Prostaglandin E2 Secreted by Thyroid Cancer Cells Contributes to Immune Escape Through the Suppression of Natural Killer (NK) Cell Cytotoxicity and NK Cell Differentiation

Mast Cell–Tumor Interactions: Molecular Mechanisms of Recruitment, Intratumoral Communication and Potential Therapeutic Targets for Tumor Growth

Mast cells (MCs) are tissue-resident immune cells that are important players in diseases associated with chronic inflammation such as cancer. Since MCs can infiltrate solid tumors and promote or limit tumor growth, a possible polarization of MCs to pro-tumoral or anti-tumoral phenotypes has been proposed and remains as a challenging research field. Here, we review the recent evidence regarding the complex relationship between MCs and tumor cells. In particular, we consider: (1) the multifaceted role of MCs on tumor growth suggested by histological analysis of tumor biopsies and studies performed in MC-deficient animal models; (2) the signaling pathways triggered by tumor-derived chemotactic mediators and bioactive lipids that promote MC migration and modulate their function inside tumors; (3) the possible phenotypic changes on MCs triggered by prevalent conditions in the tumor microenvironment (TME) such as hypoxia; (4) the signaling pathways that specifically lead to the production of angiogenic factors, mainly VEGF; and (5) the possible role of MCs on tumor fibrosis and metastasis. Finally, we discuss the novel literature on the molecular mechanisms potentially related to phenotypic changes that MCs undergo into the TME and some therapeutic strategies targeting MC activation to limit tumor growth.

Integrated analysis of fibroblasts molecular features in papillary thyroid cancer combining single-cell and bulk RNA sequencing technology

BACKGROUND

Papillary thyroid cancer (PTC) is the most common pathological type of thyroid cancer with a high incidence globally. Increasing evidence reported that fibroblasts infiltration in cancer was correlated with prognostic outcomes. However, fibroblasts related study in thyroid cancer remains deficient.

METHODS

Single-cell sequencing data of PTC were analyzed by Seurat R package to explore the ecosystem in PTC and identify fibroblasts cluster. The expression profiles and prognostic values of fibroblast related genes were assessed in TCGA dataset. A fibrosis score model was established for prognosis prediction in thyroid cancer patients. Differentially expressed genes and functional enrichment between high and low fibrosis score groups in TCGA dataset were screened. The correlation of immune cells infiltration and fibrosis score in thyroid cancer patients was explored. Expression levels and prognostic values of key fibroblast related factor were validated in clinical tissues another PTC cohort.

RESULTS

Fibroblasts were highly infiltrated in PTC and could interact with other type of cells by single-cell data analysis. 34 fibroblast related terms were differentially expressed in thyroid tumor tissues. COX regression analysis suggested that the constructed fibrosis score model was an independent prognostic predictor for thyroid cancer patients (HR = 5.17, 95%CI 2.31-11.56, P = 6.36E-05). Patients with low fibrosis scores were associated with a significantly better overall survival (OS) than those with high fibrosis scores in TCGA dataset (P = 7.659E-04). Specific immune cells infiltration levels were positively correlated with fibrosis score, including monocytes, M1 macrophages and eosinophils.

CONCLUSION

Our research demonstrated a comprehensive horizon of fibroblasts features in thyroid cancer microenvironment, which may provide potential value for thyroid cancer treatment.

Role of NK Cells in Tumor Progression

Natural Killer (NK) cells are effector lymphocytes with the ability to generate an antitumor response. NK cells encompass a diverse group of subsets with different properties and have the capacity to kill cancer cells by different means. However, tumor cells have developed several mechanisms to evade NK cell-mediated killing. In this chapter, we summarize some aspects of NK cell biology with the aim to understand the competence of these cells and explore some of the challenges that NK cells have to face in different malignancies. Moreover, we will review the current knowledge about the role of NK cells in tumor progression and describe their phenotype and effector functions in tumor tissues and peripheral blood from cancer patients. Finally, we will recapitulate several findings from different studies focused on determining the prognostic value of NK cells in distinct cancers.

Challenges and Recent Advances in NK Cell-Targeted Immunotherapies in Solid Tumors

Natural killer (NK) cell is a powerful malignant cells killer, providing rapid immune responses via direct cytotoxicity without the need of antigen processing and presentation. It plays an essential role in preventing early tumor, metastasis and minimal residual disease. Although adoptive NK therapies achieved great success in clinical trials against hematologic malignancies, their accumulation, activation, cytotoxic and immunoregulatory functions are severely impaired in the immunosuppressive microenvironment of solid tumors. Now with better understandings of the tumor evasive mechanisms from NK-mediated immunosurveillance, immunotherapies targeting the key molecules for NK cell dysfunction and exhaustion have been developed and tested in both preclinical and clinical studies. In this review, we introduce the challenges that NK cells encountered in solid tumor microenvironment (TME) and the therapeutic approaches to overcome these limitations, followed by an outline of the recent preclinical advances and the latest clinical outcomes of NK-based immunotherapies, as well as promising strategies to optimize current NK-targeted immunotherapies for solid tumors.

Ferroptosis-related gene signature predicts the prognosis of papillary thyroid carcinoma

Background

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer (TC), accounting for more than 80% of all cases. Ferroptosis is a novel iron-dependent and Reactive oxygen species (ROS) reliant type of cell death which is distinct from the apoptosis, necroptosis and pyroptosis. Considerable studies have demonstrated that ferroptosis is involved in the biological process of various cancers. However, the role of ferroptosis in PTC remains unclear. This study aims at exploring the expression of ferroptosis-related genes (FRG) and their prognostic values in PTC.

Methods

A ferroptosis-related gene signature was constructed using lasso regression analysis through the PTC datasets of the Cancer Genome Atlas (TCGA). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to investigate the bioinformatics functions of significantly different genes (SDG) of ferroptosis. Additionally, the correlations of ferroptosis and immune cells were assessed through the single-sample gene set enrichment analysis (ssGSEA) and CIBERSORT database. Finally, SDG were test in clinical PTC specimens and normal thyroid tissues.

Results

LASSO regression model was utilized to establish a novel FRG signature with 10 genes (ANGPTL7, CDKN2A, DPP4, DRD4, ISCU, PGD, SRXN1, TF, TFRC, TXNRD1) to predicts the prognosis of PTC, and the patients were separated into high-risk and low-risk groups by the risk score. The high-risk group had poorer survival than the low-risk group (p < 0.001). Receiver operating characteristic (ROC) curve analysis confirmed the signature's predictive capacity. Multivariate regression analysis identified the prognostic signature-based risk score was an independent prognostic indicator for PTC. The functional roles of the DEGs in the TGCA PTC cohort were explored using GO enrichment and KEGG pathway analyses. Immune related analysis demonstrated that the most types of immune cells and immunological function in the high-risk group were significant different with those in the low-risk group. Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) verified the SDG have differences in expression between tumor tissue and normal thyroid tissue. In addition, cell experiments were conducted to observe the changes in cell morphology and expression of signature’s genes with the influence of ferroptosis induced by sorafenib.

Conclusions

We identified differently expressed FRG that may involve in PTC. A ferroptosis-related gene signature has significant values in predicting the patients’ prognoses and targeting ferroptosis may be an alternative for PTC’s therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02389-7.

