czech Republic).

RESULTS

OPSCC tumour samples obtained from women showed lower global DNA methylation levels than those from men (1.3% vs. 3.5%, p = 0.049). The margin samples from OPSCC patients with HPV and EBV coinfection showed global DNA methylation lower than those without coinfection (p = 0.042). G3 tumours from OSCC patients had significantly lower levels of global DNA methylation than G2 tumours (0.98% ± 0.74% vs. 3.77% ± 4.97%, p = 0.010). Additionally, tumours from HPV-positive OSCC patients had significantly lower global DNA methylation levels than those from HPV-negative patients (p = 0.013). In the margin samples, we observed a significant negative correlation between global DNA methylation and the N stage of OSCC patients (rS = -0.33, p = 0.039). HPV-positive OPSCC patients had higher global DNA methylation levels than HPV-positive OSCC patients (p = 0.015).

CONCLUSION

We confirmed that methylation could be changed in relation to viral factors, such as HPV and EBV, as well as clinical and demographical parameters.

De-Escalated Therapy and Early Treatment of Recurrences in HPV-Associated Head and Neck Cancer: The Potential for Biomarkers to Revolutionize Personalized Therapy

Human papillomavirus-associated (HPV+) head and neck squamous cell carcinoma (HNSCC) is the most common HPV-associated cancer in the United States, with a rapid increase in incidence over the last two decades. The burden of HPV+ HNSCC is likely to continue to rise, and given the long latency between infection and the development of HPV+ HNSCC, it is estimated that the effect of the HPV vaccine will not be reflected in HNSCC prevalence until 2060. Efforts have begun to decrease morbidity of standard therapies for this disease, and its improved characterization is being leveraged to identify and target molecular vulnerabilities. Companion biomarkers for new therapies will identify responsive tumors. A more basic understanding of two mechanisms of HPV carcinogenesis in the head and neck has identified subtypes of HPV+ HNSCC that correlate with different carcinogenic programs and that identify tumors with good or poor prognosis. Current development of biomarkers that reliably identify these two subtypes, as well as biomarkers that can detect recurrent disease at an earlier time, will have immediate clinical application.

Role of DNA Methylation Profiles as Potential Biomarkers and Novel Therapeutic Targets in Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide and is associated with high mortality. The main reasons for treatment failure are a low rate of early diagnosis, high relapse rates, and distant metastasis with poor outcomes. These are largely due to a lack of diagnostic, prognostic, and predictive biomarkers in HNSCC. DNA methylation has been demonstrated to play an important role in the pathogenesis of HNSCC, and recent studies have also valued DNA methylation as a potential biomarker in HNSCC. This review summarizes the current knowledge on DNA methylation profiles in HPV-positive and HPV-negative HNSCC and how these may contribute to the pathogenesis of HNSCC. It also summarizes the potential value of DNA methylation as a biomarker in the diagnosis, prognosis, and prediction of the response to therapy. With the recent immunotherapy era in head and neck treatment, new strategies to improve immune responses by modulating TIMEs have been intensely investigated in early-phase trials. Therefore, this study additionally summarizes the role of DNA methylation in the regulation of TIMEs and potential predictive immunotherapy response biomarkers. Finally, this study reviews ongoing clinical trials using DNA methylation inhibitors in HNSCC.

Advances in molecular mechanism of HPV16 E5 oncoprotein carcinogenesis

For a considerable duration, cervical cancer has posed a significant risk to the well-being and survival of women. The emergence and progression of cervical cancer have garnered extensive attention, with prolonged chronic infection of HPV serving as a crucial etiological factor. Consequently, investigating the molecular mechanism underlying HPV-induced cervical cancer has become a prominent research area. The HPV molecule is composed of a long control region (LCR), an early coding region and a late coding region.The early coding region encompasses E1, E2, E4, E5, E6, E7, while the late coding region comprises L1 and L2 ORF.The investigation into the molecular structure and function of HPV has garnered significant attention, with the aim of elucidating the carcinogenic mechanism of HPV and identifying potential targets for the treatment of cervical cancer. Research has demonstrated that the HPV gene and its encoded protein play a crucial role in the invasion and malignant transformation of host cells. Consequently, understanding the function of HPV oncoprotein is of paramount importance in comprehending the pathogenesis of cervical cancer. E6 and E7, the primary HPV oncogenic proteins, have been the subject of extensive study. Moreover, a number of contemporary investigations have demonstrated the significant involvement of HPV16 E5 oncoprotein in the malignant conversion of healthy cells through its regulation of cell proliferation, differentiation, and apoptosis via diverse pathways, albeit the precise molecular mechanism remains unclear. This manuscript aims to provide a comprehensive account of the molecular structure and life cycle of HPV.The HPV E5 oncoprotein mechanism modulates cellular processes such as proliferation, differentiation, apoptosis, and energy metabolism through its interaction with cell growth factor receptors and other cellular proteins. This mechanism is crucial for the survival, adhesion, migration, and invasion of tumor cells in the early stages of carcinogenesis. Recent studies have identified the HPV E5 oncoprotein as a promising therapeutic target for early-stage cervical cancer, thus offering a novel approach for treatment.

Whole-genome DNA methylation and DNA methylation-based biomarkers in lung squamous cell carcinoma

Exploring early detection methods through comprehensive evaluation of DNA methylation for lung squamous cell carcinoma (LUSC) patients is of great significance. By using different machine learning algorithms for feature selection and model construction based on The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, five methylation biomarkers in LUSC (along with mapped genes) were identified including cg14823851 (TBX4), cg02772121 (TRIM15), cg10424681 (C6orf201), cg12910906 (ARHGEF4), and cg20181079 (OR4D11), achieving extremely high sensitivity and specificity in distinguishing LUSC from normal samples in independent cohorts. Pyrosequencing assay verified DNA methylation levels, meanwhile qRT-PCR and immunohistochemistry results presented their accordant methylation-related gene expression statuses in paired LUSC and normal lung tissues. The five methylation-based biomarkers proposed in this study have great potential for the diagnosis of LUSC and could guide studies in methylation-regulated tumor development and progression.

Methylation of Immune Gene Promoters in Oral and Oropharyngeal Cancer

The proportion of oral and oropharyngeal squamous cell carcinoma (OOSCC) that can be attributed to human papillomavirus (HPV) infection is growing nowadays. A potential factor indicating the occurrence of HPV-positive OSCC is a change in the degree of methylation of gene promoters that play a key role in the immune response. In this study, we investigated the difference in the methylation of EDARADD, GBP4, HAVCR2, HLA DPB1, IL12RB1, MARCO, and SIGLEC12 gene promoters in samples of healthy oral mucosa versus samples of oral and oropharyngeal cancer. The presence of HPV infection in samples was examined earlier. To determine the difference in methylation of those gene promotors, isolated and bisulfite-modified DNA was analysed by the methylation-specific PCR method. The investigated gene promoters were found to be more hypomethylated in the oral and oropharyngeal cancer samples in comparison to normal tissue. The proportion of unmethylated gene promoters was similar in HPV-positive and HPV-negative cancers, although the data should be confirmed on a larger set of samples. To conclude, in samples of healthy oral mucosa, the investigated gene promoters were found to be methylated in a high percentage (73.3% to 100%), while in oral and oropharyngeal cancer samples, they were methylated in a low percentage (11.1% to 37%), regardless of HPV infection.

