Disruption of CCR5-dependent homing of regulatory T cells inhibits tumor growth in a murine model of pancreatic cancer

The dual CCR2/CCR5 chemokine receptor antagonist Cenicriviroc reduces macrophage infiltration and disease severity in Duchenne muscular dystrophy (Dmdmdx-4Cv) mice

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle weakness which is ultimately fatal, most often due to involvement of the diaphragm. Macrophage infiltration of dystrophic muscles has been strongly linked to muscle damage and fibrosis in DMD. We hypothesized that cenicriviroc (CVC), a dual chemokine receptor (CCR2/CCR5) antagonist currently under clinical evaluation for other diseases, could prevent macrophage accumulation and blunt disease progression in the diaphragms of mdx mice (genetic homologue of DMD). Treatment with CVC (20 mg/kg/day intraperitoneally) or vehicle was initiated in mdx mice at 2 weeks of age (prior to the onset of muscle necrosis) and continued for 4 weeks. Flow cytometry to assess inflammatory cell subsets as well as histological and force generation parameters were determined in mdx diaphragms at the conclusion of the treatment. CVC therapy induced a major (3.9-fold) reduction in total infiltrating macrophages, whereas total numbers of neutrophils and T lymphocytes (CD4+ and CD8+) were unaffected. No changes in macrophage polarization status (inflammatory versus anti-inflammatory skewing based on iNOS and CD206 expression) were observed. Muscle fiber size and fibrosis were not altered by CVC, whereas a significant reduction in centrally nucleated fibers was found suggesting a decrease in prior necrosis-regeneration cycles. In addition, maximal isometric force production by the diaphragm was increased by CVC therapy. These results suggest that CVC or other chemokine receptor antagonists which reduce pathological macrophage infiltration may have the potential to slow disease progression in DMD.

Targeting Myeloid-Derived Suppressor Cells to Bypass Tumor-Induced Immunosuppression

The immune system has many sophisticated mechanisms to balance an extensive immune response. Distinct immunosuppressive cells could protect from excessive tissue damage and autoimmune disorders. Tumor cells take an advantage of those immunosuppressive mechanisms and establish a strongly immunosuppressive tumor microenvironment (TME), which inhibits antitumor immune responses, supporting the disease progression. Myeloid-derived suppressor cells (MDSC) play a crucial role in this immunosuppressive TME. Those cells represent a heterogeneous population of immature myeloid cells with a strong immunosuppressive potential. They inhibit an antitumor reactivity of T cells and NK cells. Furthermore, they promote angiogenesis, establish pre-metastatic niches, and recruit other immunosuppressive cells such as regulatory T cells. Accumulating evidences demonstrated that the enrichment and activation of MDSC correlated with tumor progression, recurrence, and negative clinical outcome. In the last few years, various preclinical studies and clinical trials targeting MDSC showed promising results. In this review, we discuss different therapeutic approaches on MDSC targeting to overcome immunosuppressive TME and enhance the efficiency of current tumor immunotherapies.

Challenges and Perspectives for Immunotherapy in Adenocarcinoma of the Pancreas: The Cancer Immunity Cycle

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with a devastating 5-year overall survival of only approximately 7%. Although just 4% of all malignant diseases are accounted to PDAC, it will become the second leading cause of cancer-related deaths before 2030. Immunotherapy has proven to be a promising therapeutic option in various malignancies such as melanoma, non-small cell lung cancer (NSCLC), microsatellite instability-high gastrointestinal cancer, urinary tract cancer, kidney cancer, and others. In this review, we summarize recent findings about immunological aspects of PDAC with the focus on the proposed model of the "cancer immunity cycle". By this model, a deeper understanding of the underlying mechanism in achieving a T-cell response against cancer cells is provided. There is currently great interest in the field around designing novel immunotherapy combination studies for PDAC based on a sound understanding of the underlying immunobiology.

Regulatory T-Cell Dynamics in Cutaneous and Mucocutaneous Leishmaniasis due to Leishmania braziliensis

To evaluate the dynamics of regulatory T cells (Tregs) during tegumentary leishmaniasis, we assessed peripheral blood and biopsies from 54 patients. Patients with cutaneous leishmaniasis (CL) had a decreased proportion of Tregs in the peripheral blood, but the proportion was higher in the biopsies of lesions. During treatment of CL, circulating Tregs increased reaching normal proportions, whereas antigen-specific interferon-γ responses diminished. By contrast, circulating Tregs from mucosal leishmaniasis patients failed to normalize during treatment. C-C chemokine receptor type 5 was expressed on a large proportion of Tregs at the site of infection. These results demonstrate increased Tregs at the site of infection, possibly homing from the peripheral circulation.

High expression of CC chemokine receptor 5 (CCR5) promotes disease progression in patients with B-cell non-Hodgkin lymphomas

Chemokines are small proteins, that regulate cell migration in many physiological and pathologic processes in human body. They are also responsible for cancer progression. CC chemokine receptor 5 (CCR5) is responsible for cell recruitment in inflammation and may be involved in antitumor immune response controlling. Aberrant CCR5 can be found in different kind of cancers, not only hematological, but also solid tumors. Non-Hodgkin lymphomas consist of many lymphoma subtypes. They predominantly derive from B cells and can have very heterogenous clinical course. That is why new prognostic factors are still needed to predict and select high-risk patients. We evaluated CCR5 expression in lymph nodes derived from B-cell lymphomas in comparison to reactive lymphatic tissue (reactive lymph nodes): samples of lymphoma lymph nodes, peripheral blood, and bone marrow aspirates of patients with B-cell non-Hodgkin lymphoma were taken at diagnosis and after completed chemotherapy. Gene expression was determined by the reverse transcription-polymerase chain reaction method. Expression was estimated from 0AU (no amplificate signal) to 3AU (maximal amplificate signal). We found low CCR5 expression in lymphomas and reactive lymph nodes. Higher CCR5 gene expression in lymphoma patients was correlated with advanced stage of the disease, high proliferation index (Ki-67), and international prognostic index. Patients with higher CCR5 expression had shorter survival. CCR5 high expression may have a role in non-Hodgkin's lymphomas progression and can influence patients' survival. CCR5 also can become an immunotherapeutic target for novel treatment options in the future as well as new prognostic factor.

Blockade of CCR5-mediated myeloid derived suppressor cell accumulation enhances anti-PD1 efficacy in gastric cancer

PURPOSE

Myeloid derived suppressor cells (MDSC) play an important role in tumor immune evasion and its level significantly increased in patients with gastric cancer. Studies confirmed the associations between MDSC and various cytokines in the peripheral blood. However, little is known about the mechanism drawing MDSC into tumor parenchyma. This study was to analyze the correlation between MDSC subsets and CCR5 level in gastric cancer.

MATERIALS AND METHODS

G-MDSC and M-MDSC from the peripheral blood and tumor parenchyma were analyzed by flow cytometry. CCR5 ligand CCL5 was detected by ELISA. CCR5 was detected by real-time PCR, western blot and flow cytometry. Furthermore, the therapeutic effects of CCR5 blockade was assessed by the tumor model.

RESULTS

CCR5 ligand, gene and protein expression of CCR5, and surface expression of CCR5 significantly increased in blood and tumor of tumor-bearing mice, suggesting MDSC may be attracted into the parenchyma by CCL5/CCR5. Anti-CCR5 treatment decreased G-MDSC and M-MDSC in the periphery and tumor. In addition, combination treatment enhanced CD4+ and CD8+ T cell infiltration and decreased the tumor burden of tumor-bearing mice.