Cross-Talk Between Tumor Cells Undergoing Epithelial to Mesenchymal Transition and Natural Killer Cells in Tumor Microenvironment in Colorectal Cancer

Tumor cells undergoing epithelial to mesenchymal transition (EMT) and immune cells in tumor microenvironment (TME) reciprocally influence each other. Immune cells, by supplying TME with bioactive molecules including cytokines, chemokines, enzymes, metabolites, and by physical interactions with tumor cells via their receptors, represent an important factor that affects EMT. Chronical inflammation in TME favorizes tumor growth and invasiveness and stimulates synthesis of EMT promoting transcription factors. Natural killer (NK) cells, owing to their unique ability to exert cytotoxic function independent of major histocompatibility (MHC)-mediated antigen presentation, play a significant role in the control of metastasis in colorectal cancer (CRC). Although, the cross-talk between immune cells and tumor cells in general favors the induction of EMT and inhibition of antitumor immune responses, there are some changes in the immunogenicity of tumor cells during EMT of CRC cells that increase their susceptibility to NK cell cytotoxic lysis. However, suppressive TME downmodulates the expression of activating NK cell receptors, decreases the expression of activating and increases the expression of inhibitory NK cell ligands on tumor cells, and impairs NK cell metabolism that altogether negatively affects the overall NK cell function. Furthermore, process of EMT is often associated with increased expression of programmed cell death ligand (PD-L) and expression of immune checkpoint molecules PD-1, TIGIT, and TIM3 on functionally exhausted NK cells in TME in CRC. In this review we discuss modalities of cross-talk between tumor cells and NK cells, with regard of EMT-driven changes.

The impact of hypoxia on immune state in cancer

Hypoxia is a known feature of solid tumors and a critical promoter of tumor hallmarks. Hypoxia influences tumor immunity in a way favoring immune evasion and resistance. Extreme hypoxia and aberrant hypoxia-inducible factor-1 (HIF-1) activity in tumor microenvironment (TME) is a drawback for effective immunotherapy. Infiltration and activity of CD8⁺ T cells is reduced in such condition, whereas regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) show high activities. Highly hypoxic TME also impairs maturation and activity of dendritic cell (DCs) and natural killer (NK) cells. In addition, the hypoxic TME positively is linked positively with metabolic changes in cells of immune system. These alterations are indicative of a need for hypoxia modulation as a complementary targeting strategy to go with immune checkpoint inhibitor (ICI) therapy.

The Signaling Pathway of PGE2 and Its Regulatory Role in T Cell Differentiation

Prostaglandin E2 (PGE2) is a lipid mediator derived from the fatty acid arachidonic acid. As an essential inflammatory factor, PGE2 has a critical impact on immune regulation through the prostanoid E (EP) receptor pathway. T cells, including CD4+ and CD8+ T cell subsets, play crucial roles in the adaptive immune response. Previous studies have shown that PGE2 is involved in regulating CD4+ T cell differentiation and inflammatory cytokine production via the EP receptor pathway, thereby affecting the development of diseases mediated by CD4+ T cells. In this review, we summarize the signaling pathway of PGE2 and describe the relationship between PGE2 and T cell differentiation. Hence, this review may provide important evidence for immune therapies and may even promote the development of biomedicines.

Lipid metabolism in cancer progression and therapeutic strategies

Dysregulated lipid metabolism represents an important metabolic alteration in cancer. Fatty acids, cholesterol, and phospholipid are the three most prevalent lipids that act as energy producers, signaling molecules, and source material for the biogenesis of cell membranes. The enhanced synthesis, storage, and uptake of lipids contribute to cancer progression. The rewiring of lipid metabolism in cancer has been linked to the activation of oncogenic signaling pathways and cross talk with the tumor microenvironment. The resulting activity favors the survival and proliferation of tumor cells in the harsh conditions within the tumor. Lipid metabolism also plays a vital role in tumor immunogenicity via effects on the function of the noncancer cells within the tumor microenvironment, especially immune‐associated cells. Targeting altered lipid metabolism pathways has shown potential as a promising anticancer therapy. Here, we review recent evidence implicating the contribution of lipid metabolic reprogramming in cancer to cancer progression, and discuss the molecular mechanisms underlying lipid metabolism rewiring in cancer, and potential therapeutic strategies directed toward lipid metabolism in cancer. This review sheds new light to fully understanding of the role of lipid metabolic reprogramming in the context of cancer and provides valuable clues on therapeutic strategies targeting lipid metabolism in cancer.

An Update on the Anticancer Activity of Xanthone Derivatives: A Review

The annual number of cancer deaths continues increasing every day; thus, it is urgent to search for and find active, selective, and efficient anticancer drugs as soon as possible. Among the available anticancer drugs, almost all of them contain heterocyclic moiety in their chemical structure. Xanthone is a heterocyclic compound with a dibenzo-γ-pyrone framework and well-known to have "privileged structures" for anticancer activities against several cancer cell lines. The wide anticancer activity of xanthones is produced by caspase activation, RNA binding, DNA cross-linking, as well as P-gp, kinase, aromatase, and topoisomerase inhibition. This anticancer activity depends on the type, number, and position of the attached functional groups in the xanthone skeleton. This review discusses the recent advances in the anticancer activity of xanthone derivatives, both from natural products isolation and synthesis methods, as the anticancer agent through in vitro, in vivo, and clinical assays.

A Forgotten Corner in Cancer Immunotherapy: The Role of Lipids

In the past decade, cancer immunotherapy has achieved great success owing to the unravelling of unknown molecular forces in cancer immunity. However, it is critical that we address the limitations of current immunotherapy, including immune-related adverse events and drug resistance, and further enhance current immunotherapy. Lipids are reported to play important roles in modulating immune responses in cancer. Cancer cells use lipids to support their aggressive behaviour and allow immune evasion. Metabolic reprogramming of cancer cells destroys the equilibrium between lipid anabolism and catabolism, resulting in lipid accumulation within the tumour microenvironment (TME). Consequently, ubiquitous lipids, mainly fatty acids, within the TME can impact the function and phenotype of infiltrating immune cells. Determining the complex roles of lipids and their interactions with the TME will provide new insight for improving anti-tumour immune responses by targeting lipids. Herein, we present a review of recent literature that has demonstrated how lipid metabolism reprogramming occurs in cancer cells and influences cancer immunity. We also summarise the potential for lipid-based clinical translation to modify immune treatment.

Chronic and Cycling Hypoxia: Drivers of Cancer Chronic Inflammation through HIF-1 and NF-κB Activation: A Review of the Molecular Mechanisms

Chronic (continuous, non-interrupted) hypoxia and cycling (intermittent, transient) hypoxia are two types of hypoxia occurring in malignant tumors. They are both associated with the activation of hypoxia-inducible factor-1 (HIF-1) and nuclear factor κB (NF-κB), which induce changes in gene expression. This paper discusses in detail the mechanisms of activation of these two transcription factors in chronic and cycling hypoxia and the crosstalk between both signaling pathways. In particular, it focuses on the importance of reactive oxygen species (ROS), reactive nitrogen species (RNS) together with nitric oxide synthase, acetylation of HIF-1, and the action of MAPK cascades. The paper also discusses the importance of hypoxia in the formation of chronic low-grade inflammation in cancerous tumors. Finally, we discuss the effects of cycling hypoxia on the tumor microenvironment, in particular on the expression of VEGF-A, CCL2/MCP-1, CXCL1/GRO-α, CXCL8/IL-8, and COX-2 together with PGE₂. These factors induce angiogenesis and recruit various cells into the tumor niche, including neutrophils and monocytes which, in the tumor, are transformed into tumor-associated neutrophils (TAN) and tumor-associated macrophages (TAM) that participate in tumorigenesis.

