Immune and genomic signatures in oral (head and neck) cancer

Oral cancer immunology: state of the art and future perspectives

Oral cancer is a multifactorial disease involving genetic, epigenetic, and environmental factors. The literature indicates that inflammatory cells at the advancing front of the tumor induce a host immune response, preventing the spread of the tumor. However, cancer cells adopt various continued strategies to circumvent this immune surveillance. The complexity of immune mechanisms suggests that there must be virtually individual patterns of anti-tumor immune responses. Due to this important interaction of cancer with the immune system, the objective of the present study was to provide an up-to-date overview of immuno-oncology focused on oral cancer, summarizing the basic immunology, the classic risk factors, immunotherapy, and future treatment and prognostic perspectives.

Causal associations of MICB, CTSA, and MMP9 proteins with oral cancer: Mendelian randomization study

Oral cancer (ORCA) is the most prevalent histological subtype of oral malignancies in which immune modulation is relevant. The goal of this work was to employ Mendelian randomization (MR) to investigate the causal connection between the immune-related proteins MICB, CTSA, MMP9, and ORCA. The Open GWAS database of the Integrative Epidemiology Unit (IEU) was accessed to collect GWAS data for ORCA (ieu-b-4961), MICB (prot-a-1898), CTSA (prot-a-717) and MMP9 (prot-a-1921). From 372,373 samples, the ORCA dataset comprises 7,723,107 single nucleotide polymorphisms (SNPs). MICB, CTSA, and MMP9 all have 10,534,735 SNPs and 3,301 sample sizes. Then, the primary SVMR implementation approaches were weighted mode, simple mode, inverse variance weighted (IVW), weighted median, and MR-Egger. IVW was the most effective technique. A sensitivity study was also carried out to assess the correctness of SVMR data, with special focus devoted to heterogeneity, horizontal pleiotropy, and Leave-One-Out (LOO). MVMR was eventually implemented as well. A Mendelian randomization analysis of the three exposure factors in the dataset (ieu-b-94, ebi-a-GCST012237) was also performed to validate the study results. According to the SVMR results, there was a noteworthy causal interaction between ORCA and MICB (P = 0.0014), MMP9 (P = 0.0343), and CTSA (P = 0.0003). Furthermore, odds ratios (ORs) values revealed that MMP9 (OR = 1.0005) was an ORCA risk factor, whereas MICB (OR = 0.9994) and CTSA (OR = 0.9993) were security factors. The robustness of the SVMR findings was confirmed by the p-values of the heterogeneity and horizontal pleiotropy, both of which were greater than 0.05. The MVMR result did not affect any of the safety or hazard features of these three exposure factors. However, the P value for MMP9 was greater than 0.05, implying that MICB and CTSA may have a greater influence on ORCA than MMP9. The validation outcomes in both datasets harmonized with the findings from previous research, thereby solidifying the reliability of results. Our investigation provided a crucial resource for further research on the subject by demonstrating a causal relationship between ORCA and MICB, CTSA, and MMP9.

The Three-Dimensional In Vitro Cell Culture Models in the Study of Oral Cancer Immune Microenvironment

The onset and progression of oral cancer are accompanied by a dynamic interaction with the host immune system, and the immune cells within the tumor microenvironment play a pivotal role in the development of the tumor. By exploring the cellular immunity of oral cancer, we can gain insight into the contribution of both tumor cells and immune cells to tumorigenesis. This understanding is crucial for developing effective immunotherapeutic strategies to combat oral cancer. Studies of cancer immunology present unique challenges in terms of modeling due to the extraordinary complexity of the immune system. With its multitude of cellular components, each with distinct subtypes and various activation states, the immune system interacts with cancer cells and other components of the tumor, ultimately shaping the course of the disease. Conventional two-dimensional (2D) culture methods fall short of capturing these intricate cellular interactions. Mouse models enable us to learn about tumor biology in complicated and dynamic physiological systems but have limitations as the murine immune system differs significantly from that of humans. In light of these challenges, three-dimensional (3D) culture systems offer an alternative approach to studying cancer immunology and filling the existing gaps in available models. These 3D culture models provide a means to investigate complex cellular interactions that are difficult to replicate in 2D cultures. The direct study of the interaction between immune cells and cancer cells of human origin offers a more relevant and representative platform compared to mouse models, enabling advancements in our understanding of cancer immunology. This review explores commonly used 3D culture models and highlights their significant contributions to expanding our knowledge of cancer immunology. By harnessing the power of 3D culture systems, we can unlock new insights that pave the way for improved strategies in the battle against oral cancer.