Effects of CpG sites methylation modification of HPV16 integration essential gene on the proliferation of cervical cancer cells

PURPOSE

The mechanism of methylation of HPV CpG sites in the occurrence and prognosis of cervical carcinogenesis remains unclear. We investigated the effects of demethylation of the CpG sites of E2 and E6, essential genes of HPV16 integration, on cervical cancer cell expression, integration, and proliferation.

MATERIALS AND METHODS

HPV16-positive (Caski) cells were treated with different concentrations of the demethylation compound 5-aza-dc (0, 5, 10, 20 μmol/l) in vitro. After the intervention, the methylation statuses of HPV16 E2 and E6 were detected by TBS, the expression levels of E2 and E6 mRNA and protein were detected by real-time PCR and western blot, cell proliferation activity was detected by CCK8, and cell cycle and apoptosis were determined by FCM. GraphPad Prism version 8.4.2 and R version 4.2.3 were used for relevant data analyses.

RESULTS

The methylation levels of HPV16 E2 and E6 CpG sites decreased gradually with increasing 5-aza-dc intervention concentrations. With decreasing E2 and E6 methylation rates, E2 expression increased, the E2/E6 ratio increased, E6 expression decreased, and the growth inhibition rate of Caski cells increased. E2 and E6 expression were negatively and positively correlated with their degrees of methylation respectively, while the E2/E6 mRNA to protein ratio was negatively correlated with the methylation degrees of E2 and E6.

CONCLUSION

Demethylation can be used as a prospective treatment to affect HPV expression and persistent infection, providing a new theoretical basis for the clinical treatment of viral infections.

Exploring ABOBEC3A and APOBEC3B substrate specificity and their role in HPV positive head and neck cancer

APOBEC3 family members are cytidine deaminases catalyzing conversion of cytidine to uracil. Many studies have established a link between APOBEC3 expression and cancer development and progression, especially APOBEC3A (A3A) and APOBEC3B (A3B). Preclinical studies with human papillomavirus positive (HPV+) head and neck squamous cell carcinoma (HNSCC) and clinical trial specimens revealed induction of A3B, but not A3A expression after demethylation. We examined the kinetic features of the cytidine deaminase activity for full length A3B and found that longer substrates and a purine at −2 position favored by A3B, whereas A3A prefers shorter substrates and an adenine or thymine at −2 position. The importance and biological significance of A3B catalytic activity rather than A3A and a preference for purine at the −2 position was also established in HPV+ HNSCCs. Our study explored factors influencing formation of A3A and A3B-related cancer mutations that are essential for understanding APOBEC3-related carcinogenesis and facilitating drug discovery.

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A3B is upregulated after 5-AzaC treatment and related to 5-AzaC sensitivity in HPV+ HNSCC

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Full-length A3B prefers longer substrates and a purine at −2 site biochemically

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A3B also prefers a purine at −2 site in both HPV+ and HPV− HNSCC cells

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A3B signature at -2 site linked to poor patient survival in HPV+ HNSCC low smokers

Hypermethylation of PRKCZ Regulated by E6 Inhibits Invasion and EMT via Cdc42 in HPV-Related Head and Neck Squamous Cell Carcinoma

Purpose: To study the role of target genes with aberrant DNA methylation in HPV+ HNSCC. Methods: A HumanMethylation450 BeadChip array (Illumina) was used to identify differentially methylated genes. CCK-8, flow cytometry, wound healing, and cell invasion assays were conducted to analyze the biological roles of PRKCZ. Western blot, qRT-PCR, immunohistochemistry, and animal studies were performed to explore the mechanisms underlying the functions of PRKCZ. Results: We selected PRKCZ, which is associated with HPV infection, as our target gene. PRKCZ was hypermethylated in HPV+ HNSCC patients, and PRKCZ methylation status was negatively related to the pathological grading of HNSCC patients. Silencing PRKCZ inhibited the malignant capacity of HPV+ HNSCC cells. Mechanistically, HPV might promote DNMT1 expression via E6 to increase PRKCZ methylation. Cdc42 was required for the PRKCZ-mediated mechanism of action, contributing to the occurrence of epithelial-mesenchymal transition (EMT) in HPV+ HNSCC cells. In addition, blocking PRKCZ delayed tumor growth in HPV16-E6/E7 transgenic mice. Cdc42 expression was decreased, whereas E-cadherin levels increased. Conclusion: We suggest that PRKCZ hypermethylation induces EMT via Cdc42 to act as a potent tumor promoter in HPV+ HNSCC.

FBXL7 Body Hypomethylation Is Frequent in Tumors from the Digestive and Respiratory Tracts and Is Associated with Risk-Factor Exposure

Squamous cell carcinoma is the main histological tumor type in the upper aerodigestive tract (UADT), including the esophagus (ESCC) and the head and neck sites, as well as the oral cavity (OCSCC), larynx (LSCC) and oropharynx (OPSCC). These tumors are induced by alcohol and tobacco exposure, with the exception of a subgroup of OPSCC linked to human papillomavirus (HPV) infection. Few genes are frequently mutated in UADT tumors, pointing to other molecular mechanisms being involved during carcinogenesis. The F-box and leucine-rich repeat protein 7 (FBXL7) is a potential tumor-suppressing gene, one that is frequently hypermethylated in pancreatic cancer and where the encoded protein promotes the degradation of AURKA, BIRC5 and c-SRC. Thus, the aim of this study was to evaluate the methylation and expression profile of FBXL7 in the UADT and the gene’s association with the clinical, etiological and pathological characteristics of patients, as well as the expression of its degradation targets. Here we show that the FBXL7 gene’s body is hypomethylated in the UADT, independently of histology, but not in virus-associated tumors. FBXL7 body methylation and gene expression levels were correlated in the ESCC, LSCC, OCSCC and OPSCC. Immunohistochemistry analysis showed that FBXL7 protein levels are not correlated with the levels of its degradation targets, AURKA and BIRC5, in the UADT. The high discriminatory potential of FBXL7 body hypomethylation between non-tumor and tumor tissues makes it a promising biomarker.