Tumor Secretome to Adoptive Cellular Immunotherapy: Reduce Me Before I Make You My Partner

Adoptive cellular immunotherapy using chimeric antigen receptor (CAR)-modified T cells and Natural Killer (NK) cells are common immune cell sources administered to treat cancer patients. In detail, whereas CAR-T cells induce outstanding responses in a subset of hematological malignancies, responses are much more deficient in solid tumors. Moreover, NK cells have not shown remarkable results up to date. In general, immune cells present high plasticity to change their activity and phenotype depending on the stimuli they receive from molecules secreted in the tumor microenvironment (TME). Consequently, immune cells will also secrete molecules that will shape the activities of other neighboring immune and tumor cells. Specifically, NK cells can polarize to activities as diverse as angiogenic ones instead of their killer activity. In addition, tumor cell phagocytosis by macrophages, which is required to remove dying tumor cells after the attack of NK cells or CAR-T cells, can be avoided in the TME. In addition, chemotherapy or radiotherapy treatments can induce senescence in tumor cells modifying their secretome to a known as “senescence-associated secretory phenotype” (SASP) that will also impact the immune response. Whereas the SASP initially attracts immune cells to eliminate senescent tumor cells, at high numbers of senescent cells, the SASP becomes detrimental, impacting negatively in the immune response. Last, CAR-T cells are an attractive option to overcome these events. Here, we review how molecules secreted in the TME by either tumor cells or even by immune cells impact the anti-tumor activity of surrounding immune cells.

Single-cell transcriptome analysis reveals the dynamics of human immune cells during early fetal skin development

The immune system of skin develops in stages in mice. However, the developmental dynamics of immune cells in human skin remains elusive. Here, we perform transcriptome profiling of CD45⁺ hematopoietic cells in human fetal skin at an estimated gestational age of 10-17 weeks by single-cell RNA sequencing. A total of 13 immune cell types are identified. Skin macrophages show dynamic heterogeneity over the course of skin development. A major shift in lymphoid cell developmental states occurs from the first to the second trimester that implies an in situ differentiation process. Gene expression analysis reveals a typical developmental program in immune cells in accordance with their functional maturation, possibly involving metabolic reprogramming. Finally, we identify transcription factors (TFs) that potentially regulate cellular transitions by comparing TFs and TF target gene networks. These findings provide detailed insight into how the immune system of the human skin is established during development.

Leveraging NKG2D Ligands in Immuno-Oncology

Immune checkpoint inhibitors (ICI) revolutionized the field of immuno-oncology and opened new avenues towards the development of novel assets to achieve durable immune control of cancer. Yet, the presence of tumor immune evasion mechanisms represents a challenge for the development of efficient treatment options. Therefore, combination therapies are taking the center of the stage in immuno-oncology. Such combination therapies should boost anti-tumor immune responses and/or target tumor immune escape mechanisms, especially those created by major players in the tumor microenvironment (TME) such as tumor-associated macrophages (TAM). Natural killer (NK) cells were recently positioned at the forefront of many immunotherapy strategies, and several new approaches are being designed to fully exploit NK cell antitumor potential. One of the most relevant NK cell-activating receptors is NKG2D, a receptor that recognizes 8 different NKG2D ligands (NKG2DL), including MICA and MICB. MICA and MICB are poorly expressed on normal cells but become upregulated on the surface of damaged, transformed or infected cells as a result of post-transcriptional or post-translational mechanisms and intracellular pathways. Their engagement of NKG2D triggers NK cell effector functions. Also, MICA/B are polymorphic and such polymorphism affects functional responses through regulation of their cell-surface expression, intracellular trafficking, shedding of soluble immunosuppressive isoforms, or the affinity of NKG2D interaction. Although immunotherapeutic approaches that target the NKG2D-NKG2DL axis are under investigation, several tumor immune escape mechanisms account for reduced cell surface expression of NKG2DL and contribute to tumor immune escape. Also, NKG2DL polymorphism determines functional NKG2D-dependent responses, thus representing an additional challenge for leveraging NKG2DL in immuno-oncology. In this review, we discuss strategies to boost MICA/B expression and/or inhibit their shedding and propose that combination strategies that target MICA/B with antibodies and strategies aimed at promoting their upregulation on tumor cells or at reprograming TAM into pro-inflammatory macrophages and remodeling of the TME, emerge as frontrunners in immuno-oncology because they may unleash the antitumor effector functions of NK cells and cytotoxic CD8 T cells (CTL). Pursuing several of these pipelines might lead to innovative modalities of immunotherapy for the treatment of a wide range of cancer patients.

MHC Class I Deficiency in Solid Tumors and Therapeutic Strategies to Overcome It

It is now well accepted that the immune system can control cancer growth. However, tumors escape immune-mediated control through multiple mechanisms and the downregulation or loss of major histocompatibility class (MHC)-I molecules is a common immune escape mechanism in many cancers. MHC-I molecules present antigenic peptides to cytotoxic T cells, and MHC-I loss can render tumor cells invisible to the immune system. In this review, we examine the dysregulation of MHC-I expression in cancer, explore the nature of MHC-I-bound antigenic peptides recognized by immune cells, and discuss therapeutic strategies that can be used to overcome MHC-I deficiency in solid tumors, with a focus on the role of natural killer (NK) cells and CD4 T cells.

Current Advance of Immune Evasion Mechanisms and Emerging Immunotherapies in Renal Cell Carcinoma

Renal cell carcinoma is a highly heterogeneous cancer group, and the complex microenvironment of the tumor provides appropriate immune evasion opportunities. The molecular mechanism of immune escape in renal cell carcinoma is currently a hot issue, focusing primarily on the major complex of histocompatibility, immunosuppressive cells, their secreted immunosuppressive cytokines, and apoptosis molecule signal transduction. Immunotherapy is the best treatment option for patients with metastatic or advanced renal cell carcinoma and combination immunotherapy based on a variety of principles has shown promising prospects. Comprehensive and in-depth knowledge of the molecular mechanism of immune escape in renal cell carcinoma is of vital importance for the clinical implementation of effective therapies. The goal of this review is to address research into the mechanisms of immune escape in renal cell carcinoma and the use of the latest immunotherapy. In addition, we are all looking forward to the latest frontiers of experimental combination immunotherapy.

Cyclooxygenase-2 Inhibitor: A Potential Combination Strategy With Immunotherapy in Cancer

The clinical application of immunotherapy is the milestone of cancer treatment. However, some patients have bad reaction. Cyclooxygenase-2 (COX-2) is frequently expressed in multiple cancer cells and is associated with poor prognosis. It is the key enzyme of prostaglandin E₂ (PGE2) that has been proved to promote the development, proliferation and metastasis of tumor cells. Recent studies further find the PGE2 in tumor microenvironment (TME) actively triggers tumor immune evasion via many ways, leading to poor response of immunotherapy. COX-2 inhibitor is suggested to restrain the immunosuppression of PGE2 and may enhance or reverse the response of immune checkpoint inhibitors (ICIs). This review provides insight into the mechanism of COX-2/PGE2 signal in immunosuppressive TME and summarizes the clinical application and trials in cancer treatment.