The Role of Different Immunocompetent Cell Populations in the Pathogenesis of Head and Neck Cancer-Regulatory Mechanisms of Pro- and Anti-Cancer Activity and Their Impact on Immunotherapy

Head and neck squamous cell carcinoma (HNSCC) is one of the most aggressive and heterogeneous groups of human neoplasms. HNSCC is characterized by high morbidity, accounting for 3% of all cancers, and high mortality with ~1.5% of all cancer deaths. It was the most common cancer worldwide in 2020, according to the latest GLOBOCAN data, representing the seventh most prevalent human malignancy. Despite great advances in surgical techniques and the application of modern combinations and cytotoxic therapies, HNSCC remains a leading cause of death worldwide with a low overall survival rate not exceeding 40-60% of the patient population. The most common causes of death in patients are its frequent nodal metastases and local neoplastic recurrences, as well as the relatively low response to treatment and severe drug resistance. Much evidence suggests that the tumour microenvironment (TME), tumour infiltrating lymphocytes (TILs) and circulating various subpopulations of immunocompetent cells, such regulatory T cells (CD4+CD25+Foxp3+Tregs), cytotoxic CD3+CD8+ T cells (CTLs) and CD3+CD4+ T helper type 1/2/9/17 (Th1/Th2/Th9/Th17) lymphocytes, T follicular helper cells (Tfh) and CD56dim/CD16bright activated natural killer cells (NK), carcinoma-associated fibroblasts (CAFs), myeloid-derived suppressor cells (MDSCs), tumour-associated neutrophils (N1/N2 TANs), as well as tumour-associated macrophages (M1/M2 phenotype TAMs) can affect initiation, progression and spread of HNSCC and determine the response to immunotherapy. Rapid advances in the field of immuno-oncology and the constantly growing knowledge of the immunosuppressive mechanisms and effects of tumour cancer have allowed for the use of effective and personalized immunotherapy as a first-line therapeutic procedure or an essential component of a combination therapy for primary, relapsed and metastatic HNSCC. This review presents the latest reports and molecular studies regarding the anti-tumour role of selected subpopulations of immunocompetent cells in the pathogenesis of HNSCC, including HPV+ve (HPV+) and HPV-ve (HPV-) tumours. The article focuses on the crucial regulatory mechanisms of pro- and anti-tumour activity, key genetic or epigenetic changes that favour tumour immune escape, and the strategies that the tumour employs to avoid recognition by immunocompetent cells, as well as resistance mechanisms to T and NK cell-based immunotherapy in HNSCC. The present review also provides an overview of the pre- and clinical early trials (I/II phase) and phase-III clinical trials published in this arena, which highlight the unprecedented effectiveness and limitations of immunotherapy in HNSCC, and the emerging issues facing the field of HNSCC immuno-oncology.

Immunology of Oral Squamous Cell Carcinoma-A Comprehensive Insight with Recent Concepts

This review aims to understand the concept of oral cancer immunology through the notion of immune profiling, immunoediting and immunotherapy, and to gain knowledge regarding its application for the management of oral cancer patients. Oral cancer is an immunogenic tumor where the cells of the tumor microenvironment play an important role in tumorigenesis. Understanding the mechanism of these modulations can help design immunotherapeutic strategies in oral cancer patients. This article gives an overview of immunomodulation in the oral cancer tumor microenvironment, with concepts of immune profiling, immunoediting and immunotherapy. English literature searches via Google Scholar, Web of Science, EBSCO, Scopus, and PubMed database were performed with the key words immunology, tumor microenvironment, cells, cross talk, immune profiling, biomarkers, inflammation, gene expression, techniques, immunoediting, immunosurveillance, tumor escape, immunotherapy, immune checkpoint inhibitors, vaccines in cancer, oral cancer, and head and neck cancer. Original research articles, reviews, and case reports published from 2016-2021 (n = 81) were included to appraise different topics, and were discussed under the following subsections. Literature published on oral cancer immunology reveals that oral cancer immune profiling with appropriate markers and techniques and knowledge on immunoediting concepts can help design and play an effective role in immunotherapeutic management of oral cancer patients. An evaluation of oral cancer immunology helps to determine its role in tumorigenesis, and immunotherapy could be the emerging drift in the effective management of oral cancer.