CONCLUSIONS

This study elucidated a possible association between MDSC subsets and CCR5, in addition to provide a new potential target to enhance the efficacy of immunotherapy in patients with gastric cancer.

Immune Evasion in Pancreatic Cancer: From Mechanisms to Therapy

Pancreatic ductal adenocarcinoma (PDA), the most frequent type of pancreatic cancer, remains one of the most challenging problems for the biomedical and clinical fields, with abysmal survival rates and poor therapy efficiency. Desmoplasia, which is abundant in PDA, can be blamed for much of the mechanisms behind poor drug performance, as it is the main source of the cytokines and chemokines that orchestrate rapid and silent tumor progression to allow tumor cells to be isolated into an extensive fibrotic reaction, which results in inefficient drug delivery. However, since immunotherapy was proclaimed as the breakthrough of the year in 2013, the focus on the stroma of pancreatic cancer has interestingly moved from activated fibroblasts to the immune compartment, trying to understand the immunosuppressive factors that play a part in the strong immune evasion that characterizes PDA. The PDA microenvironment is highly immunosuppressive and is basically composed of T regulatory cells (Tregs), tumor-associated macrophages (TAMs), and myeloid-derived suppressive cells (MDSCs), which block CD8⁺ T-cell duties in tumor recognition and clearance. Interestingly, preclinical data have highlighted the importance of this immune evasion as the source of resistance to single checkpoint immunotherapies and cancer vaccines and point at pathways that inhibit the immune attack as a key to solve the therapy puzzle. Here, we will discuss the molecular mechanisms involved in PDA immune escape as well as the state of the art of the PDA immunotherapy.

Ovarian cancer stem cells promote tumour immune privilege and invasion via CCL5 and regulatory T cells

Emerging evidence indicates a link between the increased proportion of regulatory T cells (Tregs ) and reduced survival in patients who have been diagnosed with cancer. Cancer stem cells (CSCs) have been indicated to play a vital role in tumour initiation, drug resistance and recurrence. However, the relationship between Tregs and CSCs remains largely unknown. Here, we sorted out ovarian cancer stem-like side population (SP) cells and CD133+ cells to investigate the influence of ovarian CSCs on Tregs . Among the various immune-related molecules that we assessed, C-C motif chemokine ligand 5 (CCL5) was the most elevated in ovarian CSCs relative to that in the non-CSCs. The expression of its receptor, C-C motif chemokine receptor 5 (CCR5), was also increased on the surface of Tregs in ovarian cancer patients. This receptor-ligand expression profile indicated that ovarian CSCs recruit Tregs via CCL5-CCR5 interactions. We further assessed the expression of interleukin (IL)-10 in Tregs cultured with different cancer cells. Tregs cultured in conditioned medium (CM) from ovarian CD133+ cells expressed a higher level of IL-10 than Tregs cultured in CM from CD133- cells, indicating that Tregs exert pronounced immune-inhibitory functions in CSC-rich environments. Furthermore, co-culture with ovarian cancer cell lines induced the expression of matrix metalloproteinase-9 (MMP9) in Tregs which, in turn, enhanced the degradation of the extracellular matrix and enabled the invasion of tumour cells, thereby facilitating tumour metastasis. For the first time, to our knowledge, our findings describe the relationship between ovarian CSCs and Tregs , and demonstrated that these two cell populations co-operate to promote tumour immune tolerance and enhance tumour progression.

C-C motif chemokine receptors in gastric cancer

Gastric cancer is the fifth most common cancer and the third leading cause of cancer-associated mortality worldwide. Despite recent advances in molecular and clinical research, patients with gastric cancer at an advanced stage have a dismal prognosis and poor survival rates, and systemic treatment relies predominantly on traditional cytotoxic chemotherapy. To improve patients' quality of life and survival, an improved understanding of the complex molecular mechanisms involved in gastric cancer progression and treatment resistance, and of its clinical application in the development of novel targeted therapies, is urgently required. Chemokines are a group of small chemotactic cytokines that interact with seven-transmembrane G-protein-coupled receptors, and this interaction serves a crucial role in various physiological processes, including organ development and the host immune response, to recruit cells to specific sites in the body. There is also accumulating evidence that chemokines and chemokine receptors (CCRs) contribute to tumor development and progression, as well as metastasis. However, research regarding the functional roles of chemokines and their receptors in cancer is dynamic and context-dependent, and much remains to be elucidated, although various aspects have been explored extensively. In gastric cancer, C-C motif CCRs are involved in the biological behavior of tumor cells, including the processes of growth, invasion and survival, as well as the epithelial-mesenchymal transition. In the present review, attention is given to the clinical relevance of C-C motif CCRs in the development, progression, and metastasis of gastric cancer, particularly CCR7 and CCR5, which have been investigated extensively, as well as their potential therapeutic implications.

Phenotypic and Functional Properties of Tumor-Infiltrating Regulatory T Cells

Regulatory T (Treg) cells maintain immune homeostasis by suppressing excessive immune responses. Treg cells induce tolerance against self- and foreign antigens, thus preventing autoimmunity, allergy, graft rejection, and fetus rejection during pregnancy. However, Treg cells also infiltrate into tumors and inhibit antitumor immune responses, thus inhibiting anticancer therapy. Depleting whole Treg cell populations in the body to enhance anticancer treatments will produce deleterious autoimmune diseases. Therefore, understanding the precise nature of tumor-infiltrating Treg cells is essential for effectively targeting Treg cells in tumors. This review summarizes recent results relating to Treg cells in the tumor microenvironment, with particular emphasis on their accumulation, phenotypic, and functional properties, and targeting to enhance the efficacy of anticancer treatment.

GM-CSF Promotes Chronic Disability in Experimental Autoimmune Encephalomyelitis by Altering the Composition of Central Nervous System-Infiltrating Cells, but Is Dispensable for Disease Induction

GM-CSF has been portrayed as a critical cytokine in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) and, ostensibly, in multiple sclerosis. C57BL/6 mice deficient in GM-CSF are resistant to EAE induced by immunization with myelin oligodendrocyte glycoprotein (MOG)_35-55 The mechanism of action of GM-CSF in EAE is poorly understood. In this study, we show that GM-CSF augments the accumulation of MOG_35-55-specific T cells in the skin draining lymph nodes of primed mice, but it is not required for the development of encephalitogenic T cells. Abrogation of GM-CSF receptor signaling in adoptive transfer recipients of MOG_35-55-specific T cells did not alter the incidence of EAE or the trajectory of its initial clinical course, but it limited the extent of chronic CNS tissue damage and neurologic disability. The attenuated clinical course was associated with a relative dearth of MOG_35-55-specific T cells, myeloid dendritic cells, and neutrophils, as well as an abundance of B cells, within CNS infiltrates. Our data indicate that GM-CSF drives chronic tissue damage and disability in EAE via pleiotropic pathways, but it is dispensable during early lesion formation and the onset of neurologic deficits.

HDAC inhibition potentiates immunotherapy in triple negative breast cancer

Triple-negative breast cancer (TNBC) represents a more aggressive and difficult subtype of breast cancer where responses to chemotherapy occur, but toxicity is significant and resistance often follows. Immunotherapy has shown promising results in various types of cancer, including breast cancer. Here, we investigated a new combination strategy where histone deacetylase inhibitors (HDACi) are applied with immune checkpoint inhibitors to improve immunotherapy responses in TNBC.

