Adoptive transfer of Tc1 or Tc17 cells elicits antitumor immunity against established melanoma through distinct mechanisms

Deciphering and overcoming Anti-PD-1 resistance in Melanoma: A comprehensive review of Mechanisms, biomarker Developments, and therapeutic strategies

Worldwide, tens of thousands of people die from melanoma each year, making it the most frequently fatal form of cutaneous cancer. Immunotherapeutic advancements, particularly with anti-PD-1 medications, have significantly enhanced treatment outcomes over recent decades. With the broad application of anti-PD-1 therapies, insights into the mechanisms of resistance have evolved. Despite the development of combination treatments and early predictive biomarkers, a comprehensive synthesis of these advancements is absent in the current literature. This review underscores the prevailing knowledge of anti-PD-1 resistance mechanisms and underscores the critical role of robust predictive biomarkers in stratifying patients for targeted combinations of anti-PD-1 and other conventional or innovative therapeutic approaches. Additionally, we offer insights that may shape future melanoma treatment strategies.

RORγT agonists as immune modulators in anticancer therapy

RORγT is a transcription factor that directs the development of Th17 lymphocytes and other IL-17-expressing cells (e.g., Tc17 and ILC3 cells). These cells are involved in the body's defense against pathogenic bacteria and fungi, but they also participate in maintaining the proinflammatory environment in some autoimmune diseases and play a role in the immune system's response to cancer. Similar to other members of the nuclear receptor superfamily, the activity of RORγT is regulated by low-molecular-weight ligands. Therefore, extensive efforts have been dedicated to identifying inverse agonists that diminish the activity of this receptor and subsequently inhibit the development of autoimmune diseases. Unfortunately, in the pursuit of an ideal inverse agonist, the development of agonists has been overlooked. It is important to remember that these types of compounds, by stimulating lymphocytes expressing RORγT (Th17 and Tc17), can enhance the immune system's response to tumors. In this review, we present recent advancements in the biology of RORγT agonists and their potential application in anticancer therapy.

Friend or Foe - Tc17 cell generation and current evidence for their importance in human disease

The term Tc17 cells refers to interleukin 17 (IL-17)-producing CD8+ T cells. While IL-17 is an important mediator of mucosal defense, it is also centrally involved in driving the inflammatory response in immune-mediated diseases, such as psoriasis, multiple sclerosis, and inflammatory bowel disease. In this review, we aim to gather the current knowledge on the phenotypic and transcriptional profile, the in vitro and in vivo generation of Tc17 cells, and the evidence pointing towards a relevant role of Tc17 cells in human diseases such as infectious diseases, cancer, and immune-mediated diseases.

PD-1 limits differentiation and plasticity of Tc17 cells

Blockade of surface co-inhibitory receptor programmed cell death-1 (PD-1; CD279) has been established as an important immunotherapeutic approach to treat malignancies. On a cellular level, PD-1 is demonstrated to be of particular importance in inhibiting differentiation and effector function of cytotoxic Tc1 cells (CTLs). Nevertheless, the role of PD-1 in modulating interleukin (IL)-17-producing CD8⁺ T-cells (Tc17 cells), which generally display suppressed cytotoxic nature, is not well understood. To evaluate the impact of PD-1 in Tc17 responses, we examined its functioning using different in vitro and in vivo models. Upon activation of CD8⁺ T-cells in Tc17 environment, we found that PD-1 was rapidly expressed on the surface of CD8⁺ T-cells and triggered a T-cell-internal mechanism that inhibited the expression of IL-17 and Tc17-supporting transcription factors pSTAT3 and RORγt. Expression of type17-polarising cytokine IL-21 and the receptor for IL-23 were also suppressed. Intriguingly, adoptively transferred, PD-1^-/- Tc17 cells were highly efficient in rejection of established B16 melanoma in vivo and displayed Tc1 like characteristics ex vivo. When using IL-17A-eGFP reporter mice for in vitro fate tracking, IL-17A-eGFP expressing cells lacking PD-1 signaling upon re-stimulation with IL-12 quickly acquired Tc1 characteristics such as IFN-γ, and granzyme B expression, implicating lineage independent upregulation of CTL-characteristics that are needed for tumor control. In line with plasticity characteristics, absence of PD-1 signaling in Tc17 cells increased the expression of the stemness and persistence-associated molecules TCF1 and BCL6. Thus, PD-1 plays a central role in the specific suppression of Tc17 differentiation and its plasticity in relation to CTL-driven tumor rejection, which provides further explanation as to why the blockade of PD-1 is such an efficient therapeutic target for inducing tumor rejection.

Dendritic cells modified by tumor associated antigen SMP30 have enhanced antitumor effect against mouse hepatocarcinoma cells in vitro and in vivo

OBJECTIVES

Tumor immunotherapy based on dendritic cells (DC) is one of the most promising approaches to treat cancers. This therapy uses an immunogenic tumor antigen to present it to T cells. Senescence marker protein 30 (SMP30) is identified as a tumor associated antigen (TAA) with high immunogenicity and specificity for hepatocellular carcinoma (HCC). DCs are the most potent antigen presenting cells, and can be transduced with tumor antigens to enhance antitumor immune response. The purpose of this study was to investigate the antitumor effect of DCs transduced with a recombinant lentiviral vector (LV-SMP30) expressing SMP30.

METHODS

A recombinant lentiviral vector (LV-SMP30) expressing SMP30 was constructed and transduced into DCs. The expression of SMP30 was detected by western blot. Mouse bone marrow-derived DCs were divided into four groups: LV-SMP30 group (transduced with LV-SMP30), Protein group (co-cultured with SMP30 protein), LV group (transduced with the empty vector) and Untreated group (the normal DCs). The effect of LV-SMP30 on DCs was detected through surface markers (CD123, CD11c, CD80 and CD86) and cytokine production. The activation and proliferation of CD3⁺CD8⁺ T cells were detected by CCK-8 kit. Flow cytometry was used to detect CD3⁺CD8⁺ T cell-mediated cytotoxicity. After construction of a mouse subcutaneous xenograft model, the volume and growth of tumors in different groups were observed. The changes in serum immune indexes in the treated groups were compared with those in the control group.

RESULTS

The LV-SMP30 recombinant was constructed and transduced into DCs successfully, and LV-SMP30-transduced DCs stably expressed SMP30. The percentages of expression in the LV-SMP30 and Protein groups were significantly higher than those in the LV or Untreated groups (P<0.05). Meanwhile, after the DCs were cultured for 72 hours, the levels of IL-2, IL-6, IL-12, and IFN-γ were significantly higher in the LV-SMP30 and Protein groups than in the LV group or Untreated group (P<0.05). After the DCs were continuously cultured for one week, however, the cytokine levels in the LV-SMP30 group were significantly higher than those in the Protein group (P<0.05). In addition, CD3⁺CD8⁺ T cell proliferation and activation levels were substantially higher in the LV-SMP30 and Protein groups than in the LV or Untreated groups (P<0.05). Furthermore, as the ratio of effectors/target cells increasing in the LV-SMP30 group, CD3⁺CD8⁺ T cell-mediated cytotoxicity in H22 cells became higher (0:1, 10:1; 20:1; 40:1, respectively). In comparison to the control group, the cytotoxicity of the LV-SMP30 group was considerably increased at the ratios of 10:1, 20:1 and 40:1 (P<0.05). However, in the case of Hep1-6 cells, there was no significant difference in CD3⁺CD8⁺ T cell-mediated cytotoxicity among the groups. In addition, when compared with other groups, the mice in the LV-SMP30 group showed the most volume reduction, the slowest tumor growth, and the highest level of IL-2 and IFN-γ (P<0.05).

CONCLUSION

DCs transduced with LV-SMP30 can dramatically enhance specific CD3⁺CD8⁺ T cell immune responses against mouse hepatocarcinoma cells in vitro and in vivo. These findings lend significant support to the development of the DC-based SMP30 antigen vaccine for hepatocarcinoma immunotherapy.

Adoptive transfer of IL-4 reprogrammed Tc17 cells elicits anti-tumor immunity through functional plasticity

Ability of IL-17-producing CD8⁺ T cells (Tc17) to transform into cytotoxic anti-tumor effectors makes them a promising candidate for immune effector cell (IEC) therapy. However, key factors regulating Tc17 reprograming remain poorly defined, hindering translation of Tc17-based IEC use from bench to bedside. We probed the effects of multiple cytokines and underlying signaling pathways on Tc17 cells and identified pivotal role for IL-4 and PI3K/AKT in promoting Tc17 transformation into cytotoxic IFN-γ-producing IECs, an effect dependent on Eomes expression. IL-4 not only triggered Tc17 cytotoxicity, but also induced cell expansion, which significantly improved the antitumor potential of Tc17 cells compared to that of IFN-γ-producing CD8⁺ T cells (Tc1) in a murine model. Furthermore, IL-4/AKT signaling drove the upregulation of the T-cell receptor-associated transmembrane adaptor 1 (Trat1) in Tc17 cells to promote IL-4-induced T-cell receptor stabilization and Tc17 cytotoxicity. Finally, we proposed a possible procedure to expand human Tc17 from peripheral blood of cancer patients, and confirmed the function of IL-4 in Tc17 reprogramming. Collectively, these results document a novel IL-4/AKT/Eomes/Trat1 axis that promotes expansion and transformation of Tc17 cells into cytotoxic effectors with a therapeutic potential. IL-4 priming of Tc17 cells should be further explored as a cell therapy engineering strategy to generate IECs to augment anti-tumor responses. This article is protected by copyright. All rights reserved.