Harnessing the cDC1-NK Cross-Talk in the Tumor Microenvironment to Battle Cancer

Immunotherapeutic approaches have revolutionized the treatment of several diseases such as cancer. The main goal of immunotherapy for cancer is to modulate the anti-tumor immune responses by favoring the recognition and destruction of tumor cells. Recently, a better understanding of the suppressive effect of the tumor microenvironment (TME) on immune cells, indicates that restoring the suppressive effect of the TME is crucial for an efficient immunotherapy. Natural killer (NK) cells and dendritic cells (DCs) are cell types that are currently administered to cancer patients. NK cells are used because of their ability to kill tumor cells directly via cytotoxic granzymes. DCs are employed to enhance anti-tumor T cell responses based on their ability to present antigens and induce tumor-antigen specific CD8⁺ T cell responses. In preclinical models, a particular DC subset, conventional type 1 DCs (cDC1s) is shown to be specialized in cross-presenting extracellular antigens to CD8⁺ T cells. This feature makes them a promising DC subset for cancer treatment. Within the TME, cDC1s show a bidirectional cross-talk with NK cells, resulting in a higher cDC1 recruitment, differentiation, and maturation as well as activation and stimulation of NK cells. Consequently, the presence of cDC1s and NK cells within the TME might be of utmost importance for the success of immunotherapy. In this review, we discuss the function of cDC1s and NK cells, their bidirectional cross-talk and potential strategies that could improve cancer immunotherapy.

The Roles of circRNAs in Liver Cancer Immunity

Circular RNAs (circRNAs) are stable covalently closed non-coding RNAs (ncRNAs). Many studies indicate that circRNAs are involved in the pathological and physiological processes of liver cancer. However, the functions of circRNAs in liver cancer immunity are less known. In this review, we summarized the functions of circRNAs in liver cancer, including proliferative, metastasis and apoptosis, liver cancer stemness, cell cycle, immune evasion, glycolysis, angiogenesis, drug resistance/sensitizer, and senescence. Immune escape is considered to be one of the hallmarks of cancer development, and circRNA participates in the immune escape of liver cancer cells by regulating natural killer (NK) cell function. CircRNAs may provide new ideas for immunotherapy in liver cancer.

The footprint of kynurenine pathway in every cancer: a new target for chemotherapy

Treatment of cancers has always been a challenge for physicians. Typically, several groups of anti-cancer medications are needed for effective management of an invasive and metastatic cancer. Recently, therapeutic potentiation of immune system markedly improved treatment of cancers. Kynurenine pathway has an interwoven correlation with immune system. Kynurenine promotes T Reg (regulatory) differentiation, which leads to increased production of anti-inflammatory cytokines and suppression of cytotoxic activity of T cells. Overactivation of kynurenine pathway in cancers provides an immunologically susceptible microenvironment for mutant cells to survive and invade surrounding tissues. Interestingly, kynurenine pathway vigorously interacts with other molecular pathways involved in tumorigenesis. For instance, kynurenine pathway interacts with phospoinosisitide-3 kinase (PI3K), extracellular signal-regulated kinase (ERK), Wnt/β-catenin, P53, bridging integrator 1 (BIN-1), cyclooxygenase 2 (COX-2), cyclin-dependent kinase (CDK) and collagen type XII α1 chain (COL12A1). Overactivation of kynurenine pathway, particularly overactivation of indoleamine 2,3-dioxygenase (IDO) predicts poor prognosis of several cancers such as gastrointestinal cancers, gynecological cancers, hematologic malignancies, breast cancer, lung cancer, glioma, melanoma, prostate cancer and pancreatic cancer. Furthermore, kynurenine increases the invasion, metastasis and chemoresistance of cancer cells. Recently, IDO inhibitors entered clinical trials and successfully passed their safety tests and showed promising therapeutic efficacy for cancers such as melanoma, brain cancer, renal cell carcinoma, prostate cancer and pancreatic cancer. However, a phase III trial of epacadostat, an IDO inhibitor, could not increase the efficacy of treatment with pembrolizumab for melanoma. In this review the expanding knowledge towards kynurenine pathway and its application in each cancer is discussed separately.

Immuno-Metabolism: The Role of Cancer Niche in Immune Checkpoint Inhibitor Resistance

The use of immune checkpoint inhibitors (ICI) in treating cancer has revolutionized the approach to eradicate cancer cells by reactivating immune responses. However, only a subset of patients benefits from this treatment; the majority remains unresponsive or develops resistance to ICI therapy. Increasing evidence suggests that metabolic machinery in the tumor microenvironment (TME) plays a role in the development of ICI resistance. Within the TME, nutrients and oxygen are scarce, forcing immune cells to undergo metabolic reprogramming to adapt to harsh conditions. Cancer-induced metabolic deregulation in immune cells can attenuate their anti-cancer properties, but can also increase their immunosuppressive properties. Therefore, targeting metabolic pathways of immune cells in the TME may strengthen the efficacy of ICIs and prevent ICI resistance. In this review, we discuss the interactions of immune cells and metabolic alterations in the TME. We also discuss current therapies targeting cellular metabolism in combination with ICIs for the treatment of cancer, and provide possible mechanisms behind the cellular metabolic rewiring that may improve clinical outcomes.

Phosphodiesterase 4A confers resistance to PGE2-mediated suppression in CD25+ /CD54+ NK cells

Inadequate persistence of tumor‐infiltrating natural killer (NK) cells is associated with poor prognosis in cancer patients. The solid tumor microenvironment is characterized by the presence of immunosuppressive factors, including prostaglandin E2 (PGE2), that limit NK cell persistence. Here, we investigate if the modulation of the cytokine environment in lung cancer with IL‐2 or IL‐15 renders NK cells resistant to suppression by PGE2. Analyzing Cancer Genome Atlas (TCGA) data, we found that high NK cell gene signatures correlate with significantly improved overall survival in patients with high levels of the prostaglandin E synthase (PTGES). In vitro, IL‐15, in contrast to IL‐2, enriches for CD25⁺/CD54⁺ NK cells with superior mTOR activity and increased expression of the cAMP hydrolyzing enzyme phosphodiesterase 4A (PDE4A). Consequently, this distinct population of NK cells maintains their function in the presence of PGE2 and shows an increased ability to infiltrate lung adenocarcinoma tumors in vitro and in vivo. Thus, strategies to enrich CD25⁺/CD54⁺ NK cells for adoptive cell therapy should be considered.

Association between Inflammation and Function of Cell Adhesion Molecules Influence on Gastrointestinal Cancer Development

Gastrointestinal cancer is highly associated with inflammatory processes inducing the release of cytokines from cancer or immune cells, including interferons, interleukins, chemokines, colony-stimulating factors, and growth factors, which promote or suppress tumor progression. Inflammatory cytokines within the tumor microenvironment promote immune cell infiltration. Infiltrating immune, and tumor-surrounding stromal cells support tumor growth, angiogenesis, metastasis, and immunosuppression through communication with inflammatory cytokines and cell adhesion molecules. Notably, infiltrating immune and tumor cells present immunosuppressive molecules, such as programmed death-ligand 1 (PD-L1) and CD80/CD86. Suppression of cytotoxic T cells promotes tumor avoidance of immune surveillance and greater malignancy. Moreover, glycosylation and sialylation of proteins hyperexpressed on the cancer cell surface have been shown to enhance immune escape and metastasis. Cytokine treatments and immune checkpoint inhibitors are widely used in clinical practice. However, the tumor microenvironment is a rapidly changing milieu involving several factors. In this review, we have provided a summary of the interactions of inflammation and cell adhesion molecules between cancer and other cell types, to improve understanding of the tumor microenvironment.

Tumor-Infiltrating Natural Killer Cells

Because of their potent antitumor activity and their proinflammatory role, natural killer (NK) cells are at the forefront of efforts to develop immuno-oncologic treatments. NK cells participate in immune responses to tumors by killing target cells and producing cytokines. However, in the immunosuppressive tumor microenvironment, NK cells become dysfunctional through exposure to inhibitory molecules produced by cancer cells, leading to tumor escape. We provide an overview of what is known about NK tumor infiltration and surveillance and about the mechanisms by which NK cells become dysfunctional. SIGNIFICANCE: The functions of tumor-infiltrating NK cells may be impaired. This review aims to describe the various mechanisms by which tumors alter NK-cell functions.

