Dendritic cells integrate signals from the tumor microenvironment to modulate immunity and tumor growth

cDC2 plasticity and acquisition of a DC3-like phenotype mediated by IL-6 and PGE2 in a patient-derived colorectal cancer organoids model

Metastatic colorectal cancer (CRC) is highly resistant to therapy and prone to recur. The tumor-induced local and systemic immunosuppression allows cancer cells to evade immunosurveillance, facilitating their proliferation and dissemination. Dendritic cells (DCs) are required for the detection, processing, and presentation of tumor antigens, and subsequently for the activation of antigen-specific T cells to orchestrate an effective antitumor response. Notably, successful tumors have evolved mechanisms to disrupt and impair DC functions, underlining the key role of tumor-induced DC dysfunction in promoting tumor growth, metastasis initiation, and treatment resistance. Conventional DC type 2 (cDC2) are highly prevalent in tumors and have been shown to present high phenotypic and functional plasticity in response to tumor-released environmental cues. This plasticity reverberates on both the development of antitumor responses and on the efficacy of immunotherapies in cancer patients. Uncovering the processes, mechanisms, and mediators by which CRC shapes and disrupts cDC2 functions is crucial to restoring their full antitumor potential. In this study, we use our recently developed 3D DC-tumor co-culture system to investigate how patient-derived primary and metastatic CRC organoids modulate cDC2 phenotype and function. We first demonstrate that our collagen-based system displays extensive interaction between cDC2 and tumor organoids. Interestingly, we show that tumor-corrupted cDC2 shift toward a CD14+ population with defective expression of maturation markers, an intermediate phenotype positioned between cDC2 and monocytes, and impaired T-cell activating abilities. This phenotype aligns with the newly defined DC3 (CD14+ CD1c+ CD163+) subset. Remarkably, a comparable population was found to be present in tumor lesions and enriched in the peripheral blood of metastatic CRC patients. Moreover, using EP2 and EP4 receptor antagonists and an anti-IL-6 neutralizing antibody, we determined that the observed phenotype shift is partially mediated by PGE2 and IL-6. Importantly, our system holds promise as a platform for testing therapies aimed at preventing or mitigating tumor-induced DC dysfunction. Overall, our study offers novel and relevant insights into cDC2 (dys)function in CRC that hold relevance for the design of therapeutic approaches.

Myeloid cells as potential targets for immunotherapy in pediatric gliomas

Pediatric high-grade glioma (pHGG) including pediatric glioblastoma (pGBM) are highly aggressive pediatric central nervous system (CNS) malignancies. pGBM comprises approximately 3% of all pediatric CNS malignancies and has a 5-year survival rate of approximately 20%. Surgical resection and chemoradiation are often the standard of care for pGBM and pHGG, however, even with these interventions, survival for children diagnosed with pGBM and pHGG remains poor. Due to shortcomings associated with the standard of care, many efforts have been made to create novel immunotherapeutic approaches targeted to these malignancies. These efforts include the use of vaccines, cell-based therapies, and immune-checkpoint inhibitors. However, it is believed that in many pediatric glioma patients an immunosuppressive tumor microenvironment (TME) possess barriers that limit the efficacy of immune-based therapies. One of these barriers includes the presence of immunosuppressive myeloid cells. In this review we will discuss the various types of myeloid cells present in the glioma TME, including macrophages and microglia, myeloid-derived suppressor cells, and dendritic cells, as well as the specific mechanisms these cells can employ to enable immunosuppression. Finally, we will highlight therapeutic strategies targeted to these cells that are aimed at impeding myeloid-cell derived immunosuppression.

Advances in dendritic cell vaccination therapy of cancer

Traditionally, vaccines have helped eradication of several infectious diseases and also saved millions of lives in the human history. Those prophylactic vaccines have acted through inducing immune responses against a live attenuated, killed organism or antigenic subunits to protect the recipient against a real infection caused by the pathogenic microorganism. Nevertheless, development of anticancer vaccines as valuable targets in human health has faced challenges and requires further optimizations. Dendritic cells (DCs) are the most potent antigen presenting cells (APCs) that play essential roles in tumor immunotherapies through induction of CD8+ T cell immunity. Accordingly, various strategies have been tested to employ DCs as therapeutic vaccines for exploiting their activity against tumor cells. Application of whole tumor cells or purified/recombinant antigen peptides are the most common approaches for pulsing DCs, which then are injected back into the patients. Although some hopeful results are reported for a number of DC vaccines tested in animal and clinical trials of cancer patients, such approaches are still inefficient and require optimization. Failure of DC vaccination is postulated due to immunosuppressive tumor microenvironment (TME), overexpression of checkpoint proteins, suboptimal avidity of tumor-associated antigen (TAA)-specific T lymphocytes, and lack of appropriate adjuvants. In this review, we have an overview of the current experiments and trials evaluated the anticancer efficacy of DC vaccination as well as focusing on strategies to improve their potential including combination therapy with immune checkpoint inhibitors (ICIs).

Prognostic biomarker NEIL3 and its association with immune infiltration in renal clear cell carcinoma

Background

Kidney renal clear cell carcinoma (KIRC) is a malignant tumor with a high degree of immune infiltration. Identifying immune biomarkers is essential for the treatment of KIRC. Studies have identified the potential of NEIL3 to modulate the immune microenvironment and promote tumor progression. However, the role of NEIL3 in KIRC remains uncertain. This study was to investigate the effect of NEIL3 on the prognosis and immune infiltration of patients with KIRC.

Methods

TCGA and GEO databases were used to study the expression of NEIL3 in KIRC. Cox regression analysis was used to examine the relationship between the expression of NEIL3 and clinicopathological variables and survival. Furthermore, Gene Set Cancer Analysis (GSCA) was applied to study the impact of NEIL3 methylation on outcomes of KIRC. Through gene ontology (GO) and Gene set enrichment (GSEA) analysis, the biological processes and signal pathways related to NEIL3 expression were identified. In addition, immune infiltration analysis was conducted via CIBERSORT analysis, ssGSEA analysis and TISIDB database.

Results

NEIL3 was overexpressed in KIRC, and it was significantly related with histologic grade, pathologic stage, T stage, M stage, and vital status of KIRC patients (P < 0.001). The expression of NEIL3 was associated with worse outcomes. Univariate and multivariate Cox analysis showed that NEIL3 may be an indicator of adverse outcomes in KIRC. GSEA analysis revealed that NEIL3 may be involved in signal pathways including cell cycle, DNA replication, mismatch repair, P53 signal pathway, and antigen processing and presentation. In addition, immune infiltration analysis showed a positive correlation between NEIL3 expression and multiple immune cells (activated CD8 T cells, activated dendritic cells, myeloid-derived suppressor cells, follicular helper T cells, and regulatory T cells) and immunoinhibitors (PD1, CTLA4, LAG3, TIGHT, IL10, and CD96).

Conclusion

NEIL3 is a potential independent biomarker of KIRC, which is relevant to immune infiltration.

Dendritic cell phenotype and function in a 3D co-culture model of patient-derived metastatic colorectal cancer organoids

Colorectal cancer (CRC) remains one of the most aggressive and lethal cancers, with metastasis accounting for most deaths. As such, there is an unmet need for improved therapies for metastatic CRC (mCRC). Currently, the research focus is shifting towards the reciprocal interactions within the tumor microenvironment (TME), which prevent tumor clearance by the immune system. Dendritic cells (DCs) play a key role in the initiation and amplification of anti-tumor immune responses and in driving the clinical success of immunotherapies. Dissecting the interactions between DCs and CRC cells may open doors to identifying key mediators in tumor progression, and possible therapeutic targets. This requires representative, robust and versatile models and tools. Currently, there is a shortage of such in vitro systems to model the CRC TME and its tumor-immune cell interactions. Here we develop and establish a dynamic organotypic 3D co-culture system to recapitulate and untangle the interactions between DCs and patient-derived mCRC tumor organoids. To our knowledge, this is the first study investigating human DCs in co-culture with tumor organoids in a 3D, organotypic setting. This system reveals how mCRC organoids modulate and shape monocyte-derived DCs (MoDCs) behavior, phenotype, and function, within a collagen matrix, using techniques such as brightfield and fluorescence microscopy, flow cytometry, and fluorescence-activated cell sorting. Our 3D co-culture model shows high viability and extensive interaction between DCs and tumor organoids, and its structure resembles patient tissue sections. Furthermore, it is possible to retrieve DCs from the co-cultures and characterize their phenotypic and functional profile. In our study, the expression of activation markers in both mature and immature DCs and their ability to activate T cells were impacted by co-culture with tumor organoids. In the future, this direct co-culture platform can be adapted and exploited to study the CRC-DC interplay in more detail, enabling novel and broader insights into CRC-driven DC (dys)function.