Epigenetic and Transcriptomic Regulation Landscape in HPV+ Cancers: Biological and Clinical Implications

Human Papillomavirus (HPV) is an oncogenic virus that causes the highest number of viral-associated cancer cases and deaths worldwide, with more than 690,000 new cases per year and 342,000 deaths only for cervical cancer (CC). Although the incidence and mortality rates for CC are declining in countries where screening and vaccination programs have been implemented, other types of cancer in which HPV is involved, such as oropharyngeal cancer, are increasing, particularly in men. Mutational and transcriptional profiles of various HPV-associated neoplasms have been described, and accumulated evidence has shown the oncogenic capacity of E6, E7, and E5 genes of high-risk HPV. Interestingly, transcriptomic analysis has revealed that although a vast majority of the human genome is transcribed into RNAs, only 2% of transcripts are translated into proteins. The remaining transcripts lacking protein-coding potential are called non-coding RNAs. In addition to the transfer and ribosomal RNAs, there are regulatory non-coding RNAs classified according to size and structure in long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and small RNAs; such as microRNAs (miRNAs), piwi-associated RNAs (piRNAs), small nucleolar RNAs (snoRNAs) and endogenous short-interfering RNAs. Recent evidence has shown that lncRNAs, miRNAs, and circRNAs are aberrantly expressed under pathological conditions such as cancer. In addition, those transcripts are dysregulated in HPV-related neoplasms, and their expression correlates with tumor progression, metastasis, poor prognosis, and recurrence. Nuclear lncRNAs are epigenetic regulators involved in controlling gene expression at the transcriptional level through chromatin modification and remodeling. Moreover, disruption of the expression profiles of those lncRNAs affects multiple biological processes such as cell proliferation, apoptosis, and migration. This review highlights the epigenetic alterations induced by HPV, from infection to neoplastic transformation. We condense the epigenetic role of non-coding RNA alterations and their potential as biomarkers in transformation’s early stages and clinical applications. We also summarize the molecular mechanisms of action of nuclear lncRNAs to understand better their role in the epigenetic control of gene expression and how they can drive the malignant phenotype of HPV-related neoplasia. Finally, we review several chemical and epigenetic therapy options to prevent and treat HPV-associated neoplasms.

Differential responses to immune checkpoint inhibitor dictated by pre-existing differential immune profiles in squamous cell carcinomas caused by same initial oncogenic drivers

BACKGROUND

While immune checkpoint inhibitors (ICI) were approved for head and neck squamous cell carcinomas (HNSCCs), the response rate remains relatively low. Mechanisms underlying ICI unresponsiveness versus sensitivity are not fully understood.

METHOD

To better delineate differential responses to ICI treatment, we employed mouse SCC models, termed KPPA tumors that were caused by deleting p53 and hyperactivating PIK3CA, two most frequently mutated genes in human HNSCCs. We transplanted two KPPA tumor lines (TAb2 versus TCh3) into C57BL/6 recipients and examined the immune tumor microenvironment using flow cytometry. Furthermore, we employed single-cell RNA sequencing to identify the difference in tumor infiltrating lymphocytes (TILs).

RESULTS

We found that different KPPA tumors exhibited heterogeneous immune profiles pre-existing treatment that dictated their sensitivity or unresponsiveness to anti-PD-L1. Unresponsive TAb2 tumors were highly enriched with functional tumor-associated macrophages (TAMs), especially M2-TAMs. In contrast, sensitive TCh3 tumors contained more CD8 TILs with better effector functions. TAb2 tumor cells drastically expanded F4/80⁺ TAMs from bone marrow precursors, requiring CSF1 and VEGF. Consistently, a higher combined expression of VEGF-C and CSF1 predicts worse survival in PIK3CA^Amp/TP53^Mutated HNSCC patients. Unresponsive TAb2 tumors upregulated distinct signaling pathways that correlate with aggressive tumor phenotypes. While anti-PD-L1 did not affect the TME of TAb2 tumors, it significantly increased the number of CD8 TILs in TCh3 tumors.

CONCLUSIONS

We uncovered tumor-intrinsic differences that may underlie the differential responses to ICI by establishing and employing two SCC tumor lines, TAb2 vs. TCh3, both of which harbor TP53 deletion and PIK3CA hyperactivation. Our study indicates the limitation of stratifying cancers according to their genetic alterations and suggests that evaluating HNSCC tumor-intrinsic cues along with immune profiles in the TME may help better predict ICI responses. Our experimental models may provide a platform for pinpointing tumor-intrinsic differences underlying an immunosuppressive TME in HNSCCs and for testing combined immunotherapies targeting either tumor-specific or TAM-specific players to improve ICI efficacy.

High Risk-Human Papillomavirus in HNSCC: Present and Future Challenges for Epigenetic Therapies

Head and Neck Squamous Cell Carcinoma (HNSCC) is a highly heterogeneous group of tumors characterized by an incidence of 650,000 new cases and 350,000 deaths per year worldwide and a male to female ratio of 3:1. The main risk factors are alcohol and tobacco consumption and Human Papillomavirus (HPV) infections. HNSCC cases are divided into two subgroups, the HPV-negative (HPV−) and the HPV-positive (HPV+) which have different clinicopathological and molecular profiles. However, patients are still treated with the same therapeutic regimens. It is thus of utmost importance to characterize the molecular mechanisms underlying these differences to find new biomarkers and novel therapeutic targets towards personalized therapies. Epigenetic alterations are a hallmark of cancer and can be exploited as both promising biomarkers and potential new targets. E6 and E7 HPV oncoviral proteins besides targeting p53 and pRb, impair the expression and the activity of several epigenetic regulators. While alterations in DNA methylation patterns have been well described in HPV+ and HPV− HNSCC, accurate histone post-translational modifications (hPTMs) characterization is still missing. Herein, we aim to provide an updated overview on the impact of HPV on the hPTMs landscape in HNSCC. Moreover, we will also discuss the sex and gender bias in HNSCC and how the epigenetic machinery could be involved in this process, and the importance of taking into account sex and/or gender also in this field.

Harnessing the role of epigenetic histone modification in targeting head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent form of cancer worldwide. Despite advancements made in treatment strategies, the fatality rate of HNSCC is very high. An accumulating body of evidence suggests that epigenetic modification of histones plays an influential role in the development and progression of the disease. In this review we discuss the role of epigenetic modifications in HNSCC and the inter-relationships of human papillomavirus oncoproteins and histone-modifying agents. Further, we explore the possibility of identifying these modifications as biomarkers for their use as drugs in treatment strategies.

Epigenetic Regulation of Human T-Cell Leukemia Virus Gene Expression

Viral and cellular gene expression are regulated by epigenetic alterations, including DNA methylation, histone modifications, nucleosome positioning, and chromatin looping. Human T-cell leukemia virus type 1 (HTLV-1) is a pathogenic retrovirus associated with inflammatory disorders and T-cell lymphoproliferative malignancy. The transforming activity of HTLV-1 is driven by the viral oncoprotein Tax, which acts as a transcriptional activator of the cAMP response element-binding protein (CREB) and nuclear factor kappa B (NFκB) pathways. The epigenetic effects of Tax and the induction of lymphoproliferative malignancy include alterations in DNA methylation and histone modifications. In addition, alterations in nucleosome positioning and DNA looping also occur in HTLV-1-induced malignant cells. A mechanistic definition of these effects will pave the way to new therapies for HTLV-1-associated disorders.

HPV-induced cancers: preclinical therapeutic advancements

INTRODUCTION

High-risk HPV infections are related to several epithelial cancers. Despite the availability of prophylactic vaccines, HPV infections are still responsible for about 5% of all human malignancies worldwide. While therapeutic vaccines are ongoing clinical trials, genotoxic agents and surgical interventions represent current clinical treatments, with no specific anti-HPV drugs yet available in the clinics.

