COX-2 promotes metastasis in nasopharyngeal carcinoma by mediating interactions between cancer cells and myeloid-derived suppressor cells

Immune Cell Migration to Cancer

Immune cell migration is required for the development of an effective and robust immune response. This elegant process is regulated by both cellular and environmental factors, with variables such as immune cell state, anatomical location, and disease state that govern differences in migration patterns. In all cases, a major factor is the expression of cell surface receptors and their cognate ligands. Rapid adaptation to environmental conditions partly depends on intrinsic cellular immune factors that affect a cell's ability to adjust to new environment. In this review, we discuss both myeloid and lymphoid cells and outline key determinants that govern immune cell migration, including molecules required for immune cell adhesion, modes of migration, chemotaxis, and specific chemokine signaling. Furthermore, we summarize tumor-specific elements that contribute to immune cell trafficking to cancer, while also exploring microenvironment factors that can alter these cellular dynamics within the tumor in both a pro and antitumor fashion. Specifically, we highlight the importance of the secretome in these later aspects. This review considers a myriad of factors that impact immune cell trajectory in cancer. We aim to highlight the immunotherapeutic targets that can be harnessed to achieve controlled immune trafficking to and within tumors.

Key players of immunosuppression in epithelial malignancies: Tumor-infiltrating myeloid cells and γδ T cells

BACKGROUND

The tumor microenvironment of solid tumors governs the differentiation of otherwise non-immunosuppressive macrophages and gamma delta (γδ) T cells into strong immunosuppressors while promoting suppressive abilities of known immunosuppressors such as myeloid-derived suppressor cells (MDSCs) upon infiltration into the tumor beds.

RECENT FINDINGS

In epithelial malignancies, tumor-associated macrophages (TAMs), precursor monocytic MDSCs (M-MDSCs), and gamma delta (γδ) T cells often acquire strong immunosuppressive abilities that dampen spontaneous immune responses by tumor-infiltrating T cells and B lymphocytes against cancer. Both M-MDSCs and γδ T cells have been associated with worse prognosis for multiple epithelial cancers.

CONCLUSION

Here we discuss recent discoveries on how tumor-associated macrophages and precursor M-MDSCs as well as tumor associated-γδ T cells acquire immunosuppressive abilities in the tumor beds, promote cancer metastasis, and perspectives on how possible novel interventions could restore the effective adaptive immune responses in epithelial cancers.

The protective effect of intranasal immunization with influenza virus recombinant adenovirus vaccine on mucosal and systemic immune response

Influenza virus is a kind of virus that poses several hazards of animal and human health. Therefore, it is important to develop an effective vaccine to prevent influenza. To this end we successfully packaged recombinant adenovirus rAd-NP-M2e-GFP expressing multiple copies of influenza virus conserved antigens NP and M2e and packaged empty vector adenovirus rAd-GFP. The effect of rAd-NP-M2e-GFP on the activation of dendritic cell (DC) in vitro and in vivo was detected by intranasal immunization. The results showed that rAd-NP-M2e-GFP promoted the activation of DC in vitro and in vivo. After the primary immunization and booster immunization of mice through the nasal immune way, the results showed that rAd-NP-M2e-GFP induced enhanced local mucosal-specific T cell responses, increased the content of SIgA in broncho alveolar lavage fluids (BALF) and triggered the differentiation of B cells in the germinal center. It is proved that rAd-NP-M2e-GFP can significantly elicit mucosal immunity and systemic immune response. In addition, rAd-NP-M2e-GFP could effectively protect mice after H1N1 influenza virus challenge. To lay the foundation and provide reference for further development of influenza virus mucosal vaccine in the future.

Advances in tumor immune microenvironment of head and neck squamous cell carcinoma: A review of literature

Squamous cell carcinoma is seen as principal malignancy of head and neck. Tumor immune microenvironment plays a vital role in the occurrence, development and treatment of head and neck squamous cell carcinoma (HNSCC). The effect of immunotherapy, in particular, is closely related to tumor immune microenvironment. This review searched for high-quality literature included within PubMed, Web of Science, and Scopus using the keywords "head and neck cancers," "tumor microenvironment" and "immunotherapy," with the view to summarizing the characteristics of HNSCC immune microenvironment and how various subsets of immune cells promote tumorigenesis. At the same time, based on the favorable prospects of immunotherapy having been shown currently, the study is committed to pinpointing the latest progress of HNSCC immunotherapy, which is of great significance in not only further guiding the diagnosis and treatment of HNSCC, but also conducting its prognostic judgement.

Reciprocal relationship between cancer stem cells and myeloid-derived suppressor cells: implications for tumor progression and therapeutic strategies

Recently, there has been an increased focus on cancer stem cells (CSCs) due to their resilience, making them difficult to eradicate. This resilience often leads to tumor recurrence and metastasis. CSCs adeptly manipulate their surroundings to create an environment conducive to their survival. In this environment, myeloid-derived suppressor cells (MDSCs) play a crucial role in promoting epithelial-mesenchymal transition and bolstering CSCs' stemness. In response, CSCs attract MDSCs, enhancing their infiltration, expansion and immunosuppressive capabilities. This interaction between CSCs and MDSCs increases the difficulty of antitumor therapy. In this paper, we discuss the interplay between CSCs and MDSCs based on current research and highlight recent therapeutic strategies targeting either CSCs or MDSCs that show promise in achieving effective antitumor outcomes.

The role of stromal cells in epithelial-mesenchymal plasticity and its therapeutic potential

The epithelial-mesenchymal transition (EMT) is a critical tumor invasion and metastasis process. EMT enables tumor cells to migrate, detach from their original location, enter the circulation, circulate within it, and eventually exit from blood arteries to colonize in foreign sites, leading to the development of overt metastases, ultimately resulting in death. EMT is intimately tied to stromal cells around the tumor and is controlled by a range of cytokines secreted by stromal cells. This review summarizes recent research on stromal cell-mediated EMT in tumor invasion and metastasis. We also discuss the effects of various stromal cells on EMT induction and focus on the molecular mechanisms by which several significant stromal cells convert from foes to friends of cancer cells to fuel EMT processes via their secretions in the tumor microenvironment (TME). As a result, a better knowledge of the role of stromal cells in cancer cells' EMT may pave the path to cancer eradication.

Regulation of T cells by myeloid-derived suppressor cells: emerging immunosuppressor in lung cancer

Myeloid-derived suppressor cells (MDSCs), major components maintaining the immune suppressive microenvironment in lung cancer, are relevant to the invasion, metastasis, and poor prognosis of lung cancer, through the regulation of epithelial-mesenchymal transition, remodeling of the immune microenvironment, and regulation of angiogenesis. MDSCs regulate T-cell immune functions by maintaining a strong immunosuppressive microenvironment and promoting tumor invasion. This raises the question of whether reversing the immunosuppressive effect of MDSCs on T cells can improve lung cancer treatment. To understand this further, this review explores the interactions and specific mechanisms of different MDSCs subsets, including regulatory T cells, T helper cells, CD8 + T cells, natural killer T cells, and exhausted T cells, as part of the lung cancer immune microenvironment. Second, it focuses on the guiding significance confirmed via clinical liquid biopsy and tissue biopsy that different MDSC subsets improve the prognosis of lung cancer. Finally, we conclude that targeting MDSCs through action targets or signaling pathways can help regulate T-cell immune functions and suppress T-cell exhaustion. In addition, immune checkpoint inhibitors targeting MDSCs may serve as a new approach for enhancing the efficiency of immunotherapy and targeted therapy for lung cancer in the future, providing better comprehensive options for lung cancer treatment.