Natural adjuvants (PC and G2) induce activated natural killer cells with NKG2D expression and cytotoxic properties in colorectal cancer

Aim

This study aimed to investigate the effects of natural adjuvants (G2 and PC) to activate natural killer cells in colorectal cancer.

Background

Natural killer (NK) cells are an element of the innate immune system that can recognize and kill cancer cells and provide hope for cancer therapy. One of the current methods in cancer immunotherapy is NK cell therapy. Immunotherapy with NK cells has been limited because of the low number and cytotoxicity level of NK cells. Natural adjuvants such as PC and G2 may stimulate the immune system. It seems that these adjuvants could increase cytotoxic NK cells.

Methods

Twelve patients with colorectal cancer and six healthy individuals qualified for inclusion in this study. Peripheral blood mononuclear cells (PBMCs) from each patient with two distinctive concentrations (105and 5×104 cells/well) were treated with Interleukin2 (IL2), PC, and G2 adjuvant separately. The NK cell's surface markers, including CD16, CD56, and NKG2D, were evaluated by flow cytometry. The cytotoxicity effect of treated PBMCs as effector cells against NK sensitive cell line (K562) was assessed using the LDH assay method.

Results

The results revealed a significant increase in the level of CD16+NKG2D+ NK cells in PBMCs treated with the G2 group compared with the control group in CRC PBMC (p<0.001) as well as the normal PBMC group (p < 0.01). In addition, the results indicated a significant increase in the level of CD56+NKG2D+ cells in the PBMC treated with PC (p < 0.05) and G2 (p < 0.001) groups compared with the PBMC group. The cytotoxicity result of PBMC from CRC patients in 10:1 ratio of the effector: target showed that the cells' cytotoxicity in the PBMCs treated with PC (p<0.01) and G2 (p<0.05) was significantly higher than the untreated PBMC.

Conclusion

According to the result of this study, it can be stated that the PC and G2 adjuvants could be candidates for inducing cytotoxic natural killer cells.

Rationalizing heptadecaphobia: TH 17 cells and associated cytokines in cancer and metastasis

Cancer is one of the leading causes of death worldwide. When cancer patients are diagnosed with metastasis, meaning that the primary tumor has spread to at least one different site, their life expectancy decreases dramatically. In the past decade, the immune system´s role in fighting cancer and metastasis has been studied extensively. Importantly, immune cells and inflammatory reactions generate potent antitumor responses but also contribute to tumor development. However, the molecular and cellular mechanisms underlying this dichotomic interaction between the immune system and cancer are still poorly understood. Recently, a spotlight has been cast on the distinct subsets of immune cells and their derived cytokines since evidence has implicated their crucial impact on cancer development. T helper 17 cell (TH 17) cells, which express the master transcriptional factor Retinoic acid-receptor-related orphan receptor gamma t, are among these critical cell subsets and are defined by their production of type 3 cytokines, such as IL-17A, IL-17F, and IL-22. Depending on the tumor microenvironment, these cytokines can also be produced by other immune cell sources, such as T cytotoxic 17 cell, innate lymphoid cells, NKT cells, or γδ T cells. To date, a lot of data have been collected describing the divergent functions of IL-17A, IL-17F, and IL-22 in malignancies. In this comprehensive review, we discuss the role of these TH 17- and non-TH 17-derived type 3 cytokines in different tumor entities. Furthermore, we will provide a structured insight into the strict regulation and subsequent downstream mechanisms of these cytokines in cancer and metastasis.

Human MAIT cells endowed with HBV specificity are cytotoxic and migrate towards HBV-HCC while retaining antimicrobial functions

BACKGROUND & AIMS

Virus-specific T cell dysfunction is a common feature of HBV-related hepatocellular carcinoma (HBV-HCC). Conventional T (ConT) cells can be redirected towards viral antigens in HBV-HCC when they express an HBV-specific receptor; however, their efficacy can be impaired by liver-specific physical and metabolic features. Mucosal-associated invariant T (MAIT) cells are the most abundant innate-like T cells in the liver and can elicit potent intrahepatic effector functions. Here, we engineered ConT and MAIT cells to kill HBV expressing hepatoma cells and compared their functional properties.

METHODS

Donor-matched ConT and MAIT cells were engineered to express an HBV-specific T cell receptor (TCR). Cytotoxicity and hepatocyte homing potential were investigated using flow cytometry, real-time killing assays, and confocal microscopy in 2D and 3D HBV-HCC cell models. Major histocompatibility complex (MHC) class I-related molecule (MR1)-dependent and MR1-independent activation was evaluated in an Escherichia coli THP-1 cell model and by IL-12/IL-18 stimulation, respectively.

RESULTS

HBV TCR-MAIT cells demonstrated polyfunctional properties (CD107a, interferon [IFN] γ, tumour necrosis factor [TNF], and IL-17A) with strong HBV target sensitivity and liver-homing chemokine receptor expression when compared with HBV TCR-ConT cells. TCR-mediated lysis of hepatoma cells was comparable between the cell types and augmented in the presence of inflammation. Coculturing with HBV+ target cells in a 3D microdevice mimicking aspects of the liver microenvironment demonstrated that TCR-MAIT cells migrate readily towards hepatoma targets. Expression of an ectopic TCR did not affect the ability of the MAIT cells to be activated via MR1-presented bacterial antigens or IL-12/IL-18 stimulation.

CONCLUSIONS

HBV TCR-MAIT cells demonstrate anti-HBV functions without losing their endogenous antimicrobial mechanisms or hepatotropic features. Our results support future exploitations of MAIT cells for liver-directed immunotherapies.

LAY SUMMARY

Chronic HBV infection is a leading cause of liver cancer. T cell receptor (TCR)-engineered T cells are patients' immune cells that have been modified to recognise virus-infected and/or cancer cells. Herein, we evaluated whether mucosal-associated invariant T cells, a large population of unconventional T cells in the liver, could recognise and kill HBV infected hepatocytes when engineered with an HBV-specific TCR. We show that their effector functions may exceed those of conventional T cells currently used in the clinic, including antimicrobial properties and chemokine receptor profiles better suited for targeting liver tumours.

Type 17 immunity promotes the exhaustion of CD8+ T cells in cancer

Background

Multiple types of immune cells producing IL-17 are found in the tumor microenvironment. However, their roles in tumor progression and exhaustion of CD8⁺ tumor-infiltrating lymphocytes (TILs) remain unclear.

Methods

To determine the role of type 17 immunity in tumor, we investigated the growth of B16F10 melanoma and the exhaustion of CD8⁺ TILs in Il17a^−/− mice, Il17a^CreR26^DTA mice, RORγt inhibitor-treated mice, or their respective control mice. Adoptive transfer of tumor-specific IL-17-producing T cells was performed in B16F10-bearing congenic mice. Anti-CD4 or anti-Ly6G antibodies were used to deplete CD4⁺ T cells or CD11b⁺Gr-1^hi myeloid cells in vivo, respectively. Correlation between type 17 immunity and T cell exhaustion in human cancer was evaluated by interrogating TCGA dataset.

Results

Depletion of CD4⁺ T cells promotes the exhaustion of CD8⁺ T cells with a concomitant increase in IL-17-producing CD8⁺ T (Tc17) cells in the tumor. Unlike IFN-γ-producing CD8⁺ T (Tc1) cells, tumor-infiltrating Tc17 cells exhibit CD103⁺KLRG1⁻IL-7Rα^hi tissue resident memory-like phenotypes and are poorly cytolytic. Adoptive transfer of IL-17-producing tumor-specific T cells increases, while depletion of IL-17-producing cells decreases, the frequency of PD-1^hiTim3⁺TOX⁺ terminally exhausted CD8⁺ T cells in the tumor. Blockade of IL-17 or RORγt pathway inhibits exhaustion of CD8⁺ T cells and also delays tumor growth in vivo. Consistent with these results, human TCGA analyses reveal a strong positive correlation between type 17 and CD8⁺ T cell exhaustion signature gene sets in multiple cancers.

Conclusion

IL-17-producing cells promote terminal exhaustion of CD8⁺ T cells and tumor progression in vivo, which can be reversed by blockade of IL-17 or RORγt pathway. These findings unveil a novel role for IL-17-producing cells as tumor-promoting cells facilitating CD8⁺ T cell exhaustion, and propose type 17 immunity as a promising target for cancer immunotherapy.