AREAS COVERED

We offer a comprehensive report of small molecules in preclinical studies proposed as potential anticancer agents against HPV-driven tumors. Given the importance of HPV oncoproteins for cancer maintenance, particularly E6 and E7, we present a classification of both non-targeted and targeted agents, with a further subdivision of the latter into two categories according to their either direct or indirect activity against viral protein functions.

EXPERT OPINION

Prophylactic vaccines can prevent the insurgence of HPV-related cancers, but have no effect against pre-existing infections. Moreover, their high cost, genotype-restricted effect and the growing worldwide distrust for vaccines make the availability of a specific drug an unmet medical need. Different viral early proteins emerge as ideal candidates for drug development. We highlight the most promising strategies and address future challenges in this field to herald the prospect of a specific therapeutic regimen against HPV-related cancers.

Association between promoter methylation and gene expression of CGB3 and NOP56 in HPV-infected cervical cancer cells

Overexpression of the E7 gene of human papillomavirus (HPV) type 16 is one of the primary causes of cervical cancer. The E7 protein can bind with DNA methyltransferase I and induce methylation of tumor suppressor genes, such as cyclin-A1 (CCNA1), leading to suppression of their expression, and thus, cancer progression. In the present study, the confirmation of methylation-related expression of chorionic gonadotropin subunit 3 (CGB3) and nucleolar protein 56 (NOP56) genes in 5-Azacytidine (5'-aza)-treated HPV16-positive SiHa and HPV16-negative C33A cell lines was shown. Using methylation-specific-PCR and quantitative PCR, the results showed that CGB3 and NOP56 methylation significantly decreased as the 5'-aza concentration was increased, and this was inversely associated with their expression. Moreover, overexpression of E7 contributed to the augmentation of CGB3 and NOP56 methylation levels in C33A cells, resulting in a decrease in their expression. This study extends on previous observations of E7 HPV16 oncogenic function in terms of methylation-repressing expression in more genes, which may be wholly applied to gene therapy in cervical cancer prevention.

Epigenetic Modifiers as Novel Therapeutic Targets and a Systematic Review of Clinical Studies Investigating Epigenetic Inhibitors in Head and Neck Cancer

Simple Summary

Head and neck cancer is the sixth most common malignancy worldwide and it affects approximately 50,000 patients annually in the United States. Current treatments are suboptimal and induce significant long-term toxicities that permanently affect quality of life. Novel therapeutic approaches are thus urgently needed to increase the survival and quality of life of these patients. Epigenetic modifications have been recognized as potential therapeutic targets in various cancer types, including head and neck cancer. The objective of this review is to provide a brief overview of the function of important epigenetic modifiers in head and neck cancer, and to discuss the results of past and ongoing clinical trials evaluating epigenetic interventions targeting these epigenetic modifiers in head and neck cancer patients. The field of epigenetic therapy in head and neck cancer is still nascent; however, it holds significant promise. Although more specific epigenetic drugs are being developed, we envision the rational design of clinical trials that will target a select group of head and neck cancer patients with epigenetic vulnerabilities that can be targeted in combination with immunotherapy, chemotherapy and/or radiotherapy, rendering higher and durable responses while minimizing chronic complications for patients with head and neck cancer.

Abstract

The survival rate of head and neck squamous cell carcinoma patients with the current standard of care therapy is suboptimal and is associated with long-term side effects. Novel therapeutics that will improve survival rates while minimizing treatment-related side effects are the focus of active investigation. Epigenetic modifications have been recognized as potential therapeutic targets in various cancer types, including head and neck cancer. This review summarizes the current knowledge on the function of important epigenetic modifiers in head and neck cancer, their clinical implications and discusses results of clinical trials evaluating epigenetic interventions in past and ongoing clinical trials as monotherapy or combination therapy with either chemotherapy, radiotherapy or immunotherapy. Understanding the function of epigenetic modifiers in both preclinical and clinical settings will provide insight into a more rational design of clinical trials using epigenetic interventions and the patient subgroups that may benefit from such interventions.

The Mouse Papillomavirus Epigenetic Signature Is Characterised by DNA Hypermethylation after Lesion Regression

Papillomaviruses (PVs) are double-stranded DNA tumour viruses that can infect cutaneous and mucosal epidermis. Human papillomavirus (HPV) types have been linked to the causality of cutaneous squamous cell carcinoma (cSCC); however, HPV DNA is not always detected in the resultant tumour. DNA methylation is an epigenetic change that can contribute to carcinogenesis. We hypothesise that the DNA methylation pattern in cells is altered following PV infection. We tested if DNA methylation was altered by PV infection in the mouse papillomavirus (MmuPV1) model. Immunosuppressed mice were infected with MmuPV1 on cutaneous tail skin. Immunosuppression was withdrawn for some mice, causing lesions to spontaneously regress. Reduced representation bisulphite sequencing was carried out on DNA from the actively infected lesions, visibly regressed lesions, and mock-infected control mice. DNA methylation libraries were generated and analysed for differentially methylated regions throughout the genome. The presence of MmuPV1 sequences was also assessed. We identified 834 predominantly differentially hypermethylated fragments in regressed lesions, and no methylation differences in actively infected lesions. The promoter regions of genes associated with tumorigenicity, including the tumour suppressor protein DAPK1 and mismatch repair proteins MSH6 and PAPD7, were hypermethylated. Viral DNA was detected in active lesions and in some lesions that had regressed. This is the first description of the genome-wide DNA methylation landscape for active and regressed MmuPV1 lesions. We propose that the DNA hypermethylation in the regressed lesions that we report here may increase the susceptibility of cells to ultraviolet-induced cSCC.

5-aza-2'-deoxycytidine induces apoptosis and inhibits tumour growth in vivo of FaDu cells, a specific HPVnegative HNSCC cell line

Head and neck cancer squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide, resulting in over 600,000 new diagnoses annually. Traditionally, HNCC has been related to tobacco and alcohol exposure; however, over the past decade, a growing number of head and neck cancers are attributed to human papillomavirus (HPV) infection. 5-Aza-2'-deoxycytidine (5-AzaD) was demonstrated as an effective chemotherapeutic agent for acute myelogenous leukaemia. Preclinical data revealed that 5-aza inhibits growth and increases cell death of HPV(+) cancer cells. These effects are associated with reduced expression of HPV genes, stabilization of TP53, and activation of TP53-dependent apoptosis. The aim of the present study is to test the effect of 5-AzaD on growth of human squamous cell carcinoma (FaDu), a HPV(-) and p53 mutated cells, in vitro and in vivo. The effect of 5-AzaD on cell viability, cell cycle progression and induction of apoptosis was tested in vitro. The effect of 5-AzaD on tumour growth in vivo was tested using xenograft mice inoculated with FaDu cells. The results indicated that 5-AzaD reduced cell viability and induced apoptosis in FaDu cells in vitro. In vivo studies revealed that 5-AzaD suppresses the growth of tumours in xenograft mice inoculated with FaDu cells through inhibition of proliferation and induction of apoptosis. These findings may emphasis that 5-AzaD is effective in treatment of HPV(-) HNSCC tumours through TP53 independent pathway. Future studies are needed in order to clarify the molecular mechanism of action of 5-AzaD in HPV(-) cancer cells.