Immunosuppression in tumor immune microenvironment and its optimization from CAR-T cell therapy

Chimeric antigen receptor (CAR)-T cell therapy represents a landmark advance in personalized cancer treatment. CAR-T strategy generally engineers T cells from a specific patient with a new antigen-specificity, which has achieved considerable success in hematological malignancies, but scarce benefits in solid tumors. Recent studies have demonstrated that tumor immune microenvironment (TIME) cast a profound impact on the immunotherapeutic response. The immunosuppressive landscape of TIME is a critical obstacle to the effector activity of CAR-T cells. Nevertheless, every cloud has a silver lining. The immunosuppressive components also shed new inspiration on reshaping a friendly TIME by targeting them with engineered CARs. Herein, we summarize recent advances in disincentives of TIME and discuss approaches and technologies to enhance CAR-T cell efficacy via addressing current hindrances. Simultaneously, we firmly believe that by parsing the immunosuppressive components of TIME, rationally manipulating the complex interactions of immunosuppressive components, and optimizing CAR-T cell therapy for each patient, the CAR-T cell immunotherapy responsiveness for solid malignancies will be substantially enhanced, and novel therapeutic targets will be revealed.

Clinical Correlation of Function and TCR vβ Diversity of MAGE-C2–Specific CD8+ T Cell Response in Esophageal Cancer

Melanoma-associated Ag (MAGE)-C2, an immunogenic cancer germline (testis) Ag, is highly expressed by various tumor cells, thymic medullary epithelial cells, and germ cells. In this study, we aimed to explore the immunologic properties of MAGE-C2–specific CD8+ T cells and the relationship of its TCR β-chain V region (TCR vβ) subfamily distribution to prognosis of patients with esophageal cancer. PBMCs and tumor-infiltrating lymphocytes expanded by CD3/CD28 Dynabeads and MAGE-C2 peptides in vitro resulted in the induction of lysosome-associated membrane protein-1 (LAMP-1 or CD107a) on the cell surface and the production of IFN-γ by MAGE-C2–specific CD8+ T cells. We found differential TCR vβ subfamily distribution among flow-sorted CD107a+IFN-γ+ and CD107a−IFN-γ− CD8+ T cells. The proportion of CD107a+ and/or IFN-γ+ tetramer+ CD8+ T cells was lower in patients with lymph node metastasis, late tumor stage, and poorly differentiated state (p &lt; 0.05). T-box transcription factor was positively correlated with CD107a and IFN-γ. Kaplan–Meier analysis showed that patients whose MAGE-C2–specific CD8+ T cells expressed high CD107a and/or IFN-γ had a longer survival time when compared with patients whose MAGE-C2–specific CD8+ T cells expressed low levels of CD107a and/or IFN-γ. Moreover, analysis of TCR vβ subfamily distribution revealed that a higher frequency of TCR vβ16 in MAGE-C2–specific CD8+ T cells was positively correlated with a better prognosis. These results suggest that the presence of functional MAGE-C2–specific CD8+ T cells had an independent prognostic impact on the survival of patients with esophageal cancer.

The application of the natural killer cells, macrophages and dendritic cells in treating various types of cancer

Innate immune cells such as natural killer (NK) cells, macrophages and dendritic cells (DCs) are involved in the surveillance and clearance of tumor. Intensive research has exposed the mechanisms of recognition and elimination of tumor cells by these immune cells as well as how cancers evade immune response. Hence, harnessing the immune cells has proven to be an effective therapy in treating a variety of cancers. Strategies aimed to harness and augment effector function of these cells for cancer therapy have been the subject of intense researches over the decades. Different immunotherapeutic possibilities are currently being investigated for anti-tumor activity. Pharmacological agents known to influence immune cell migration and function include therapeutic antibodies, modified antibody molecules, toll-like receptor agonists, nucleic acids, chemokine inhibitors, fusion proteins, immunomodulatory drugs, vaccines, adoptive cell transfer and oncolytic virus–based therapy. In this review, we will focus on the preclinical and clinical applications of NK cell, macrophage and DC immunotherapy in cancer treatment.

CD1a- and CD83-positive dendritic cells as prognostic markers of metastasis development in early breast cancer patients

PURPOSE

Dendritic cells (DCs) are the most potent antigen-presenting cells that play a major role in initiating the antitumor immune response in different types of cancer. However, the prognostic significance of the accumulation of these cells in human early breast tumors is not totally clear. The aim of this study is to evaluate the prognostic relevance of CD1a( +) and CD83( +) dendritic cells in early breast cancer patients.

METHODS

We conducted immunohistochemical assays to determine the number of stromal CD1a( +) and CD83( +) DCs in primary tumors from early invasive ductal breast cancer patients, and analyzed their association with clinico-pathological characteristics.

RESULTS

Patients with high CD1a( +) DC number had lower risk of bone metastatic occurrence, as well as, longer disease-free survival (DFS), bone metastasis-free survival (BMFS) and overall survival (OS). Moreover, CD1a( +) DC number was an independent prognostic factor for BMFS and OS. In contrast, we found that patients with high number of CD83( +) DCs had lower risk of mix (bone and visceral)-metastatic occurrence. Likewise, these patients presented better prognosis with longer DFS, mix-MFS and OS. Furthermore, CD83( +) DC number was an independent prognostic factor for DFS and OS.

CONCLUSION

The quantification of the stromal infiltration of DCs expressing CD1a or CD83 in early invasive breast cancer patients serves to indicate the prognostic risk of developing metastasis in a specific site.

The Therapeutic Potential of Tackling Tumor-Induced Dendritic Cell Dysfunction in Colorectal Cancer

Colorectal cancer (CRC) is the third most diagnosed malignancy and the second leading cause of cancer-related deaths worldwide. Locally advanced and metastatic disease exhibit resistance to therapy and are prone to recurrence. Despite significant advances in standard of care and targeted (immuno)therapies, the treatment effects in metastatic CRC patients have been modest. Untreatable cancer metastasis accounts for poor prognosis and most CRC deaths. The generation of a strong immunosuppressive tumor microenvironment (TME) by CRC constitutes a major hurdle for tumor clearance by the immune system. Dendritic cells (DCs), often impaired in the TME, play a critical role in the initiation and amplification of anti-tumor immune responses. Evidence suggests that tumor-mediated DC dysfunction is decisive for tumor growth and metastasis initiation, as well as for the success of immunotherapies. Unravelling and understanding the complex crosstalk between CRC and DCs holds promise for identifying key mechanisms involved in tumor progression and spread that can be exploited for therapy. The main goal of this review is to provide an overview of the current knowledge on the impact of CRC-driven immunosuppression on DCs phenotype and functionality, and its significance for disease progression, patient prognosis, and treatment response. Moreover, present knowledge gaps will be highlighted as promising opportunities to further understand and therapeutically target DC dysfunction in CRC. Given the complexity and heterogeneity of CRC, future research will benefit from the use of patient-derived material and the development of in vitro organoid-based co-culture systems to model and study DCs within the CRC TME.