TNF-a Is a Potent Stimulator of Tc9-Cell Differentiation

Tumor-specific Tc9 cells exhibit an excellent antitumor potential in tumor immunotherapy. Identification of factors that contribute to Tc9-cell differentiation may have important clinical significance. In this study, we found that tumor necrosis factor (TNF)-α promotes Tc9 differentiation in vitro, and the TNF-α-induced Tc9 cells display enhanced cell survival and cell proliferation. More importantly, the TNF-α-induced tumor-specific Tc9 cells have increased antitumor capabilities in vivo. TNF-α activates its downstream signaling through 2 cell surface receptors, TNFR1 and TNFR2. In this study, we found that TNF-α promotes Tc9-cell differentiation through TNFR2, but not TNFR1. Furthermore, we found that TNF-α-TNFR2 activates STAT5 and nuclear factor-κB signaling during Tc9-cell differentiation. Blocking STAT5 or nuclear factor-κB by their specific inhibitors partially abrogates TNF-α-induced promotion of Tc9-cell differentiation. Thus, our study demonstrated TNF-α as a potent stimulator of Tc9-cell differentiation and may have important clinical implications.

Obesity and CD8 T cell metabolism: Implications for anti-tumor immunity and cancer immunotherapy outcomes

Obesity is an established risk factor for many cancers and has recently been found to alter the efficacy of T cell-based immunotherapies. Currently, however, the effects of obesity on immunometabolism remain unclear. Understanding these associations is critical, given the fact that T cell metabolism is tightly linked to effector function. Thus, any obesity-associated changes in T cell bioenergetics are likely to drive functional changes at the cellular level, alter the metabolome and cytokine/chemokine milieu, and impact cancer immunotherapy outcomes. Here, we provide a brief overview of T cell metabolism in the presence and absence of solid tumor growth and summarize current literature regarding obesity-associated changes in T cell function and bioenergetics. We also discuss recent findings related to the impact of host obesity on cancer immunotherapy outcomes and present potential mechanisms by which T cell metabolism may influence therapeutic efficacy. Finally, we describe promising pharmaceutical therapies that are being investigated for their ability to improve CD8 T cell metabolism and enhance cancer immunotherapy outcomes in patients, regardless of their obesity status.

IL-9 and IL-9-producing cells in tumor immunity

Abstract

Interleukin (IL)-9 belongs to the IL-2Rγc chain family and is a multifunctional cytokine that can regulate the function of many kinds of cells. It was originally identified as a growth factor of T cells and mast cells. In previous studies, IL-9 was mainly involved in the development of allergic diseases, autoimmune diseases and parasite infections. Recently, IL-9, as a double-edged sword in the development of cancers, has attracted extensive attention. Since T-helper 9 (Th9) cell-derived IL-9 was verified to play a powerful antitumor role in solid tumors, an increasing number of researchers have started to pay attention to the role of IL-9-skewed CD8⁺ T (Tc9) cells, mast cells and Vδ2 T cell-derived IL-9 in tumor immunity. Here, we review recent studies on IL-9 and several kinds of IL-9-producing cells in tumor immunity to provide useful insight into tumorigenesis and treatment.

IL6 Induces an IL22+ CD8+ T-cell Subset with Potent Antitumor Function

CD8+ T cells can be polarized into several different subsets as defined by the cytokines they produce and the transcription factors that govern their differentiation. Here, we identified the polarizing conditions to induce an IL22-producing CD8+ Tc22 subset, which is dependent on IL6 and the aryl hydrocarbon receptor transcription factor. Further characterization showed that this subset was highly cytolytic and expressed a distinct cytokine profile and transcriptome relative to other subsets. In addition, polarized Tc22 were able to control tumor growth as well as, if not better than, the traditional IFNγ-producing Tc1 subset. Tc22s were also found to infiltrate the tumors of human patients with ovarian cancer, comprising up to approximately 30% of expanded CD8+ tumor-infiltrating lymphocytes (TIL). Importantly, IL22 production in these CD8+ TILs correlated with improved recurrence-free survival. Given the antitumor properties of Tc22 cells, it may be prudent to polarize T cells to the Tc22 lineage when using chimeric antigen receptor (CAR)-T or T-cell receptor (TCR) transduction-based immunotherapies.

IL-17-Producing Cells in Tumor Immunity: Friends or Foes?

IL-17 is produced by RAR-related orphan receptor gamma t (RORγt)-expressing cells including Th17 cells, subsets of γδT cells and innate lymphoid cells (ILCs). The biological significance of IL-17-producing cells is well-studied in contexts of inflammation, autoimmunity and host defense against infection. While most of available studies in tumor immunity mainly focused on the role of T-bet-expressing cells, including cytotoxic CD8⁺ T cells and NK cells, and their exhaustion status, the role of IL-17-producing cells remains poorly understood. While IL-17-producing T-cells were shown to be anti-tumorigenic in adoptive T-cell therapy settings, mice deficient in type 17 genes suggest a protumorigenic potential of IL-17-producing cells. This review discusses the features of IL-17-producing cells, of both lymphocytic and myeloid origins, as well as their suggested pro- and/or anti-tumorigenic functions in an organ-dependent context. Potential therapeutic approaches targeting these cells in the tumor microenvironment will also be discussed.

IL-17A Is Critical for CD8+ T Effector Response in Airway Epithelial Injury After Transplantation

BACKGROUND

Airway epithelium is the primary target of trachea and lung transplant rejection, the degree of epithelial injury is closely correlated with obliterative bronchiolitis development. In this study, we investigated the cellular and molecular mechanisms of IL-17A-mediated airway epithelial injury after transplantation.

METHODS

Murine orthotopic allogeneic trachea or lung transplants were implemented in wild type or RORγt mice. Recipients received anti-IL-17A or anti-IFNγ for cytokine neutralization, anti-CD8 for CD8 T-cell depletion, or STAT3 inhibitor to suppress type 17 CD4+/CD8+ T cell development. Airway injury and graft inflammatory cell infiltration were examined by histopathology and immunohistochemistry. Gene expression of IL-17A, IFNγ, perforin, granzyme B, and chemokines in grafts was quantitated by real-time RT-PCR.

RESULTS

IL-17A and IFNγ were rapidly expressed and associated with epithelial injury and CD8 T-cell accumulation after allotransplantation. Depletion of CD8 T cells prevented airway epithelial injury. Neutralization of IL-17A or devoid of IL-17A production by RORγt deficiency improved airway epithelial integrity of the trachea allografts. Anti-IL-17A reduced the expression of CXCL9, CXCL10, CXCL11, and CCL20, and abolished CD8 T-cell accumulation in the trachea allografts. Inhibition of STAT3 activation significantly reduced IL-17A expression in both trachea and lung allografts; however, it increased IFNγ expression and cytotoxic activities, which resulted in the failure of airway protection.

CONCLUSIONS

Our data reveal the critical role of IL-17A in mediating CD8 T effector response that causes airway epithelial injury and lung allograft rejection, and indicate that inhibition of STAT3 signals could drive CD8 T cells from Tc17 toward Tc1 development.

Cytotoxic Pathways in Allogeneic Hematopoietic Cell Transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative treatment for hematologic malignancies, and other hematologic and immunologic diseases. Donor-derived immune cells identify and attack cancer cells in the patient producing a unique graft-vs.-tumor (GVT) effect. This beneficial response renders allo-HCT one of the most effective forms of tumor immunotherapy. However, alloreactive donor T cells can damage normal host cells thereby causing graft-vs.-host disease (GVHD), which results in substantial morbidity and mortality. To date, GVHD remains as the major obstacle for more successful application of allo-HCT. Of special significance in this context are a number of cytotoxic pathways that are involved in GVHD and GVT response as well as donor cell engraftment. In this review, we summarize progress in the investigation of these cytotoxic pathways, including Fas/Fas ligand (FasL), perforin/granzyme, and cytokine pathways. Many studies have delineated their distinct operating mechanisms and how they are involved in the complex cellular interactions amongst donor, host, tumor, and infectious pathogens. Driven by progressing elucidation of their contributions in immune reconstitution and regulation, various interventional strategies targeting these pathways have entered translational stages with aims to improve the effectiveness of allo-HCT.

Locally Targeting the IL-17/IL-17RA Axis Reduced Tumor Growth in a Murine B16F10 Melanoma Model

Interleukin (IL)-17 and the cells that produce it within the tumor microenvironment appear to promote tumor development and are associated with survival in cancer patients. Here we investigated the role of the IL-17/IL-17 receptor A (IL-17RA) axis in regulating melanoma progression and evaluated the therapeutic potential of blocking the IL-17/IL-17RA pathway. First, recombinant mouse IL-17 (γmIL-17) treatment significantly increased proliferation of mouse B16F10 cells and human A375 and A2058 cells. Silencing IL-17RA by small hairpin RNA (shRNA) in B16F10 cells reduced the γmIL-17-elicited cell proliferation, migration, and invasion, and significantly reduced vascular endothelial growth factor and matrix metalloproteinase production. Remarkably, knockdown of IL-17RA led to a significantly decreased capability of B16F10 cells to form tumors in vivo, similar to that in IL-17-deficient mice. Finally, local application of an adenovirus delivering a shRNA against IL-17RA mRNA not only significantly suppressed tumor development, but also enhanced antitumor immunity by increasing the interferon γ-expressing T cells and not T regulatory cells. Our results highlight the critical role of the IL-17/IL-17RA pathway in tumor progression and imply that targeting IL-17RA represents a promising therapeutic strategy.