Targeted Therapy as a Potential De-Escalation Strategy in Locally Advanced HPV-Associated Oropharyngeal Cancer: A Literature Review

The treatment landscape of locally advanced HPV-oropharyngeal squamous cell carcinoma (OPSCC) is undergoing transformation. This is because the high cures rates observed in OPSCC are paired with severe treatment-related, long-term toxicities. These significant adverse effects have led some to conclude that the current standard of care is over-treating patients, and that de-intensifying the regimens may achieve comparable survival outcomes with lower toxicities. Consequently, several de-escalation approaches involving locally advanced OPSCC are underway. These include the reduction of dosage and volume of intensive cytotoxic regimens, as well as elimination of invasive surgical procedures. Such de-intensifying treatments have the potential to achieve efficacy and concurrently alleviate morbidity. Targeted therapies, given their overall safer toxicity profiles, also make excellent candidates for de-escalation, either alone or alongside standard treatments. However, their role in these endeavors is currently limited, because few targeted therapies are currently in clinical use for head and neck cancers. Unfortunately, cetuximab, the only FDA-approved targeted therapy, has shown inferior outcomes when paired with radiation as compared to cisplatin, the standard radio-sensitizer, in recent de-escalation trials. These findings indicate the need for a better understanding of OPSCC biology in the design of rational therapeutic strategies and the development of novel, OPSCC-targeted therapies that are safe and can improve the therapeutic index of standard therapies. In this review, we summarize ongoing research on mechanism-based inhibitors in OPSCC, beginning with the salient molecular features that modulate tumorigenic processes and response, then exploring pharmacological inhibition and pre-clinical validation studies of candidate targeted agents, and finally, summarizing the progression of those candidates in the clinic.

Role of Virus-Induced Host Cell Epigenetic Changes in Cancer

The tumor viruses human T-lymphotropic virus 1 (HTLV-1), hepatitis C virus (HCV), Merkel cell polyomavirus (MCPyV), high-risk human papillomaviruses (HR-HPVs), Epstein-Barr virus (EBV), Kaposi’s sarcoma-associated herpes virus (KSHV) and hepatitis B virus (HBV) account for approximately 15% of all human cancers. Although the oncoproteins of these tumor viruses display no sequence similarity to one another, they use the same mechanisms to convey cancer hallmarks on the infected cell. Perturbed gene expression is one of the underlying mechanisms to induce cancer hallmarks. Epigenetic processes, including DNA methylation, histone modification and chromatin remodeling, microRNA, long noncoding RNA, and circular RNA affect gene expression without introducing changes in the DNA sequence. Increasing evidence demonstrates that oncoviruses cause epigenetic modifications, which play a pivotal role in carcinogenesis. In this review, recent advances in the role of host cell epigenetic changes in virus-induced cancers are summarized.

A review on the DNA methyltransferase family of insects: Aspect and prospects

The DNA methyltransferase family contains a conserved set of DNA-modifying enzymatic proteins. They are responsible for epigenetic gene modulation, such as transcriptional silencing, transcription activation, and post-transcriptional modulation. Recent research has revealed that the canonical DNA methyltransferases (DNMTs) biological roles go beyond their traditional functions of establishing and maintaining DNA methylation patterns. Although a complete DNA methylation toolkit is absent in most insect orders, recent evidence indicates the de novo DNA methylation and maintenance function remain conserved. Studies using various molecular approaches provided evidence that DNMTs are multi-functional proteins. However, still in-depth studies on their biological role lack due to the least studied area in insects. Here, we review the DNA methylation toolkit of insects, focusing on recent research on various insect orders, which exhibit DNA methylation at different levels, and for which DNMTs functional studies have become available in recent years. We survey research on the potential roles of DNMTs in the regulation of gene transcription in insect species. DNMTs participate in different physiological processes by interacting with other epigenetic factors. Future studies on insect's DNMTs will benefit to understand developmental processes, responses to various stimuli, and adaptability of insects to different environmental conditions.

The Biological Function, Mechanism, and Clinical Significance of m6A RNA Modifications in Head and Neck Carcinoma: A Systematic Review

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers, yet the molecular mechanisms underlying its onset and development have not yet been fully elucidated. Indeed, an in-depth understanding of the potential molecular mechanisms underlying HNSCC oncogenesis may aid the development of better treatment strategies. Recent epigenetic studies have revealed that the m6A RNA modification plays important roles in HNSCC. In this review, we summarize the role of m6A modification in various types of HNSCC, including thyroid, nasopharyngeal, hypopharyngeal squamous cell, and oral carcinoma. In addition, we discuss the regulatory roles of m6A in immune cells within the tumor microenvironment, as well as the potential molecular mechanisms. Finally, we review the development of potential targets for treating cancer based on the regulatory functions of m6A, with an aim to improving targeted therapies for HNSCC. Together, this review highlights the important roles that m6A modification plays in RNA synthesis, transport, and translation, and demonstrates that the regulation of m6A-related proteins can indirectly affect mRNA and ncRNA function, thus providing a novel strategy for reengineering intrinsic cell activity and developing simpler interventions to treat HNSCC.

Targeting aberrant DNA hypermethylation as a driver of ATL leukemogenesis by using the new oral demethylating agent OR-2100

Adult T-cell leukemia-lymphoma (ATL) is an aggressive hematological malignancy of CD4+ T cells transformed by human T-cell lymphotropic virus-1 (HTLV-1). Most HTLV-1-infected individuals are asymptomatic, and only 3% to 5% of carriers develop ATL. Here, we describe the contribution of aberrant DNA methylation to ATL leukemogenesis. HTLV-1-infected T-cells and their uninfected counterparts were separately isolated based on CADM1 and CD7 expression status, and differentially methylated positions (DMPs) specific to HTLV-infected T cells were identified through genome-wide DNA methylation profiling. Accumulation of DNA methylation at hypermethylated DMPs correlated strongly with ATL development and progression. In addition, we identified 22 genes downregulated because of promoter hypermethylation in HTLV-1-infected T cells, including THEMIS, LAIR1, and RNF130, which negatively regulate T-cell receptor (TCR) signaling. Phosphorylation of ZAP-70, a transducer of TCR signaling, was dysregulated in HTLV-1-infected cell lines but was normalized by reexpression of THEMIS. Therefore, we hypothesized that DNA hypermethylation contributes to growth advantages in HTLV-1-infected cells during ATL leukemogenesis. To test this idea, we investigated the anti-ATL activities of OR-1200 and OR-2100 (OR21), novel decitabine (DAC) prodrugs with enhanced oral bioavailability. Both DAC and OR21 inhibited cell growth, accompanied by global DNA hypomethylation, in xenograft tumors established by implantation of HTLV-1-infected cells. OR21 was less hematotoxic than DAC, whereas tumor growth inhibition was almost identical between the 2 compounds, making it suitable for long-term treatment of ATL patient-derived xenograft mice. Our results demonstrate that regional DNA hypermethylation is functionally important for ATL leukemogenesis and an effective therapeutic target.