Increased miR-6875-5p inhibits plasmacytoid dendritic cell differentiation via the STAT3/E2-2 pathway in recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) is a common complication of early pregnancy. Dendritic cells (DCs) are thought to confer fetal–maternal immunotolerance and play a crucial role in ensuring a successful pregnancy. A decrease of plasmacytoid dendritic cells (pDCs) was found to be involved in RSA, but the underlying mechanisms of decreased pDC in RSA remain unclear. MicroRNAs (miRNAs) play critical roles in RSA as well as the development, differentiation and functional regulation of pDCs; however, the regulatory effect of miRNAs on pDC in RSA has not been fully investigated. Here we demonstrated that both the proportion of pDC and signal transducer and activator of transcription (STAT3)/transcription factor 4 (Tcf4/E2-2) expression decreased in the peripheral blood mononuclear cells and decidua of patients with RSA compared to those with normal pregnancy (NP), and there was a significantly positive correlation between pDC and STAT3 mRNA. MiRNA microarray assay and quantitative reverse transcription PCR results showed that miR-6875-5p expression was markedly increased in women with RSA and negatively correlated with mRNA expression level of STAT3. Up-regulated miR-6875-5p could sensitively discriminate patients with RSA from NP subjects. Overexpression of miR-6875-5p significantly down-regulated the mRNA expression of STAT3 and E2-2 as well as the protein and phosphorylation level of STAT3, while miR-6875-5p knockdown showed opposite results. Dual luciferase reporter verified that miR-6875-5p regulated STAT3 expression by directly binding to its 3'untranslated region. Overall, our results suggested that increased miR-6875-5p is involved in RSA by decreasing the differentiation of pDCs via inhibition of the STAT3/E2-2 signaling pathway. miR-6875-5p may be explored as a promising diagnostic marker and therapeutic target for RSA.

Characterization of Tumor-Associated Macrophages and the Immune Microenvironment in Limited-Stage Neuroendocrine-High and -Low Small Cell Lung Cancer

Simple Summary

To date, the therapeutic strategy and guidelines in small cell lung cancer (SCLC) are based on cancer cell-related attributes with no biomarker used in the clinical practice. In the present study, using RNAseq and IHC, we aim to characterize in the frontline the latest biomarkers of tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSC) and related critical elements, regulating the anti-tumor immune response. Accordingly, we extensively evaluated the TME associations in primary tumors and matched lymph node metastases in different tumor compartments (stroma and tumor nests) and neuroendocrine (NE) subtypes in limited-stage SCLC. We show the RNA gene enrichment of the most critical molecular pathways based on the Gene Ontology (GO) iteration system using thorough bioinformatics analysis to identify new molecular targets in distinct NE subtypes.

Abstract

This study aims to characterize tumor-infiltrating macrophages (TAMs), myeloid-derived suppressor cells (MDSC), and the related molecular milieu regulating anti-tumor immunity in limited-stage neuroendocrine (NE)-high and NE-low small cell lung cancer. Primary tumors and matched lymph node (LN) metastases of 32 resected, early-stage SCLC patients were analyzed by immunohistochemistry (IHC) with antibodies against pan-macrophage marker CD68, M2-macrophage marker CD163, and MDSC marker CD33. Area-adjusted cell counting on TMAs showed that TAMs are the most abundant cell type in the TME, and their number in tumor nests exceeds the number of CD3 + T-cells (64% vs. 38% in NE-low and 71% vs. 18% in NE-high). Furthermore, the ratio of CD163-expressing M2-polarized TAMs in tumor nests was significantly higher in NE-low vs. NE-high tumors (70% vs. 31%). TAM density shows a strong positive correlation with CD45 and CD3 in tumor nests, but not in the stroma. fGSEA analysis on a targeted RNAseq oncological panel of 2560 genes showed that NE-high tumors exhibited increased enrichment in pathways related to cell proliferation, whereas in NE-low tumors, immune response pathways were significantly upregulated. Interestingly, we identified a subset of NE-high tumors representing an immune-oasis phenotype, but with a different gene expression profile compared to NE-low tumors. In contrast, we found that a limited subgroup of NE-low tumors is immune-deserted and express distinct cellular pathways from NE-high tumors. Furthermore, we identified potential molecular targets based on our expression data in NE-low and immune-oasis tumor subsets, including CD70, ANXA1, ITGB6, TP63, IFI27, YBX3 and CXCR2.

Epigenetic Modifiers: Anti-Neoplastic Drugs With Immunomodulating Potential

Cancer cells are under the surveillance of the host immune system. Nevertheless, a number of immunosuppressive mechanisms allow tumors to escape protective responses and impose immune tolerance. Epigenetic alterations are central to cancer cell biology and cancer immune evasion. Accordingly, epigenetic modulating agents (EMAs) are being exploited as anti-neoplastic and immunomodulatory agents to restore immunological fitness. By simultaneously acting on cancer cells, e.g. by changing expression of tumor antigens, immune checkpoints, chemokines or innate defense pathways, and on immune cells, e.g. by remodeling the tumor stroma or enhancing effector cell functionality, EMAs can indeed overcome peripheral tolerance to transformed cells. Therefore, combinations of EMAs with chemo- or immunotherapy have become interesting strategies to fight cancer. Here we review several examples of epigenetic changes critical for immune cell functions and tumor-immune evasion and of the use of EMAs in promoting anti-tumor immunity. Finally, we provide our perspective on how EMAs could represent a game changer for combinatorial therapies and the clinical management of cancer.

The role of dendritic cells in cancer and anti-tumor immunity

Dendritic cells (DC) are key sentinels of the host immune response with an important role in linking innate and adaptive immunity and maintaining tolerance. There is increasing recognition that DC are critical determinants of initiating and sustaining effective T-cell-mediated anti-tumor immune responses. Recent progress in immuno-oncology has led to the evolving insight that the presence and function of DC within the tumor microenvironment (TME) may dictate efficacy of cancer immunotherapies as well as conventional cancer therapies, including immune checkpoint blockade, radiotherapy and chemotherapy. As such, improved understanding of dendritic cell immunobiology specifically focusing on their role in T-cell priming, migration into tissues and TME, and the coordinated in vivo responses of functionally specialized DC subsets will facilitate a better mechanistic understanding of how tumor-immune surveillance can be leveraged to improve patient outcomes and to develop novel DC-targeted therapeutic approaches.

Heme oxygenase-1 (HO-1) assists inorganic arsenic-induced immune tolerance in murine dendritic cells

Inorganic arsenic, a well-known human carcinogen, poses a major threat to global health. Given the immunosuppressive potentials of inorganic arsenic as well as limited understanding of this metalloid on antigen-presenting dendritic cells (DCs), we systematically screened the immune targets in response to arsenic treatment, as well as its possible molecular mechanism in cultured murine DCs. Our results denoted that arsenite (As) significantly induced immune tolerance by down-regulating the expression of phenotypic molecules, pro-inflammatory factors and T-lymphocyte helper (Th)1/Th17-inducible cytokines in lipopolysaccharides (LPS)-stimulated myeloid-derived dendritic cells (BMDCs). Inconsistent with dampened phosphorylation of immune-related proteins (nuclear factor kappa-B) NF-κB, p38 and JNK, the metalloid drastically induced the expression of Heme oxygenase-1 (HO-1) protein, which enlightened us to continuously explore the possible roles of HO-1 pathway in As-induced immune tolerance in BMDCs. In this respect, immunosuppressive properties of HO-1 pathway in BMDCs were firstly confirmed through pharmacological overexpression of HO-1 by both CoPP and CORM-2. By contrast, limited HO-1 expression by HO-1 inhibitor ZnPP specifically alleviated As-mediated down-regulation of CD80, chemokine factor C-C chemokine receptor 7 (CCR7), tumor necrosis factor (TNF) -α, Interleukin (IL)-23 and IL-6, which reminds us the peculiarity of HO-1 in As-induced immune tolerance in murine DCs. Based on these experimental findings, we postulated the immunosuppressive property of inorganic arsenic might be mediated partially by HO-1 in DCs, thus contributing to the interactions of DCs-polarized differentiation of T-lymphocyte subtype as well as the development of infections and malignant diseases.