Prostaglandin E2 and Cancer: Insight into Tumor Progression and Immunity

The involvement of inflammation in cancer progression has been the subject of research for many years. Inflammatory milieu and immune response are associated with cancer progression and recurrence. In different types of tumors, growth and metastatic phenotype characterized by the epithelial mesenchymal transition (EMT) process, stemness, and angiogenesis, are increasingly associated with intrinsic or extrinsic inflammation. Among the inflammatory mediators, prostaglandin E2 (PGE2) supports epithelial tumor aggressiveness by several mechanisms, including growth promotion, escape from apoptosis, transactivation of tyrosine kinase growth factor receptors, and induction of angiogenesis. Moreover, PGE2 is an important player in the tumor microenvironment, where it suppresses antitumor immunity and regulates tumor immune evasion, leading to increased tumoral progression. In this review, we describe the current knowledge on the pro-tumoral activity of PGE2 focusing on its role in cancer progression and in the regulation of the tumor microenvironment.

The Tumor Microenvironment-A Metabolic Obstacle to NK Cells' Activity

NK cells have unique capabilities of recognition and destruction of tumor cells, without the requirement for prior immunization of the host. Maintaining tolerance to healthy cells makes them an attractive therapeutic tool for almost all types of cancer. Unfortunately, metabolic changes associated with malignant transformation and tumor progression lead to immunosuppression within the tumor microenvironment, which in turn limits the efficacy of various immunotherapies. In this review, we provide a brief description of the metabolic changes characteristic for the tumor microenvironment. Both tumor and tumor-associated cells produce and secrete factors that directly or indirectly prevent NK cell cytotoxicity. Here, we depict the molecular mechanisms responsible for the inhibition of immune effector cells by metabolic factors. Finally, we summarize the strategies to enhance NK cell function for the treatment of tumors.

Non-steroidal anti-inflammatory drugs, prostaglandins, and COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the novel coronavirus disease 2019 (COVID-19), a highly pathogenic and sometimes fatal respiratory disease responsible for the current 2020 global pandemic. Presently, there remains no effective vaccine or efficient treatment strategies against COVID-19. Non-steroidal anti-inflammatory drugs (NSAIDs) are medicines very widely used to alleviate fever, pain, and inflammation (common symptoms of COVID-19 patients) through effectively blocking production of prostaglandins (PGs) via inhibition of cyclooxyganase enzymes. PGs can exert either proinflammatory or anti-inflammatory effects depending on the inflammatory scenario. In this review, we survey the potential roles that NSAIDs and PGs may play during SARS-CoV-2 infection and the development and progression of COVID-19. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

Identification of FADS1 Through Common Gene Expression Profiles for Predicting Survival in Patients with Bladder Cancer

Purpose

Aim of this study was to identify biomarkers between different grades of bladder cancer (BLCA) and its prognostic value.

Methods

mRNA expression data from GSE32549 and GSE71576 were extracted for further analysis. Differentially expressed genes (DEGs) were identified using GEO2R web tool. Gene ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and protein–protein interaction (PPI) network were conducted to explore the function and relationship of DEGs. The Cancer Genome Atlas (TCGA) database was used for external validation and Gene set enrichment analysis (GSEA) analysis was used to further identify FADS1 pathways. Bladder cancer cells and patient specimens were used to further demonstrate the function of FADS1.

Results

Datasets from GEO identified a panel of DEGs. Functional enrichment analysis highlighted that DEGs were associated with nuclear division, spindle, cell cycle and p53 signaling pathway. External validation from TCGA demonstrated that FADS1 was an independent prognostic marker in BLCA patients. In cell lines and tumor specimen analysis, FADS1 was overexpressed in the tumor specimen, compared with adjacent tissues, and positively correlated with tumor grade of BLCA. Moreover, FADS1 could enhance the proliferation ability and influence cell cycle of bladder cancer cells.

Conclusion

FADS1 was an independent prognostic biomarker for BLCA and could confer the bladder cancer cells increased proliferation ability.

Boosting Natural Killer Cell-Based Cancer Immunotherapy with Selenocystine/Transforming Growth Factor-Beta Inhibitor-Encapsulated Nanoemulsion

Natural killer (NK) cell-based immunotherapy represents a promising strategy to overcome the bottlenecks of cancer treatment. However, the therapeutic efficacy is greatly limited by downregulation of recognition ligands on the tumor cell surface, and the immunosuppressive effects can be thwarted by the tumor microenvironment such as secretion of transforming growth factor-beta (TGF-β), which could stunt the NK cell-mediated immune response. To overcome these limitations, herein we developed a nanoemulsion system (SSB NMs) to co-deliver TGF-β inhibitor and selenocysteine (SeC) to achieve amplified anticancer efficacy. SSB NMs significantly enhanced the lytic potency of NK92 cells by 2.1-fold. Moreover, a subtoxic dose of SSB NMs effectively sensitized MDA-MB-231 triple-negative breast cancer (TNBC) cells to NK cells derived from seven clinical patients, resulting in an up to 13.8-fold increase in cancer lysis. Mechanistic studies reveal that the sensitizing effects relied on natural killer group 2, member D (NKG2D)/NKG2D ligands (NKG2DLs) signaling with the involvement of DNA damage response. SSB NMs also effectively restrained TGF-β/TGF-β RI/Smad2/3 signaling, which thus enhanced NKG2DL expression on tumor cells and stimulated NKG2D surface expression on NK92 cells, ultimately contributing to the enhanced immune response. Furthermore, SSB NMs sustained release of SeC and TGF-β inhibitor and synergized with NK92 cells to induce significant anticancer effects in vivo. Together, this study not only demonstrates a simple strategy for the design of a nanoemulsion to co-deliver synergistic drugs but also sheds light on the application and action mechanisms in NK cell adaptive therapy against breast cancer, especially TNBCs.

Knockdown of TXNDC9 induces apoptosis and autophagy in glioma and mediates cell differentiation by p53 activation

Glioma is the most common malignant brain tumor. Because of its high degree of malignancy, the effect of surgical treatment, radiotherapy, chemotherapy, or immunotherapy is not ideal. TXNDC9 belongs to thioredoxin domain-containing proteins, which is involved in tumor progression. However, no research associated with TXNDC9 has been reported in glioma. In this study, we found that TXNDC9 was upregulated in glioma. Knockdown of TXNDC9 would prevent proliferation and metastasis, induce the apoptosis rate of glioma cells, and promote the expression Cleaved-caspase3, Cleaved-caspase8, Cleaved-caspase9. Meanwhile, knockdown of TXNDC9 induced autophagy by increasing the level of LC3 and Beclin-1. Cell morphology and expression analysis of GFAP, Vimentin, verified that TXNDC9 could regulate glioma cell differentiation. During this program, the expression of p53 changes dramatically. The apoptosis, autophagy, and cell differentiation program were blocked by p53 inhibitor treatment. In conclusion, the silencing of TXNDC9 induces apoptosis and autophagy in glioma and promotes cell differentiation by controlling p53 and may function as a new mechanism in glioma.

Potential predictive value of SCN4A mutation status for immune checkpoint inhibitors in melanoma

Melanoma refers to a pigmented nevus with malignant changes. The preferred treatment for primary melanoma is surgical excision and postoperative radiotherapy, but the prognosis is poor. Immune checkpoint inhibitors (ICIs) have been remarkably successful in different types of cancers, but not all cancer patients can benefit from it. Therefore, it is essential to find predictable biomarkers and improve the accuracy of treatment. In this study, we used survival analysis, gene panorama analysis, immune cell enrichment analysis, TMB analysis, and GSEA to demonstrate that SCN4A gene mutations may be used as one of the indicators to predict the prognosis of melanoma patients undergoing ICI treatment. The research further indicates that SCN4A gene mutations improve the prognosis of ICI treatment. It is hoped that the effect of SCN4A on immunogenicity and tumor immunity can be demonstrated to further suggest the effect of this gene on the efficacy of ICIs.