The epithelial-mesenchymal plasticity landscape: principles of design and mechanisms of regulation

Epithelial-mesenchymal plasticity (EMP) enables cells to interconvert between several states across the epithelial-mesenchymal landscape, thereby acquiring hybrid epithelial/mesenchymal phenotypic features. This plasticity is crucial for embryonic development and wound healing, but also underlies the acquisition of several malignant traits during cancer progression. Recent research using systems biology and single-cell profiling methods has provided novel insights into the main forces that shape EMP, which include the microenvironment, lineage specification and cell identity, and the genome. Additionally, key roles have emerged for hysteresis (cell memory) and cellular noise, which can drive stochastic transitions between cell states. Here, we review these forces and the distinct but interwoven layers of regulatory control that stabilize EMP states or facilitate epithelial-mesenchymal transitions (EMTs) and discuss the therapeutic potential of manipulating the EMP landscape.

The Activation of PPARγ by (2Z,4E,6E)-2-methoxyocta-2,4,6-trienoic Acid Counteracts the Epithelial–Mesenchymal Transition Process in Skin Carcinogenesis

Cutaneous squamous cell carcinoma (cSCC) is the most common UV-induced keratinocyte-derived cancer, and its progression is characterized by the epithelial–mesenchymal transition (EMT) process. We previously demonstrated that PPARγ activation by 2,4,6-octatrienoic acid (Octa) prevents cutaneous UV damage. We investigated the possible role of the PPARγ activators Octa and the new compound (2Z,4E,6E)-2-methoxyocta-2,4,6-trienoic acid (A02) in targeting keratinocyte-derived skin cancer. Like Octa, A02 exerted a protective effect against UVB-induced oxidative stress and DNA damage in NHKs. In the squamous cell carcinoma A431 cells, A02 inhibited cell proliferation and increased differentiation markers’ expression. Moreover, Octa and even more A02 counteracted the TGF-β1-dependent increase in mesenchymal markers, intracellular ROS, the activation of EMT-related signal transduction pathways, and cells’ migratory capacity. Both compounds, especially A02, counterbalanced the TGF-β1-induced cell membrane lipid remodeling and the release of bioactive lipids involved in EMT. In vivo experiments on a murine model useful to study cell proliferation in adult animals showed the reduction of areas characterized by active cell proliferation in response to A02 topical treatment. In conclusion, targeting PPARγ may be useful for the prevention and treatment of keratinocyte-derived skin cancer.

Deciphering the roles of myeloid derived suppressor cells in viral oncogenesis

Myeloid derived suppressor cells (MDSCs) are a heterogenous population of myeloid cells derived from monocyte and granulocyte precursors. They are pathologically expanded in conditions of ongoing inflammation where they function to suppress both innate and adaptive immunity. They are subdivided into three distinct subsets: monocytic (M-) MDSC, polymorphonuclear (or neutrophilic) (PMN-) MDSC and early-stage (e-) MDSC that may exhibit differential function in different pathological scenarios. However, in cancer they are associated with inhibition of the anti-tumour immune response and are universally associated with a poor prognosis. Seven human viruses classified as Group I carcinogenic agents are jointly responsible for nearly one fifth of all human cancers. These viruses represent a large diversity of species, including DNA, RNA and retroviridae. They include the human gammaherpesviruses (Epstein Barr virus (EBV) and Kaposi's Sarcoma-Associated Herpesvirus (KSHV), members of the high-risk human papillomaviruses (HPVs), hepatitis B and C (HBV, HCV), Human T cell leukaemia virus (HTLV-1) and Merkel cell polyomavirus (MCPyV). Each of these viruses encode an array of different oncogenes that perturb numerous cellular pathways that ultimately, over time, lead to cancer. A prerequisite for oncogenesis is therefore establishment of chronic infection whereby the virus persists in the host cells without being eradicated by the antiviral immune response. Although some of the viruses can directly modulate the immune response to enable persistence, a growing body of evidence suggests the immune microenvironment is modulated by expansions of MDSCs, driven by viral persistence and oncogenesis. It is likely these MDSCs play a role in loss of immune recognition and function and it is therefore essential to understand their phenotype and function, particularly given the increasing importance of immunotherapy in the modern arsenal of anti-cancer therapies. This review will discuss the role of MDSCs in viral oncogenesis. In particular we will focus upon the mechanisms thought to drive the MDSC expansions, the subsets expanded and their impact upon the immune microenvironment. Importantly we will explore how MDSCs may modulate current immunotherapies and their impact upon the success of future immune-based therapies.

Regulation of epithelial-mesenchymal transition by tumor microenvironmental signals and its implication in cancer therapeutics

Epithelial-mesenchymal transition (EMT) has been implicated in various aspects of tumor development, including tumor invasion and metastasis, cancer stemness, and therapy resistance. Diverse stroma cell types along with biochemical and biophysical factors in the tumor microenvironment impinge on the EMT program to impact tumor progression. Here we provide an in-depth review of various tumor microenvironmental signals that regulate EMT in cancer. We discuss the molecular mechanisms underlying the role of EMT in therapy resistance and highlight new therapeutic approaches targeting the tumor microenvironment to impact EMT and tumor progression.

Potential Molecular Mechanism of Upregulated Aryl Hydrocarbon Receptor Nuclear Translocator 2 in Nasopharyngeal Carcinoma

Background. Currently, the benefits of nasopharyngeal carcinoma (NPC) therapy are limited, and it is necessary to further explore possible therapeutic targets. Aryl hydrocarbon receptor nuclear translocator 2 (ARNT2) has been extensively studied in other cancer species, but little has been explored in NPC. The aim of this study was to verify the expression level of ARNT2 and its underlying mechanism in NPC. Methods. Datasets containing ARNT2 mRNA expression levels were retrieved and collected from various databases to explore the expression status of ARNT2 in NPC. ARNT2-related coexpressed genes, differential expressed genes, and target genes were obtained for functional enrichment analysis. The potential target gene of ARNT2 and their regulatory relationship were studied through ChIP-seq data. CIBERSORTx was used to assess the immune infiltration of NPC, and the association with ARNT2 expression was calculated through correlation analysis. Results. ARNT2 was upregulated and possessed an excellent discriminatory capability in NPC samples. ARNT2 positively correlated target genes were clustered in pathways in cancer, while negatively correlated target genes were enriched in immune-related pathway. The ChIP-seq information of ARNT2 and histone showed that prostaglandin-endoperoxide synthase 2 (PTGS2) was a potential target gene of ARNT2. CIBERSORTx revealed the immunity status in NPC, and ARNT2 expression was correlated with infiltration of five immune cells. Conclusions. ARNT2 is overexpressed in NPC and may regulate PTGS2 to participate in the cancer process. ARNT2 serves as a key oncogenic target in NPC patients.

Integrated analysis of bulk and single-cell RNA sequencing reveals the interaction of PKP1 and tumor-infiltrating B cells and their therapeutic potential for nasopharyngeal carcinoma

Immunotherapy is an individualized therapeutic strategy for nasopharyngeal carcinoma (NPC). However, few molecular targets are clinically satisfactory. This work aimed to integrate bulk and single-cell RNA sequencing data to identify novel biomarkers involved in NPC. We performed differentially expressed gene (DEG) analysis, Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and immune cell infiltration analysis prior to correlation analysis of the identified genes and immune cells and further assessed the prognostic effects of the biomarkers and immune cells in NPC. As a result, PKP1, a potential molecular biomarker associated with immune infiltration, and tumor-infiltrating lymphocyte-B cells (TIL-Bs) were identified as promising therapeutic targets for NPC. Importantly, immunohistochemistry (IHC) validated that PKP1 protein expression was mainly found in NPC cells rather than noncancerous cells. In addition, the tumor microenvironment (TME) of NPC was characterized by the infiltration of more dendritic cells (DCs) and γδT cells but fewer B cells. Our results suggest that the interaction of PKP1 and TIL-B cells is involved in NPC development. It is possible that TIL-B cells produce immunoglobulin G (IgG) to tumor antigens, such as PKP1, or viral antigens, including EBV and HPV, to execute antitumor ability through DC and T cells. In response, NPC cells express proteins such as PKP1 (absent in normal nasopharynx) to induce myeloid-derived suppressor cell (MDSC) expansion, which subsequently impairs the proliferation of B cells and results in B-cell death by generating iNOS and NOX2. In summary, our findings provide a potential therapeutic strategy for NPC by disrupting the interaction of PKP1 and TIL-Bs in the TME.