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.

Cytokine-chemokine network driven metastasis in esophageal cancer; promising avenue for targeted therapy

Esophageal cancer (EC) is a disease often marked by aggressive growth and poor prognosis. Lack of targeted therapies, resistance to chemoradiation therapy, and distant metastases among patients with advanced disease account for the high mortality rate. The tumor microenvironment (TME) contains several cell types, including fibroblasts, immune cells, adipocytes, stromal proteins, and growth factors, which play a significant role in supporting the growth and aggressive behavior of cancer cells. The complex and dynamic interactions of the secreted cytokines, chemokines, growth factors, and their receptors mediate chronic inflammation and immunosuppressive TME favoring tumor progression, metastasis, and decreased response to therapy. The molecular changes in the TME are used as biological markers for diagnosis, prognosis, and response to treatment in patients. This review highlighted the novel insights into the understanding and functional impact of deregulated cytokines and chemokines in imparting aggressive EC, stressing the nature and therapeutic consequences of the cytokine-chemokine network. We also discuss cytokine-chemokine oncogenic potential by contributing to the Epithelial-Mesenchymal Transition (EMT), angiogenesis, immunosuppression, metastatic niche, and therapeutic resistance development. In addition, it discusses the wide range of changes and intracellular signaling pathways that occur in the TME. Overall, this is a relatively unexplored field that could provide crucial insights into tumor immunology and encourage the effective application of modulatory cytokine-chemokine therapy to EC.

Peritumoral plasmacytoid dendritic cells predict a poor prognosis for intrahepatic cholangiocarcinoma after curative resection

BACKGROUND

Plasmacytoid dendritic cells (pDCs) are present in various primary and metastatic human neoplasms; however, their clinical significance in intrahepatic cholangiocarcinoma is not clear.

METHODS

To evaluate pDCs' distributions in and around tumors as well as their potential function and predictive value for prognosis in patients undergoing curative resection, we performed immunohistochemistry to examine the expression of pDC marker BDCA2, and CD3, CD4, CD8 and Foxp3 in intratumoral and peritumoral tissues from 359 patients with intrahepatic cholangiocarcinoma and compared with prognostic and clinicopathologic factors.

RESULTS

Results showed that patients with high numbers of BDCA2⁺ pDCs in peritumoral tissues were more likely to have elevated levels of carbohydrate antigen 19-9 and gamma-glutamyl transferase, larger and more tumors, advanced tumor-node-metastasis staging, more vascular/bile duct invasion, and lymphatic metastasis in association with greater chance of recurrence and shorter overall survival. Peritumoral tissues with larger numbers of pDCs also showed increased Foxp3⁺ regulatory T cell infiltration, both of which were found to be independent factors for predicting time to recurrence and overall survival. By contrast, patient outcomes were not associated with the presence of intratumoral pDCs.

CONCLUSIONS

Peritumoral pDC infiltration may indicate an immune tolerogenic peritumor microenvironment and can be used to predict a poor prognosis for patients undergoing curative resection for intrahepatic cholangiocarcinoma.

Monocytic and granulocytic myeloid-derived suppressor cell plasticity and differentiation are organ-specific

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that proliferate in the setting of cancer and have potent immunosuppressive functions hindering anti-tumor immunity. Here we establish that the immunologic landscape and tumor microenvironments (TME) vary between different organs which discretely shape MDSC repertoires. We found that pSTAT3 signaling exerts a dominant effect on MDSC programming in liver metastasis (LM). In contrast, in lung metastasis (LuM), MDSC programming is driven mainly by pSTAT5. Adoptive transfer of LM-MDSC into LuM resulted in a shift from pSTAT3 signaling to pSTAT5, in association with an overall shift toward lung MDSC programming. A shift from more immunosuppressive M-MDSC to G-MDSC, along with enhanced differentiation of MDSCs into pro-inflammatory M1 macrophages in LuM, indicated that MDSC plasticity and differentiation patterns are environmentally dependent. Using mass spectroscopy, we confirmed that LM-MDSCs showed enhanced expression of key proliferation pathway markers. This confirmed that liver-specific MDSC programing was comprehensive but reversible, implying that therapeutic targeting of LM-MDSC could prime the TME in a favorable manner. Our data suggest that MDSC programming in response to malignancy is highly dependent on organ-specific conditions and is modifiable.

Immune profiling before treatment is predictive of TLR9-induced antitumor efficacy

TLR9 targeting has been a dynamic research field with promising potential in tumor immunotherapy. However, why most patients do not respond to TLR9 agonists remains unknown. In our attempt to resolve this issue, we observed that anti-tumor response to our TLR9-targeting cancer nanomedicines varied according to the initial immune profile of the animals. Speculating that immune profiling before treatment, including the measurement of IFN-α, IL-12, IL-6, TNF, tumor-infiltrating lymphocytes and spleen-residing lymphocytes, could be used to predictively distinguish responders from non-responders, we performed experiments in two different tumor models 4T1-BALB/c and B16-C57BL/6, to validate the hypothesis. Results confirmed that antitumor efficacy with respect to tumor growth, immune cell infiltration, and cytokines release, correlated with the different condition of individuals, as well as the categorization of the animals. This work suggests that immune profiling before treatment might be able to predict the antitumor efficacy of TLR9 agonists in vivo.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

Pre-activation with TLR7 in combination with thioridazine and loratadine promotes tumoricidal T-cell activity in colorectal cancer

Colorectal cancer (CRC) is the third most common malignancy worldwide. Our previous studies have shown that combinatorial treatment with thioridazine and loratadine may effectively inhibit CRC. However, the translation of these research findings to clinical practice was impaired by issues related to a lack of therapeutic specificity and to immune evasion. Toll-like receptor (TLR) agonists have been used as adjuvants to enhance the effectiveness of cancer vaccines. The aim of this study was to evaluate the therapeutic efficiency of immunotherapy with thioridazine and loratadine in combination with resiqumiod (R848), a small-molecule TLR7 agonist, in suppressing CRC growth in a mouse model. Twenty-four BALB/c mice were randomly assigned to treatment with PBS, R848, thioridazine + loratadine, or thioridazine + loratadine + R848. Cytokine levels were measured with ELISA. Overall survival, as well as tumor volume and tumor weight, was recorded. Cytotoxicity was measured by counting the numbers of CD8 and CD3-positive (CD8CD3) or CD4 and CD3-positive (CD3CD4) T-cells. The immune response induced by cytokines (as interferon-γ, interleukin-6, and tumor necrosis factor-α) was significantly stronger in mice treated with thioridazine + loratadine + R848. Moreover, thioridazine + loratadine + R848 significantly delayed tumor development and prolonged survival, which was associated with enhanced immune response and dendritic cell maturation. This study suggested that thioridazine + loratadine + R848 combinatorial treatment may be effective in overcoming immune evasion by tumor cells, with promising therapeutic potential in CRC.

The tumour microenvironment shapes dendritic cell plasticity in a human organotypic melanoma culture

The tumour microenvironment (TME) forms a major obstacle in effective cancer treatment and for clinical success of immunotherapy. Conventional co-cultures have shed light onto multiple aspects of cancer immunobiology, but they are limited by the lack of physiological complexity. We develop a human organotypic skin melanoma culture (OMC) that allows real-time study of host-malignant cell interactions within a multicellular tissue architecture. By co-culturing decellularized dermis with keratinocytes, fibroblasts and immune cells in the presence of melanoma cells, we generate a reconstructed TME that closely resembles tumour growth as observed in human lesions and supports cell survival and function. We demonstrate that the OMC is suitable and outperforms conventional 2D co-cultures for the study of TME-imprinting mechanisms. Within the OMC, we observe the tumour-driven conversion of cDC2s into CD14+ DCs, characterized by an immunosuppressive phenotype. The OMC provides a valuable approach to study how a TME affects the immune system.