IL-33 drives the antitumor effects of dendritic cells via the induction of Tc9 cells

Dendritic cell (DC) tumor vaccines exert their antitumor effects through the induction of effector T cells. We recently identified Tc9 cells as a new potent antitumor effector T cell subset. However, approaches to direct DCs to preferably prime antitumor Tc9 cells should be further exploited. Here, we demonstrate that the addition of interleukin (IL)-33 potently promotes the induction of Tc9 cells by DCs in vitro and in vivo. IL-33 treatment also drives the cytotoxic activities of DC-induced Tc9 cells. Notably, IL-33 treatment enhances cell survival and proliferation of DC-primed CD8⁺ T cells. More importantly, the addition of IL-33 during in vitro priming of tumor-specific Tc9 cells by DCs increases the antitumor capability of Tc9 cells. Mechanistic studies demonstrated that IL-33 treatment inhibits exhaustive CD8⁺ T cell differentiation by inhibiting PD-1 and 2B4 expression and increasing IL-2 and CD127 (IL-7 receptor-α, IL-7Rα) expression in CD8⁺ T cells. Finally, the addition of IL-33 further promotes the therapeutic efficacy of DC-based tumor vaccines in the OT-I mouse model. Our study demonstrates the important role of IL-33 in DC-induced Tc9 cell differentiation and antitumor immunity and may have important clinical implications.

Molecular properties of gp100-reactive T-cell receptors drive the cytokine profile and antitumor efficacy of transgenic host T cells

To study the contribution of T-cell receptors (TCR) to resulting T-cell responses, we studied three different human αβ TCRs, reactive to the same gp100-derived peptide presented in the context of HLA-A*0201. When expressed in primary CD8 T cells, all receptors elicited classic antigen-induced IFN-γ responses, which correlated with TCR affinity for peptide-MHC in the order T4H2 > R6C12 > SILv44. However, SILv44 elicited superior IL-17A release. Importantly, in vivo, SILv44-transgenic T cells mediated superior antitumor responses to 888-A2 + human melanoma tumor cells upon adoptive transfer into tumor-challenged mice while maintaining IL-17 expression. Modeling of the TCR ternary complexes suggested architectural differences between SILv44 and the other complexes, providing a potential structural basis for the observed differences. Overall, the data reveal a more prominent role for the T-cell receptor in defining host T-cell physiology than traditionally assumed, while parameters beyond IFN-γ secretion and TCR affinity ultimately determine the reactivity of tumor-reactive T cells.

IL-27 Receptor Signaling on T cells Augments GVHD Severity through Enhancing Th1 Responses

IL-27 is a heterodimeric cytokine comprised of IL-27p28 and EBI3. As a relatively new member of the IL-12 family, the biological mechanisms associated with the role of IL-27 in the immune response are ambiguous, displaying both proinflammatory and suppressive functions that seem to be dependent on the disease model. A recent report demonstrates that pharmacological blockade of IL-27p28 alleviates graft-versus-host disease (GVHD) in mice. However, the specific role of the IL-27Rα/gp130 signaling complex that forms the IL-27 receptor (IL-27R) on T cells has not been well characterized in the context of allogeneic hematopoietic stem cell transplantation (allo-HCT). Here, we demonstrate that IL-27Rα expression on T cells exacerbates GVHD after allo-HCT, which was consistent across 3 different MHC- mismatched murine models of allo-HCT. Expression of IL-27Rα on T cells was required for acquisition of optimal Th1 effector function and subsequent inhibition of Th2 and T regulatory subsets after allo-HCT. Furthermore, administration of IL-27significantly increased mortality after allo-HCT; suggesting that the suppressive functions linked to IL-27 in T cell responses may be relatively modest in this model. Hence, IL-27Rα signaling on T cells promotes the development of GVHD.

In Vitro-Generated Tc17 Cells Present a Memory Phenotype and Serve As a Reservoir of Tc1 Cells In Vivo

Memory CD8⁺ T cells are ideal candidates for cancer immunotherapy because they can mediate long-term protection against tumors. However, the therapeutic potential of different in vitro-generated CD8⁺ T cell effector subsets to persist and become memory cells has not been fully characterized. Type 1 CD8⁺ T (Tc1) cells produce interferon-γ and are endowed with high cytotoxic capacity, whereas IL-17-producing CD8⁺ T (Tc17) cells are less cytotoxic but display enhanced self-renewal capacity. We sought to evaluate the functional properties of in vitro-generated Tc17 cells and elucidate their potential to become long lasting memory cells. Our results show that in vitro-generated Tc17 cells display a greater in vivo persistence and expansion in response to secondary antigen stimulation compared to Tc1 cells. When transferred into recipient mice, Tc17 cells persist in secondary lymphoid organs, present a recirculation behavior consistent with central memory T cells, and can shift to a Tc1 phenotype. Accordingly, Tc17 cells are endowed with a higher mitochondrial spare respiratory capacity than Tc1 cells and express higher levels of memory-related molecules than Tc1 cells. Together, these results demonstrate that in vitro-generated Tc17 cells acquire a central memory program and provide a lasting reservoir of Tc1 cells in vivo, thus supporting the use of Tc17 lymphocytes in the design of novel and more effective therapies.

CD38-NAD+Axis Regulates Immunotherapeutic Anti-Tumor T Cell Response

Heightened effector function and prolonged persistence, the key attributes of Th1 and Th17 cells, respectively, are key features of potent anti-tumor T cells. Here, we established ex vivo culture conditions to generate hybrid Th1/17 cells, which persisted long-term in vivo while maintaining their effector function. Using transcriptomics and metabolic profiling approaches, we showed that the enhanced anti-tumor property of Th1/17 cells was dependent on the increased NAD⁺-dependent activity of the histone deacetylase Sirt1. Pharmacological or genetic inhibition of Sirt1 activity impaired the anti-tumor potential of Th1/17 cells. Importantly, T cells with reduced surface expression of the NADase CD38 exhibited intrinsically higher NAD⁺, enhanced oxidative phosphorylation, higher glutaminolysis, and altered mitochondrial dynamics that vastly improved tumor control. Lastly, blocking CD38 expression improved tumor control even when using Th0 anti-tumor T cells. Thus, strategies targeting the CD38-NAD⁺ axis could increase the efficacy of anti-tumor adoptive T cell therapy.

Cytotoxic lymphocytes and atherosclerosis: significance, mechanisms and therapeutic challenges

Cytotoxic lymphocytes encompass natural killer lymphocytes (cells) and cytotoxic T cells that include CD8+ T cells, natural killer (NK) T cells, γ, δ (γδ)-T cells and human CD4 + CD28- T cells. These cells play critical roles in inflammatory diseases and in controlling cancers and infections. Cytotoxic lymphocytes can be activated via a number of mechanisms that may involve dendritic cells, macrophages, cytokines or surface proteins on stressed cells. Upon activation, they secrete pro-inflammatory cytokines as well as anti-inflammatory cytokines, chemokines and cytotoxins to promote inflammation and the development of atherosclerotic lesions including vulnerable lesions, which are strongly implicated in myocardial infarctions and strokes. Here, we review the mechanisms that activate and regulate cytotoxic lymphocyte activity, including activating and inhibitory receptors, cytokines, chemokine receptors-chemokine systems utilized to home to inflamed lesions and cytotoxins and cytokines through which they affect other cells within lesions. We also examine their roles in human and mouse models of atherosclerosis and the mechanisms by which they exert their pathogenic effects. Finally, we discuss strategies for therapeutically targeting these cells to prevent the development of atherosclerotic lesions and vulnerable plaques and the challenge of developing highly targeted therapies that only minimally affect the body's immune system, avoiding the complications, such as increased susceptibility to infections, which are currently associated with many immunotherapies for autoimmune diseases.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

Deletion of Lactate Dehydrogenase-A in Myeloid Cells Triggers Antitumor Immunity

Immunometabolism is emerging as a critical determinant of cancer pathophysiology. In this study, we explored the contributions of macrophage-expressed lactate dehydrogenase-A (LDH-A) to tumor formation in a K-Ras murine model of lung carcinoma. Myeloid-specific deletion of LDH-A promoted accumulation of macrophages with a CD86^high and MCP-1^high M1-like phenotype that suppressed tumor growth. This phenotypic effect was accompanied by reduced VEGF expression and angiogenesis, diminished numbers of PD-L1⁺ cancer cells, increased numbers of CD3⁺ T cells, and activation status of CD8⁺ T cells. Furthermore, it was associated with more pronounced antitumor T-cell immunity via induction of IL17 and IFNγ-producing CD8⁺ T (Tc17 and Tc1) cells, likely via suppression of lactate-driven PD-L1 expression. Our results suggest that expressions of LDH-A and lactate by macrophage in the tumor microenvironment are major drivers of T-cell immunosuppression, strongly supporting the concept of targeting stromal LDH-A as an effective strategy to blunt tumoral immune escape. Cancer Res; 77(13); 3632-43. ©2017 AACR.