Therapeutic strategies of different HPV status in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the 9^th most common malignant tumor in the world. Based on the etiology, HNSCC has two main subtypes: human papillomavirus (HPV) -related and HPV-unrelated. HPV-positive HNSCC is more sensitive to treatment with favorable survival. Due to the different biological behaviors, individual therapy is necessary and urgently required to deduce the therapeutic intensity of HPV-positive disease and look for a more effective and toxicity-acceptable regimen for HPV-negative disease. EGFR amplification and PI3K/AKT/mTOR pathway aberrant activation are quite common in HPV-positive HNSCC. Besides, HPV infection alters immune cell infiltrating in HNSCC and encompasses a diverse and heterogeneous landscape with more immune infiltration. On the other hand, the chance of HPV-negative cancers harboring mutation on the P53 gene is significantly higher than that of HPV-positive disease. This review focuses on the updated preclinical and clinical data of HPV-positive and HPV-negative HNSCC and discusses the therapeutic strategies of different HPV status in HNSCC.

Global Genome Demethylation Causes Transcription-Associated DNA Double Strand Breaks in HPV-Associated Head and Neck Cancer Cells

High levels of DNA methylation at CpG loci are associated with transcriptional repression of tumor suppressor genes and dysregulation of DNA repair genes. Human papilloma virus (HPV)-associated head and neck squamous cell carcinomas (HNSCC) have high levels of DNA methylation and methylation has been associated with dampening of an innate immune response in virally infected cells. We have been exploring demethylation as a potential treatment in HPV+ HNSCC and recently reported results of a window clinical trial showing that HNSCCs are particularly sensitive to demethylating agent 5-azacytidine (5-aza). Mechanistically, sensitivity is partially due to downregulation of HPV genes expression and restoration of tumor suppressors p53 and Rb. Here, for the first time, we show that 5-azaC treatment of HPV+ HNSCC induces replication and transcription-associated DNA double strand breaks (DSBs) that occur preferentially at demethylated genomic DNA. Blocking replication or transcription prevented formation of DNA DSBs and reduced sensitivity of HPV-positive head and neck cancer cells to 5-azaC, demonstrating that both replication and active transcription are required for formation of DSBs associated with 5-azaC.

Methylation-mediated LINC00261 suppresses pancreatic cancer progression by epigenetically inhibiting c-Myc transcription

Background: Due to the limitations of strategies for its early diagnosis and treatment, pancreatic cancer (PC) remains a substantial human health threat. We previously discovered a methylation-mediated lncRNA, LINC00261, which is downregulated in PC tissues. However, the underlying role of LINC00261 in PC remains largely unknown. Methods: Quantitative real-time PCR and in situ hybridization were performed to evaluate the expression levels of LINC00261 in PC, adjacent nontumor and normal pancreas tissues. The clinical significance of LINC00261 was assessed in multicenter PC samples. The functions of LINC00261 in PC were investigated by gain- and loss-of-function assays in vitro and in vivo. Potential downstream pathways and mechanisms were explored via RNA sequencing and bioinformatic analyses. RNA immunoprecipitation and chromatin immunoprecipitation assays were used to validate the underlying mechanisms. Pyrosequencing and targeted demethylation of the LINC00261 promoter were performed to explore the upstream epigenetic mechanisms and therapeutic potential. Results: LINC00261 was significantly downregulated in PC tissues, and its expression was positively associated with the prognosis of PC patients. Phenotypic studies indicated that LINC00261 overexpression significantly suppressed PC cell proliferation, migration and metastasis in vitro and in vivo. c-Myc was identified as a downstream target of LINC00261. LINC00261 repressed c-Myc transcription by physically interacting and binding with the bromo domain of p300/CBP, preventing the recruitment of p300/CBP to the promoter region of c-Myc and decreasing the H3K27Ac level. Moreover, the methylation level of the LINC00261 promoter was high in PC tissues and was correlated with poor prognosis. Targeted demethylation of the LINC00261 promoter inhibited PC progression both in vitro and in vivo. Conclusions: Our findings indicate that methylation-mediated LINC00261 suppresses PC progression by epigenetically repressing c-Myc expression. These findings expand the therapeutic potential of LINC00261, possibly providing evidence to support the development of epigenetic drugs or therapeutic strategies. This research adds further insights into the etiology of PC and indicates that LINC00261 may be a prognostic and therapeutic target in PC.

DNA Methylation Changes in Human Papillomavirus-Driven Head and Neck Cancers

Disruption of DNA methylation patterns is one of the hallmarks of cancer. Similar to other cancer types, human papillomavirus (HPV)-driven head and neck cancer (HNC) also reveals alterations in its methylation profile. The intrinsic ability of HPV oncoproteins E6 and E7 to interfere with DNA methyltransferase activity contributes to these methylation changes. There are many genes that have been reported to be differentially methylated in HPV-driven HNC. Some of these genes are involved in major cellular pathways, indicating that DNA methylation, at least in certain instances, may contribute to the development and progression of HPV-driven HNC. Furthermore, the HPV genome itself becomes a target of the cellular DNA methylation machinery. Some of these methylation changes appearing in the viral long control region (LCR) may contribute to uncontrolled oncoprotein expression, leading to carcinogenesis. Consistent with these observations, demethylation therapy appears to have significant effects on HPV-driven HNC. This review article comprehensively summarizes DNA methylation changes and their diagnostic and therapeutic indications in HPV-driven HNC.

Impact of Respiratory Syncytial Virus Infection on Host Functions: Implications for Antiviral Strategies

Respiratory syncytial virus (RSV) is one of the leading causes of viral respiratory tract infection in infants, the elderly, and the immunocompromised worldwide, causing more deaths each year than influenza. Years of research into RSV since its discovery over 60 yr ago have elucidated detailed mechanisms of the host-pathogen interface. RSV infection elicits widespread transcriptomic and proteomic changes, which both mediate the host innate and adaptive immune responses to infection, and reflect RSV's ability to circumvent the host stress responses, including stress granule formation, endoplasmic reticulum stress, oxidative stress, and programmed cell death. The combination of these events can severely impact on human lungs, resulting in airway remodeling and pathophysiology. The RSV membrane envelope glycoproteins (fusion F and attachment G), matrix (M) and nonstructural (NS) 1 and 2 proteins play key roles in modulating host cell functions to promote the infectious cycle. This review presents a comprehensive overview of how RSV impacts the host response to infection and how detailed knowledge of the mechanisms thereof can inform the development of new approaches to develop RSV vaccines and therapeutics.