Metabolism of Natural Killer Cells and Other Innate Lymphoid Cells

Natural killer (NK) cells are the host's first line of defense against tumors and viral infections without prior sensitization. It is increasingly accepted that NK cells belong to the innate lymphoid cell (ILC) family. Other ILCs, comprising ILC1s, ILC2s, ILC3s and lymphoid tissue inducer (LTi) cells, are largely non-cytotoxic, tissue-resident cells, which function to protect local microenvironments against tissue insults and maintain homeostasis. Recently, evidence has accumulated that metabolism supports many aspects of the biology of NK cells and other ILCs, and that metabolic reprogramming regulates their development and function. Here, we outline the current understanding of ILC metabolism, and describe how metabolic processes are affected, and how metabolic defects are coupled to dysfunction of ILCs, in disease settings. Furthermore, we summarize the current and potential directions for immunotherapy involving targeting of ILC metabolism. Finally, we discuss the open questions in the rapidly expanding field of ILC metabolism.

Natural killer cells in cancer biology and therapy

The tumor microenvironment is highly complex, and immune escape is currently considered an important hallmark of cancer, largely contributing to tumor progression and metastasis. Named for their capability of killing target cells autonomously, natural killer (NK) cells serve as the main effector cells toward cancer in innate immunity and are highly heterogeneous in the microenvironment. Most current treatment options harnessing the tumor microenvironment focus on T cell-immunity, either by promoting activating signals or suppressing inhibitory ones. The limited success achieved by T cell immunotherapy highlights the importance of developing new-generation immunotherapeutics, for example utilizing previously ignored NK cells. Although tumors also evolve to resist NK cell-induced cytotoxicity, cytokine supplement, blockade of suppressive molecules and genetic engineering of NK cells may overcome such resistance with great promise in both solid and hematological malignancies. In this review, we summarized the fundamental characteristics and recent advances of NK cells within tumor immunometabolic microenvironment, and discussed potential application and limitations of emerging NK cell-based therapeutic strategies in the era of presicion medicine.

Aspirin Use Is Not Associated with Lower Thyroid Cancer Risk: A Nationwide Nested Case-Control Study

Background: While aspirin use is known to be associated with reduced incidence of various cancer types, it is unclear whether this benefit extends to thyroid cancer. We aimed to evaluate the association between aspirin use and thyroid cancer development. Methods: This nested case-control study used nationwide data from the Korean National Health Insurance Service-National Sample Cohort 2002-2015. In total, 4547 individuals with newly developed thyroid cancer were matched with 13,641 controls based on age, sex, and follow-up period. Odds ratios (ORs) and 95% confidence intervals (CIs) for thyroid cancer development according to aspirin use were analyzed using a multivariable conditional logistic regression model. Results: The number of days for which patients with thyroid cancer used aspirin (the proportions of no use, <30 days/year, 30-90 days/year, and ≥90 days/year were 93.03%, 6.51%, 0.31%, and 0.15%, respectively) was comparable with that of the controls (p = 0.371, chi-squared test). The risk of thyroid cancer development was not associated with the duration of aspirin use (ORs [CI] for aspirin use <30 days/year, 30-90 days/year, and ≥90 days/year were 1.11 [0.96-1.28], 1.01 [0.54-1.88], and 1.23 [0.50-3.06], respectively, compared with no use) after adjusting for body mass index, smoking status, hypertension, Charlson comorbidity index, and number of outpatient visits per year. In addition, subgroup analyses stratified by age, sex, and follow-up duration did not reveal any significant association between aspirin use and thyroid cancer. Conclusions: Our findings suggest that even extended aspirin use may not impact the prevention or onset of thyroid cancer.

Eicosanoids in Cancer: Prostaglandin E2 Receptor 4 in Cancer Therapeutics and Immunotherapy

The cyclooxygenase-2 (COX-2) enzyme is frequently overexpressed in epithelial malignancies including those of the breast, prostate, lung, kidney, ovary, and liver and elevated expression is associated with worse outcomes. COX-2 catalyzes the metabolism of arachidonic acid to prostaglandins. The COX-2 product prostaglandin E2 (PGE2) binds to four G-protein-coupled EP receptors designated EP1-EP4. EP4 is commonly upregulated in cancer and supports cell proliferation, migration, invasion, and metastasis through activation of multiple signaling pathways including ERK, cAMP/PKA, PI3K/AKT, and NF-κB. EP4 antagonists inhibit metastasis in preclinical models. Cancer stem cells, that underlie therapy resistance and disease relapse, are driven by the expression of EP4. Resistance to several chemotherapies is reversed in the presence of EP4 antagonists. In addition to tumor cell-autonomous roles of EP4, many EP4-positive host cells play a role in tumor behavior. Endothelial cell-EP4 supports tumor angiogenesis and lymphangiogenesis. Natural Killer (NK) cells are critical to the mechanism by which systemically administered EP4 antagonists inhibit metastasis. PGE2 acts on EP4 expressed on the NK cell to inhibit tumor target cell killing, cytokine production, and chemotactic activity. Myeloid-derived suppressor cells (MDSCs), that inhibit the development of cytotoxic T cells, are induced by PGE2 acting on myeloid-expressed EP2 and EP4 receptors. Inhibition of MDSC-EP4 leads to maturation of effector T cells and suppresses the induction of T regulatory cells. A number of EP4 antagonists have proven useful in dissecting these mechanisms. There is growing evidence that EP4 antagonism, particularly in combination with either chemotherapy, endocrine therapy, or immune-based therapies, should be investigated further as a promising novel approach to cancer therapy. Several EP4 antagonists have now progressed to early phase clinical trials and we eagerly await the results of those studies.

Mechanisms of Apoptosis Resistance to NK Cell-Mediated Cytotoxicity in Cancer

Natural killer (NK) cells are major contributors to immunosurveillance and control of tumor development by inducing apoptosis of malignant cells. Among the main mechanisms involved in NK cell-mediated cytotoxicity, the death receptor pathway and the release of granules containing perforin/granzymes stand out due to their efficacy in eliminating tumor cells. However, accumulated evidence suggest a profound immune suppression in the context of tumor progression affecting effector cells, such as NK cells, leading to decreased cytotoxicity. This diminished capability, together with the development of resistance to apoptosis by cancer cells, favor the loss of immunogenicity and promote immunosuppression, thus partially inducing NK cell-mediated killing resistance. Altered expression patterns of pro- and anti-apoptotic proteins along with genetic background comprise the main mechanisms of resistance to NK cell-related apoptosis. Herein, we summarize the main effector cytotoxic mechanisms against tumor cells, as well as the major resistance strategies acquired by tumor cells that hamper the extrinsic and intrinsic apoptotic pathways related to NK cell-mediated killing.

Hypoxia and cancer related pathology

Hypoxic environments occur normally at high altitude, or in underground burrows and in deep sea habitats. They also occur pathologically in human ischemia and in hypoxic solid tumors. Hypoxia in various cancer types and its related molecular mechanisms are associated with a poor clinical outcome. This review will discuss how hypoxia can influence two aspects of tumorigenesis, namely the direct, cell-intrinsic oncogenic effects, as well as the indirect effects on tumor progression mediated by an altered tumor microenvironment. We will also discuss recent progress in identifying the functional roles of hypoxia-related factors (HIFs), along with their regulators and downstream target genes, in cancer stem cells and therapy. Importantly, we propose, using convergent evolution schemes to identify novel biomarkers for both hypoxia adaptation and hypoxic solid tumors as an important strategy in the future.