Poria Acid, Triterpenoids Extracted from Poria cocos, Inhibits the Invasion and Metastasis of Gastric Cancer Cells

Background: Poria cocos (P. cocos) is an important medicinal fungus in traditional Chinese medicine. Poria acid (PA), a triterpenoid compound, is an effective component of traditional Chinese medicine P. cocos. This experiment investigated the anti-gastric cancer biological activity of PA in vitro. Methods: The effect of PA on the viability of gastric cancer cells was detected by the thiazolyl blue (MTT) assay. Cell adhesion assays were used to detect changes in the adhesion of cells treated after PA (0, 20, 40, and 80 µmol/L). The ability of cell invasion and migration were detected by Transwell assays and wound healing assays. A high-content imaging system was used to dynamically record the motility of the gastric cancer cells after PA (0, 20, 40, and 80 µmol/L) treatment. Western blotting was used to detect the expression of epithelial–mesenchymal transformation (EMT), invasion and migration related proteins. Results: The MTT assay showed that the proliferation of gastric cancer cells was significantly inhibited after PA treatment. Cell adhesion experiments showed that the adhesion of gastric cancer cells was significantly decreased after PA treatment. Compared with the control group, the wound healing area of the gastric cancer cells treated with different concentrations of PA decreased. The Transwell assay showed that the number of gastric cancer cells passing through the cell membrane were significantly reduced after PA treatment. In addition, after PA treatment, the cells’ movement distance and average movement speed were significantly lower than those of the control group. Finally, PA can significantly alter the expression of EMT-related proteins E-cadherin, N-cadherin, and Vimentin and decreased the expressions of metastasis-related proteins matrix metalloproteinase (MMP) 2, MMP-9 and tissue inhibition of matrix metalloproteinase (TIMP)1 in the gastric cancer cells. Conclusions: Triterpenoids from P. cocos have significant biological activity against gastric cancer, and the mechanism may be involved in the process of epithelial–mesenchymal transformation.

Extracellular vesicles rich in HAX1 promote angiogenesis by modulating ITGB6 translation

Tumour-associated angiogenesis plays a critical role in metastasis, the main cause of malignancy-related death. Extracellular vesicles (EVs) can regulate angiogenesis to participate in tumour metastasis. Our previous study showed that EVs rich in HAX1 are associated with in metastasis of nasopharyngeal carcinoma (NPC). However, the mechanism by which HAX1 of EVs promotes metastasis and angiogenesis is unclear. In this study, we demonstrated that EVs rich in HAX1 promote angiogenesis phenotype by activating the FAK pathway in endothelial cells (ECs) by increasing expression level of ITGB6. The expression level of HAX1 is markedly correlated with microvessel density (MVDs) in NPC and head and neck cancers based on an analysis of IHC. In addition to a series of in vitro cellular analyses, in vivo models revealed that HAX1 was correlated with migration and blood vessel formation of ECs, and metastasis of NPC. Using ribosome profiling, we found that HAX1 regulates the FAK pathway to influence microvessel formation and promote NPC metastasis by enhancing the translation efficiency of ITGB6. Our findings demonstrate that HAX1 can be used as an important biomarker for NPC metastasis, providing a novel basis for antiangiogenesis therapy in clinical settings.

Upregulation of PNCK Promotes Metastasis and Angiogenesis via Activating NF-κB/VEGF Pathway in Nasopharyngeal Carcinoma

Background

Distant metastasis is the major cause of treatment failure in patients with nasopharyngeal carcinoma (NPC). Thus, the identification of the molecular mechanisms and the development of novel therapeutic strategies are important. Previous studies suggest that PNCK promotes tumor growth by suppressing PI3K/AKT/mTOR signaling in NPC. However, the underlying regulatory mechanism of PNCK for NPC invasion and metastasis remains unclear.

Methods

The PNCK expression level was evaluated in nonmetastatic and metastatic NPC specimens by mRNA sequencing and immunohistochemistry. In vitro migration and invasion and in vivo nude mouse metastasis model and zebrafish model were used to evaluate the effects of PNCK ectopic expression on the metastatic ability of NPC cells. Gene set enrichment and western blot analyses were used to investigate the PNCK downstream signaling pathway.

Results

Human metastatic NPC samples showed elevated PNCK expression at both mRNA and protein levels. Upregulated PNCK promoted in vitro NPC cell migration, invasion, and the formation of lung metastases; the vascular-labeled fluorescence signal increased in the in vivo zebrafish model. Mechanistically, pathway analysis showed that the upregulation of PNCK may promote cell metastasis by activating the NF-κB/VEGF signaling pathway.

Conclusions

These findings revealed the specific critical role of PNCK in promoting NPC metastasis and angiogenesis, which suggested that PNCK may have implications as a potential therapeutic target for individualized NPC treatment.

The immune modulation effects of gemcitabine plus cisplatin induction chemotherapy in nasopharyngeal carcinoma

Background

Studies are trying to add immunotherapy to gemcitabine and cisplatin (GP) induction chemotherapy, the standard therapy, in nasopharyngeal carcinoma (NPC) patients with locoregionally advanced disease. However, how the immune system responds to GP remains unknown.

Method

We examined the dynamic changes of circulating immune cells and plasma cytokines in NPC patients administered with GP.

Result

After GP administration, immunosuppressive myeloid cells, including CD11b+CD14+ monocytes, CD33+ myeloid cells, CD33+CD11+ myeloid cells, total MDSCs (CD33+CD11+HLA‐DR−/low), monocytic MDSCs, and granulocytic MDSCs decreased significantly. The regulatory T cells and B cells, two important suppressive lymphocyte subpopulations, also decreased. On the other hand, the levels of CD3+ T cells, total B cells, central memory CD4+ T cells, and pro‐inflammatory cytokines (including Interleukin [IL]‐1β, IL‐6, IL‐2, IL‐5, and IL‐8) increased significantly after GP administration. Besides, GP chemotherapy did not weaken the cytotoxic activity and proliferative capacity of T cells.

Conclusion

Our results showed the immune modulation effect of GP induction chemotherapy in locoregionally advanced NPC, providing a solid basis for its combination with immunotherapy.

Nasopharyngeal Carcinoma and Its Microenvironment: Past, Current, and Future Perspectives

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy that raises public health concerns in endemic countries. Despite breakthroughs in therapeutic strategies, late diagnosis and drug resistance often lead to unsatisfactory clinical outcomes in NPC patients. The tumor microenvironment (TME) is a complex niche consisting of tumor-associated cells, such as fibroblasts, endothelial cells, leukocytes, that influences tumor initiation, progression, invasion, and metastasis. Cells in the TME communicate through various mechanisms, of note, exosomes, ligand-receptor interactions, cytokines and chemokines are active players in the construction of TME, characterized by an abundance of immune infiltrates with suppressed immune activities. The NPC microenvironment serves as a target-rich niche for the discovery of potential promising predictive or diagnostic biomarkers and the development of therapeutic strategies. Thus, huge efforts have been made to exploit the role of the NPC microenvironment. The whole picture of the NPC microenvironment remains to be portrayed to understand the mechanisms underlying tumor biology and implement research into clinical practice. The current review discusses the recent insights into the role of TME in the development and progression of NPC which results in different clinical outcomes of patients. Clinical interventions with the use of TME components as potential biomarkers or therapeutic targets, their challenges, and future perspectives will be introduced. This review anticipates to provide insights to the researchers for future preclinical, translational and clinical research on the NPC microenvironment.

Identification of Novel Kinase-Transcription Factor-mRNA-miRNA Regulatory Network in Nasopharyngeal Carcinoma by Bioinformatics Analysis

Purpose

Nasopharyngeal carcinoma (NPC) is one of the most common malignant tumors of the head and neck. This study aimed to investigate the crucial genes and regulatory networks involved in the carcinogenesis of NPC using a bioinformatics approach.