Small-Molecule Antiviral β-d-N4-Hydroxycytidine Inhibits a Proofreading-Intact Coronavirus with a High Genetic Barrier to Resistance

Coronaviruses (CoVs) have emerged from animal reservoirs to cause severe and lethal disease in humans, but there are currently no FDA-approved antivirals to treat the infections. One class of antiviral compounds, nucleoside analogues, mimics naturally occurring nucleosides to inhibit viral replication. While these compounds have been successful therapeutics for several viral infections, mutagenic nucleoside analogues, such as ribavirin and 5-fluorouracil, have been ineffective at inhibiting CoVs. This has been attributed to the proofreading activity of the viral 3'-5' exoribonuclease (ExoN). β-d-N4-Hydroxycytidine (NHC) (EIDD-1931; Emory Institute for Drug Development) has recently been reported to inhibit multiple viruses. Here, we demonstrate that NHC inhibits both murine hepatitis virus (MHV) (50% effective concentration [EC50] = 0.17 μM) and Middle East respiratory syndrome CoV (MERS-CoV) (EC50 = 0.56 μM) with minimal cytotoxicity. NHC inhibited MHV lacking ExoN proofreading activity similarly to wild-type (WT) MHV, suggesting an ability to evade or overcome ExoN activity. NHC inhibited MHV only when added early during infection, decreased viral specific infectivity, and increased the number and proportion of G:A and C:U transition mutations present after a single infection. Low-level NHC resistance was difficult to achieve and was associated with multiple transition mutations across the genome in both MHV and MERS-CoV. These results point to a virus-mutagenic mechanism of NHC inhibition in CoVs and indicate a high genetic barrier to NHC resistance. Together, the data support further development of NHC for treatment of CoVs and suggest a novel mechanism of NHC interaction with the CoV replication complex that may shed light on critical aspects of replication.IMPORTANCE The emergence of coronaviruses (CoVs) into human populations from animal reservoirs has demonstrated their epidemic capability, pandemic potential, and ability to cause severe disease. However, no antivirals have been approved to treat these infections. Here, we demonstrate the potent antiviral activity of a broad-spectrum ribonucleoside analogue, β-d-N4-hydroxycytidine (NHC), against two divergent CoVs. Viral proofreading activity does not markedly impact sensitivity to NHC inhibition, suggesting a novel interaction between a nucleoside analogue inhibitor and the CoV replicase. Further, passage in the presence of NHC generates only low-level resistance, likely due to the accumulation of multiple potentially deleterious transition mutations. Together, these data support a mutagenic mechanism of inhibition by NHC and further support the development of NHC for treatment of CoV infections.

DNA demethylation agent 5azadC downregulates HPV16 E6 expression in cervical cancer cell lines independently of TBX2 expression

HPV16 is the most carcinogenic human papillomavirus and causes >50% of cervical cancers, the majority of anal cancers and 30% of oropharyngeal squamous cell carcinomas. HPV carcinogenesis relies on the continuous expression of the two main viral oncoproteins E6 and E7 that target >150 cellular proteins. Among them, epigenetic modifiers, including DNA Methyl Transferases (DNMT), are dysregulated, promoting an aberrant methylation pattern in HPV-positive cancer cells. It has been previously reported that the treatment of HPV-positive cervical cancer cells with DNMT inhibitor 5-aza-2'-deoxycytidine (5azadC) caused the downregulation of E6 expression due to mRNA destabilization that was mediated by miR-375. Recently, the T-box transcription factor 2 (TBX2) has been demonstrated to repress HPV LCR activity. In the current study, the role of TBX2 in E6 repression was investigated in HPV16 cervical cancer cell lines following 5azadC treatment. A decrease of E6 expression was accompanied by p53 and p21 restoration. While TBX2 mRNA was upregulated in 5azadC-treated SiHa and Ca Ski cells, TBX2 protein was not detectable. Furthermore, the overexpression of TBX2 protein in cervical cancer cells did not allow the repression of E6 expression. The TBX2 transcription factor is therefore unlikely to be associated with the repression of E6 following 5azadC treatment of SiHa and Ca Ski cells.

Identification and chemoresistance of cancer stem cells in HPV-negative oropharyngeal cancer

The underlying mechanisms of resistance to chemoradiotherapy of human papilloma virus (HPV)-negative patients with oropharyngeal cancer (OPC) remain unclear. The present study aimed to characterize cancer stem cells (CSC) of the HPV-negative OPC cell line in terms of chemotherapy resistance. CSCs were isolated through magnetic activated cell sorting using the CSC specific marker aldehyde dehydrogenase 1 antibody, and characterized by sphere formation capacity, immunofluorescence staining, and CSC marker expression. CSC response to cisplatin treatment was evaluated via XTT-assays. Spheres of CSCs of the HPV-negative UTSCC-60A cell line were highly dark holospheres. RNA expression levels of CSC markers OCT4, SOX2, Kruppel-like factor 4 and BMI1 were significantly higher in CSC. CSCs were significantly resistant to cisplatin treatment at various dosages compared with nonCSC. The present study suggested that the proportion of CSCs is very low in the tumor bulk, CSCs are resistant to cisplatin in HPV-negative OPC, which requires further investigation to define their mechanism.

DNA methylomes and transcriptomes analysis reveal implication of host DNA methylation machinery in BmNPV proliferation in Bombyx mori

BACKGROUND

Bombyx mori nucleopolyhedrosis virus (BmNPV) is a major pathogen that threatens the sustainability of the sericultural industry. DNA methylation is a widespread gene regulation mode in epigenetics, which plays an important role in host immune response. Until now, little has been known about epigenetic regulation on virus diseases in insects. This study aims to explore the role of DNA methylation in BmNPV proliferation.

RESULTS

Inhibiting DNA methyltransferase (DNMT) activity of silkworm can suppress BmNPV replication. The integrated analysis of transcriptomes and DNA methylomes in silkworm midguts infected with or without BmNPV showed that both the expression pattern of transcriptome and DNA methylation pattern are changed significantly upon BmNPV infection. A total of 241 differentially methylated regions (DMRs) were observed in BmNPV infected midguts, among which, 126 DMRs were hyper-methylated and 115 DMRs were hypo-methylated. Significant differences in both mRNA transcript level and DNA methylated levels were found in 26 genes. BS-PCR validated the hypermethylation of BGIBMGA014008, a structural maintenance of chromosomes protein gene in the BmNPV-infected midgut. In addition, DNMT inhibition reduced the expression of inhibitor of apoptosis family genes, iap1 from BmNPV, Bmiap2, BmSurvivin1 and BmSurvivin2.

CONCLUSION

Our results indicate that DNA methylation plays positive roles in BmNPV proliferation and loss of DNMT activity could induce the apoptosis of infected cells to suppress BmNPV proliferation. Our results may provide a new idea and research direction for the molecular mechanism on insect-virus interaction.