Immune biomarkers for prognosis and prediction of responses to immune checkpoint blockade in cutaneous melanoma

Existing clinical, anatomopathological and molecular biomarkers fail to reliably predict the prognosis of cutaneous melanoma. Biomarkers for determining which patients receive adjuvant therapies are needed. The emergence of new technologies and the discovery of new immune populations with different prognostic values allow the immune network in the tumor to be better understood. Importantly, new molecules identified and expressed by immune cells have been shown to reduce the antitumor immune efficacy of therapies, prompting researchers to develop antibodies targeting these so-called "immune checkpoints", which have now entered the oncotherapeutic armamentarium.

The differentiation and plasticity of Tc17 cells are regulated by CTLA-4-mediated effects on STATs

As the blockade of inhibitory surface-molecules such as CTLA-4 on T cells has led to recent advances in antitumor immune therapy, there is great interest in identifying novel mechanisms of action of CD8⁺ T cells to evoke effective cytotoxic antitumor responses. Using in vitro and in vivo models, we investigated the molecular pathways underlying the CTLA-4-mediated differentiation of IL-17-producing CD8⁺ T cells (Tc17 cells) that strongly impairs cytotoxicity. Our studies demonstrate that Tc17 cells lacking CTLA-4 signaling have limited production of STAT3-target gene products such as IL-17, IL-21, IL-23R and RORγt. Upon re-stimulation with IL-12, these cells display fast downregulation of Tc17 hallmarks and acquire Tc1 characteristics such as IFNγ and TNF-α co-expression, which is known to correlate with tumor control. Indeed, upon adoptive transfer, these cells were highly efficient in the antigen-specific rejection of established OVA-expressing B16 melanoma in vivo. Mechanistically, in primary and re-stimulated Tc17 cells, STAT3 binding to the IL-17 promoter was strongly augmented by CTLA-4, associated with less binding of STAT5 and reduced relative activation of STAT1 which is known to block STAT3 activity. Inhibiting CTLA-4-induced STAT3 activity reverses enhancement of signature Tc17 gene products, rendering Tc17 cells susceptible to conversion to Tc1-like cells with enhanced cytotoxic potential. Thus, CTLA-4 critically shapes the characteristics of Tc17 cells by regulating relative STAT3 activation, which provides new perspectives to enhance cytotoxicity of antitumor responses.

Interleukin-12 bypasses common gamma-chain signalling in emergency natural killer cell lymphopoiesis

Differentiation and homeostasis of natural killer (NK) cells relies on common gamma-chain (γc)-dependent cytokines, in particular IL-15. Consequently, NK cells do not develop in mice with targeted γc deletion. Herein we identify an alternative pathway of NK-cell development driven by the proinflammatory cytokine IL-12, which can occur independently of γc-signalling. In response to viral infection or upon exogenous administration, IL-12 is sufficient to elicit the emergence of a population of CD122+CD49b+ cells by targeting NK-cell precursors (NKPs) in the bone marrow (BM). We confirm the NK-cell identity of these cells by transcriptome-wide analyses and their ability to eliminate tumour cells. Rather than using the conventional pathway of NK-cell development, IL-12-driven CD122+CD49b+ cells remain confined to a NK1.1lowNKp46low stage, but differentiate into NK1.1+NKp46+ cells in the presence of γc-cytokines. Our data reveal an IL-12-driven hard-wired pathway of emergency NK-cell lymphopoiesis bypassing steady-state γc-signalling.

IL-17A-producing T cells are associated with the progression of lung adenocarcinoma

Accumulating evidence has shown that T cells are crucial in shaping the tumor microenvironment and regulating tumor development. However, the roles of IL-17A-producing T cells (IL-17A⁺CD4⁺ Th17, IL-17A⁺CD8⁺ Tc17 and IL-17A⁺ γδT17 cells) and related cytokines in the progression of lung cancer (LC) remain uncertain. Here, we found that the frequencies of both Th17 and γδT17 cells in the peripheral blood of patients with lung adenocarcinoma (LA) were higher than those in healthy controls (HCs), whereas the frequency of Tc17 cells in the patients with LA was decreased. In addition, the frequencies of circulating Th17 and γδT17 cells, but not Tc17 cells, were positively associated with tumor invasion and metastasis. Furthermore, the major source of IL-17A production was Th17 cells, followed by Tc17 and γδT17 cells, in peripheral blood from patients with LA and HCs; but the percentages of Th17 and γδT17 cells in total intracellular IL-17A⁺ cells obtained from the patients with LC were higher than those from HCs. Moreover, the protein and corresponding mRNA levels of IL-17A, IL-23, IL-1β, and TGF-β1 were much higher in the patients with LA than those in HCs, and the levels of IL-17A in patients were positively correlated with numbers of both Th17 and γδT17 cells, but not Tc17 cells. Finally, the frequencies of circulating Th17 and γδT17 cells, along with the levels of IL-17A, IL-23, IL-1β, and TGF-β1 were decreased in the patients with LA after tumor resection, whereas the frequency of circulating Tc17 cells was inversely increased in these patients. Our findings indicate that Th17, Tc17, γδT17 cells, and IL-17A-associated cytokines contribute to the development of LA and thus represent promising targets for therapeutic strategies.

TGF-β and IL-21 cooperatively stimulate activated CD8(+) T cells to differentiate into Tc17 cells

TGF-β together with IL-21 or IL-6 can drive the differentiation of naïve CD8(+) T cells into IL-17-producing CD8(+) T cells. These IL-17-producing CD8(+) T cells are termed Tc17 cells. Tc17 cells preserve plasticity under various conditions in vitro and in vivo. IFN-γ-producing CD8(+) T cells are termed Tc1 cells. However, Tc1 cells are considered relatively stable. In the present study, we show that the combination of TGF-β plus IL-21, but not IL-6, converts Tc1 cells into Tc17 cells; this conversion is associated with elevated RORα, RORγt, and Batf mRNA levels. These results indicate that Tc1 cells are skewed to the Tc17 cell phenotype under TGF-β plus IL-21-polarizing conditions. Furthermore, IL-6R is expressed on naïve, but not activated, CD8(+) T cells. In contrast, IL-21R is expressed on both naïve and activated CD8(+) T cells. Thus, differential expression profiles of IL-6R and IL-21R on naïve and activated CD8(+) T cells may be one mechanism by which TGF-β plus IL-21, but not IL-6, can drive activated CD8(+) T cells to differentiate into IL-17-producing cells. Taken together, these results provide a novel viewpoint for the plasticity of Tc1 cells.

Cyclosporine A Inhibits the T-bet-Dependent Antitumor Response of CD8(+) T Cells

Transplant recipients face an increased risk of cancer compared with the healthy population. Although several studies have examined the direct effects of immunosuppressive drugs on cancer cells, little is known about the interactions between pharmacological immunosuppression and cancer immunosurveillance. We investigated the different effects of rapamycin (Rapa) versus cyclosporine A (CsA) on tumor-reactive CD8(+) T cells. After adoptive transfer of CD8(+) T cell receptor-transgenic OTI T cells, recipient mice received either skin grafts expressing ovalbumin (OVA) or OVA-expressing B16F10 melanoma cells. Animals were treated daily with Rapa or CsA. Skin graft rejection and tumor growth as well as molecular and cellular analyses of skin- and tumor-infiltrating lymphocytes were performed. Both Rapa and CsA were equally efficient in prolonging skin graft survival when applied at clinically relevant doses. In contrast to Rapa-treated animals, CsA led to accelerated tumor growth in the presence of adoptively transferred tumor-reactive CD8(+) OTI T cells. Further analyses showed that T-bet was downregulated by CsA (but not Rapa) in CD8(+) T cells and that cancer cytotoxicity was profoundly inhibited in the absence of T-bet. CsA reduces T-bet-dependent cancer immunosurveillance by CD8(+) T cells. This may contribute to the increased cancer risk in transplant recipients receiving calcineurin inhibitors.