The role of T-cells in head and neck squamous cell carcinoma: From immunity to immunotherapy

Head and neck squamous cell carcinoma (HNSCC) encompass a group of complex entities of tumours affecting the aerodigestive upper tract. The main risk factors are strongly related to tobacco and alcohol consumption, but also HPV infection is often associated. Surgery, radiotherapy and/or chemotherapy are the standard treatments, though the 5-year overall survival is less than 50%. The advances in genomics, molecular medicine, immunology, and nanotechnology have shed a light on tumour biology which helps clinical researchers to obtain more efficacious and less toxic therapies. Head and neck tumours possess different immune escape mechanisms including diminishing the immune response through modulating immune checkpoints, in addition to the recruitment and differentiation of suppressive immune cells. The insights into the HNSCC biology and its strong interaction with the tumour microenvironment highlights the role of immunomodulating agents. Recently, the knowledge of the immunological features of these tumours has paved the way for the discovery of effective biomarkers that allow a better selection of patients with odds of improving overall survival through immunotherapy. Specially biomarkers regarding immune checkpoint inhibitors antibodies, such as anti-PD-1/PD-L1 and anti-CTLA-4 in combination with standard therapy or as monotherapy. New immunotherapies to treat head and neck cancer carcinomas, such as CAR T cells and nanoparticles have been the center of attention and in this review, we discuss the necessity of finding targets for the T cell in the cancer cells to generate CAR T cells, but also the relevance of evaluating specificity and safety of those therapies.

Methionine enkephalin inhibited cervical carcinoma via apoptosis promotion and reduction of myeloid derived suppressor cell infiltrated in tumor

Immunotherapy for cervical carcinoma is becoming increasingly important recently. In these studies methionine enkephalin (menk) is shown to inhibit cervical tumor cell proliferation in vitro in association with an increase in the expression of apoptosis markers and mediators, including an increase in fas, caspase 8, and caspase 3 expression and intrinsic expression of the signaling pathway mediator bax. In vivo, tumor growth was restrained in mice xenotransplant model with typical pathological features of apoptosis. Furthermore, myeloid derived suppressor cells (MDSCs) had a significant decrease in circulation and in tumor site. In brief, these findings showed menk could inhibit tumor growth in vitro and in vivo, providing direction of further research and clinical application prospect.

An Immune Feature-Based, Three-Gene Scoring System for Prognostic Prediction of Head-and-Neck Squamous Cell Carcinoma

Head-and-neck squamous cell carcinoma (HNSCC) is characterized by a high frequency of neck lymph node metastasis (LNM), a key prognostic factor. Therefore, identifying the biological processes during LNM of HNSCC has significant clinical implications for risk stratification. This study performed Gene Ontology enrichment analysis of differentially expressed genes between tumors with LNM and those without LNM and identified the involvement of immune response in the lymphatic metastasis of HNSCC. We further identified greater infiltrations of CD8⁺ T cells in tumors than in adjacent normal tissues through immunochemistry in the patient cohort (n = 62), indicating the involvement of CD8⁺ T cells in the antitumor immunity. Hierarchical clustering analysis was conducted to initially identify the candidate genes relevant to lymphocyte-mediated antitumor response. The candidate genes were applied to construct a LASSO Cox regression analysis model. Three genes were eventually screened out as progression-related differentially expressed candidates in HNSCC and a risk scoring system was established based on LASSO Cox regression model to predict the outcome in patients with HNSCC. The score was calculated using the formula: 0.0636 × CXCL11 - 0.4619 × CXCR3 + 0.2398 × CCR5. Patients with high scores had significantly worse overall survival than those with low scores (p < 0.001). The risk score showed good performance in characterizing tumor-infiltrating lymphocytes and provided a theoretical basis for stratifying patients receiving immune therapies. Additionally, a nomogram including the risk score, age, and TNM stage was constructed. The prediction model displayed marginally better discrimination ability and higher agreement in predicting the survival of patients with HNSCC compared with the TNM stage.

Biological implications of the immune factors in the tumour microenvironment of oral cancer

OBJECTIVE

The objective of this review is to decipher the biological implications of the immune factors in the tumour microenvironment in oral cancer. The restoration of balance between tumour tolerance and tumour eradication by the host immune cells is critical to provide effective therapeutic strategies.