Targeting Mononuclear Phagocyte Receptors in Cancer Immunotherapy: New Perspectives of the Triggering Receptor Expressed on Myeloid Cells (TREM-1)

Inflammatory cells are major players in the onset of cancer. The degree of inflammation and type of inflammatory cells in the tumor microenvironment (TME) are responsible for tilting the balance between tumor progression and regression. Cancer-related inflammation has also been shown to influence the efficacy of conventional therapy. Mononuclear phagocytes (MPs) represent a major component of the inflammatory circuit that promotes tumor progression. Despite their potential to activate immunosurveillance and exert anti-tumor responses, MPs are subverted by the tumor to support its growth, immune evasion, and spread. MP responses in the TME are dictated by a network of stimuli integrated through the cross-talk between activatory and inhibitory receptors. Alterations in receptor expression/signaling can create excessive inflammation and, when chronic, promote tumorigenesis. Research advances have led to the development of new therapeutic strategies aimed at receptor targeting to induce a tumor-infiltrating MP switch from a cancer-supportive toward an anti-tumor phenotype, demonstrating efficacy in different human cancers. This review provides an overview of the role of MP receptors in inflammation-mediated carcinogenesis and discusses the most recent updates regarding their targeting for immunotherapeutic purposes. We focus in particular on the TREM-1 receptor, a major amplifier of MP inflammatory responses, highlighting its relevance in the development and progression of several types of inflammation-associated malignancies and the promises of its inhibition for cancer immunotherapy.

Gadolinium-doped Au@prussian blue nanoparticles as MR/SERS bimodal agents for dendritic cell activating and tracking

In vivo tracking of dendritic cell (DC) migration to the lymphatic system is essential for evaluating the outcome of DC-based immunotherapies. Novel multimodal imaging strategies with high analytical performance are urgently needed to supply complementary information about the migration and colonization of DCs. In this study, we designed a bimodal imaging agent, namely Au@Prussian blue-Gd@ovalbumin nanoparticles (APG@OVA NPs), for activating DCs and real-time tracking of DC migration process by magnetic resonance imaging (MRI). Moreover, the distribution of the colonized DCs in the lymphatic system was profiled at the single-cell levels based on surface-enhanced Raman scattering (SERS) technique.

Methods: In this strategy, PBs as cyanide (CN)-bridged coordination blocks were assembled onto the gold nanoparticles core to provide SERS signal in the Raman-silent region (1800 and 2800 cm^-1), which could avoid background signal interference. The doping Gd³⁺ located in the lattice of PB enables the MRI ability with high relaxivity of the probe. Ovalbumin, an egg allergen, was used as an antigen to activate DCs due to its immunological properties. The prepared APG@OVA NP agents were used to activate DCs with high efficacy and to track their migration and distribution in vivo through SERS/MR bimodal imaging.

Results: The APG@OVA NP agents could not only enable DC activating and labeling, but also achieve real-time monitoring of DC migration in vivo and accurate profiling of DC distribution in the lymphatic system. MR imaging indicated the time-dependent migration of the APG@OVA NP-labeled DCs from the footpad to the sentinel lymph node. The background-free Raman mapping of the lymph node tissue slice demonstrated that the activated DCs have successfully colonized to the sentinel lymph node.

Conclusion: Concerning the high activating efficacy, dual complementary imaging readouts, and low biological toxicity, the APG@OVA NPs act as high-performance tracking agents for DC-based immunotherapies.

Immune Monitoring After Allogeneic Hematopoietic Cell Transplantation: Toward Practical Guidelines and Standardization

Hematopoietic cell transplantation (HCT) is often a last resort, but potentially curative treatment option for children suffering from hematological malignancies and a variety of non-malignant disorders, such as bone marrow failure, inborn metabolic disease or immune deficiencies. Although efficacy and safety of the HCT procedure has increased significantly over the last decades, the majority of the patients still suffer from severe acute toxicity, viral reactivation, acute or chronic graft-versus-host disease (GvHD) and/or, in case of malignant disease, relapses. Factors influencing HCT outcomes are numerous and versatile. For example, there is variation in the selected graft sources, type of infused cell subsets, cell doses, and the protocols used for conditioning, as well as immune suppression and treatment of adverse events. Moreover, recent pharmacokinetic studies show that medications used in the conditioning regimen (e.g., busulphan, fludarabine, anti-thymocyte globulin) should be dosed patient-specific to achieve optimal exposure in every individual patient. Due to this multitude of variables and site-specific policies/preferences, harmonization between HCT centers is still difficult to achieve. Literature shows that adequate immune recovery post-HCT limits both relapse and non-relapse mortality (death due to viral reactivations and GvHD). Monitoring immune parameters post-HCT may facilitate a timely prediction of outcome. The use of standardized assays to measure immune parameters would facilitate a fast comparison between different strategies tested in different centers or between different clinical trials. We here discuss immune cell markers that may contribute to clinical decision making and may be worth to standardize in multicenter collaborations for future trials.

Immune Escape after Hematopoietic Stem Cell Transplantation (HSCT): From Mechanisms to Novel Therapies

Acute myeloid leukemia (AML) is the most common type of acute leukemia in adults. Recent advances in understanding its molecular basis have opened the way to new therapeutic strategies, including targeted therapies. However, despite an improvement in prognosis it has been documented in recent years (especially in younger patients) that allogenic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative treatment in AML and the first therapeutic option for high-risk patients. After allo-HSCT, relapse is still a major complication, and is observed in about 50% of patients. Current evidence suggests that relapse is not due to clonal evolution, but instead to the ability of the AML cell population to escape immune control by a variety of mechanisms including the altered expression of HLA-molecules, production of anti-inflammatory cytokines, relevant metabolic changes and expression of immune checkpoint (ICP) inhibitors capable of “switching-off” the immune response against leukemic cells. Here, we review the main mechanisms of immune escape and identify potential strategies to overcome these mechanisms.

Severe depletion of peripheral blood dendritic cell subsets in obstructive sleep apnea patients: A new link with cancer?

Recent evidence suggests that alterations of the immune responses are associated with the inflammatory nature of obstructive sleep apnea (OSA) and of its related co-morbidities. In this scenario, we asked whether circulating dendritic cell (DC) subsets may be possible players as their role has not yet been detailed. The frequency distribution of peripheral blood myeloid (mDC1 and mDC2) and plasmacytoid (p) DCs was investigated by mean of multi-parametric flow cytometry in 45 OSA patients (mean age: 53 yrs; M = 29) at the time of the first diagnosis and compared to 30 age- and sex-matched healthy controls. Oxidative burst (OB) and serum levels of tumor necrosis factor (TNF)-α, (interleukin) (IL)-6, interferon (INF)-γ, IL-2, IL-4, IL-10 and vascular endothelial growth factor (VEGF) were also analyzed. All subsets of circulating DCs were significantly depleted in OSA patients as compared to healthy subjects (p < 0.01, in all instances), with mDC2 and pDC subtypes being more severely compromised. These findings were co-existing with higher levels of OB along with an increased expression of IL-6, IL-10, TNF-α, IFN-γ, and VEGF (p < 0.005 in all instances). In particular, IL6 levels were significantly higher (p = 0.013) in severe OSA patients (apnea/hypopnea index >30) and were inversely correlated with both mDC2 (r = -0.802, p < 0.007) and pDC (r = -0.317, p = 0.04) subsets. We first provide evidence for a constitutive reduction of all circulating DC subsets in OSA patients. Perturbation of DCs coexists with an inflammatory milieu and is negatively correlated with the expression of IL-6, which is actually recognized as a pivotal inhibitor of DC maturation. Future studies exploring the contribution of DCs in the pathogenesis of OSA and of its complications should be encouraged.