Role of interferon-γ and cytotoxic T lymphocytes in intraocular tumor rejection

The eye is normally an immunosuppressive environment. This condition is better known as immune privilege and protects the eye from immune-mediated inflammation of tissues that cannot regenerate. However, immune privilege creates a dilemma for the eye when intraocular neoplasms arise. In some cases, immune privilege is suspended, resulting in the immune rejection of intraocular tumors. This study employed a mouse model in which interferon-γ-dependent intraocular tumor rejection occurs. We tested the hypothesis that this rejection requires interferon-γ for the generation and functional capacity of cytotoxic T lymphocyte-mediated rejection of intraocular tumors. Tumors grew progressively in the eyes of interferon-γ knockout mice, even though the mice generated tumor-specific cytotoxic T lymphocyte responses in the periphery. However, interferon-γ knockout mice rejected tumors that were introduced into extraocular sites. Subcutaneous tumor immunization before intraocular challenge led to tumor rejection and preservation of the eye in wild-type mice. By contrast, tumors grew progressively in the eyes of interferon-γ knockout mice despite their ability to generate peripheral tumor-specific cytotoxic T lymphocytes as well as the capacity of CD8(+) T cells to enter the eye as shown by the presence of CD8 and perforin message and CD3(+)CD8(+) leukocytes within the tumor-bearing eye. We found that cytotoxic T lymphocytes generated in wild-type mice and adoptively transferred into interferon-γ knockout mice mediated the rejection of intraocular tumors in interferon-γ knockout hosts. The results indicate that interferon-γ is critical for the initial priming and differentiation of cytotoxic T lymphocytes residing in the periphery to produce the most effect antitumor function within the eye.

IL-17A-producing T cells and associated cytokines are involved in the progression of gastric cancer

Interleukin-17A-producing T cells (IL-17A+ T) (IL-17A+CD4+ Th17, IL-17A+CD8+ Tc17 and IL-17A+ γδT17 cells) and associated cytokines (IL-17A, IL-23 and IL-1β) play crucial roles in inflammation-associated diseases, such as infection, autoimmunity and tumors. Th17 cells promote human gastric cancer (GC), although the source of intracellular IL‑17A and the roles of Tc17 and γδT17 cells remain poorly understood. In this study, the frequencies of circulating Th17 and γδT17 cells in patients with GC were found to be significantly increased compared to those in healthy donors; however, Tc17 cells were decreased in these patients, and a negative relationship was found between the frequencies of Th17 and Tc17 cells. Moreover, the cytokine IL‑17A was found to be produced mainly by Th17 cells in human peripheral blood. Similarly, serum cytokine levels and relative mRNA expression levels of IL‑17A, IL‑23 and IL‑1β were significantly increased in patients with GC, and the frequency of Th17 cells was closely associated with serum IL‑17A concentrations in patients with GC. Additionally, Th17 cells and associated cytokines were present at significantly different levels during the progression and metastasis of GC, as were Tc17 and γδT17 cells. Taken together, these findings suggest that IL-17A+ T cells and associated cytokines might play crucial roles in human GC progression and metastasis and thus represent potential targets for treatment.

Intrinsic MyD88-Akt1-mTOR Signaling Coordinates Disparate Tc17 and Tc1 Responses during Vaccine Immunity against Fungal Pneumonia

Fungal infections have skyrocketed in immune-compromised patients lacking CD4⁺ T cells, underscoring the need for vaccine prevention. An understanding of the elements that promote vaccine immunity in this setting is essential. We previously demonstrated that vaccine-induced IL-17A⁺ CD8⁺ T cells (Tc17) are required for resistance against lethal fungal pneumonia in CD4⁺ T cell-deficient hosts, whereas the individual type I cytokines IFN-γ, TNF-α and GM-CSF, are dispensable. Here, we report that T cell-intrinsic MyD88 signals are crucial for these Tc17 cell responses and vaccine immunity against lethal fungal pneumonia in mice. In contrast, IFN-γ⁺ CD8⁺ cell (Tc1) responses are largely normal in the absence of intrinsic MyD88 signaling in CD8⁺ T cells. The poor accumulation of MyD88-deficient Tc17 cells was not linked to an early onset of contraction, nor to accelerated cell death or diminished expression of anti-apoptotic molecules Bcl-2 or Bcl-xL. Instead, intrinsic MyD88 was required to sustain the proliferation of Tc17 cells through the activation of mTOR via Akt1. Moreover, intrinsic IL-1R and TLR2, but not IL-18R, were required for MyD88 dependent Tc17 responses. Our data identify unappreciated targets for augmenting adaptive immunity against fungi. Our findings have implications for designing fungal vaccines and immune-based therapies in immune-compromised patients.

Patients with AIDS, cancer or immune suppressive treatments are vulnerable to infection with invasive fungi. We have found that even when helper CD4 T cells are profoundly reduced in a mouse model that mimics this defect in AIDS, other remaining T cells are capable of mounting vaccine immunity against a deadly fungal infection, and they do so by producing the powerful, soluble product, IL-17. It has been widely believed that the activation and instruction of such cells, called Tc17 cells, is governed by another population of immune cells in the body, but we have found here that pathways within these Tc17 cells themselves mediate their activation and ability to produce the IL-17 needed for resistance to infection. We have also identified elements of the circuitry controlling this pathway—elements called MyD88, Akt1 and mTOR—and found that they control the production of IL-17 and not other products such as IFN-γ often produced by these cells. Further, we determined that this circuitry controls the development of Tc17 cells by regulating their ability to divide and expand. Thus, in a mouse model of vaccination against lethal fungal pneumonia caused by Blastomyces dermatitidis, we uncovered an important cellular arsenal that can be recruited to bolster resistance against a fungal infection, and identified novel ways in which the cells develop and expand into potent killers of fungi.

Interleukin-12 enhances the function and anti-tumor activity in murine and human CD8(+) T cells

Mouse CD8(+) T cells conditioned with interleukin (IL)-12 ex vivo mediate the potent regression of established melanoma when transferred into lymphodepleted mice. However, the quantitative and qualitative changes induced by IL-12 in the responding mouse CD8(+) T cells have not been well defined. Moreover, the mechanisms by which IL-12-conditioning impacts human CD8(+) T cells, and how such cells might be expanded prior to infusion into patients is not known. We found that ex vivo IL-12-conditioning of mouse CD8(+) T cells led to a tenfold-100-fold increase in persistence and anti-tumor efficacy upon adoptive transfer into lymphodepleted mice. The enhancing effect of IL-12 was associated with maintenance of functional avidity. Importantly, in the context of ongoing ACT clinical trials, human CD8(+) T cells genetically modified with a tyrosinase-specific T cell receptor (TCR) exhibited significantly enhanced functional activity when conditioned with IL-12 as indicated by heightened granzyme B expression and elevated peptide-specific CD107a degranulation. This effect was sustainable despite the 20 days of in vitro cellular expansion required to expand cells over 1,000-fold allowing adequate cell numbers for administration to cancer patients. Overall, these findings support the efficacy and feasibility of ex vivo IL-12-conditioning of TCR-modified human CD8(+) T cells for adoptive transfer and cancer therapy.

Dendritic Cells in Irradiated Mice Trigger the Functional Plasticity and Antitumor Activity of Adoptively Transferred Tc17 Cells via IL12 Signaling

PURPOSE

The adoptive cell transfer (ACT) of CD8(+) T cells is a promising treatment for advanced malignancies. Lymphodepletion before ACT enhances IFNγ(+)CD8(+) T cell (Tc0)-mediated tumor regression. Yet, how lymphodepletion regulates the function and antitumor activity of IL17A(+)CD8(+) T cells (Tc17) is unknown.

EXPERIMENTAL DESIGN

To address this question, pmel-1 CD8(+) T cells were polarized to secrete either IL17A or IFNγ. These subsets were then infused into mice with B16F10 melanoma that were lymphoreplete [no total body irradiation (TBI)], or lymphodepleted with nonmyeloablative (5 Gy) or myeloablative (9 Gy with hematopoietic stem cell transplantation) TBI. The activation of innate immune cells and function of donor T-cell subsets were monitored in recipient mice.

RESULTS

Tc17 cells regress melanoma in myeloablated mice to a greater extent than in lymphoreplete or nonmyeloablated mice. TBI induced functional plasticity in Tc17 cells, causing conversion from IL17A to IFNγ producers. Additional investigation revealed that Tc17 plasticity and antitumor activity were mediated by IL12 secreted by irradiated host dendritic cells (DC). Neutralization of endogenous IL12 reduced the antitumor activity of Tc17 cells in myeloablated mice, whereas ex vivo priming with IL12 enhanced their capacity to regress melanoma in nonmyeloablated animals. This, coupled with exogenous administration of low-dose IL12, obviated the need for host preconditioning, creating curative responses in nonirradiated mice.

CONCLUSIONS

Our findings indicate that TBI-induced IL12 augments Tc17 cell-mediated tumor immunity and underline the substantial implications of in vitro preparation of antitumor Tc17 cells with IL12 in the design of T-cell immunotherapies.