DESIGN

The specific role of the stromal and the immune components in oral cancer was reviewed with a tailored search strategy using relevant keywords. The articles were retrieved from bibliometric databases indexed in PubMed, Scopus, and Embase. An in silico analysis was performed to identify potential drug candidates for immunotherapy, by accessing the Drug-Gene Interactions Database (DGIdb) using the rDGIdb package.

RESULTS

There is compelling evidence for the role of the cellular and extracellular components of the tumour microenvironment in inducing immunosuppression and progression of oral cancer. The druggable candidates specifically targeting the immune system are a viable option in the treatment of oral cancer as they can regulate the tumour microenvironment.

CONCLUSION

A complex interaction between the tumour and the immunological microenvironment influences the disease outcome in oral cancer. Targeting specific components of the immune system might be relevant, as immunotherapy may become the new standard of care for oral cancer.

Integrated multiplex network based approach for hub gene identification in oral cancer

Background: The incidence of Oral Cancer (OC) is high in Asian countries, which goes undetected at its early stage. The study of genetics, especially genetic networks holds great promise in this endeavor. Hub genes in a genetic network are prominent in regulating the whole network structure of genes. Thus identification of such genes related to specific cancer types can help in reducing the gap in OC prognosis. Methods: Traditional study of network biology is unable to decipher the inter-dependencies within and across diverse biological networks. Multiplex network provides a powerful representation of such systems and encodes much richer information than isolated networks. In this work, we focused on the entire multiplex structure of the genetic network integrating the gene expression profile and DNA methylation profile for OC. Further, hub genes were identified by considering their connectivity in the multiplex structure and the respective protein-protein interaction (PPI) network as well. Results: 46 hub genes were inferred in our approach with a high prediction accuracy (96%), outstanding Matthews coefficient correlation value (93%) and significant biological implications. Among them, genes PIK3CG, PIK3R5, MYH7, CDC20 and CCL4 were differentially expressed and predominantly enriched in molecular cascades specific to OC. Conclusions: The identified hub genes in this work carry ontological signatures specific to cancer, which may further facilitate improved understanding of the tumorigenesis process and the underlying molecular events. Result indicates the effectiveness of our integrated multiplex network approach for hub gene identification. This work puts an innovative research route for multi-omics biological data analysis.

Molecular landscape of head and neck cancer and implications for therapy

Head and neck squamous cell carcinomas (HNSCC) arising from the oral cavity, pharynx, and larynx constitute the 6^th most common human cancer. Human papillomavirus (HPV)-positive tumours are distinct from HPV-negative counterparts, with HPV status affording clear clinical utility, prognostic benefit and better treatment outcomes. In contrast to their HPV-positive counterparts, HPV-negative tumours are characterized by high mutational load and chromosomal aberrations, with varying copy number alteration (CNA) profiles. HNSCC are distinct tumours at the chromosomal, gene and expression levels, with additional insight gained from immune profiling. Based on mutational analyses, HNSCC are categorized as HPV-positive, HPV-negative CNA-silent, and HPV-negative CNA-high tumours. Furthermore, gene expression profiling segregates these tumours into atypical, classical, basal, and mesenchymal, with clear differences observed between tumours of the oral cavity, oropharynx, hypopharynx and larynx. Additional immune profiling further classifies tumours as either immune-active or immune-exhausted. The clinical utility and impact of these tumour molecular subtypes however remains to be determined. HNSCC harbor high levels of somatic mutations. They display loss at 3p and 18q and gain at 3q and 8q, with mutations in CDKN2A, TP53, CCND1, EGFR, PIK3CA, PTEN, NOTCH1, NSD1, FAT1, AJUBA and KMT2D. Important pathways include the p53 and RB pathways which are involved in cell cycle control and are frequently lost in HPV-negative tumours, the WNT-β-catenin pathway related to the mesenchymal subtype and smoking etiology, and the PI3K pathway which includes the most common genetic alteration in HPV-positive HNSCC. Understanding the mutational, genomic and transcriptomic landscape of HNSCC has leveraged better therapeutic approaches to manage this group of diseases, and it is hoped that additional insight into the molecular subtypes of HNSCC and its specific subsites will further drive improved strategies to stratify and treat patients with this debilitating disease.