Effective Radiotherapy in Tumor Assisted by Ganoderma lucidum Polysaccharide-Conjugated Bismuth Sulfide Nanoparticles through Radiosensitization and Dendritic Cell Activation

Radiotherapy is a traditional method for cancer therapy but may become ineffective likely due to the radiation-induced immunosuppression. Instead of simply increasing the radiation dose, reactivation of immunosuppression in the tumor microenvironment is an alternative strategy for successful cancer treatment. In this work, we synthesized bismuth sulfide nanoparticles (BiNP) and conjugated with immunoactive Ganoderma lucidum polysaccharide (GLP). GLP-BiNP were able to increase the sensitivity of radiotherapy, attributing to the efficient X-ray absorption of bismuth element. BiNP alone can mildly activate dendritic cells (DC) in vitro, while GLP-BiNP further enhanced the level of DC maturation, shown as the increase in phenotypic maturation markers, cytokine release, acid phosphatase activity, and T cell proliferation in DC/T cell co-culture. Compared to BiNP, GLP-BiNP altered the tissue distribution with faster accumulation in the tumor. Meanwhile, mature DC greatly increased in both tumor and spleen by GLP-BiNP within 24 h. GLP-BiNP combination with radiation achieved remarkable inhibition of tumor growth through apoptosis. Alternatively, lung metastasis was largely prohibited by GLP-BiNP, shown as a reduced amount of tumor nodules and cancer cell invasion by pathological findings. Mechanistically, GLP-BiNP altered the tumor immunosuppression microenvironment by preferably increasing the number of intratumor CD8⁺ T cell proliferation, as well as the improved immunobalance shown as the increased serum interferon-γ/interleukin-4 ratio. Specifically, GLP conjugation seemed to protect the kidney from injury occasionally introduced by bare BiNP. As a result, GLP-BiNP play a dual role in tumor treatment through radiosensitization and immunoactivities.

Intratumoral plasmacytoid dendritic cells as a poor prognostic factor for hepatocellular carcinoma following curative resection

Plasmacytoid dendritic cells (pDCs) are present in various primary and metastatic human neoplasms; however, their clinical significance in hepatocellular carcinoma (HCC) is unclear. In this study, we investigated the distribution, prognostic value, and potential function of pDCs in HCC patients undergoing curative resection. We performed immunohistochemical analyses of whole tumor sections from 224 patients to assess the expression of BDCA2, CD3, CD4, CD8, Foxp3, granzyme B, IL-17, and CD34. The findings were validated using tissue microarrays from another two independent cohorts totaling 841 HCC patients undergoing curative resection. Our results demonstrated that high numbers of BDCA2+ pDCs within tumors correlated with high alpha-fetoprotein levels, greater vascular invasion, advanced tumor-node-metastasis stage, shorter overall survival, and a higher recurrence rate. However, patient outcomes were not associated with pDCs in peritumoral stromal or nontumor tissues. Furthermore, an increase in intratumoral pDCs was associated with increased intratumoral infiltration of Foxp3+ regulatory T cells and IL-17-producing cells and correlated with tumor vascular density. Univariate and multivariate analyses revealed that the presence of intratumoral pDCs alone or in combination with regulatory T and/or IL-17-producing cells was an independent predictor of time to recurrence and overall survival. In conclusion, our study demonstrated that intratumoral infiltration by pDCs is a novel indicator for poor prognosis in patients with HCC, possibly through the induction of an immune tolerogenic and inflammatory tumor microenvironment comprising regulatory T and IL-17-producing cells. An assessment of the combination of these cells represents a superior predictor of patient outcome.

Recent advances in understanding dendritic cell development, classification, and phenotype

Dendritic cells (DCs) play an essential role in the induction of adaptive immune responses against infectious agents and in the generation of tolerance to self-antigens. In this mini-review, we summarize new evidence suggesting that the tissue of residence significantly shapes the last developmental steps of DCs into locally adapted cellular entities, enabling them to perform tissue-specific tasks while maintaining the core DC properties. We also discuss recent advances that have highlighted DCs’ rather complex phenotypic and functional heterogeneity in the tumor microenvironment, based on their physical characteristics, such as activation status, maturity, and polarization, illustrating a key role for DCs in the induction of anti-tumor immunity.

TIGIT and PD-1 dual checkpoint blockade enhances antitumor immunity and survival in GBM

The use of inhibitory checkpoint blockade in the management of glioblastoma has been studied in both preclinical and clinical settings. TIGIT is a novel checkpoint inhibitor recently discovered to play a role in cancer immunity. In this study, we sought to determine the effect of anti-PD-1 and anti-TIGIT combination therapy on survival in a murine glioblastoma (GBM) model, and to elucidate the underlying immune mechanisms. Using mice with intracranial GL261-luc⁺ tumors, we found that TIGIT expression was upregulated on CD8⁺ and regulatory T cells (Tregs) in the brain compared to draining cervical lymph nodes (CLN) and spleen. We then demonstrated that treatment using anti-PD-1 and anti-TIGIT dual therapy significantly improved survival compared to control and monotherapy groups. The therapeutic effect was correlated with both increased effector T cell function and downregulation of suppressive Tregs and tumor-infiltrating dendritic cells (TIDCs). Clinically, TIGIT expression on tumor-infiltrating lymphocytes was shown to be elevated in patient GBM samples, suggesting that the TIGIT pathway may be a valuable therapeutic target. Expression of the TIGIT ligand, PVR, further portended a poor survival outcome in patients with low-grade glioma. We conclude that anti-TIGIT is an effective treatment strategy against murine GBM when used in combination with anti-PD-1, improving overall survival via modifications of both the T cell and myeloid compartments. Given evidence of PVR expression on human GBM cells, TIGIT presents as a promising immune therapeutic target in the management of these patients.

Distribution of M1 and M2 macrophages in tumor islets and stroma in relation to prognosis of non-small cell lung cancer

BACKGROUND

Non-small cell lung cancer (NSCLC) remains the most common cause of cancer related death worldwide. Tumor-infiltrating macrophages are believed to play an important role in growth, progression, and metastasis of tumors. In NSCLC, the role of macrophages remains controversial; therefore, we aimed to evaluate the distribution of macrophages (M1 and M2) in tumor islets and stroma and to analyze their relations to patients' survival.

METHODS

Lung tissue specimens from 80 NSCLC patients who underwent surgical resection for NSCLC (pathological stage I-III) and 16 control group subjects who underwent surgery because of recurrent spontaneous pneumothorax were analyzed. Immunohistochemical double staining of CD68/iNOS (markers for M1 macrophages) and CD68/CD163 (markers for M2 macrophages) was performed and evaluated in a blinded manner. The numbers of M1 and M2 macrophages in tumor islets and stroma were counted manually.

RESULTS

Predominant infiltration of M1 and M2 macrophages was observed in the tumor stroma compared with the tumor islets. M2 macrophages predominated over M1 macrophages in the tumor tissue. Tumor islets-infiltrating M1 macrophages and the number of total tumor-infiltrating M2 macrophages were independent predictors of patients survival: high infiltration of M1 macrophages in tumor islets was associated with increased overall survival in NSCLC (P < 0.05); high infiltration of total M2 macrophages in tumor (islets and stroma) was associated with reduced overall survival in NSCLC (P < 0.05).

CONCLUSIONS

This study demonstrated that high infiltration of M1 macrophages in the tumor islets and low infiltration of total tumor-infiltrating M2 macrophages were associated with improved NSCLC patients' survival.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01955343 , registered on September 27, 2013.

IL-33 in Tumor Immunity: Nothing to Sneeze At

Although immunotherapy has been at the forefront of cancer therapy for the last several years, better clinical responses are still desired. Interleukin-33 is perhaps one of the most overlooked antitumor cytokines. Its ability to promote type 1 immune responses, which control tumor growth in preclinical animal models is overshadowed by its association with type 2 immunity and poor prognosis in some human cancers. Accumulating evidence shows that IL-33 is a powerful new tool for restoring and enhancing the body's natural antitumor immunity cycle. Furthermore, the antitumor mechanisms of IL-33 are two-fold, as it can directly boost CD8+ T cell function and restore dendritic cell dysfunction in vivo. Mechanistic studies have identified a novel pathway induced by IL-33 and its receptor ST2 in which dendritic cells avoid dysfunction and retain cross-priming abilities in tumor-bearing conditions. Here, we also comment on IL-33 data in human cancers and explore the idea that endogenous IL-33 may not deserve its reputation for promoting tumor growth. In fact, tumors may hijack the IL-33/ST2 axis to avoid immune surveillance and escape antitumor immunity.