SUMO2 overexpression enhances the generation and function of interleukin-17-producing CD8⁺ T cells in mice

Small ubiquitin-like modifier (SUMO) 2 is a small protein that controls the activity and stability of other proteins by SUMOylation. In this study, T cell-specific SUMO2 overexpressing transgenic mice were generated to study the effect of SUMO2 on T lymphocytes. SUMO2 overexpression promoted differentiation of interleukin (IL)-17-producing CD8(+) T cells, and significantly suppressed the growth of EL4 tumor cells in vivo. Moreover, the tumor tissue from SUMO2-overexpressing mice had higher interferon (IFN)-γ and granzyme B mRNA levels. Although SUMO2 overexpression did not increase IFN-γ or granzyme B production in cytotoxic T lymphocytes, IL-12 treatment restored and increased IFN-γ secretion in IL-17-producing CD8(+) T cells. SUMO2 overexpression also increased gene expression of chemokines, CCL4, and CXCL10, which attract cytotoxic T lymphocytes to tumor tissues. Additionally, SUMO2-overexpressing T cells exhibited increased STAT3 phosphorylation, implying a SUMO2 target which up-regulates STAT3 activity governing IL-17A-producing CD8(+) T cell differentiation and antitumor immune responses.

Cytokine crowdsourcing: multicellular production of TH17-associated cytokines

In the 2 decades since its discovery, IL-17A has become appreciated for mounting robust, protective responses against bacterial and fungal pathogens. When improperly regulated, however, IL-17A can play a profoundly pathogenic role in perpetuating inflammation and has been linked to a wide variety of debilitating diseases. IL-17A is often present in a composite milieu that includes cytokines produced by TH17 cells (i.e., IL-17F, IL-21, IL-22, and IL-26) or associated with other T cell lineages (e.g., IFN-γ). These combinatorial effects add mechanistic complexity and more importantly, contribute differentially to disease outcome. Whereas TH17 cells are among the best-understood cell types that secrete IL-17A, they are frequently neither the earliest nor dominant producers. Indeed, non-TH17 cell sources of IL-17A can dramatically alter the course and severity of inflammatory episodes. The dissection of the temporal regulation of TH17-associated cytokines and the resulting net signaling outcomes will be critical toward understanding the increasingly intricate role of IL-17A and TH17-associated cytokines in disease, informing our therapeutic decisions. Herein, we discuss important non-TH17 cell sources of IL-17A and other TH17-associated cytokines relevant to inflammatory events in mucosal tissues.

IL-17A-producing CD8(+)T cells as therapeutic targets in autoimmunity

INTRODUCTION

The involvement of IL-17-producing CD8(+)T cells (TC17) in various conditions, such as infection, cancer and autoimmune inflammation, has been documented in both humans and mice; however, TC17 cells have received only marginal attention.

AREAS COVERED

Here, we provide an overview of the cytokines, chemokines, and cytokine and chemokine receptors that characterize the murine and human TC17 cell phenotype. We also discuss signaling pathways, molecular interactions, and transcriptional and epigenetic events that contribute to TC17 differentiation and acquisition of effector functions. Heterogeneity and inherent phenotypic instability of TC17 cells were shown both in humans and murine models. Aberrant expression of TC17 cells was observed in many autoimmune conditions. Moreover, functional analysis demonstrated in vivo plasticity of TC17 cells may be a key feature of TC17 cell biology in autoimmune diseases.

EXPERT OPINION

Due to its important roles in inflammation and autoimmunity, TC17 cell pathway may have promise as a potential therapeutic target for autoimmune diseases. The strategies include the suppression of TC17 cell generation and migration and the blockade of TC17 cell instability and heterogeneity. TMP778 may open an avenue to novel therapeutic strategies.

The inducible costimulator augments Tc17 cell responses to self and tumor tissue

The inducible costimulator (ICOS) plays a key role in the development of Th17 cells, but its role in the development and antitumor activity of IL-17-producing CD8(+) T cells (Tc17) remains unknown. We found that ICOS costimulation was important for the functional maintenance, but not differentiation, of Tc17 cells in vitro. Blocking the ICOS pathway using an antagonist mAb or by using recipient mice genetically deficient in the ICOS ligand reduced the antitumor activity of adoptively transferred Tc17 cells. Conversely, activating Tc17 cells with an ICOS agonist in vitro enhanced their capacity to eradicate melanoma and induce autoimmune vitiligo when infused into mice. However, ICOS stimulation did not augment the antitumor activity of IL-2 expanded T cells. Additional investigation revealed that ICOS stimulation not only increased IL-2Rα, CXCR3, and IL-23R expression on Tc17 cells, but also dampened their expression of suppressive molecule CD39. Although Tc17 cells activated with an ICOS agonist cosecreted heightened IL-17A, IL-9, and IFN-γ, their therapeutic effectiveness was critically dependent on IFN-γ production. Depletion of IL-17A and IL-9 had little impact on antitumor Tc17 cells activated with an ICOS agonist. Collectively, our work reveals that the ICOS pathway potentiates the antitumor activity of adoptively transferred Tc17 cells. This work has major implications for the design of vaccine, Ab and cell-based therapies for autoimmunity, infectious disease, and cancer.

Lessons from patient-derived xenografts for better in vitro modeling of human cancer

The development of novel cancer therapeutics is often plagued by discrepancies between drug efficacies obtained in preclinical studies and outcomes of clinical trials. The inconsistencies can be attributed to a lack of clinical relevance of the cancer models used for drug testing. While commonly used in vitro culture systems are advantageous for addressing specific experimental questions, they are often gross, fidelity-lacking simplifications that largely ignore the heterogeneity of cancers as well as the complexity of the tumor microenvironment. Factors such as tumor architecture, interactions among cancer cells and between cancer and stromal cells, and an acidic tumor microenvironment are critical characteristics observed in patient-derived cancer xenograft models and in the clinic. By mimicking these crucial in vivo characteristics through use of 3D cultures, co-culture systems and acidic culture conditions, an in vitro cancer model/microenvironment that is more physiologically relevant may be engineered to produce results more readily applicable to the clinic.

Activation of CD1d-restricted natural killer T cells can inhibit cancer cell proliferation during chemotherapy by promoting the immune responses in murine mesothelioma

We studied the impact of natural killer T (NKT) cell activation by alpha-galactocysylceramide (α-GalCer, α-GC) on cancer cell repopulation during chemotherapy in murine mesothelioma. The number of NKT cells was found to be increased during the development of murine mesothelioma. NKT cells specifically recognize α-GC through CD1d resulting in their activation and expansion. Tumor-bearing mice were treated with chemotherapy once weekly, and α-GC was followed after each cycle of chemotherapy. Anti-tumor effect was evaluated on wild-type (WT) and CD1d knockout (CD1dKO) mice. Cancer cell proliferation and apoptosis were evaluated by Ki67 and TUNEL immunohistochemistry. CD4(+) and CD8(+) T cell proportion and activation in tumor, spleen, draining lymph node and peripheral blood were determined by flow cytometry, and gene expression of activated T cell-related cytokines was quantified by reverse transcription PCR. NKT cells were identified by CD1d-α-GC-tetramer staining. In WT mice, tumor growth delay was achieved by cisplatin (Cis), and this effect was improved in combination with α-GC, but α-GC alone had little effect. Cancer cell proliferation during chemotherapy was significantly inhibited by α-GC, while cancer cell death was significantly upregulated. α-GC following chemotherapy resulted in NKT cell expansion and an increase of interferon-γ production in the draining lymph node, blood and spleen. Gene expression of immune-associated cytokines was upregulated. Strikingly, the percentage of inducible T cell co-stimulator(+)CD4 T cells, Th17/Tc17 cells increased in splenocytes. In CD1d KO mice, however, Cis alone was less effective and Cis + α-GC provided no additional benefit over Cis alone. α-GC alone had minimal effect in both mice. NKT activation between cycles of chemotherapy could improve the outcome of mesothelioma treatment.

Tc17 Cells in Immunity and Systemic Autoimmunity

Tc17 cells-a subset of CD8(+)T cells-have recently been identified that are characterized by the production of interleukin (IL)-17. Cytokines IL-6 and transforming growth factor-beta 1 (TGF-β1) and transcription factors signaling transducers and activators of transcription (STAT)3, retinoic acid receptor-related orphan nuclear receptor gamma (RORγt), and interferon regulatory factor (IRF)4 are necessary for differentiation of Tc17 cells, controlling expression of molecules essential for Tc17 cell trafficking and function. Current human researches have determined the significance of CD161 expression as either a marker of Tc17 cells or as an effector and regulator of Tc17 cell function. Noncytotoxic Tc17 cells possess a high plasticity to convert into IFN-γ producing cells, which exhibit strong cytotoxic activity. The importance of in vivo plasticity of Tc17 cells for the induction of autoimmune diseases has been demonstrated and Tc17 cells potentially represent novel therapeutic targets in autoimmune diseases. The involvement of interleukin (IL)-17-producing CD8(+)T cells (Tc17) in various conditions, such as infection, cancer, and autoimmune inflammation, has been documented in both humans and mice; however, Tc17 cells have received only marginal attention. Here, we provide an overview of the cytokines and chemokines that characterize the murine and human Tc17 cells. Moreover, we discuss signaling pathways, molecular interactions, and transcriptional events that contribute to Tc17 differentiation and acquisition of effector functions. Also considered is the basis of Tc17 cell plasticity toward the Tc1 lineage, and we suggest that in vivo plasticity of Tc17 cells may be a key feature of Tc17 cell biology in autoimmune diseases. Furthermore, current human researches have revealed that Tc17 cells are different than that in mice because all of them express CD161 and exclusively originate from CD161 precursors present in umbilical cord blood. Finally, we focus on the recent evidence for long-lived Tc17 memory cell populations in mouse models and humans, and their functional roles in mediating disease memory. Hopefully, the information obtained will benefit for developing novel therapeutic strategies.