Methods

Five mRNA and two miRNA expression datasets were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) and miRNAs (DEMs) between NPC and normal samples were analyzed using R software. The WebGestalt tool was used for functional enrichment analysis, and protein-protein interaction (PPI) network analysis of DEGs was performed using STRING database. Transcription factors (TFs) were predicted using TRRUST and Transcriptional Regulatory Element Database (TRED). Kinases were identified using X2Kgui. The miRNAs of DEGs were predicted using miRWalk database. A kinase-TF-mRNA-miRNA integrated network was constructed, and hub nodes were selected. The hub genes were validated using NPC datasets from the GEO and Oncomine databases. Finally, candidate small-molecule agents were predicted using CMap.

Results

A total of 122 DEGs and 44 DEMs were identified. DEGs were associated with the immune response, leukocyte activation, endoplasmic reticulum stress in GO analysis, and the NF-κB signaling pathway in KEGG analysis. Four significant modules were identified using PPI network analysis. Subsequently, 26 TFs, 73 kinases, and 2499 miRNAs were predicted. The predicted miRNAs were cross-referenced with DEMs, and seven overlapping miRNAs were selected. In the kinase-TF-mRNA-miRNA integrated network, eight genes (PTGS2, FN1, MMP1, PLAU, MMP3, CD19, BMP2, and PIGR) were identified as hub genes. Hub genes were validated with consistent results, indicating the reliability of our findings. Finally, six candidate small-molecule agents (phenoxybenzamine, luteolin, thioguanosine, reserpine, blebbistatin, and camptothecin) were predicted.

Conclusion

We identified DEGs and an NPC regulatory network involving kinases, TFs, mRNAs, and miRNAs, which might provide promising insight into the pathogenesis, treatment, and prognosis of NPC.

Epstein-Barr Virus-Associated Malignancies and Immune Escape: The Role of the Tumor Microenvironment and Tumor Cell Evasion Strategies

Simple Summary

The Epstein–Barr virus, also termed human herpes virus 4, is a human pathogenic double-stranded DNA virus. It is highly prevalent and has been linked to the development of 1–2% of cancers worldwide. EBV-associated malignancies encompass various structural and epigenetic alterations. In addition, EBV-encoded gene products and microRNAs interfere with innate and adaptive immunity and modulate the tumor microenvironment. This review provides an overview of the characteristic features of EBV with a focus on the intrinsic and extrinsic immune evasion strategies, which contribute to EBV-associated malignancies.

Abstract

The detailed mechanisms of Epstein–Barr virus (EBV) infection in the initiation and progression of EBV-associated malignancies are not yet completely understood. During the last years, new insights into the mechanisms of malignant transformation of EBV-infected cells including somatic mutations and epigenetic modifications, their impact on the microenvironment and resulting unique immune signatures related to immune system functional status and immune escape strategies have been reported. In this context, there exists increasing evidence that EBV-infected tumor cells can influence the tumor microenvironment to their own benefit by establishing an immune-suppressive surrounding. The identified mechanisms include EBV gene integration and latent expression of EBV-infection-triggered cytokines by tumor and/or bystander cells, e.g., cancer-associated fibroblasts with effects on the composition and spatial distribution of the immune cell subpopulations next to the infected cells, stroma constituents and extracellular vesicles. This review summarizes (i) the typical stages of the viral life cycle and EBV-associated transformation, (ii) strategies to detect EBV genome and activity and to differentiate various latency types, (iii) the role of the tumor microenvironment in EBV-associated malignancies, (iv) the different immune escape mechanisms and (v) their clinical relevance. This gained information will enhance the development of therapies against EBV-mediated diseases to improve patient outcome.

Src-1 and SP2 promote the proliferation and epithelial-mesenchymal transition of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is characterized by high morbidity and morality, especially in Southern China. Transcription factors intensively participate in the initiation and development of NPC. This study aimed to investigate the roles of Src-1 in NPC. mRNA level was determined by qRT-PCR. Western blot was carried out for the protein level. CCK-8 assay was performed to determine cell viability, colony formation for NPC cell proliferation, and transwell for cell migration and invasion ability. The results showed Steroid receptor coactivator 1 (Src-1) was overexpressed in SNE-2 and 6-10B. The expression of Src-1 and SP2 was in positive correlation. Overexpression of Src-1 promoted the cell viability, colony formation, and epithelial-mesenchymal transition (EMT), manifested by the increase of migration and invasion ability, while knockdown of Src-1 exerted opposite effects. Additionally, knockdown or overexpression of SP2 reversed the effects of overexpressed or downregulated Src-1, which was reversed by the depletion of SP2. Moreover, Src-1 interacted with SP2 to regulate EMT-related genes such as E-cad, N-cad, Vimentin, and ZEB1, and proliferation- and apoptosis-related genes, such as bax, cytochrome c, and cleaved caspase3 and bcl-2. Thus, blocking the interaction between Src-1 and SP2 may be a therapeutic target for inhibiting the metastasis of NPC.

The Inflammatory Profile of the Tumor Microenvironment, Orchestrated by Cyclooxygenase-2, Promotes Epithelial-Mesenchymal Transition

The tumor microenvironment (TME) corresponds to a complex and dynamic interconnection between the extracellular matrix and malignant cells and their surrounding stroma composed of immune and mesenchymal cells. The TME has constant cellular communication through cytokines that sustain an inflammatory profile, which favors tumor progression, angiogenesis, cell invasion, and metastasis. Although the epithelial-mesenchymal transition (EMT) represents a relevant metastasis-initiating event that promotes an invasive phenotype in malignant epithelial cells, its relationship with the inflammatory profile of the TME is poorly understood. Previous evidence strongly suggests that cyclooxygenase-2 (COX-2) overexpression, a pro-inflammatory enzyme related to chronic unresolved inflammation, is associated with common EMT-signaling pathways. This review article summarizes how COX-2 overexpression, within the context of the TME, orchestrates the EMT process and promotes initial metastatic-related events.

Nuclear exosome HMGB3 secreted by nasopharyngeal carcinoma cells promotes tumour metastasis by inducing angiogenesis

Distant metastasis accompanied by angiogenesis is the main cause of nasopharyngeal carcinoma (NPC)-related death. Nuclear exosomes (nEXOs) are potential tumour biomarkers. High mobility group box 3 (HMGB3), a nuclear protein, is known to be overexpressed in cancers. However, its role in NPC has not been elucidated. Here, we explore for the first time the function of nEXO HMGB3 in tumour angiogenesis involved in NPC metastasis using a series of in vitro experiments with NPC cell lines and clinical specimens and in vivo experiments with tumour xenograft zebrafish angiogenesis model. We found a high expression of HMGB3 in NPC, accompanied by the formation of micronuclei, to be associated with metastasis. Furthermore, the NPC-secreted HMGB3 expression was associated with tumour angiogenesis. Moreover, HMGB3-containing nEXOs, derived from the micronuclei of NPC cells, were ingested by the human umbilical vein endothelial cells (HUVECs), and accelerated angiogenesis in vitro and in vivo. Importantly, western blotting and flow cytometry analysis showed that circulating nEXO HMGB3 positively correlated with NPC metastasis. In summary, nEXO HMGB3 can be a significant biomarker of NPC metastasis and provide a novel basis for anti-angiogenesis therapy in clinical metastasis.

Epithelial-mesenchymal transition: When tumor cells meet myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous myeloid cell population characterized by protumoral functions in the tumor immune network. An increasing number of studies have focused on the biological functions of MDSCs in tumor immunity. Epithelial-mesenchymal transition (EMT) is a cellular plasticity process accompanied by a loss of epithelial phenotypes and an acquisition of mesenchymal phenotypes. In general, tumor cells that undergo EMT are more likely to invade and metastasize. Recently, extensive evidence suggests that EMT is closely related to a highly immunosuppressive environment. This review will summarize the immunosuppressive capacities of MDSC subsets and their distinct role in tumor EMT and further discuss immunotherapy for tumor EMT by targeting MDSCs.