Testing different epigenetic modifiers, we focused on the mechanisms underlying HDACi as priming modulators of immunotherapy. Tumor cells were co-cultured with human peripheral blood mononuclear cells (PBMCs) and flow cytometric immunophenotyping was performed to define the role of epigenetic priming in promoting tumor antigen presentation and immune cell activation. We found that HDACi up-regulate PD-L1 mRNA and protein expression in a time-dependent manner in TNBC cells, but not in hormone responsive cells. Focusing on TNBC, HDACi up-regulated PD-L1 and HLA-DR on tumor cells when co-cultured with PBMCs and down-regulated CD4⁺ Foxp3⁺ Treg in vitro. HDACi significantly enhanced the in vivo response to PD-1/CTLA-4 blockade in the triple-negative 4T1 breast cancer mouse model, the only currently available experimental system with functional resemblance to human TNBC. This resulted in a significant decrease in tumor growth and increased survival, associated with increased T cell tumor infiltration and a reduction in CD4⁺ Foxp3⁺ T cells in the tumor microenvironment. Overall, our results suggest a novel role for HDAC inhibition in combination with immune checkpoint inhibitors and identify a promising therapeutic strategy, supporting its further clinical evaluation for TNBC treatment.

Inflammatory Cytokine Signaling during Development of Pancreatic and Prostate Cancers

Inflammation is essential for many diseases including cancer. Activation and recruitment of immune cells during inflammation result in a cytokine- and chemokine-enriched cell environment, which affects cancer development. Since each type of cancer has its unique tumor environment, effects of cytokines from different sources such as tumor-infiltrating immune cells, stromal cells, endothelial cells, and cancer cells on cancer development can be quite complex. In this review, how immune cells contribute to tumorigenesis of pancreatic and prostate cancers through their secreted cytokines is discussed. In addition, the cytokine signaling that tumor cells of pancreatic and prostate cancers utilize to benefit their own survival is delineated.

Immunotherapy in pancreatic ductal adenocarcinoma: an emerging entity?

The genomic-plasticity of the immune system creates a broad immune repertoire engaged to tackle cancer cells. Promising clinical activity has been observed with several immune therapy strategies in solid tumors including melanoma, lung, kidney, and bladder cancers, albeit as yet immunotherapy-based treatment approaches in pancreatic ductal adenocarcinoma (PDAC) remain to have proven value. While translational and early clinical studies have demonstrated activation of antitumor immunity, most recent late-phase clinical trials have not confirmed the early promise in PDAC except in MSI-High PDAC patients. These results may in part be explained by multiple factors, including the poorly immunogenic nature of PDAC along with immune privilege, the complex tumor microenvironment, and the genetic plasticity of PDAC cells. These challenges have led to disappointments in the field, nonetheless they have also advanced our understanding that may tailor the future steps for immunotherapy for PDAC. Therefore, there is significant hope that progress is on the horizon.

Acceleration of pancreatic tumorigenesis under immunosuppressive microenvironment induced by Reg3g overexpression

Reg3g is a potential risk for pancreatic ductal adenocarcinoma (PDAC). We previously demonstrated that Reg3g promoted pancreatic carcinogenesis via a STAT3 signaling pathway in a murine model of chronic pancreatitis. Whether the immune response is involved in tumorigenesis induced by Reg3g remains unknown. In this study, Reg3g-regulated tumor immunity was evaluated in tumor-implanted murine models, immune cells, and tumor microenvironment. In mice that had been orthotopically or ectopically implanted with Panc02 cells, Reg3g overexpression increased EGFR and Ki67, diminished MHC-I and caspase-3 expression, and accelerated growth of tumors. By interacting with PD-1/PD-L1, Reg3g also promoted differentiation of Tregs and recruitment of MDSC, retarded maturation of DCs and inactivation of CD8+ T cells, and suppressed cross-priming of CD8+ T-cell responses by DCs in tumor-bearing mice. Knockdown of Reg3g delayed tumor development in normal mice, but not in CD8+ T-cell-deficient mice. In vitro, Reg3g upregulated EGFR in DCs, activated heme oxygenase-1 (Hmox1) involved JAK2/STAT3 signaling, raised levels of Th2 cytokines in and suppressed maturation of DCs, and enhanced tumor cell proliferation. These results reveal a novel role of Reg3g as an immunosuppressive promoter that weakens tumor-specific antigenicity and suppresses antitumor effects of CD8+ T cells in a murine model of pancreatic cancer. Reg3g produces these effects by activating the JAK2/STAT3 signaling pathway in DCs, triggering the generation of an immunosuppressive tumor microenvironment.

Immune Cell Population in Ovarian Tumor Microenvironment

Ovarian cancer, the third most common with highest mortality rates gynecological malignancy among women in China, is characterized by a unique tumor immune microenvironment. Immune-cell population infiltrated into the tumor tissue among patients with ovarian cancer are associated positively or negatively with antitumor activity. The imbalance between immune activation and immune suppression can result in oncogenesis and cancer progression. Therefore, intense investigation of the immunologic mechanism of ovarian cancer is urgently needed, and a comprehensive understanding of the network in which immune cells interact with the microenvironment, tumor cells and each other will greatly promote the development of more effective immunotherapies for ovarian cancer. In this review, we will focus on the main immune-cell population in ovarian tumor microenvironment, discuss their role in tumor progression and try to give the readers a new perspective in finding more promising therapeutic targets for cancers.

Myxoma Virus Optimizes Cisplatin for the Treatment of Ovarian Cancer In Vitro and in a Syngeneic Murine Dissemination Model

A therapeutic approach to improve treatment outcome of ovarian cancer (OC) in patients is urgently needed. Myxoma virus (MYXV) is a candidate oncolytic virus that infects to eliminate OC cells. We found that in vitro MYXV treatment enhances cisplatin or gemcitabine treatment by allowing lower doses than the corresponding IC₅₀ calculated for primary OC cells. MYXV also affected OC patient ascites-associated CD14⁺ myeloid cells, one of the most abundant immunological components of the OC tumor environment; without causing cell death, MYXV infection reduces the ability of these cells to secrete cytokines such as IL-10 that are signatures of the immunosuppressive tumor environment. We found that pretreatment with replication-competent but not replication-defective MYXV-sensitized tumor cells to later cisplatin treatments to drastically improve survival in a murine syngeneic OC dissemination model. We thus conclude that infection with replication-competent MYXV before cisplatin treatment markedly enhances the therapeutic benefit of chemotherapy. Treatment with replication-competent MYXV followed by cisplatin potentiated splenocyte activation and IFNγ expression, possibly by T cells, when splenocytes from treated mice were stimulated with tumor cell antigen ex vivo. The impact on immune responses in the tumor environment may thus contribute to the enhanced antitumor activity of combinatorial MYXV-cisplatin treatment.

C-C Chemokine Receptor Type 5 (CCR5)-Mediated Docking of Transferred Tregs Protects Against Early Blood-Brain Barrier Disruption After Stroke

BACKGROUND

Despite recent evidence demonstrating a potent protective effect of adoptively transferred regulatory T cells (Tregs) in ischemic stroke, the mechanism for Treg mobilization and activation in the ischemic brain is, remarkably, unknown. This study determines the role of C-C chemokine receptor type 5 (CCR5) in mediating the docking and activation of transferred Tregs in their protection of early blood-brain barrier disruption after stroke.