Impact of Epigenetic Regulation on Head and Neck Squamous Cell Carcinoma

The most common type of head and neck cancer, head and neck squamous cell carcinoma (HNSCC), can develop therapeutic resistance that complicates its treatment. The 5-y survival rate for HNSCC remains at ~50%, and improving these outcomes requires a better understanding of the pathogenesis of HNSCC. Studies of HNSCC using in vitro, ex vivo, and in vivo approaches provide a novel conceptual framework based on epigenetic mechanisms for developing future clinical applications. Normal oral tissues are influenced by environmental factors that induce pathological changes affecting the network of epigenetic enzymes and signaling pathways to induce HNSCC growth and metastasis. Although various epigenetic regulator families, such as DNA methyltransferases, ten-eleven translocation proteins, histone acetyltransferases, histone deacetylases, BET bromodomain proteins, protein arginine methyltransferases, histone lysine methyltransferases, and histone lysine demethylases, have a role in diverse cancers, specific members have a function in HNSCC. Recently, lysine-specific demethylases have been identified as a potential, attractive, and novel target of HNSCC. Lysine-specific demethylase 1 (LSD1) expression is inappropriately upregulated in HNSCC and an orthotopic HNSCC mouse model. LSD1 can demethylate lysine at specific histone positions to repress gene expression or stimulate transcription, indicating a dual and context-dependent role in transcriptional regulation. Our study showed that LSD1 promotes HNSCC growth and metastasis. Pharmacological attenuation of LSD1 inhibits orthotopic and patient-derived HNSCC xenograft growth-specific target genes and signaling pathways. This review provides recent evidence demonstrating the function of epigenetic regulator enzymes in HNSCC progression, including potential therapeutic applications for such enzymes in combination and immunotherapy.

HPV-driven oropharyngeal cancer: current knowledge of molecular biology and mechanisms of carcinogenesis

Understanding of oropharyngeal squamous cell carcinoma has significantly progressed over the last decades, and the concept that this disease can be subdivided into two distinct entities based on human papilloma virus (HPV) status has gained acceptance. To combat the constantly growing epidemic of HPV+ oropharyngeal cancer, further investigation and characterization the unique features of the disease, along with the development and implementation of new, targeted therapies, is crucial. In this review, we summarize the etiology, pathogenesis, diagnosis, treatment, and molecular characteristics of HPV-associated oropharyngeal squamous cell carcinoma.

p53 and the Viral Connection: Back into the Future ‡

The discovery of the tumor suppressor p53, through its interactions with proteins of tumor-promoting viruses, paved the way to the understanding of p53 roles in tumor virology. Over the years, accumulating data suggest that WTp53 is involved in the viral life cycle of non-tumor-promoting viruses as well. These include the influenza virus, smallpox and vaccinia viruses, the Zika virus, West Nile virus, Japanese encephalitis virus, Human Immunodeficiency Virus Type 1, Human herpes simplex virus-1, and more. Viruses have learned to manipulate WTp53 through different strategies to improve their replication and spreading in a stage-specific, bidirectional way. While some viruses require active WTp53 for efficient viral replication, others require reduction/inhibition of WTp53 activity. A better understanding of WTp53 functionality in viral life may offer new future clinical approaches, based on WTp53 manipulation, for viral infections.

Novel Therapeutic Targets in Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (SCC) is one of the common cancers in Caucasians, accounting for 20–30% of cutaneous malignancies. The risk of metastasis is low in most patients; however, aggressive SCC is associated with very high mortality and morbidity. Although cutaneous SCC can be treated with surgical removal, radiation and chemotherapy singly or in combination, the prognosis of patients with metastatic SCC is poor. Recently, the usage of immune checkpoint blockades has come under consideration. To develop effective therapies that are less toxic than existing ones, it is crucial to achieve a detailed characterization of the molecular mechanisms that are involved in cutaneous SCC pathogenesis and to identify new drug targets. Recent studies have identified novel molecules that are associated with SCC carcinogenesis and progression. This review focuses on recent advances in molecular studies involving SCC tumor development, as well as in new therapeutics that have become available to clinicians.

DNA Tumor Virus Regulation of Host DNA Methylation and Its Implications for Immune Evasion and Oncogenesis

Viruses have evolved various mechanisms to evade host immunity and ensure efficient viral replication and persistence. Several DNA tumor viruses modulate host DNA methyltransferases for epigenetic dysregulation of immune-related gene expression in host cells. The host immune responses suppressed by virus-induced aberrant DNA methylation are also frequently involved in antitumor immune responses. Here, we describe viral mechanisms and virus–host interactions by which DNA tumor viruses regulate host DNA methylation to evade antiviral immunity, which may contribute to the generation of an immunosuppressive microenvironment during cancer development. Recent trials of immunotherapies have shown promising results to treat multiple cancers; however, a significant number of non-responders necessitate identifying additional targets for cancer immunotherapies. Thus, understanding immune evasion mechanisms of cancer-causing viruses may provide great insights for reversing immune suppression to prevent and treat associated cancers.

Leveraging Genomics for Head and Neck Cancer Treatment

The genomic landscape of head and neck squamous cell carcinoma (HNSCC) has been recently elucidated. Key epigenetic and genetic characteristics of this cancer have been reported and substantiated in multiple data sets, including those distinctive to the growing subset of human papilloma virus (HPV)-associated tumors. This increased understanding of the molecular underpinnings of HNSCC has not resulted in new approaches to treatment. Three Food and Drug Administration-approved molecular targeting agents are currently available to treat recurrent/metastatic disease, but these have exhibited efficacy only in subsets of HNSCC patients, and thus surgery, chemotherapy, and/or radiation remain as standard approaches. The lack of predictive biomarkers to any therapy represents an obstacle to achieving the promise of precision medicine. This review aims to familiarize the reader with current insights into the HNSCC genomic landscape, discuss the currently approved and promising molecular targeting agents under exploration in laboratories and clinics, and consider precision medicine approaches to HNSCC.

Runt-related Transcription Factor 3 Promoter Hypermethylation and Gastric Cancer Risk: A Meta-analysis

OBJECTIVE

The aim of this study was to investigate the correlation between runt-related transcription factor 3 (RUNX3) gene promoter hypermethylation and gastric cancer risk by meta-analysis.

METHODS

By searching Medline, PubMed, Embase, Cochrane, Ovid and CNKI electronic databases, the open published studies about the association between RUNX3 gene promoter hypermethylation and gastric cancer risk were screened. The hypermethylation rate in cancer tissue and autologous control tissue (normal gastric tissue of gastric cancer patients) were extracted from each included study. The odds ratio (OR) and corresponding 95% confidence interval (95% CI) of RUNX3 gene promoter hypermethylation in cancer tissue versus autologous control tissue of gastric cancer patients were pooled with random or fixed effect models. The publication bias was evaluated by Begg's funnel plot and Egger's line regression test.

RESULTS

Finally, twenty three relevant studies were included in this meta-analysis. The hypermethylation rate in cancer tissue and autologous control tissue of gastric cancer patients were 0.56±0.16 and 0.18±0.22 respectively, which demonstrated a hypermethylation rate in cancer tissue significantly higher than that of autologous controls (P<0.05). A significant positive correlation of hypermethylation rate between cancer tissue and autologous control existed for the included 23 studies(r_pearson =0.62, P<0.05). For significant heterogeneity across the studies, the OR was pooled by random effects model. The combined OR was 8.06 with the 95% CI of 5.73~11.32, which indicated the hypermethylation frequency in cancer tissue was higher than that of autologous controls.

CONCLUSION

The RUNX3 gene promoter hypermethylation rate was much higher in cancer tissue than that of normal gastric tissue in patients with gastric cancer, which indicates a close association between gastric cancer and RUNX3 gene promoter hypermethylation. Furthermore, RUNX3 gene promoter hypermethylation may be a potential biomarker for gastric cancer diagnosis.