Comprehensive single-cell sequencing reveals the stromal dynamics and tumor-specific characteristics in the microenvironment of nasopharyngeal carcinoma

The tumor microenvironment (TME) of nasopharyngeal carcinoma (NPC) harbors a heterogeneous and dynamic stromal population. A comprehensive understanding of this tumor-specific ecosystem is necessary to enhance cancer diagnosis, therapeutics, and prognosis. However, recent advances based on bulk RNA sequencing remain insufficient to construct an in-depth landscape of infiltrating stromal cells in NPC. Here we apply single-cell RNA sequencing to 66,627 cells from 14 patients, integrated with clonotype identification on T and B cells. We identify and characterize five major stromal clusters and 36 distinct subpopulations based on genetic profiling. By comparing with the infiltrating cells in the non-malignant microenvironment, we report highly representative features in the TME, including phenotypic abundance, genetic alternations, immune dynamics, clonal expansion, developmental trajectory, and molecular interactions that profoundly influence patient prognosis and therapeutic outcome. The key findings are further independently validated in two single-cell RNA sequencing cohorts and two bulk RNA-sequencing cohorts. In the present study, we reveal the correlation between NPC-specific characteristics and progression-free survival. Together, these data facilitate the understanding of the stromal landscape and immune dynamics in NPC patients and provides deeper insights into the development of prognostic biomarkers and therapeutic targets in the TME.

An Overview of Advances in Cell-Based Cancer Immunotherapies Based on the Multiple Immune-Cancer Cell Interactions

Tumors have a complex ecosystem in which behavior and fate are determined by the interaction of diverse cancerous and noncancerous cells at local and systemic levels. A number of studies indicate that various immune cells participate in tumor development (Fig. 1). In this review, we will discuss interactions among T lymphocytes (T cells), B cells, natural killer (NK) cells, dendritic cells (DCs), tumor-associated macrophages (TAMs), neutrophils, and myeloid-derived suppressor cells (MDSCs). In addition, we will touch upon attempts to either use or block subsets of immune cells to target cancer.

Accumulation of LOX-1+ PMN-MDSCs in nasopharyngeal carcinoma survivors with chronic hepatitis B might permit immune tolerance to epstein-barr virus and relate to tumor recurrence

Chronic hepatitis B (CHB) has been reported to be associated with impaired prognosis for patients with nasopharyngeal carcinoma (NPC). However, the latent mechanism is unclear. Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) induce immune suppression in CHB and promote the development of hepatocellular carcinoma. Lectin-type oxidized LDL receptor-1 (LOX-1) was recently identified as a specific marker for PMN-MSDC. We found NPC survivors with CHB had high levels of LOX-1⁺ PMN-MDSCs. LOX-1⁺ PMN-MDSCs significantly reduced T cell proliferation and activation. Endoplasmic reticulum stress was induced in LOX-1⁺ PMN-MDSCs. In addition, LOX-1⁺ PMN-MDSCs increased their expression of NOX2, a key reactive oxygen species (ROS)-related genes, and levels of ROS illustrated by the DCFDA test. The ROS inhibitor N-acetylcysteine abrogated the suppression of LOX-1⁺ PMN-MDSCs on T cell activation. The EBV DNA-positivity rate was higher in NPC survivors with CHB than in NPC patients without CHB. Those presenting with positive EBV DNA displayed higher LOX-1⁺ PMN-MDSC levels. LOX-1⁺ PMN-MDSCs suppressed the CD8⁺ T cell response against EBV. This study revealed LOX-1⁺ PMN-MDSC accumulation and activation in NPC survivors with CHB. LOX-1⁺ PMN-MDSCs might suppress the host immune response to EBV through ER stress/ROS pathway. These results explained the association of CHB with unfavorable NPC prognosis.

LncRNA GAS5/miR‑4465 axis regulates the malignant potential of nasopharyngeal carcinoma by targeting COX2

Nasopharyngeal carcinoma is a malignant tumor that not only negatively affects the physical and mental health but also the quality of life of the patients. Growth arrest-specific transcript 5 (GAS5) is a common long-chain non-coding RNA (lncRNA) that has been reported to participate in the development of various cancers. However, the biological functions of lncRNA GAS5 in the occurrence and development of nasopharyngeal carcinoma are elusive. The expression of lncRNA GAS5 in nasopharyngeal carcinoma and normal samples were analyzed. Bioinformatic tool was utilized to predict the potential function of lncRNA in nasopharyngeal carcinoma. Transplanted mice were used for in vivo experiments. We observed that the expression of lncRNA GAS5 was upregulated in nasopharyngeal carcinoma tissues and cells. Down-regulation of lncRNA GAS5 inhibited the proliferation and promoted apoptosis of nasopharyngeal carcinoma cells. The expression of miR-4465 was down regulated in nasopharyngeal carcinoma tissues and cells. LncRNA GAS5 could directly bind to miR-4465 and regulated the expression of miR-4465. It was further confirmed that miR-4465 could directly bind with COX2 and inhibit the expression of COX2. Down-regulation of lncRNA GAS5 suppressed tumor growth, promoted the expression levels of miR-18a-5p and suppressed the expression of COX2 in vivo. LncRNA GAS5 regulated nasopharyngeal carcinoma malignancy through targeting miR-4465 and modulating COX2. The GAS5/miR-4465/COX2 axis in nasopharyngeal carcinoma pathogenesis was confirmed, which would provide a new therapeutic target for nasopharyngeal carcinoma.

Connecting METTL3 and intratumoural CD33+ MDSCs in predicting clinical outcome in cervical cancer

Background

Methyltransferase-like 3 (METTL3) is a member of the m⁶A methyltransferase family and acts as an oncogene in cancers. Recent studies suggest that host innate immunity is regulated by the enzymes controlling m⁶A epitranscriptomic changes. Here, we aim to explore the associations between the levels of METTL3 and CD33⁺ myeloid-derived suppressor cells (MDSCs) in tumour tissues and the survival of patients with cervical cancer (CC).

Methods

Specimens of paraffin embedded tumour from 197 CC patients were collected. The expression levels of METTL3 and CD33 were measured by immunohistochemical (IHC) staining. The clinical associations of the IHC variants were analysed by Pearson’s or Spearman’s chi-square tests. Overall survival (OS) and disease-free survival (DFS) were estimated by the Kaplan–Meier method and log-rank test. Hazard ratios (HRs) and independent significance were obtained via Cox proportional hazards models for multivariate analyses. METTL3 in CD33⁺ cells or CC-derived cells was knocked down by METTL3-specific siRNA, and MDSC induction in vitro was performed in a co-culture system in the presence of METTL3-siRNA and METTL3-knockdown-CC-derived cells compared with that of the corresponding controls.

Results

We found that tumour tissues displayed increased levels of METTL3 and CD33⁺ MDSCs compared with tumour-adjacent tissues from the same CC patients. Importantly, METTL3 expression was positively related to the density of CD33⁺ cells in tumour tissues (P = 0.011). We further found that the direct CD33⁺CD11b⁺HLA-DR⁻ MDSC induction and tumour-derived MDSC induction in vitro were decreased in the absence of METTL3. The level of METTL3 in tumour microenvironments was significantly related to advanced tumour stage. The levels of METTL3 and CD33⁺ MDSCs in tumour tissues were notably associated with reduced DFS or OS. Cox model analysis revealed that the level of METTL3 in tumour cells was an independent factor for patient survival, specifically for DFS (HR = 3.157, P = 0.022) and OS (HR = 3.271, P = 0.012), while the CD33⁺ MDSC number was an independent predictor for DFS (HR: 3.958, P = 0.031). Interestingly, in patients with advanced-disease stages (II–IV), METTL3 in tumour cells was an independent factor for DFS (HR = 6.725, P = 0.010) and OS (HR = 5.140, P = 0.021), while CD33⁺ MDSC density was an independent factor for OS (HR = 8.802, P = 0.037).

Conclusion

Our findings suggest that CD33⁺ MDSC expansion is linked to high levels of METTL3 and that METTL3 and CD33⁺ MDSCs are independent prognostic factors in CC.