Sphingosine 1-Phosphate- and C-C Chemokine Receptor 2-Dependent Activation of CD4+ Plasmacytoid Dendritic Cells in the Bone Marrow Contributes to Signs of Sepsis-Induced Immunosuppression

Sepsis is the dysregulated response of the host to systemic, mostly bacterial infection, and is associated with an enhanced susceptibility to life-threatening opportunistic infections. During polymicrobial sepsis, dendritic cells (DCs) secrete enhanced levels of interleukin (IL) 10 due to an altered differentiation in the bone marrow and contribute to the development of immunosuppression. We investigated the origin of the altered DC differentiation using murine cecal ligation and puncture (CLP), a model for human polymicrobial sepsis. Bone marrow cells (BMC) were isolated after sham or CLP operation, the cellular composition was analyzed, and bone marrow-derived DCs (BMDCs) were generated in vitro. From 24 h on after CLP, BMC gave rise to BMDC that released enhanced levels of IL-10. In parallel, a population of CD11c^hiMHCII⁺CD4⁺ DCs expanded in the bone marrow in a MyD88-dependent manner. Prior depletion of the CD11c^hiMHCII⁺CD4⁺ DCs from BMC in vitro reversed the increased IL-10 secretion of subsequently differentiating BMDC. The expansion of the CD11c^hiMHCII⁺CD4⁺ DC population in the bone marrow after CLP required the function of sphingosine 1-phosphate receptors and C-C chemokine receptor (CCR) 2, the receptor for C-C chemokine ligand (CCL) 2, but was not associated with monocyte mobilization. CD11c^hiMHCII⁺CD4⁺ DCs were identified as plasmacytoid DCs (pDCs) that had acquired an activated phenotype according to their increased expression of MHC class II and CD86. A redistribution of CD4⁺ pDCs from MHC class II⁻ to MHC class II⁺ cells concomitant with enhanced expression of CD11c finally led to the rise in the number of CD11c^hiMHCII⁺CD4⁺ DCs. Enhanced levels of CCL2 were found in the bone marrow of septic mice and the inhibition of CCR2 dampened the expression of CD86 on CD4⁺ pDCs after CLP in vitro. Depletion of pDCs reversed the bias of splenic DCs toward increased IL-10 synthesis after CLP in vivo. Thus, during polymicrobial sepsis, CD4⁺ pDCs are activated in the bone marrow and induce functional reprogramming of differentiating BMDC toward an immunosuppressive phenotype.

Hematologic neoplasms: Dendritic cells vaccines in motion

Dendritic cells (DCs) are bone-marrow-derived immune cells accounted for a key role in cancer vaccination as potent antigen-presenting cells within the immune system. Cancer microenvironment can modulate DCs maturation resulting in their accumulation into functional states associated with a reduced antitumor immune response. In this regard, a successful cancer vaccine needs to mount a potent antitumor immune response able to overcome the immunosuppressive tumor milieu. As a consequence, DCs-based approaches are a safe and promising strategy for improving the therapeutic efficacy in hematological malignancies, particularly in combinations with additional treatments. This review summarizes the most significant evidence about the immunotherapeutic strategies performed to target hematologic neoplasms including the tumoral associated antigens (TAA) pulsed on DCs, whole tumor cell vaccines or leukemia-derived DCs.

Irradiation enhances dendritic cell potential antitumor activity by inducing tumor cell expressing TNF-α

Dendritic cells (DCs)-based tumor vaccines have shown to be the promising methods for inducing therapeutic antitumor response. However, DCs alone rarely carry curative antitumor activity, and the immunosuppressive microenvironment may contribute to this defect of DC vaccinal function. Irradiation in combination with DCs has been shown to promote immune-mediated tumor destruction in preclinical studies. However, little is known about how irradiation alters the tumor microenvironment, and what host pathways modulate the activity of administrated DCs. In this study, BALB/c mice and the 4T1 breast cancer cell line were used in a tumor-bearing model. The tumor-bearing mice were irradiated locally up to 10 Gy for 3 consecutive days or a single dose of 30 Gy using a cesium source. Studies of dynamic change of the tumor microenvironment in irradiated versus untreated tumors revealed that there was no obvious change on IL-10, IL-6 and TGF-β expression or production, whereas increased TNF-α level within the first 2 weeks of irradiation. The increased TNF-α level is exactly right timing window for DCs injection, corresponding to the significant elevation of intratumoral CD8⁺ T infiltration and the regression of tumor size. With attention to scheduling, combination X-ray with DCs i.t. injection may offer a practical strategy to improve treatment outcomes.

Exogenous IL-33 Restores Dendritic Cell Activation and Maturation in Established Cancer

The role of IL-33, particularly in tumor growth and tumor immunity, remains ill-defined. We show that exogenous IL-33 can induce robust antitumor effect through a CD8⁺ T cell-dependent mechanism. Systemic administration of rIL-33 alone was sufficient to inhibit growth of established tumors in transplant and de novo melanoma tumorigenesis models. Notably, in addition to a direct action on CD8⁺ T cell expansion and IFN-γ production, rIL-33 therapy activated myeloid dendritic cells (mDCs) in tumor-bearing mice, restored antitumor T cell activity, and increased Ag cross-presentation within the tumor microenvironment. Furthermore, combination therapy consisting of rIL-33 and agonistic anti-CD40 Abs demonstrated synergistic antitumor activity. Specifically, MyD88, an essential component of the IL-33 signaling pathway, was required for the IL-33-mediated increase in mDC number and upregulation in expression of costimulatory molecules. Importantly, we identified that the IL-33 receptor ST2, MyD88, and STAT1 cooperate to induce costimulatory molecule expression on mDCs in response to rIL-33. Thus, our study revealed a novel IL-33-ST2-MyD88-STAT1 axis that restores mDC activation and maturation in established cancer and, thereby, the magnitude of antitumor immune responses, suggesting a potential use of rIL-33 as a new immunotherapy option to treat established cancer.

STAT3 signaling in immunity

The transcriptional regulator STAT3 has key roles in vertebrate development and mature tissue function including control of inflammation and immunity. Mutations in human STAT3 associate with diseases such as immunodeficiency, autoimmunity and cancer. Strikingly, however, either hyperactivation or inactivation of STAT3 results in human disease, indicating tightly regulated STAT3 function is central to health. Here, we attempt to summarize information on the numerous and distinct biological actions of STAT3, and highlight recent discoveries, with a specific focus on STAT3 function in the immune and hematopoietic systems. Our goal is to spur investigation on mechanisms by which aberrant STAT3 function drives human disease and novel approaches that might be used to modulate disease outcome.

The dual role of complement in cancer and its implication in anti-tumor therapy

Chronic inflammation has been linked to the initiation of carcinogenesis, as well as the advancement of established tumors. The polarization of the tumor inflammatory microenvironment can contribute to either the control, or the progression of the disease. The emerging participation of members of the complement cascade in several hallmarks of cancer, renders it a potential target for anti-tumor treatment. Moreover, the presence of complement regulatory proteins (CRPs) in most types of tumor cells is known to impede anti-tumor therapies. This review focuses on our current knowledge of complement's potential involvement in shaping the inflammatory tumor microenvironment and its role on the regulation of angiogenesis and hypoxia. Furthermore, we discuss approaches using complement-based therapies as an adjuvant in tumor immunotherapy.