METHODS AND RESULTS

Adoptive transfer of CCR5-/- Tregs failed to reduce brain infarct or neurological deficits, indicating an indispensable role of CCR5 in Treg-afforded protection against cerebral ischemia. Two-photon live imaging demonstrated that CCR5 was critical for Treg docking at the injured vessel wall, where they interact with blood-borne neutrophils/macrophages after cerebral ischemic injury. CCR5 deficiency on donor Tregs deprived of their early protection against blood-brain barrier damage. Using flow cytometry, real-time polymerase chain reaction, and immunostaining, we confirmed that the expression of CCL5, a CCR5 ligand, was significantly elevated on the injured endothelium after cerebral ischemia, accompanied by CCR5 upregulation on circulating Tregs. In a Treg-endothelial cell coculture, CCR5 expression was induced on Tregs on their exposure to ischemia-injured endothelial cells. Furthermore, CCR5 induction on Tregs enhanced expression of the inhibitory molecule programmed death ligand 1, which in turn inhibited neutrophil-derived matrix metallopeptidase 9.

CONCLUSIONS

These results suggest that CCR5 is a critical molecule for Treg-mediated blood-brain barrier protection and a potential target to optimize Treg therapy for stroke.

An esophageal squamous cell carcinoma classification system that reveals potential targets for therapy

ESCC (Esophageal squamous cell carcinoma) is a heterogeneous cancer with diverse prognosis. Here, to explore the biological diversity of ESCC, we employed gene expression profiles from 360 ESCC tumors from East Asians to establish a comprehensive molecular classification and characterization of ESCC. Using the specific 185-gene signature generated by unsupervised consensus clustering of gene expression data, we defined four subtypes associated with distinct clinical metrics: tumors with high metastasis associated with EMT (epithelial to mesenchymal transition) and active MAP4K4/JNK signaling pathway; tumors with high chromosomal instability with up regulated MYC targes; well differentiated tumors with less aggressive and moderated tumors. The clinical relevance of these subtypes was stated by significant differences in prognosis. Importantly, 24% of all ESCCs (n = 360) were classified into the high metastasis subtype associated with poorly differentiation and unfavorable prognosis. We provided evidence that this subtype relates to tumor microenvironment. Collectively, these results might contribute to more precise personalized therapeutic strategies for each subtype of ESCC patients in the near future.

Leukocyte trafficking in tumor microenvironment

The tumor microenvironment consists of both malignant and non-malignant cells and a plethora of soluble mediators. Different types of tumors have specific tumor microenvironments characterized by distinct chemokines and chemotactic factors that influence leukocyte recruitment. The immune cell infiltrate continuously interacts with stroma cells and influence tumor growth. Emerging evidence suggests that the regulation of the composition and the metabolic state of tumor-associated leukocytes may represent a new promising intervention strategy. Here we summarize the current knowledge on the role of tumor-associated immune cells in tumor growth and dissemination, with a specific focus on the nature of the chemotactic factors responsible for their accumulation and activation in tumors.

Cancer-FOXP3 directly activated CCL5 to recruit FOXP3+Treg cells in pancreatic ductal adenocarcinoma

Forkheadbox protein 3 (FOXP3), initially identified as a key transcription factor for regulatory T cells (Treg cells), was also expressed in many tumors including pancreatic ductal adenocarcinoma (PDAC). However, its role in PDAC progression remains elusive. In this study, we utilized 120 PDAC tissues after radical resection to detect cancer-FOXP3 and Treg cells by immunohistochemistry and evaluated clinical and pathological features of these patients. Cancer-FOXP3 was positively correlated with Treg cells accumulation in tumor tissues derived from PDAC patients. In addition, high cancer-FOXP3 expression was associated with increased tumor volumes and poor prognosis in PDAC especially combined with high levels of Treg cells. Overexpression of cancer-FOXP3 promoted the tumor growth in immunocompetent syngeneic mice but not in immunocompromised or Treg cell-depleted mice. Furthermore, CCL5 was directly trans-activated by cancer-FOXP3 and promoted the recruitment of Treg cells from peripheral blood to the tumor site in vitro and in vivo. This finding has been further reinforced by the evidence that Treg cells recruitment by cancer-FOXP3 was impaired by neutralization of CCL5, thereby inhibiting the growth of PDAC. In conclusion, cancer-FOXP3 serves as a prognostic biomarker and a crucial determinant of immunosuppressive microenvironment via recruiting Treg cells by directly trans-activating CCL5. Therefore, cancer-FOXP3 could be used to select patients with better response to CCL5/CCR5 blockade immunotherapy.

Emerging roles of the CXCL12/CXCR4 axis in pancreatic cancer progression and therapy

Chemokine networks regulate a variety of cellular, physiological, and immune processes. These normal functions can become appropriated by cancer cells to facilitate a more hospitable niche for aberrant cells by enhancing growth, proliferation, and metastasis. This is especially true in pancreatic cancer, where chemokine signaling is a vital component in the development of the supportive tumor microenvironment and the signaling between the cancer cells and surrounding stromal cells. Although expression patterns vary among cancer types, the chemokine receptor CXCR4 has been implicated in nearly every major malignancy and plays a prominent role in pancreatic cancer development and progression. This receptor, in conjunction with its primary chemokine ligand CXCL12, promotes pancreatic cancer development, invasion, and metastasis through the management of the tumor microenvironment via complex crosstalk with other pathways. Thus, CXCR4 likely contributes to the poor prognoses observed in patients afflicted with this malignancy. Recent exploration of combination therapies with CXCR4 antagonists have demonstrated improved outcomes, and abolishing the contribution of this pathway may prove crucial to effectively treat pancreatic cancer at both the primary tumor and metastases.

Cancer Manipulation of Host Physiology: Lessons from Pancreatic Cancer

Homeostasis is a fundamental property of living organisms enabling the human body to withstand internal and external insults. In several chronic diseases, and especially in cancer, many homeostatic mechanisms are deranged. Pancreatic cancer in particular is notorious for its ability to invoke an intense fibroinflammatory stromal reaction facilitating its progression and resistance to treatment. In the past decade, several seminal discoveries have elucidated previously unrecognized modes of commandeering the host's defense systems. Here we review novel discoveries in pancreatic cancer immunobiology and attempt to integrate the notion of deranged homeostasis in the pathogenesis of this disease. We also highlight areas of controversy and obstacles that need to be overcome, hoping to further our mechanistic insight into this malignancy.

Engineering Chimeric Antigen Receptor T-Cells for Racing in Solid Tumors: Don't Forget the Fuel

T-cells play a critical role in tumor immunity. Indeed, the presence of tumor-infiltrating lymphocytes is a predictor of favorable patient prognosis for many indications and is a requirement for responsiveness to immune checkpoint blockade therapy targeting programmed cell death 1. For tumors lacking immune infiltrate, or for which antigen processing and/or presentation has been downregulated, a promising immunotherapeutic approach is chimeric antigen receptor (CAR) T-cell therapy. CARs are hybrid receptors that link the tumor antigen specificity and affinity of an antibody-derived single-chain variable fragment with signaling endodomains associated with T-cell activation. CAR therapy targeting CD19 has yielded extraordinary clinical responses against some hematological tumors. Solid tumors, however, remain an important challenge to CAR T-cells due to issues of homing, tumor vasculature and stromal barriers, and a range of obstacles in the tumor bed. Protumoral immune infiltrate including T regulatory cells and myeloid-derived suppressor cells have been well characterized for their ability to upregulate inhibitory receptors and molecules that hinder effector T-cells. A critical role for metabolic barriers in the tumor microenvironment (TME) is emerging. High glucose consumption and competition for key amino acids by tumor cells can leave T-cells with insufficient energy and biosynthetic precursors to support activities such as cytokine secretion and lead to a phenotypic state of anergy or exhaustion. CAR T-cell expansion protocols that promote a less differentiated phenotype, combined with optimal receptor design and coengineering strategies, along with immunomodulatory therapies that also promote endogenous immunity, offer great promise in surmounting immunometabolic barriers in the TME and curing solid tumors.