Hypoxia Induces Mitochondrial Defect That Promotes T Cell Exhaustion in Tumor Microenvironment Through MYC-Regulated Pathways

T cell exhaustion is an obstacle to immunotherapy for solid tumors. An understanding of the mechanism by which T cells develop this phenotype in solid tumors is needed. Here, hypoxia, a feature of the tumor microenvironment, causes T cell exhaustion (T_Exh) by inducing a mitochondrial defect. Upon exposure to hypoxia, activated T cells with a T_Exh phenotype are characterized by mitochondrial fragmentation, decreased ATP production, and decreased mitochondrial oxidative phosphorylation activity. The T_Exh phenotype is correlated with the downregulation of the mitochondrial fusion protein mitofusin 1 (MFN1) and upregulation of miR-24. Overexpression of miR-24 alters the transcription of many metabolism-related genes including its target genes MYC and fibroblast growth factor 11 (FGF11). Downregulation of MYC and FGF11 induces T_Exh differentiation, reduced ATP production and a loss of the mitochondrial mass in T cell receptor (TCR)-stimulated T cells. In addition, we determined that MYC regulates the transcription of FGF11 and MFN1. In nasopharyngeal carcinoma (NPC) tissues, the T cells exhibit an increased frequency of exhaustion and loss of mitochondrial mass. In addition, inhibition of miR-24 signaling decreases NPC xenograft growth in nude mice. Our findings reveal a mechanism for T cell exhaustion in the tumor environment and provide potential strategies that target mitochondrial metabolism for cancer immunotherapy.

The TGF-β1/COX-2-dependant pathway serves a key role in the generation of OKC-induced M2-polarized macrophage-like cells and angiogenesis

An odontogenic keratocyst (OKC) is a common oral cyst arising from the odontogenic epithelium, which has the characteristics of a tumor. Previous studies have demonstrated that M2-polarized macrophages and angiogenesis have important roles in the progression of OKCs. As transforming growth factor (TGF)-β1 is important in growth and developmental processes, and early studies have indicated that TGF-β1 is upregulated in OKCs, the present study aimed to investigate the expression levels of TGF-β1 as a first step. Flow cytometric analysis suggested that TGF-β1 induced M2-polarization of macrophages in a dose-dependent manner. Expression levels of cyclooxygenase (COX)-1 and −2 were measured after treatment of M2 macrophages with TGF-β1 and OKC homogenate supernatant. COX-2 expression was influenced by TGF-β1 in a concentration-dependent manner and in OKC induction. In addition, inhibition of COX-2 resulted in the induction of M2-polarization of macrophages via TGF-β1 and OKC disruption. Because the extracellular matrix (ECM) is altered in individuals with chronic diseases, the present study analyzed the expression of matrix metalloproteinase (MMP)-9, which is able to degrade the ECM. The present study observed a decrease in MMP-9 activity following treatment with TGF-β1 and OKC homogenate supernatant. Additionally, the present study analyzed tube formation caused by OKC with or without a COX-2 inhibitor. The results of the present study suggested that angiogenesis increased following treatment with OKC homogenate supernatant but decreased after treatment with a COX-2 inhibitor. These findings indicated that the TGF-β1/COX-2 pathway may have an important role in the progression of OKC.

Galectin-9 promotes a suppressive microenvironment in human cancer by enhancing STING degradation

Galectin-9 (Gal-9) is known to enhance the expansion of myeloid-derived suppressor cells (MDSCs) in murine models. Its contribution to the expansion of MDSCs in human malignancies remain to be investigated. We here report that Gal-9 expression in nasopharyngeal carcinoma (NPC) cells enhances the generation of MDSCs (CD33⁺CD11b⁺HLA-DR⁻) from CD33⁺ bystander cells. The underlying mechanisms involve both the intracellular and secreted Gal-9. Inside carcinoma cells, Gal-9 up-regulates the expression of a variety of pro-inflammatory cytokines which are critical for MDSC differentiation, including IL-1β and IL-6. This effect is mediated by accelerated STING protein degradation resulting from direct interaction of the Gal-9 carbohydrate recognition domain 1 with the STING C-terminus and subsequent enhancement of the E3 ubiquitin ligase TRIM29-mediated K48-linked ubiquitination of STING. Moreover, we showed that extracellular Gal-9 secreted by carcinoma cells can enter the myeloid cells and trigger the same signaling cascade. Consistently, high concentrations of tumor and plasma Gal-9 are associated with shortened survival of NPC patients. Our findings unearth that Gal-9 induces myeloid lineage-mediated immunosuppression in tumor microenvironments by suppressing STING signaling.

Emerging therapeutic targets for nasopharyngeal carcinoma: opportunities and challenges

Introduction: Nasopharyngeal carcinoma (NPC) is a major public health problem in several countries, especially those in Southeast Asia and North Africa. In its typical poorly differentiated form, the Epstein-Barr virus (EBV) genome is present in the nuclei of all malignant cells with restricted expression of a few viral genes. The malignant phenotype of NPC cells results from the influence of these viral products in combination with cellular genetic, epigenetic and functional alterations. With regard to host/tumor interactions, NPC is a remarkable example of immune escape in the context of a hot tumor.Areas covered: This article has an emphasis on emerging therapeutic targets that are considered upstream or at an early stage of clinical application. It examines targets related to cellular oncogenic alterations, latent EBV infection and tumor interactions with the immune system.Expert opinion: There is a remarkable emergence of new agents that target EBV products. The clinical application of these agents would benefit from a systematic and comprehensive molecular classification of NPCs and from easy access to pre-clinical models in public repositories. There is a strong rationale for more investigations on the potential of immune modulators, especially those related to NK cells.

Over-expression of cyclo-oxygenase-2 predicts poor survival of patients with nasopharyngeal carcinoma: a meta-analysis

OBJECTIVES

The conclusive prognostic significance of cyclo-oxygenase-2 has been determined in various cancers but not in nasopharyngeal carcinoma. Therefore, this study aimed to evaluate the relationship of cyclo-oxygenase-2 expression with the survival outcome and treatment response of nasopharyngeal carcinoma patients via a systematic meta-analysis approach.

METHODS

A meta-analysis was conducted in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses ('PRISMA') checklist. The primary clinical characteristics of patients, and hazard ratios with 95 per cent confidence intervals of overall survival data, were tabulated from eligible studies. The relationship of cyclo-oxygenase-2 expression with survival outcome (expressed as hazard ratio) and treatment response (expressed as odds ratio) in nasopharyngeal carcinoma patients was analysed, and explained with the aid of forest plot charts.

RESULTS AND CONCLUSION

The pooled hazard ratio for overall survival was 2.02 (95 per cent confidence interval = 1.65-2.47). This indicates that the over-expression of cyclo-oxygenase-2 is significantly associated with the poor survival of nasopharyngeal carcinoma patients. The pooled odds ratio of 0.98 (95 per cent confidence interval = 0.27-3.49) reveals that over-expression of cyclo-oxygenase-2 was not significantly related to the treatment outcome.

The Engagement Between MDSCs and Metastases: Partners in Crime

Tumor metastases represent the major cause of cancer-related mortality, confirming the urgent need to identify key molecular pathways and cell-associated networks during the early phases of the metastatic process to develop new strategies to either prevent or control distal cancer spread. Several data revealed the ability of cancer cells to establish a favorable microenvironment, before their arrival in distant organs, by manipulating the cell composition and function of the new host tissue where cancer cells can survive and outgrow. This predetermined environment is termed “pre-metastatic niche” (pMN). pMN development requires that tumor-derived soluble factors, like cytokines, growth-factors and extracellular vesicles, genetically and epigenetically re-program not only resident cells (i.e., fibroblasts) but also non-resident cells such as bone marrow-derived cells. Indeed, by promoting an “emergency” myelopoiesis, cancer cells switch the steady state production of blood cells toward the generation of pro-tumor circulating myeloid cells defined as myeloid-derived suppressor cells (MDSCs) able to sustain tumor growth and dissemination. MDSCs are a heterogeneous subset of myeloid cells with immunosuppressive properties that sustain metastatic process. In this review, we discuss current understandings of how MDSCs shape and promote metastatic dissemination acting in each fundamental steps of cancer progression from primary tumor to metastatic disease.