Human breast cancer-derived soluble factors facilitate CCL19-induced chemotaxis of human dendritic cells

Breast cancer remains as a challenging disease with high mortality in women. Increasing evidence points the importance of understanding a crosstalk between breast cancers and immune cells, but little is known about the effect of breast cancer-derived factors on the migratory properties of dendritic cells (DCs) and their consequent capability in inducing T cell immune responses. Utilizing a unique 3D microfluidic device, we here showed that breast cancers (MCF-7, MDA-MB-231, MDA-MB-436 and SK-BR-3)-derived soluble factors increase the migration of DCs toward CCL19. The enhanced migration of DCs was mainly mediated via the highly activated JNK/c-Jun signaling pathway, increasing their directional persistence, while the velocity of DCs was not influenced, particularly when they were co-cultured with triple negative breast cancer cells (TNBCs or MDA-MB-231 and MDA-MB-436). The DCs up-regulated inflammatory cytokines IL-1β and IL-6 and induced T cells more proliferative and resistant against activation-induced cell death (AICD), which secret high levels of inflammatory cytokines IL-1β, IL-6 and IFN-γ. This study demonstrated new possible evasion strategy of TNBCs utilizing their soluble factors that exploit the directionality of DCs toward chemokine responses, leading to the building of inflammatory milieu which may support their own growth.

Regulation of Langerhans cell functions in a hypoxic environment

Langerhans cells (LCs) are a specialized dendritic cell subset that resides in the epidermis and mucosal epithelia and is critical for the orchestration of skin immunity. Recent evidence suggest that LCs are involved in aberrant wound healing and in the development of hypertrophic scars and chronic wounds, which are characterized by a hypoxic environment. Understanding LCs biology under hypoxia may, thus, lead to the identification of novel pathogenetic mechanisms of wound repair disorders and open new therapeutic opportunities to improve wound healing. In this study, we characterize a previously unrecognized role for hypoxia in significantly affecting the phenotype and functional properties of human monocyte-derived LCs, impairing their ability to stimulate naive T cell responses, and identify the triggering receptor expressed on myeloid (TREM)-1, a member of the Ig immunoregulatory receptor family, as a new hypoxia-inducible gene in LCs and an activator of their proinflammatory and Th1-polarizing functions in a hypoxic environment. Furthermore, we provide the first evidence of TREM-1 expression in vivo in LCs infiltrating hypoxic areas of active hypertrophic scars and decubitous ulcers, pointing to a potential pathogenic role of this molecule in wound repair disorders.

KEY MESSAGES

Hypoxia modulates surface molecule expression and cytokine profile in Langerhans cells. Hypoxia impairs human Langerhans cell stimulatory activity on naive T cells. Hypoxia selectively induces TREM-1 expression in human Langerhans cells. TREM-1 engagement stimulates Langerhans cell inflammatory and Th1-polarizing activity. TREM-1 is expressed in vivo in Langerhans cells infiltrating hypoxic skin lesions.

Metastatic spread in patients with non-small cell lung cancer is associated with a reduced density of tumor-infiltrating T cells

Tumor-infiltrating lymphocytes play an important role in cell-mediated immune destruction of cancer cells and tumor growth control. We investigated the heterogeneity of immune cell infiltrates between primary non-small cell lung carcinomas (NSCLC) and corresponding metastases. Formalin-fixed, paraffin-embedded primary tumors and corresponding metastases from 34 NSCLC patients were analyzed by immunohistochemistry for CD4, CD8, CD11c, CD68, CD163 and PD-L1. The percentage of positively stained cells within the stroma and tumor cell clusters was recorded and compared between primary tumors and metastases. We found significantly fewer CD4(+) and CD8(+) T cells within tumor cell clusters as compared with the stromal compartment, both in primary tumors and corresponding metastases. CD8(+) T cell counts were significantly lower in metastatic lesions than in the corresponding primary tumors, both in the stroma and the tumor cell islets. Of note, the CD8/CD4 ratio was significantly reduced in metastatic lesions compared with the corresponding primary tumors in tumor cell islets, but not in the stroma. We noted significantly fewer CD11c(+) cells and CD68(+) as well as CD163(+) macrophages in tumor cell islets compared with the tumor stroma, but no difference between primary and metastatic lesions. Furthermore, the CD8/CD68 ratio was higher in primary tumors than in the corresponding metastases. We demonstrate a differential pattern of immune cell infiltration in matched primary and metastatic NSCLC lesions, with a significantly lower density of CD8(+) T cells in metastatic lesions compared with the primary tumors. The lower CD8/CD4 and CD8/CD68 ratios observed in metastases indicate a rather tolerogenic and tumor-promoting microenvironment at the metastatic site.

Myeloid cells in the tumor microenvironment: Role of adenosine

Adenosine, deriving from ATP released by dying cancer cells and then degradated in the tumor environment by CD39/CD73 enzyme axis, is linked to the generation of an immunosuppressed niche favoring the onset of neoplasia. The effects of adenosine are mediated by four adenosine receptors, named A₁, A_2A, A_2B and A₃ that are widely expressed on several immune cell populations. A critical role of this nucleoside is emerging in the modulation of myeloid cell subsets accumulation and functions into tumor microenvironment, providing new insights that might be useful for the development of novel therapeutic approaches aimed to undermine the immune privileged sites where cancer cells grow and proliferate.

T Lymphocyte Inhibition by Tumor-Infiltrating Dendritic Cells Involves Ectonucleotidase CD39 but Not Arginase-1

T lymphocytes activated by dendritic cells (DC) which present tumor antigens play a key role in the antitumor immune response. However, in patients suffering from active cancer, DC are not efficient at initiating and supporting immune responses as they participate to T lymphocyte inhibition. DC in the tumor environment are functionally defective and exhibit a characteristic of immature phenotype, different to that of DC present in nonpathological conditions. The mechanistic bases underlying DC dysfunction in cancer responsible for the modulation of T-cell responses and tumor immune escape are still being investigated. Using two different mouse tumor models, we showed that tumor-infiltrating DC (TIDC) are constitutively immunosuppressive, exhibit a semimature phenotype, and impair responder T lymphocyte proliferation and activation by a mechanism involving CD39 ectoenzyme.

AZD1480 delays tumor growth in a melanoma model while enhancing the suppressive activity of myeloid-derived suppressor cells

AZD1480 is a potent, competitive small-molecule inhibitor of JAK1/2 kinase which inhibits STAT3 phosphorylation and tumor growth. Here we investigated the effects of AZD1480 on the function of different immune cell populations in a melanoma model. When MO4 tumor-bearing mice were treated with AZD1480 we observed a strong inhibition of tumor growth as well as a prolonged survival. Moreover, a significant decrease in the percentage of myeloid-derived suppressor cells (MDSCs) was observed after treatment with AZD1480. However, AZD1480 enhanced the suppressive capacity of murine MDSCs while at the same time impairing the proliferative as well as the IFN-γ secretion capacity of murine T cells. The addition of AZD1480 to co-cultures of human MDSCs and T cells does not affect the suppressive activity of MDSCs but it does reduce the IFN-γ secretion and the proliferative capacity of T cells. We showed that although AZD1480 has the ability to delay the tumor growth of MO4 tumor-bearing mice, this drug has detrimental effects on several aspects of the immune system. These data indicate that systemic targeting of the JAK/STAT pathway by JAK1/2 inhibition can have divergent effects on tumor growth and anti-tumor immune responses.

Tumor-infiltrating dendritic cells in cancer pathogenesis

Dendritic cells (DCs) play a pivotal role in the tumor microenvironment, which is known to affect disease progression in many human malignancies. Infiltration by mature, active DCs into the tumors confers an increase in immune activation and recruitment of disease-fighting immune effector cells and pathways. DCs are the preferential target of infiltrating T cells. However, tumor cells have means of suppressing DC function or of altering the tumor microenvironment in such a way that immune-suppressive DCs are recruited. Advances in understanding these changes have led to promising developments in cancer-therapeutic strategies targeting tumor-infiltrating DCs to subdue their immunosuppressive functions and enhance their immune-stimulatory capacity.