CAR T-cell therapy for pancreatic cancer

Chimeric antigen receptor (CAR) T-cell therapy utilizes genetic engineering to redirect a patient's own T cells to target cancer cells. The remarkable results in hematological malignancies prompted investigating this approach in solid tumors such as pancreatic cancer. The complex tumor microenvironment, stromal hindrance in limiting immune response, and expression of checkpoint blockade on T cells pose hurdles. Herein, we summarize the opportunities, challenges, and state of knowledge in targeting pancreatic cancer with CAR T-cell therapy.

Integrated analysis of mRNA and miRNA expression profiles in pancreatic ductal adenocarcinoma

In the present study, to investigate the potential molecular mechanism of pancreatic ductal adenocarcinoma (PDAC), mRNA and miRNA expression profiles were integrated for systematic analysis. Results showed that a total of 76 common differentially expressed genes (DEGs) were identified from 2 mRNA expression profiles that contained 39 tumor and 15 normal samples. Notably, the tumor and normal samples were able to be clearly classified into 4 groups based on the DEGs. mRNA‑miRNA regulation network analysis indicated that 22 out of the 76 DEGs including MUC4, RRM2 and CCL2 are regulated by 5 reported miRNAs. Survival analysis using SurvExpress database demonstrated that the common DEGs were able to significantly differentiate low- and high-risk PDAC groups in 4 datasets. In summary, various biological processes are probably involved in the development and progression of PDAC. Firstly, activation of MUC4 induces nuclear translocation of β-catenin and promotes the process of angiogenesis that provides necessary nutrition or oxygen for cancer cells. Then, RRM2 induces the invasiveness of PDAC via NF-κB. Finally, the formation of an immunosuppressive tumor microenvironment by recruiting regulatory T cells with high expression of CCL2 further promotes cancer cell proliferation and vascularization. Identification of valuable biological processes and genes can be helpful for the understanding of the molecular mechanism of PDAC.

Role of Cyclooxygenase-2 Pathway in Creating an Immunosuppressive Microenvironment and in Initiation and Progression of Wilms' Tumor

Wilms' tumors (WT), which accountfor 6% of all childhood cancers, arise from dysregulated differentiation of nephrogenic progenitor cells from embryonic kidneys. Though there is an improvement in the prognosis of WT, still 10% of patients with WT die due to recurrence. Thus more effective treatment approaches are necessary. We previously characterized the inflammatory microenvironment in human WT and observed the robust expression of COX-2. The aim of this study was to extend our studies to analyze the role of COX-2 pathway components in WT progression using a mouse model of WT. Herein, COX-2 pathway components such as COX-2, HIF1-α, p-ERK1/2, and p-STAT3 were upregulated in mouse and human tumor tissues. In our RPPA analysis, COX-2 was up-regulated in M15 cells after Wt1 gene was knocked down. Flow cytometry analysis showed the increased infiltration of immune suppressive inflammatory cells such as pDC's and Treg cells in tumors. The chemotactic chemokines responsible for the infiltration of these cells were also induced in CCR5 and CXCR4 dependent manner respectively. The immunosuppressive cytokines IL-10, TGF-β, and TNF-α were also up-regulated. Furthermore, more pronounced Th2 and Treg induced cytokine response was observed than Th1 response in tumors. Basing on all these evidences it is speculated that COX-2 pathway may be a beneficial target for the treatment of WT. It may be most effective as an adjuvant therapy together with other inhibitors. Thus, our current study provides a good rationale for initiating animal studies to confirm the efficacy of COX-2 inhibitors in decreasing tumor cell growth in vivo.

T-cell programming in pancreatic adenocarcinoma: a review

Despite recent advancements in multimodal therapy, pancreatic ductal adenocarcinoma (PDA) continues to have a dismal prognosis. In the era of burgeoning immune therapies against previously difficult-to-treat malignancies, there has been growing interest in activating the immune system against PDA; however, unlike in other cancers such as melanoma and lymphoma, immunotherapy has not yielded many clinically significant results. To harness these mechanisms for therapeutic use, an in-depth understanding of T-cell programming in the immune microenvironment of PDA must be achieved. The outcome of T-cell programming against pathogens or cancer depends on the uptake and presentation of foreign antigens by dendritic cells and macrophages to T cells, and the expression of various co-stimulatory molecules and cytokines. Subsequent immune responses are kept in check via regulatory mechanisms such as immune checkpoints (for example, programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4)), as well as other immunosuppressive cell types such as regulatory T cells (Treg) and M2 macrophages. PDA presents a challenge from the perspective of immune therapy because of many immunosuppressive mechanisms at play in its microenvironment. The tumor itself produces IL-10 and transforming growth factor beta (TGF-β) that downregulate T-cell activation as well as the activity of antigen-presenting cells. At the same time, PDA also appears to recruit more regulatory elements into its milieu; higher infiltration of Treg, for instance, has been associated with poorer prognosis in PDA patients. M2 macrophages and myeloid-derived suppressive cells are also highly prevalent in the tumor microenvironment. T cells in PDA have high expression of PD-1, whereas the tumor has high expression of PD-L1, which likely inhibits activation of tumor antigen-specific T cells. Many of these immunosuppressive mechanisms have been targeted as potential immune therapies of PDA. Immune checkpoint inhibitors, which target PD-1 and CTLA-4, have been shown to be effective in other cancers such as melanoma; however, they have not demonstrated outcome benefits in PDA so far. Other novel investigational approaches under study currently include inhibiting the homing of immunosuppressive cell types to the tumor milieu, as well as vaccines designed to boost the adaptive response to PDA antigens. As our understanding of the nuanced and complex interactions of the immune microenvironment expands, more targeted approaches can be taken toward achieving therapeutic success in immune therapy against PDA.

Immunotherapy in pancreatic cancer treatment: a new frontier

Pancreatic cancer is a highly aggressive and lethal cancer characterized by high invasiveness, local and extensive dissemination at time of diagnosis and resistance to treatment. Few therapies have shown efficacy in the past and even standard of care therapies yield only modest improvements in the mortality of patients with advanced or metastatic disease. Efforts have been undertaken to study the pancreatic tumor microenvironment and have established its complex and immunosuppressive nature which could explain the high resistance to chemotherapy. Novel therapies targeting the tumor microenvironment with an aim to decrease this resistance, improve immune tolerance and increase the efficacy of the current treatment have shown some promising preliminary results in preclinical and clinical trials. We review the current advances in the field of immunotherapy and their effectiveness as a potential treatment strategy in the pancreatic cancer.