Energy metabolism manipulates the fate and function of tumour myeloid-derived suppressor cells

In recent years, a large number of studies have been carried out in the field of immune metabolism, highlighting the role of metabolic energy reprogramming in altering the function of immune cells. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells generated during a large array of pathological conditions, such as cancer, inflammation, and infection, and show remarkable ability to suppress T-cell responses. These cells can also change their metabolic pathways in response to various pathogen-derived or inflammatory signals. In this review, we focus on the roles of glucose, fatty acid (FA), and amino acid (AA) metabolism in the differentiation and function of MDSCs in the tumour microenvironment, highlighting their potential as targets to inhibit tumour growth and enhance tumour immune surveillance by the host. We further highlight the remaining gaps in knowledge concerning the mechanisms determining the plasticity of MDSCs in different environments and their specific responses in the tumour environment. Therefore, this review should motivate further research in the field of metabolomics to identify the metabolic pathways driving the enhancement of MDSCs in order to effectively target their ability to promote tumour development and progression.

High COX-2 expression in cancer-associated fibiroblasts contributes to poor survival and promotes migration and invasiveness in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) has the highest rate of metastasis among head and neck cancers, and distant metastasis is the major reason for treatment failure. We have previously shown that high cyclooxygenase-2 (COX-2) expression is associated with a poor prognosis of patients with NPC and inhibits chemotherapy-induced senescence in NPC cells. In this study, we found that COX-2 was upregulated in cancer-associated fibroblasts (CAFs) derived from NPC by RNA-Seq. Furthermore, elevated COX-2 expression in CAF was detected in NPC patients with poor survival and distant metastasis by using immunohistochemistry. Then, we identified that COX-2 is highly expressed in CAF at the distant metastasis site in seven paired NPC patients. High expression of COX-2 and secretion of prostaglandin E2, a major product catalyzed by COX-2 in fibroblasts, promotes migration and invasiveness of NPC cells in vitro. On the contrary, inhibition of COX-2 has the opposite effect in vitro as well as in the COX-2^-/- mouse with the lung metastasis model in vivo. Mechanistically, we discovered that COX-2 elevates tumor necrosis factor-α expression in CAF to promote NPC cell migration and invasiveness. Overall, our results identified a novel target in CAF promoting NPC metastasis. Our findings suggested that high expression of COX-2 in CAF may serve as a new prognostic indicator for NPC metastasis and provide the possibility of targeting CAF for treating advanced NPC.

Targeting Tumor Microenvironment by Small-Molecule Inhibitors

The tumor microenvironment (TME) is a hypoxic, acidic, and immune/inflammatory cell–enriched milieu that plays crucial roles in tumor development, growth, progression, and therapy resistance. Targeting TME is an attractive strategy for the treatment of solid tumors. Conventional cancer chemotherapies are mostly designed to directly kill cancer cells, and the effectiveness is always compromised by their penetration and accessibility to cancer cells. Small-molecule inhibitors, which exhibit good penetration and accessibility, are widely studied, and many of them have been successfully applied in clinics for cancer treatment. As TME is more penetrable and accessible than tumor cells, a lot of efforts have recently been made to generate small-molecule inhibitors that specifically target TME or the components of TME or develop special drug-delivery systems that release the cytotoxic drugs specifically in TME. In this review, we briefly summarize the recent advances of small-molecule inhibitors that target TME for the tumor treatment.

•

Tumor microenvironment (TME) is an indispensable part of tumor and is an important therapeutic target.

•

TME is more penetrable and accessible than tumor cell area.

•

Small-molecule inhibitors that target TME are very promising.

•

The target efficiency can be improved by specific deliver and release systems.

Communication between EMT and PD-L1 signaling: New insights into tumor immune evasion

Immune checkpoint blockage has been considered a breakthrough in cancer treatment, achieving encouraging anti-tumor effects in some advanced solid malignancies. However, low response rate and therapeutic resistance represent significant challenges in this field. In addition to its typical role in embryonic development and tissue fibrosis, epithelial-mesenchymal transition (EMT) plays a pivotal role in tumor immunosuppression and immune evasion. Previous studies revealed that EMT is associated with activation of different immune checkpoint molecules, including PD-L1. EMT-induced immune escape promotes cancer progression and may also provide a platform for discovery of novel therapeutic approaches and predictive biomarkers for checkpoint inhibitor therapeutic response. Here, we summarize recent findings focused on EMT-induced immune suppression and evasion in the tumor microenvironment (TME). EMT transcription factors (EMT-TFs), immune cells, cell plasticity and their regulatory role in the immune response are thoroughly reviewed. Bidirectional regulation between EMT and PD-L1 signaling is discussed in terms of cancer immune escape and possible combined therapies. Additionally, we investigated the value of preclinical or clinical trials using EMT targeted therapy combined with PD-L1 inhibitors. This review may help to further understand the role of EMT and PD-L1 signaling in cancer immune evasion. Meanwhile, additional molecular mechanistic studies and clinical trials are urgently needed.

Tumor-Infiltrating Immunosuppressive Cells in Cancer-Cell Plasticity, Tumor Progression and Therapy Response

In most tumors, cancer cells show the ability to dynamically transit from a non-cancer stem-like cell to a cancer stem-like cell (CSC) state and vice versa. This cell plasticity has been associated with the epithelial-to-mesenchymal transition program (EMT) and can be regulated by tumor cell-intrinsic mechanisms and complex interactions with various tumor microenvironment (TME) components. These interactions favor the generation of a specific "CSC niche" that helps maintain the main properties, phenotypic plasticity and metastatic potential of this subset of tumor cells. For this reason, TME has been recognized as an important promoter of tumor progression and therapy resistance. Tumors have evolved a network of immunosuppressive mechanisms that limits the cytotoxic T cell response to cancer cells. Some key players in this network are tumor-associated macrophages, myeloid-derived suppressor cells and regulatory T cells, which not only favor a pro-tumoral and immunosuppressive environment that supports tumor growth and immune evasion, but also negatively influences immunotherapy. Here, we review the relevance of cytokines and growth factors provided by immunosuppressive immune cells in regulating cancer-cell plasticity. We also discuss how cancer cells remodel their own niche to promote proliferation, stemness and EMT, and escape immune surveillance. A better understanding of CSC-TME crosstalk signaling will enable the development of effective targeted or immune therapies that block tumor growth and metastasis.

Advances in Molecular Mechanisms and Immunotherapy Involving the Immune Cell-Promoted Epithelial-to-Mesenchymal Transition in Lung Cancer

Immunotherapy has offered a new opportunity for the treatment of many malignancies. In patients with lung cancer, immune checkpoint inhibitors have significantly improved survival. However, little is known about predictive factors or primary and acquired resistance mechanisms. Epithelial-to-mesenchymal transition (EMT) is a complex of phenotypic changes involved in carcinogenesis and resistance to cancer treatments. Specifically, immune cells in the tumor microenvironment can promote EMT, and mesenchymal phenotype acquisition negatively regulates the anticancer immune response. EMT is associated with higher expression of PD-L1 and other immune checkpoints. In this review, we focused on the role of EMT in the interplay between tumor cells and the immune system, with particular emphasis on lung cancer. On the basis of our findings, we hypothesize that the effects of EMT on immune cells could be overcome in this disease by a new combination of immune checkpoint inhibitors.