The prevalence and distribution of Th17 and Tc17 cells in patients with thyroid tumor

Both Th17 and Tc17 cells have been found in various tumors and may play important roles in regulating anti-tumor immune responses. However, the prevalence and distribution of Th17 and Tc17 cells in thyroid tumors are still unclear. In the current study, we examined the percentages of Th17 and Tc17 cells in the peripheral blood of 31 thyroid adenoma and 11 thyroid carcinoma patients. The serum IL-17 levels were also examined and their associations with Th17 and Tc17 cells were evaluated. Moreover, the presence of Th17 cells was detected in both thyroid adenoma and carcinoma patients. Our results showed that compared with healthy individuals, patients with thyroid tumors had a higher proportion of Th17 and lower proportion of Tc17 cells in peripheral blood. The serum concentration of IL-17 was significantly increased in patients with thyroid tumors and it was correlated with the percent of Th17 cells. Furthermore, the number of Th17 cells was significantly increased in the tumors of the patients. Th17 and Tc17 cells were negatively correlated with the tumor size. There was no significant difference between thyroid adenoma and carcinoma patients. These results indicate that Th17 cells may contribute to thyroid tumor pathogenesis.

A Listeria vaccine and depletion of T-regulatory cells activate immunity against early stage pancreatic intraepithelial neoplasms and prolong survival of mice

BACKGROUND & AIMS

Premalignant lesions and early stage tumors contain immunosuppressive microenvironments that create barriers for cancer vaccines. Kras(G12D/+);Trp53(R172H/+);Pdx-1-Cre (KPC) mice, which express an activated form of Kras in pancreatic tissues, develop pancreatic intraepithelial neoplasms (PanIN) that progress to pancreatic ductal adenocarcinoma (PDA). We used these mice to study immune suppression in PDA.

METHODS

We immunized KPC and Kras(G12D/+);Pdx-1-Cre mice with attenuated intracellular Listeria monocytogenes (which induces CD4(+) and CD8(+) T-cell immunity) engineered to express Kras(G12D) (LM-Kras). The vaccine was given alone or in sequence with an anti-CD25 antibody (PC61) and cyclophosphamide to deplete T-regulatory (Treg) cells. Survival times were measured; pancreatic and spleen tissues were collected and analyzed by histologic, flow cytometry, and immunohistochemical analyses.

RESULTS

Interferon γ-mediated, CD8(+) T-cell responses were observed in KPC and Kras(G12D/+);Pdx-1-Cre mice given LM-Kras, but not in unvaccinated mice. Administration of LM-Kras to KPC mice 4-6 weeks old (with early stage PanINs), depleted of Treg cells, significantly prolonged survival and reduced PanIN progression (median survival, 265 days), compared with unvaccinated mice (median survival, 150 days; P = .002), mice given only LM-Kras (median survival, 150 days; P = .050), and unvaccinated mice depleted of Treg cells (median survival, 170 days; P = .048). In 8- to 12-week-old mice (with late-stage PanINs), LM-Kras, alone or in combination with Treg cell depletion, did not increase survival time or slow PanIN progression. The combination of LM-Kras and Treg cell depletion reduced numbers of Foxp3(+)CD4(+) T cells in pancreatic lymph nodes, increased numbers of CD4(+) T cells that secrete interleukin 17 and interferon γ, and caused CD11b(+)Gr1(+) cells in the pancreas to acquire an immunostimulatory phenotype.

CONCLUSIONS

Immunization of KPC mice with Listeria monocytogenes engineered to express Kras(G12D), along with depletion of Treg cells, reduces progression of early stage, but not late-stage, PanINs. This approach increases infiltration of the lesion with inflammatory cells. It might be possible to design immunotherapies against premalignant pancreatic lesions to slow or prevent progression to PDA.

CTLA-4 (CD152) enhances the Tc17 differentiation program

Although CD8(+) T cells that produce IL-17 (Tc17 cells) have been linked to host defense, Tc17 cells show reduced cytotoxic activity, which is the characteristic function of CD8(+) T cells. Here, we show that CTLA-4 enhances the frequency of IL-17 in CD8(+) T cells, indicating that CTLA-4 (CD152) specifically promotes Tc17 differentiation. Simultaneous stimulation of CTLA-4(+/+) and CTLA-4(-/-) T cells in cocultures and agonistic CTLA-4 stimulation unambiguously revealed a cell-intrinsic mechanism for IL-17 control by CTLA-4. The quality of CTLA-4-induced Tc17 cells was tested in vivo, utilizing infection with the facultative intracellular bacterium Listeria monocytogenes (LM). Unlike CTLA-4(+/+) Tc17 cells, CTLA-4(-/-) were nearly as efficient as Tc1 CTLA-4(+/+) cells in LM clearance. Additionally, adoptively transferred CTLA-4(-/-) Tc17 cells expressed granzyme B after rechallenge, and produced Tc1 cytokines such as IFN-γ and TNF-α, which strongly correlate with bacterial clearance. CTLA-4(+/+) Tc17 cells demonstrated a high-quality Tc17 differentiation program ex vivo, which was also evident in isolated IL-17-secreting Tc17 cells, with CTLA-4-mediated enhanced upregulation of Tc17-related molecules such as IL-17A, RORγt, and IRF-4. Our results show that CTLA-4 promotes Tc17 differentiation that results in robust Tc17 responses. Its inactivation might therefore represent a central therapeutic target to enhance clearance of infection.

Tc17 cells in patients with uterine cervical cancer

BACKGROUND

The existence of Tc17 cells was recently shown in several types of infectious and autoimmune diseases, but their distribution and functions in uterine cervical cancer (UCC) have not been fully elucidated.

METHODS

The frequency of Tc17 cells in peripheral blood samples obtained from UCC patients, cervical intraepithelial neoplasia (CIN) patients and healthy controls was determined by flow cytometry. Besides, the prevalence of Tc17 cells and their relationships to Th17 cells and Foxp3-expressing T cells as well as microvessels in tissue samples of the patients were assessed by immunohistochemistry staining.

RESULTS

Compared to controls, patients with UCC or CIN had a higher proportion of Tc17 cells in both peripheral blood and cervical tissues, but the level of Tc17 cells in UCC tissues was significantly higher than that in CIN tissues. Besides, the increased level of Tc17 in UCC patients was associated with the status of pelvic lymph node metastases and increased microvessel density. Finally, significant correlations of infiltration between Tc17 cells and Th17 cells or Foxp3-expressing T cells were observed in UCC and CIN tissues.

CONCLUSIONS

This study indicates that Tc17 cell infiltration in cervical cancers is associated with cancer progression accompanied by increased infiltrations of Th17 cells and regulatory T cells as well as promoted tumor vasculogenesis.

Combination of chemotherapy and immunotherapy for colon cancer in China: A meta-analysis

AIM: To investigate whether autologous dendritic cell (DC)-cytokine-induced killer (CIK) cell therapy is able to improve the therapeutic efficacy of chemotherapy in colon cancer.

METHODS: We conducted a systematic review of published papers from the sources of MEDLINE, the Cochrane Central Register of Controlled Trials, EMBASE, the Wanfang Database, the China Science and Technology Periodical Database and China Journal Net. Published data were extracted independently by two authors using predefined database templates. The quality of the data from individual papers was also assessed. The effects of chemotherapy were compared with those of chemotherapy in combination with DC-CIK immunotherapy. The pooled analysis was performed using the data from random or fixed-effect models.

RESULTS: Seven trials matched our inclusion criteria (n = 533). The overall analysis showed significant survival benefit [one-year overall survival (OS), P < 0.0001; two-year OS, P = 0.009; three-year OS, P = 0.002] in favor of DC-CIK immunotherapy combined with chemotherapy. Disease-free survival (DFS) rate was improved after the combination of DC-CIK immunotherapy and chemotherapy (one-year DFS, P < 0.0001; two-year DFS, P = 0.002; three-year DFS, P = 0.02). An improved overall response rate (P = 0.009) was also observed in patients who received DC-CIK therapy. Furthermore, the analysis of T-lymphocyte subsets in peripheral blood indicated that the number of CD4⁺ T cells significantly increased in the DC-CIK plus chemotherapy group (P < 0.05).

CONCLUSION: The combination of DC-CIK immunotherapy and chemotherapy was superior in prolonging the survival time and enhancing immunological responses.