Regulatory T Cells: Molecular and Cellular Basis for Immunoregulation

CD4⁺ regulatory T cells (Tregs) are a highly immune-suppressive subset of CD4⁺ T cells, characterized by expression of the master regulatory transcription factor FOXP3. Tregs are proven to play central roles in the maintenance of self-tolerance in healthy individuals. Tregs are involved in maintaining immune homeostasis: they protect hosts from developing autoimmune diseases and allergy, whereas in malignancies, they promote tumor progression by suppressing anti-tumor immunity. Elucidating factors influencing Treg homeostasis and function have important implications for understanding disease pathogenesis and identifying therapeutic opportunities. Thus, the manipulating Tregs for up- or down-regulation of their suppressive function is a new therapeutic strategy for treating various diseases including autoimmune disorders and cancer. This review will focus on recent advances in how Tregs integrate extracellular and intracellular signals to control their survival and stability. Deeper mechanistic understanding of disease-specific Treg development, maintenance, and function could make disease-specific Treg-targeted therapy more effective, resulting in an increase of efficacy and decrease of side effects related to manipulating Tregs.

Role of immune cells in pancreatic cancer from bench to clinical application: An updated review

BACKGROUND

Pancreatic cancer (PC) remains difficult to treat, despite the recent advances in various anticancer therapies. Immuno-inflammatory response is considered to be a major risk factor for the development of PC in addition to a combination of genetic background and environmental factors. Although patients with PC exhibit evidence of systemic immune dysfunction, the PC microenvironment is replete with immune cells.

METHODS

We searched PubMed for all relevant English language articles published up to March 2016. They included clinical trials, experimental studies, observational studies, and reviews. Trials enrolled at Clinical trial.gov were also searched.

RESULTS

PC induces an immunosuppressive microenvironment, and intratumoral activation of immunity in PC is attenuated by inhibitory signals that limit immune effector function. Multiple types of immune responses can promote an immunosuppressive microenvironment; key regulators of the host tumor immune response are dendritic cells, natural killer cells, macrophages, myeloid derived suppressor cells, and T cells. The function of these immune cells in PC is also influenced by chemotherapeutic agents and the components in tumor microenvironment such as pancreatic stellate cells. Immunotherapy of PC employs monoclonal antibodies/effector cells generated in vitro or vaccination to stimulate antitumor response. Immune therapy in PC has failed to improve overall survival; however, combination therapies comprising immune checkpoint inhibitors and vaccines have been attempted to increase the response.

CONCLUSION

A number of studies have begun to elucidate the roles of immune cell subtypes and their capacity to function or dysfunction in the tumor microenvironment of PC. It will not be long before immune therapy for PC becomes a clinical reality.

Chemokine Receptor Signaling and the Hallmarks of Cancer

The chemokines are a family of chemotactic cytokines that mediate their activity by acting on seven-transmembrane-spanning G protein-coupled receptors. Both the ability of the chemokines and their receptors to form homo- and heterodimers and the promiscuity of the chemokine-chemokine receptor interaction endow this protein family with enormous signaling plasticity and complexity that are not fully understood at present. Chemokines were initially identified as essential regulators of homeostatic and inflammatory trafficking of innate and adaptive leucocytes from lymphoid organs to tissues. Chemokines also mediate the host response to cancer. Nevertheless, chemokine function in this response is not limited to regulating leucocyte infiltration into the tumor microenvironment. It is now known that chemokines and their receptors influence most-if not all-hallmark processes of cancer; they act on both neoplastic and untransformed cells in the tumor microenvironment, including fibroblasts, endothelial cells (blood and lymphatic), bone marrow-derived stem cells, and, obviously, infiltrating leucocytes. This review begins with an overview of chemokine and chemokine receptor structure, to better define how chemokines affect the proliferation, survival, stemness, and metastatic potential of neoplastic cells. We also examine the main mechanisms by which chemokines regulate tumor angiogenesis and immune cell infiltration, emphasizing the pro- and antitumorigenic activity of this protein superfamily in these interrelated processes.

Ontogeny of Tumor-associated CD4+CD25+Foxp3+ T-regulatory Cells

The critical contribution of CD4+CD25+Foxp3+ T-regulatory cells (Treg) to immune suppression in the tumor microenvironment is well-established. Whereas the mechanisms that drive the generation and accumulation of Treg in tumors have been an active area of study, the information on their origin and population dynamics remains limited. In this review, we discuss the ontogeny of tumor-associated Treg in light of the recently identified lineage markers.

TREG Cells in Cancer: Beyond Classical Immunological Control

A prerequisite for tumor evolution toward a malignant state is the establishment of cell intrinsic and extrinsic mechanisms of immune suppression (Hanahan and Weinberg, 2000, 2011; Schreiber, Old, and Smyth, 2011). Widespread recruitment of Foxp3⁺ regulatory T cells (T_REG) is a prevailing means to dampen antitumor immunity. Advances in the characterization of T_REG cell heterogeneity and physiological function of tissue resident T_REG cells unfold new possibilities for nontraditional tumor-promoting functions of intratumoral T_REG cells. This review will focus on the nonclassical function of T_REG cells and their implicancies for cancer biology and treatment.

Chemokines, cytokines and exosomes help tumors to shape inflammatory microenvironment

Relationship between inflammation and cancer is now well-established and represents a paradigm that our immune response does not necessarily serves solely to protect us from infections and cancer. Many specific mechanisms that link chronic inflammation to cancer promotion and metastasis have been uncovered in the recent years. Here we are focusing on the effects that tumors may exert on inflammatory cascades, tuning the immune system ability to cause tumor promotion or regression. In particular, we discuss the contributions of chemokines, cytokines and exosomes to the processes such as induction of inflammation and tumorigenesis. Overall, tumor-elicited inflammation is a key driver of tumor progression and an essential component of tumor microenvironment.

RNA Sequencing of Tumor-Associated Microglia Reveals Ccl5 as a Stromal Chemokine Critical for Neurofibromatosis-1 Glioma Growth

Solid cancers develop within a supportive microenvironment that promotes tumor formation and growth through the elaboration of mitogens and chemokines. Within these tumors, monocytes (macrophages and microglia) represent rich sources of these stromal factors. Leveraging a genetically engineered mouse model of neurofibromatosis type 1 (NF1) low-grade brain tumor (optic glioma), we have previously demonstrated that microglia are essential for glioma formation and maintenance. To identify potential tumor-associated microglial factors that support glioma growth (gliomagens), we initiated a comprehensive large-scale discovery effort using optimized RNA-sequencing methods focused specifically on glioma-associated microglia. Candidate microglial gliomagens were prioritized to identify potential secreted or membrane-bound proteins, which were next validated by quantitative real-time polymerase chain reaction as well as by RNA fluorescence in situ hybridization following minocycline-mediated microglial inactivation in vivo. Using these selection criteria, chemokine (C-C motif) ligand 5 (Ccl5) was identified as a chemokine highly expressed in genetically engineered Nf1 mouse optic gliomas relative to nonneoplastic optic nerves. As a candidate gliomagen, recombinant Ccl5 increased Nf1-deficient optic nerve astrocyte growth in vitro. Importantly, consistent with its critical role in maintaining tumor growth, treatment with Ccl5 neutralizing antibodies reduced Nf1 mouse optic glioma growth and improved retinal dysfunction in vivo. Collectively, these findings establish Ccl5 as an important microglial growth factor for low-grade glioma maintenance relevant to the development of future stroma-targeted brain tumor therapies.