MicroRNAs as Therapeutic Targets in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is a malignancy of epithelial origin that is prone to local invasion and early distant metastasis. Although concurrent chemotherapy and radiotherapy improves the 5-year survival outcomes, persistent or recurrent disease still occurs. Therefore, novel therapeutic targets are needed for NPC patients. MicroRNAs (miRNAs) play important roles in normal cell homeostasis, and dysregulations of miRNA expression have been implicated in human cancers. In NPC, studies have revealed that miRNAs are dysregulated and involved in tumorigenesis, metastasis, invasion, resistance to chemo- and radiotherapy, and other disease- and treatment-related processes. The advantage of miRNA-based treatment approaches is that miRNAs can concurrently target multiple effectors of pathways involved in tumor cell differentiation and proliferation. Thus, miRNA-based cancer treatments, alone or combined with standard chemotherapy and/or radiotherapy, hold promise to improve treatment response and cure rates. In this review, we will summarize the dysregulation of miRNAs in NPC initiation, progression, and treatment as well as NPC-related signaling pathways, and we will discuss the potential applications of miRNAs as biomarkers and therapeutic targets in NPC patients. We conclude that miRNAs might be potential promising therapeutic targets in nasopharyngeal carcinoma.

Role of Metabolic Reprogramming in Epithelial⁻Mesenchymal Transition (EMT)

Activation of epithelial–mesenchymal transition (EMT) is thought to be an essential step for cancer metastasis. Tumor cells undergo EMT in response to a diverse range of extra- and intracellular stimulants. Recently, it was reported that metabolic shifts control EMT progression and induce tumor aggressiveness. In this review, we summarize the involvement of altered glucose, lipid, and amino acid metabolic enzyme expression and the underlying molecular mechanisms in EMT induction in tumor cells. Moreover, we propose that metabolic regulation through gene-specific or pharmacological inhibition may suppress EMT and this treatment strategy may be applied to prevent tumor progression and improve anti-tumor therapeutic efficacy. This review presents evidence for the importance of metabolic changes in tumor progression and emphasizes the need for further studies to better understand tumor metabolism.

Conditioned media from adipocytes promote proliferation, migration, and invasion in melanoma and colorectal cancer cells

Epidemiological evidence suggests that obesity can significantly increase the risk of various cancers, although the mechanisms underlying this link are completely unknown. Here, we analyzed the effect of adipocytes on melanoma and colon cancer cells proliferation, migration, and invasion. The potential effects of conditioned media (CM) obtained from differentiated mouse 3T3-L1 cells and human adipose tissue-derived mesenchymal stem cells (hAMSC) on the proliferation, migration, and invasion of B16BL6 melanoma and colon 26-L5 cancer cells were investigated. The 3T3-L1 and hAMSC CM increased cell proliferation, migration, and invasion in both the cell lines. In addition, adipocytes CM increased matrix metalloproteinase 9 (MMP-9) and MMP-2 activity in both B16BL6 and colon 26-L5 cells. These effects were found to be associated with an increased expression of various oncogenic proteins in B16BL6 and colon 26-L5 cells. Also, adipocyte CM induced Akt and mTOR activation in both tumor cell lines, and the pharmacological inhibition of Akt and mTOR blocked the CM induced Akt as well as mTOR activation and CM-stimulated melanoma and colon cancer cell proliferation, migration, and invasion. These data suggest that adipocyte promotes melanoma and colon cancer progression through modulating the expression of diverse proteins associated with cancer growth and metastasis as well as modulation of the Akt/mTOR signaling.

STING signaling remodels the tumor microenvironment by antagonizing myeloid-derived suppressor cell expansion

Stimulator of interferon genes (STING), a major adaptor protein in antiviral innate immune signaling, is considered as one of the most important regulators of antiviral and antitumor immunity. Although STING agonists are now intensively studied in clinical trials as a new class of adjuvants to boost cancer immunotherapy, the tumor-intrinsic role of the STING pathway in shaping the tumor microenvironment remains controversial. Here, we discovered that STING plays a vital role in regulation of myeloid-derived suppressor cell (MDSC) differentiation and antitumor immunity in Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC). Mechanistic analyses reveal that STING represses NPC-derived MDSC induction by enhancing SOCS1 expression in both tumor cells and MDSCs. SOCS1 physically interacts with STAT3 through its SH2 domain to prevent STAT3 phosphorylation and dimerization, resulting in reduced MDSC induction via inhibition of GM-CSF and IL-6 production. Notably, reduced tumoral STING expression was found to be significantly associated with a poor prognosis for NPC patients. Our findings reveal a novel mechanism linking STING to tumor microenvironmental cytokine production and MDSC induction.

The natural polyphenol curcumin induces apoptosis by suppressing STAT3 signaling in esophageal squamous cell carcinoma

Background

We and others have previously shown that the STAT3 signaling pathway is activated in some esophageal squamous cell carcinoma (ESCC) cells and is required for the survival and growth of these primary ESCC-derived xenografts. It has also been shown that the natural polyphenol curcumin is an effective anti-tumor agent.

Methods

Luciferase assay and immunoblotting were performed to examine whether curcumin suppressed STAT3 signaling. CCK-8 assay and xenografts were utilized for analyzing ESCC cell growth in culture and mice. Soft agar assay was carried out to determine the colony formation ability of ESCC cells in the presence or absence of curcumin. Cell death and cell cycle were assessed by In CELL Analyzer 2000. Immunohistochemistry and TUNEL assay were used for detecting apoptosis in ESCC tisuses. Molecular docking was performed to evaluate the interaction of curcumin with JAK2. JAK2 activity was assessed using an in vitro cell-free system. HE staining was used to evaluate the ESCC tissues.

Results

The natural polyphenol curcumin inhibited STAT3 phosphorylation rapidly and blocked STAT3-mediated signaling in ESCC cells. It also induced growth arrest and apoptosis in cultured ESCC cells, which were attenuated by enforced expression of STAT3. Furthermore, curcumin preferentially blocked the growth of primary ESCC-derived xenografts that harbored activated STAT3.

Conclusions

Curcumin is able to exert anti-tumor action through inhibiting the STAT3 signaling pathway. Giving its wide use in traditional medicines with low toxicity and few adverse reactions, it is conceivable that curcumin might be further explored as a unique STAT3 inhibitor for anti-cancer therapies.

Roles of Myeloid-Derived Suppressor Cells in Cancer Metastasis: Immunosuppression and Beyond

Metastasis is the direst face of cancer, and it is not a feature solely dependent on cancer cells; however, a complex interaction between cancer cells and host causes this process. Investigating the mechanisms of metastasis can lead to its control. Myeloid-derived suppressor cells (MDSCs) are key components of tumor microenvironment that favor cancer progression. These cells result from altered myelopoiesis in response to the presence of tumor. The most recognized function of MDSCs is suppressing anti-tumor immune responses. Strikingly, these cells are among important players in cancer dissemination and metastasis. They can exert their effect on metastatic process by affecting anti-cancer immunity, epithelial-mesenchymal transition, cancer stem cell formation, angiogenesis, establishing premetastatic niche, and supporting cancer cell survival and growth in metastatic sites. In this article, we review and discuss the mechanisms by which MDSCs contribute to cancer metastasis.

Tumor-associated macrophages promote lung metastasis and induce epithelial-mesenchymal transition in osteosarcoma by activating the COX-2/STAT3 axis

Osteosarcoma (OS) is a common, malignant musculoskeletal tumor in young people. Neoadjuvant chemotherapy has improved the survival of osteosarcoma patients but with limited benefit due to metastasis. Tumor-associated macrophages (TAMs) are involved in various mechanisms of tumor biology, which include oncogenesis, drug resistance, and tumor immune escape, as well as tumor metastasis. In this study, we proved that TAMs possess the ability to promote OS cell migration and invasion by upregulating COX-2, MMP9, and phosphorylated STAT3 and to induce the epithelial-mesenchymal transition (EMT). This evidence has also been verified in a tumor-bearing animal model, and in OS patients. Furthermore, we observed the anti-metastasis effect of COX-2 inhibition by repressing COX-2 expression, EMT-activating transcription factors and the STAT3 pathway, both in vitro and in vivo. We propose that TAMs promote OS metastasis and invasion by activating the COX-2/STAT3 axis and EMT. These findings suggest that TAMs and COX-2 may be potential targets for future anti-metastasis therapy.