Neoadjuvant immunotherapy in resectable head and neck cancer: oral cavity carcinoma as a potential research model

Squamous cell carcinoma of oral cavity (OCSCC) accounts for approximately 25% of cases of head and neck squamous cell carcinoma (HNSCC). Tobacco and alcohol consumption are the main risk factors for both cancers. Surgical resection, combined with adjuvant radiotherapy or radiochemotherapy in patients with high risk of relapse, is the key element in management in the initial stages. However, despite the availability of aggressive multidisciplinary treatments, advanced resectable OCSCC carries poor prognosis; only half of the patients are disease-free 5 years after the surgery. Immunotherapy based on the use of immune checkpoint inhibitors has been proven to be effective in a wide variety of tumours, including recurrent and metastatic HNSCC. These positive results resulted in investigations into its effectiveness in earlier stages of the disease with OCSCC emerging as an interesting research model because of the accessible location of the tumours. This article reviews the potential advantages of emerging immunotherapeutic agents [mainly monoclonal antibodies against programmed cell death-1 (PD-1) immune checkpoint inhibitors] as neoadjuvant treatment for OCSCC at locoregional stages as well as the ongoing clinical trials, challenges in evaluating tumour response, and possible predictive biomarkers of response with highlights regarding the role of oral microbiota as modulators of immune response. The efficacy and safety of anti-PD-1 drugs in these patients have been proven in preliminary trials. If there is a decrease in the relapse rate and an improvement in the overall survival after surgical resection in ongoing trials, preoperative immunotherapy may be established as a treatment option for patients with early stages of the disease.

Hypoxic Transformation of Immune Cell Metabolism Within the Microenvironment of Oral Cancers

Oral squamous cell carcinoma (OSCC) includes tumors of the lips, tongue, gingivobuccal complex, and floor of the mouth. Prognosis for OSCC is highly heterogeneous, with overall 5-year survival of ~50%, but median survival of just 8-10 months for patients with locoregional recurrence or metastatic disease. A key feature of OSCC is microenvironmental oxygen depletion due to rapid growth of constituent tumor cells, which triggers hypoxia-associated signaling events and metabolic adaptations that influence subsequent tumor progression. Better understanding of leukocyte responses to tissue hypoxia and onco-metabolite expression under low-oxygen conditions will therefore be essential to develop more effective methods of diagnosing and treating patients with OSCC. This review assesses recent literature on metabolic reprogramming, redox homeostasis, and associated signaling pathways that mediate crosstalk of OSCC with immune cells in the hypoxic tumor microenvironment. The likely functional consequences of this metabolic interface between oxygen-starved OSCC and infiltrating leukocytes are also discussed. The hypoxic microenvironment of OSCC modifies redox signaling and alters the metabolic profile of tumor-infiltrating immune cells. Improved understanding of heterotypic interactions between host leukocytes, tumor cells, and hypoxia-induced onco-metabolites will inform the development of novel theranostic strategies for OSCC.

Applications of single-cell sequencing for the field of otolaryngology: A contemporary review

OBJECTIVES

Single-cell RNA sequencing (scRNA-Seq) is a new technique used to interrogate the transcriptome of individual cells within native tissues that have already resulted in key discoveries in auditory basic science research. Rapid advances in scRNA-Seq make it likely that it will soon be translated into clinical medicine. The goal of this review is to inspire the use of scRNA-Seq in otolaryngology by giving examples of how it can be applied to patient samples and how this information can be used clinically.

METHODS

Studies were selected based on the scientific quality and relevance to scRNA-Seq. In addition to mouse auditory system (inner ear including hair cells and supporting cells, spiral ganglion neurons, and inner ear organoids), recent studies using human primary cell samples are discussed. We also perform our own analysis on publicly available, published scRNA-Seq data from oral head and neck squamous cell carcinoma (HNSCC) samples to serve as an example of a clinically relevant application of scRNA-Seq.

RESULTS

Studies focusing on patient tissues show that scRNA-Seq reveals tissue heterogeneity and rare-cell types responsible for disease pathogenesis. The heterogeneity detected by scRNA-Seq can result in both the identification of known or novel disease biomarkers and drug targets. Our analysis of HNSCC data gives an example for how otolaryngologists can use scRNA-Seq for clinical use.