The neonatal Fc receptor in cancer FcRn in cancer

Since the neonatal IgG Fc receptor (FcRn) was discovered, it was found to be involved in immunoglobulin recycling and biodistribution, immune complexes routing, antigen presentation, humoral immune response, and cancer immunosurveillance. The latest data show that FcRn plays a part in cancer pathophysiology. In various types of cancers, such as lung and colorectal cancer, FcRn has been described as an early marker for prognosis. Dysregulation of FcRn expression by cancer cells allows them to increase their metabolism, and this process could be exploited for passive targeting of cytotoxic drugs. However, the roles of this receptor depend on whether the studied cell population is the tumor tissue or the infiltrating cells, bringing forward the need for further studies.

Targeting Cancer Stem Cells by Genetically Engineered Chimeric Antigen Receptor T Cells

The term cancer stem cell (CSC) starts 25 years ago with the evidence that CSC is a subpopulation of tumor cells that have renewal ability and can differentiate into several distinct linages. Therefore, CSCs play crucial role in the initiation and the maintenance of cancer. Moreover, it has been proposed throughout several studies that CSCs are behind the failure of the conventional chemo-/radiotherapy as well as cancer recurrence due to their ability to resist the therapy and their ability to re-regenerate. Thus, the need for targeted therapy to eliminate CSCs is crucial; for that reason, chimeric antigen receptor (CAR) T cells has currently been in use with high rate of success in leukemia and, to some degree, in patients with solid tumors. This review outlines the most common CSC populations and their common markers, in particular CD133, CD90, EpCAM, CD44, ALDH, and EGFRVIII, the interaction between CSCs and the immune system, CAR T cell genetic engineering and signaling, CAR T cells in targeting CSCs, and the barriers in using CAR T cells as immunotherapy to treat solid cancers.

Mechanisms of Resistance to NK Cell Immunotherapy

Immunotherapy has recently been a major breakthrough in cancer treatment. Natural killer (NK) cells are suitable targets for immunotherapy owing to their potent cytotoxic activity that may target cancer cells in a major histocompatibility complex (MHC) and antigen-unrestricted manner. Current therapies targeting NK cells include monoclonal antibodies that promote NK cell antibody-dependent cell-mediated cytotoxicity (ADCC), hematopoietic stem cell transplantation (HSCT), the adoptive transfer of NK cells, the redirection of NK cells using chimeric antigen receptor (CAR)-NK cells and the use of cytokines and immunostimulatory drugs to boost the anti-tumor activity of NK cells. Despite some encouraging clinical results, patients receiving these therapies frequently develop resistance, and a myriad of mechanisms of resistance affecting both the immune system and cancer cells have been reported. A first contributing factor that modulates the efficacy of the NK cell therapy is the genetic profile of the individual, which regulates all aspects of NK cell biology. Additionally, the resistance of cancer cells to apoptosis and the immunoediting of cancer cells, a process that decreases their immunogenicity and promotes immunosuppression, are major determinants of the resistance to NK cell therapy. Consequently, the efficacy of NK cell anti-tumor therapy is specific to each patient and disease. The elucidation of such immunosubversive mechanisms is crucial to developing new procedures and therapeutic strategies to fully harness the anti-tumor potential of NK cells.

Prostaglandin E Receptor 4 Antagonist in Cancer Immunotherapy: Mechanisms of Action

A highly expressed prostaglandin E₂ (PGE₂) in tumor tissues suppresses antitumor immunity in the tumor microenvironment (TME) and causes tumor immune evasion leading to disease progression. In animal studies, selective inhibition of the prostaglandin E receptor 4 (EP4), one of four PGE₂ receptors, suppresses tumor growth, restoring the tumor immune response toward an antitumorigenic condition. This review summarizes PGE₂/EP4 signal inhibition in relation to the cancer-immunity cycle (C-IC), which describes fundamental tumor-immune interactions in cancer immunotherapy. PGE₂ is suggested to slow down C-IC by inhibiting natural killer cell functions, suppressing the supply of conventional dendritic cell precursors to the TME. This is critical for the tumor-associated antigen priming of CD8⁺ T cells and their translocation to the tumor tissue from the tumor-draining lymph node. Furthermore, PGE₂ activates several key immune-suppressive cells present in tumors and counteracts tumoricidal properties of the effector CD8⁺ T cells. These effects of PGE₂ drive the tumors to non-T-cell-inflamed tumors and cause refractory conditions to cancer immunotherapies, e.g., immune checkpoint inhibitor (ICI) treatment. EP4 antagonist therapy is suggested to inhibit the immune-suppressive and tumorigenic roles of PGE₂ in tumors, and it may sensitize the therapeutic effects of ICIs in patients with non-inflamed and C-IC-deficient tumors. This review provides insight into the mechanism of action of EP4 antagonists in cancer immunotherapy and suggests a C-IC modulating opportunity for EP4 antagonist therapy in combination with ICIs and/or other cancer therapies.

NK Cell-Based Immune Checkpoint Inhibition

Immunotherapy, with an increasing number of therapeutic dimensions, is becoming an important mode of treatment for cancer patients. The inhibition of immune checkpoints, which are the source of immune escape for various cancers, is one such immunotherapeutic dimension. It has mainly been aimed at T cells in the past, but NK cells are a newly emerging target. Simultaneously, the number of checkpoints identified has been increasing in recent times. In addition to the classical NK cell receptors KIRs, LIRs, and NKG2A, several other immune checkpoints have also been shown to cause dysfunction of NK cells in various cancers and chronic infections. These checkpoints include the revolutionized CTLA-4, PD-1, and recently identified B7-H3, as well as LAG-3, TIGIT & CD96, TIM-3, and the most recently acknowledged checkpoint-members of the Siglecs family (Siglec-7/9), CD200 and CD47. An interesting dimension of immune checkpoints is their candidacy for dual-checkpoint inhibition, resulting in therapeutic synergism. Furthermore, the combination of immune checkpoint inhibition with other NK cell cytotoxicity restoration strategies could also strengthen its efficacy as an antitumor therapy. Here, we have undertaken a comprehensive review of the literature to date regarding NK cell-based immune checkpoints.

Influence of the Tumor Microenvironment on NK Cell Function in Solid Tumors

Natural killer (NK) cells are a population of innate lymphoid cells playing a pivotal role in host immune responses against infection and tumor growth. These cells have a powerful cytotoxic activity orchestrated by an intricate network of inhibitory and activating signals. The importance of NK cells in controlling tumor growth and in mediating a robust anti-metastatic effect has been demonstrated in different experimental mouse cancer models. Consistently, high density of tumor-infiltrating NK cells has been linked with a good prognosis in multiple human solid tumors. However, there are also tumors that appear to be refractory to NK cell-mediated killing for the presence of an immunosuppressive microenvironment affecting NK cell function. Immunotherapeutic strategies aimed at restoring and increasing the cytotoxic activity of NK cells in solid tumors, including the adoptive transfer of NK and CAR-NK cells, are currently employed in preclinical and clinical studies. In this review, we outline recent advances supporting the direct role of NK cells in controlling expansion of solid tumors and their prognostic value in human cancers. We summarize the mechanisms adopted by cancer cells and the tumor microenvironment to affect NK cell function, and finally we evaluate current strategies to augment the antitumor function of NK cells for the treatment of solid tumors.