Cytokine Regulation of Metastasis and Tumorigenicity

The human body combats infection and promotes wound healing through the remarkable process of inflammation. Inflammation is characterized by the recruitment of stromal cell activity including recruitment of immune cells and induction of angiogenesis. These cellular processes are regulated by a class of soluble molecules called cytokines. Based on function, cell target, and structure, cytokines are subdivided into several classes including: interleukins, chemokines, and lymphokines. While cytokines regulate normal physiological processes, chronic deregulation of cytokine expression and activity contributes to cancer in many ways. Gene polymorphisms of all types of cytokines are associated with risk of disease development. Deregulation RNA and protein expression of interleukins, chemokines, and lymphokines have been detected in many solid tumors and hematopoetic malignancies, correlating with poor patient prognosis. The current body of literature suggests that in some tumor types, interleukins and chemokines work against the human body by signaling to cancer cells and remodeling the local microenvironment to support the growth, survival, and invasion of primary tumors and enhance metastatic colonization. Some lymphokines are downregulated to suppress tumor progression by enhancing cytotoxic T cell activity and inhibiting tumor cell survival. In this review, we will describe the structure/function of several cytokine families and review our current understanding on the roles and mechanisms of cytokines in tumor progression. In addition, we will also discuss strategies for exploiting the expression and activity of cytokines in therapeutic intervention.

Trial Watch-Small molecules targeting the immunological tumor microenvironment for cancer therapy

Progressing malignancies establish robust immunosuppressive networks that operate both systemically and locally. In particular, as tumors escape immunosurveillance, they recruit increasing amounts of myeloid and lymphoid cells that exert pronounced immunosuppressive effects. These cells not only prevent the natural recognition of growing neoplasms by the immune system, but also inhibit anticancer immune responses elicited by chemo-, radio- and immuno therapeutic interventions. Throughout the past decade, multiple strategies have been devised to counteract the accumulation or activation of tumor-infiltrating immunosuppressive cells for therapeutic purposes. Here, we review recent preclinical and clinical advances on the use of small molecules that target the immunological tumor microenvironment for cancer therapy. These agents include inhibitors of indoleamine 2,3-dioxigenase 1 (IDO1), prostaglandin E2, and specific cytokine receptors, as well as modulators of intratumoral purinergic signaling and arginine metabolism.

Process of hepatic metastasis from pancreatic cancer: biology with clinical significance

PURPOSE

Pancreatic cancer shows a remarkable preference for the liver to establish secondary tumors. Selective metastasis to the liver is attributed to the development of potential microenvironment for the survival of pancreatic cancer cells. This review aims to provide a full understanding of the hepatic metastatic process from circulating pancreatic cancer cells to their settlement in the liver, serving as a basic theory for efficient prediction and treatment of metastatic diseases.

METHODS

A systematic search of relevant original articles and reviews was performed on PubMed, EMBASE and Cochrane Library for the purpose of this review.

RESULTS

Three interrelated phases are delineated as the contributions of the interaction between pancreatic cancer cells and the liver to hepatic metastasis process. Chemotaxis of disseminated pancreatic cancer cells and simultaneous defensive formation of platelets or neutrophils facilitate specific metastasis toward the liver. Remodeling of extracellular matrix and stromal cells in hepatic lobules and angiogenesis induced by proangiogenic factors support the survival and growth of clinical micrometastasis colonizing the liver. The bimodal role of the immune system or prevalence of cancer cells over the immune system makes metastatic progression successfully proceed from micrometastasis to macrometastasis.

CONCLUSIONS

Pancreatic cancer is an appropriate research object of cancer metastasis representing more than a straight cascade. If any of the successive or simultaneous phases, especially tumor-induced immunosuppression, is totally disrupted, hepatic metastasis will be temporarily under control or even cancelled forever. To shrink cancers on multiple fronts and prolong survival for patients, novel oral or intravenous anti-cancer agents covering one or different phases of metastatic pancreatic cancer are expected to be integrated into innovative strategies on the premise of safety and efficacious biostability.

Roles of regulatory T cells in cancer immunity

CD4(+) regulatory T cells (Tregs) expressing the transcription factor FoxP3 are highly immune suppressive and play central roles in the maintenance of self-tolerance and immune homeostasis, yet in malignant tumors they promote tumor progression by suppressing effective antitumor immunity. Indeed, higher infiltration by Tregs is observed in tumor tissues, and their depletion augments antitumor immune responses in animal models. Additionally, increased numbers of Tregs and, in particular, decreased ratios of CD8(+) T cells to Tregs among tumor-infiltrating lymphocytes are correlated with poor prognosis in various types of human cancers. The recent success of cancer immunotherapy represented by immune checkpoint blockade has provided a new insight in cancer treatment, yet more than half of the treated patients did not experience clinical benefits. Identifying biomarkers that predict clinical responses and developing novel immunotherapies are therefore urgently required. Cancer patients whose tumors contain a large number of neoantigens stemming from gene mutations, which have not been previously recognized by the immune system, provoke strong antitumor T-cell responses associated with clinical responses following immune checkpoint blockade, depending on the resistance to Treg-mediated suppression. Thus, integration of a strategy restricting Treg-mediated immune suppression may expand the therapeutic spectrum of cancer immunotherapy towards patients with a lower number of neoantigens. In this review, we address the current understanding of Treg-mediated immune suppressive mechanisms in cancer, the involvement of Tregs in cancer immunotherapy, and strategies for effective and tolerable Treg-targeted therapy.

Immunotherapy with methyl gallate, an inhibitor of Treg cell migration, enhances the anti-cancer effect of cisplatin therapy

Foxp3(+) CD25(+)CD4(+) regulatory T (Treg) cells are crucial for the maintenance of immunological self-tolerance and are abundant in tumors. Most of these cells are chemo-attracted to tumor tissues and suppress anti-tumor responses inside the tumor. Currently, several cancer immunotherapies targeting Treg cells are being clinically tested. Cisplatin is one of the most potent chemotherapy drugs widely used for cancer treatment. While cisplatin is a powerful drug for the treatment of multiple cancers, there are obstacles that limit its use, such as renal dysfunction and the development of cisplatin-resistant cancer cells after its use. To minimize these barriers, combinatorial therapies of cisplatin with other drugs have been developed and have proven to be more effective to treat cancer. In the present study, we evaluated the eff ect of the combination therapy using methyl gallate with cisplatin in EL4 murine lymphoma bearing C57BL/6 mice. The combinatorial therapy of methyl gallate and cisplatin showed stronger anti-cancer eff ects than methyl gallate or cisplatin as single treatments. In Treg cell-depleted mice, however, the eff ect of methyl gallate vanished. It was found that methyl gallate treatment inhibited Treg cell migration into the tumor regardless of cisplatin treatment. Additionally, in both the normal and cisplatin-treated tumor-bearing mice, there was no renal toxicity attributed to methyl gallate treatment. These findings suggest that methyl gallate treatment could be useful as an adjuvant method accompanied with cisplatin therapy.

Chronic stress increases experimental pancreatic cancer growth, reduces survival and can be antagonised by beta-adrenergic receptor blockade

BACKGROUND/OBJECTIVES

Chronic stress could promote tumour growth and reduce survival of pancreatic cancer patients via beta-adrenergic receptors of tumour cells. We have tested the impact of chronic acoustic and restraint stress on tumour development in an orthotopic syngeneic murine model of pancreatic cancer.