CONCLUSIONS

Although there are limitations to the translation of scRNA-Seq to the clinic, we show that its use in otolaryngology can give physicians insight into the tissue heterogeneity within their patient's diseased tissue giving them information on disease pathogenesis, novel disease biomarkers or druggable targets, and aid in selecting patient-specific drug cocktails.

The Potential of CD16 on Plasma-Derived Exosomes as a Liquid Biomarker in Head and Neck Cancer

Head and neck squamous cell carcinomas (HNSCC) are highly immune suppressive and aggressive malignancies. As part of the tumor microenvironment, exosomes contribute to this immune suppression. The Fc receptor CD16 is widely expressed on monocytes, neutrophils, and natural killer (NK) cells and is involved in antibody-dependent cell-mediated cytotoxicity (ADCC). Here, surface levels of CD16 on total exosomes and tumor-derived exosomes (TEX) from plasma of HNSCC patients were analyzed regarding their potential as liquid biomarkers for disease stage. Exosomes were isolated from plasma using mini size exclusion chromatography. TEX were enriched by immune affinity capture with CD44v3 antibodies. On-bead flow cytometry was used to measure CD16 levels on total exosomes and TEX. The results were correlated with clinicopathological parameters. Total exosomes from HNSCC patients had significantly higher CD16 levels compared to TEX. Further, CD16 surface levels of total exosomes, but not TEX, correlated with clinicopathological parameters. Patients with advanced tumor stages T3/4 and Union for International Cancer Control (UICC) stages III/IV had significantly higher CD16 levels on total exosomes compared to patients with early tumor stages T1/2 and UICC stages I/II, respectively. Overall, CD16 positive exosomes have the potential as liquid biomarkers for HNSCC tumor stage and aggressiveness.

Assessing the potential association between Epstein-Barr virus and oral squamous cell carcinoma: a systematic review and meta-analysis

BACKGROUND

This study aims to qualitatively and quantitatively review the association between Epstein-Barr virus (EBV) and oral squamous cell carcinoma (OSCC).

METHODS

PubMed, Scopus, and Web of Science databases were searched using the keywords "EBV or Epstein Barr virus and Oral cancer or Oral squamous cell carcinoma" for published case-control studies in the English language upto August 2019.

RESULTS

The search yielded 985 articles out of which 966 articles were excluded by screening their titles and abstracts as they were irrelevant or duplicates. Based on the full-text assessment of the remaining 19 articles, only 7 satisfied the inclusion criteria and were included in the qualitative analysis, out of which only 4 were compatible to be included in the meta-analysis. The diagnostic modalities used included immunohistochemistry, in situ hybridization and polymerase chain reaction. The diagnostic targets included latent membrane protein (LMP)-1, EBV determined nuclear antigen-1, EBV-encoded small non-polyadenylated RNA-2. The meta-analysis showed that there is an association between the EBV and OSCC.

CONCLUSIONS

Determining the association of EBV with OSCC is highly tedious due to the contrasting data obtained from individuals' studies which in turn is due to the wide variations in the sensitivity and specificity of the diagnostic modalities used and diagnostic targets selected. Although the meta-analysis revealed an association between EBV and OSCC, the number and the quality of the studies included in the meta-analysis are limited, thus the association requires further validation for any conclusive inference.

The Head and Neck Squamous Cell Carcinoma Microenvironment as a Potential Target for Cancer Therapy

Similarly to other types of malignant tumours, the incidence of head and neck cancer is increasing globally. It is frequently associated with smoking and alcohol abuse, and in a broader sense also with prolonged exposure to these factors during ageing. A higher incidence of tumours observed in younger populations without a history of alcohol and tobacco abuse may be due to HPV infection. Malignant tumours form an intricate ecosystem of cancer cells, fibroblasts, blood/lymphatic capillaries and infiltrating immune cells. This dynamic system, the tumour microenvironment, has a significant impact on the biological properties of cancer cells. The microenvironment participates in the control of local aggressiveness of cancer cells, their growth, and their consequent migration to lymph nodes and distant organs during metastatic spread. In cancers originating from squamous epithelium, a similarity was demonstrated between the cancer microenvironment and healing wounds. In this review, we focus on the specificity of the microenvironment of head and neck cancer with emphasis on the mechanism of intercellular crosstalk manipulation for potential therapeutic application.