Down-regulation of the human major histocompatibility complex class I chain-related gene A (MICA) and its receptor is mediated by microRNA-146b-5p and is a potential mechanism of immunoediting in papillary thyroid carcinoma

Immune escape is one of the main reasons for the rapid progression of cancer and the poor efficacy of immunotherapy. Papillary thyroid cancer (PTC) is usually accompanied by intra-tumoral lymphocytic infiltration. The mechanisms regulating this tumor associated immune response or its evasion are not well understood. The major histocompatibility complex class I chain-related proteins A (MICA) and its receptor the natural killer group 2 member D (NKG2D) are major executers of the anti-tumor defense. This work aimed to study the expression and regulation of MICA-NKG2D and its association with the lymphocytic infiltration and miRNAs in PTC. Expression of MICA and NKG2D in thyroid tissues, and in cultured primary thyroid cancer cells and lymphocytes transfected with miR-146b-5p inhibitor/mimic was tested by RT-PCR. Results were confirmed by immunofluorescence staining and confocal microscopy. MICA is expressed in malignant and benign thyroid tissues with no association with aggressive behavior. Expression of MICA and NKG2D in PTC is concomitant with the presence of tumor associated lymphocytic response and is regulated by miR-146b-5p. MiR-146b-5p indirectly downregulates NKG2D expression in cancer cells and in lymphocytes. Overexpression of miR-146b-5p in PTC down-regulates MICA expression possibly to reduce the immunogenicity of the tumor cells. Targeting of the MICA-NKG2D axis by miR-146b-5p might be one of the ways adopted by thyroid cancer cells to aid the tumor in evading the immune response. The importance of our findings resides in the potential therapeutic use of MICA, NKG2D and miRNA-146b-5p as targets or modulators to enable the immune response against cancer.

Targeting Non-Oncogene Addiction: Focus on Thyroid Cancer

Thyroid carcinoma (TC) is the most common malignancy of endocrine organs with an increasing incidence in industrialized countries. The majority of TC are characterized by a good prognosis, even though cases with aggressive forms not cured by standard therapies are also present. Moreover, target therapies have led to low rates of partial response and prompted the emergence of resistance, indicating that new therapies are needed. In this review, we summarize current literature about the non-oncogene addiction (NOA) concept, which indicates that cancer cells, at variance with normal cells, rely on the activity of genes, usually not mutated or aberrantly expressed, essential for coping with the transformed phenotype. We highlight the potential of non-oncogenes as a point of intervention for cancer therapy in general, and present evidence for new putative non-oncogenes that are essential for TC survival and that may constitute attractive new therapeutic targets.

PGE2 ameliorated viral myocarditis development and promoted IL-10-producing regulatory B cell expansion via MAPKs/AKT-AP1 axis or AhR signaling

B10 cells, a specific subset of regulatory B cells, are capable of regulating immune response and restricting inflammation and autoimmune disease progression by producing IL-10. B10 cells frequently change significantly during inflammation and autoimmunity. However, how B10 cell populations change in viral myocarditis (VMC) remains unclear. Therefore, this work was conducted to clarify the changes in B10 cells and their potential mechanisms. Our results showed that the B10 cell frequency significantly changed in the VMC model. Changes in prostaglandin E2 (PGE2) levels in VMC model hearts were consistent with B10 expansion. PGE2 induced B10 cell expansion via the MAPKs/AKT-AP1 axis or AhR signaling. Additionally, PGE2-pretreated B10 cells inhibited naïve CD4⁺ T cell differentiation into Th17 cells. In vivo, PGE2 treatment or adoptive B10 cell transfer significantly restricted VMC development. Our results provide sufficient evidence that PGE2-induced B10 cell expansion may become a promising therapeutic approach for VMC and acute inflammatory injury.

NK Cell Metabolism and Tumor Microenvironment

Natural Killer (NK) cells are characterized by their potential to kill tumor cells by different means without previous sensitization and have, therefore, become a valuable tool in cancer immunotherapy. However, their efficacy against solid tumors is still poor and further studies are required to improve it. One of the major restrictions for NK cell activity is the immunosuppressive tumor microenvironment (TME). There, tumor and other immune cells create the appropriate conditions for tumor proliferation while, among others, preventing NK cell activation. Furthermore, NK cell metabolism is impaired in the TME, presumably due to nutrient and oxygen deprivation, and the higher concentration of tumor-derived metabolic end products, such as lactate. This metabolic restriction of NK cells limits their effector functions, and it could represent a potential target to focus on to improve the efficacy of NK cell-based therapies against solid tumors. In this review, we discuss the potential effect of TME into NK cell metabolism and its influence in NK cell effector functions.

The Immune Landscape of Thyroid Cancer in the Context of Immune Checkpoint Inhibition

Immune cells play critical roles in tumor prevention as well as initiation and progression. However, immune-resistant cancer cells can evade the immune system and proceed to form tumors. The normal microenvironment (immune cells, fibroblasts, blood and lymphatic vessels, and interstitial extracellular matrix (ECM)) maintains tissue homeostasis and prevents tumor initiation. Inflammatory mediators, reactive oxygen species, cytokines, and chemokines from an altered microenvironment promote tumor growth. During the last decade, thyroid cancer, the most frequent cancer of the endocrine system, has emerged as the fifth most incident cancer in the United States (USA), and its incidence is steadily growing. Inflammation has long been associated with thyroid cancer, raising critical questions about the role of immune cells in its pathogenesis. A plethora of immune cells and their mediators are present in the thyroid cancer ecosystem. Monoclonal antibodies (mAbs) targeting immune checkpoints, such as mAbs anti-cytotoxic T lymphocyte antigen 4 (anti-CTLA-4) and anti-programmed cell death protein-1/programmed cell death ligand-1 (anti-PD-1/PD-L1), have revolutionized the treatment of many malignancies, but they induce thyroid dysfunction in up to 10% of patients, presumably by enhancing autoimmunity. Combination strategies involving immune checkpoint inhibitors (ICIs) with tyrosine kinase (TK) or serine/threonine protein kinase B-raf (BRAF) inhibitors are showing considerable promise in the treatment of advanced thyroid cancer. This review illustrates how different immune cells contribute to thyroid cancer development and the rationale for the antitumor effects of ICIs in combination with BRAF/TK inhibitors.

Adoptive CD8+ T cell therapy against cancer:Challenges and opportunities

Cancer immunotherapy is a new and promising option for cancer treatment. Unlike traditional chemo- and radiotherapy, immunotherapy actives host immune system to attack malignancies, and this potentially offers long-term protection from recurrence with less toxicity in comparison to conventional chemo- and radiation therapy. In adoptive CD8⁺ T cell therapy (ACT), large numbers of tumor-specific T cells are sourced from patients and expanded in vitro and infused back to patients. T cells can be expanded from naturally-induced tumor-specific CD8⁺ T cells isolated from tumor infiltrating lymphocytes (TIL) or genetically-modified autologous circulating CD8⁺ T cells. The engineered T cells expressed tumor-specific antigen receptors including chimeric antigen receptors (CARs) and T cell receptors (TCRs), prepared from cultured B and T cell clones, respectively. The most successful ACT, anti-CD19 chimeric antigen receptor T (CAR-T) cell therapy directed against B cell lymphoma, is already approved for use based on evidence of efficacy. Efficacy of solid tumors is not yet forthcoming. This review summarizes current technology developments using ACT in clinical trials. In this review, differences between various ACT approaches are discussed. Furthermore, resistance factors in the tumor microenvironment are also considered, as are immune related adverse effects, critical clinic monitoring parameters and potential mitigation approaches.