METHODS AND RESULTS

Tumour-bearing C57BL/6 mice exposed to chronic stress had 45% (p = 0.0138) higher circulating steroid and 111% (p = 0.0052) higher adrenal tyrosine hydroxylase levels. Their immune response was significantly suppressed: The in vitro LPS response of splenocytes was significantly reduced regarding Th1- and Th2-cytokines including IFN-gamma, IL-6, IL-10 and MCP-1 (0.0011 < p < 0.043). Also, tumours of stressed mice showed a tendency towards fewer total CD4 cells, more regulatory T cells (Treg), less T cell/tumour cell contacts and a reduction of CTLA-4 in CD4 cells (p > 0.05). TGF-beta in vitro was increased by 23.4% using catecholamines (p < 0.012) and in vivo employing chronic stress (p < 0.001). After 5 weeks tumour volumes were 130% (p = 0.0061) larger and median survival reduced by 13.5% (p = 0.0058). Tumours expressed more VEGF (p = 0.0334), had greater microvessel densities (p = 0.047), and an increased MMP-9 expression (p = 0.0456). Beta-catecholamines increased proliferation in tumour cells by 18% (p < 0.0001) and migration by 78% (p = 0.0348) whereas the beta-blocker propranolol reduced these effects by 25% (p < 0.0001) and 53% (p = 0.045), respectively. When stressed tumour-bearing animals were treated with propranolol tumour volumes were reduced by 69% (p = 0.0088) and survival improved by 14% (p < 0.0058).

CONCLUSIONS

The potential treatment with beta-blockers of patients with pancreatic cancer or other malignancies should be further evaluated as an adjuvant anti-neoplastic agent in clinical trials.

Maraviroc decreases CCL8-mediated migration of CCR5(+) regulatory T cells and reduces metastatic tumor growth in the lungs

Regulatory T cells (Tregs) play a crucial physiological role in the regulation of immune homeostasis, although recent data suggest Tregs can contribute to primary tumor growth by suppressing antitumor immune responses. Tregs may also influence the development of tumor metastases, although there is a paucity of information regarding the phenotype and function of Tregs in metastatic target organs. Herein, we demonstrate that orthotopically implanted metastatic mammary tumors induce significant Treg accumulation in the lungs, which is a site of mammary tumor metastasis. Tregs in the primary tumor and metastatic lungs express high levels of C-C chemokine receptor type 5 (CCR5) relative to Tregs in the mammary fat pad and lungs of tumor-free mice, and Tregs in the metastatic lungs are enriched for CCR5 expression in comparison to other immune cell populations. We also identify that C-C chemokine ligand 8 (CCL8), an endogenous ligand of CCR5, is produced by F4/80(+) macrophages in the lungs of mice with metastatic primary tumors. Migration of Tregs toward CCL8 ex vivo is reduced in the presence of the CCR5 inhibitor Maraviroc. Importantly, treatment of mice with Maraviroc (MVC) reduces the level of CCR5(+) Tregs and metastatic tumor burden in the lungs. This work provides evidence of a CCL8/CCR5 signaling axis driving Treg recruitment to the lungs of mice bearing metastatic primary tumors, representing a potential therapeutic target to decrease Treg accumulation and metastatic tumor growth.

TIGIT predominantly regulates the immune response via regulatory T cells

Coinhibitory receptors are critical for the maintenance of immune homeostasis. Upregulation of these receptors on effector T cells terminates T cell responses, while their expression on Tregs promotes their suppressor function. Understanding the function of coinhibitory receptors in effector T cells and Tregs is crucial, as therapies that target coinhibitory receptors are currently at the forefront of treatment strategies for cancer and other chronic diseases. T cell Ig and ITIM domain (TIGIT) is a recently identified coinhibitory receptor that is found on the surface of a variety of lymphoid cells, and its role in immune regulation is just beginning to be elucidated. We examined TIGIT-mediated immune regulation in different murine cancer models and determined that TIGIT marks the most dysfunctional subset of CD8+ T cells in tumor tissue as well as tumor-tissue Tregs with a highly active and suppressive phenotype. We demonstrated that TIGIT signaling in Tregs directs their phenotype and that TIGIT primarily suppresses antitumor immunity via Tregs and not CD8+ T cells. Moreover, TIGIT+ Tregs upregulated expression of the coinhibitory receptor TIM-3 in tumor tissue, and TIM-3 and TIGIT synergized to suppress antitumor immune responses. Our findings provide mechanistic insight into how TIGIT regulates immune responses in chronic disease settings.

TLR9 ligation in pancreatic stellate cells promotes tumorigenesis

Zambirinis et al. show that TLR9 stimulation has a protumorigenic effect in pancreatic carcinoma by inducing pancreatic stellate cells to become fibrogenic and produce chemokines that stimulate epithelial cell proliferation. Activation of TLR9 results also in an immune suppressive tumor microenvironment via recruitment of regulatory T cells and induction of myeloid-derived suppressor cell proliferation.

Modulation of Toll-like receptor (TLR) signaling can have protective or protumorigenic effects on oncogenesis depending on the cancer subtype and on specific inflammatory elements within the tumor milieu. We found that TLR9 is widely expressed early during the course of pancreatic transformation and that TLR9 ligands are ubiquitous within the tumor microenvironment. TLR9 ligation markedly accelerates oncogenesis, whereas TLR9 deletion is protective. We show that TLR9 activation has distinct effects on the epithelial, inflammatory, and fibrogenic cellular subsets in pancreatic carcinoma and plays a central role in cross talk between these compartments. Specifically, TLR9 activation can induce proinflammatory signaling in transformed epithelial cells, but does not elicit oncogene expression or cancer cell proliferation. Conversely, TLR9 ligation induces pancreatic stellate cells (PSCs) to become fibrogenic and secrete chemokines that promote epithelial cell proliferation. TLR9-activated PSCs mediate their protumorigenic effects on the epithelial compartment via CCL11. Additionally, TLR9 has immune-suppressive effects in the tumor microenvironment (TME) via induction of regulatory T cell recruitment and myeloid-derived suppressor cell proliferation. Collectively, our work shows that TLR9 has protumorigenic effects in pancreatic carcinoma which are distinct from its influence in extrapancreatic malignancies and from the mechanistic effects of other TLRs on pancreatic oncogenesis.

Blockade of TNF-α signaling benefits cancer therapy by suppressing effector regulatory T cell expansion

Effector but not naive regulatory T cells (Treg cells) can accumulate in the peripheral blood as well as the tumor microenvironment, expand during tumor progression and be one of the main suppressors for antitumor immunity. However, the underlying mechanisms for effector Treg cell expansion in tumor are still unknown. We demonstrate that effector Treg cell-mediated suppression of antitumor CD8+ T cells is tumor-nonspecific. Furthermore, TNFR2 expression is increased in these Treg cells by Affymetrix chip analysis which was confirmed by monoclonal antibody staining in both hepatocellular carcinoma (HCC) and colorectal cancer (CRC) patients and murine models. Correspondingly, increased levels of TNF-α in both tissue and serum were also demonstrated. Interestingly, TNF-α could not only expand effector Treg cells through TNFR2 signaling, but also enhanced their suppressive activity against antitumor immunity of CD8+ T cells. Furthermore, targeting TNFR2 signaling with a TNF-α inhibitor could selectively reduce rapid resurgence of effector Treg cells after cyclophosphamide-induced lymphodepletion and markedly inhibit the growth of established tumors. Herein, we propose a novel mechanism in which TNF-α could promote tumor-associated effector Treg cell expansion and suggest a new cancer immunotherapy strategy using TNF-α inhibitors to reduce effector Treg cells expansion after cyclophosphamide-induced lymphodepletion.