Vgamma9Vdelta2 T cell-mediated recognition of human solid tumors. Potential for immunotherapy of hepatocellular and colorectal carcinomas

Progress of research on γδ T cells in colorectal cancer (Review)

Colorectal cancer (CRC) ranks as the third most prevalent malignancy and second leading cause of cancer‑related fatalities worldwide. Immunotherapy alone or in combination with chemotherapy has a favorable survival benefit for patients with CRC. Unlike αβ T cells, which are prone to drug resistance, γδ T cells do not exhibit major histocompatibility complex restriction and can target tumor cells through diverse mechanisms. Recent research has demonstrated the widespread involvement of Vδ1T, Vδ2T, and γδ T17 cells in tumorigenesis and progression. In the present review, the influence of different factors, including immune checkpoint molecules, the tumor microenvironment and microorganisms, was summarized on the antitumor/protumor effects of these cells, aiming to provide insights for the development of more efficient and less toxic immunotherapy‑based anticancer drugs.

Camelid-derived Tcell engagers harnessing human γδ T cells as promising antitumor immunotherapeutic agents

In the last decade, there has been a surge in developing immunotherapies to enhance the immune system's ability to eliminate tumor cells. Bispecific antibodies known as T cell engagers (TCEs) present an attractive strategy in this pursuit. TCEs aim to guide cytotoxic T cells toward tumor cells, thereby inducing a strong activation and subsequent tumor cell lysis. In this study, we investigated the activity of different TCEs on both conventional alpha-beta (αβ) T cells and unconventional gamma delta (γδ) T cells. TCEs were built using camelid single-domain antibodies (VHHs) targeting the tumor-associated antigen CEACAM5 (CEA), together with T cell receptor chains or a CD3 domain. We show that Vγ9Vδ2 T cells display stronger in vitro antitumor activity than αβ T cells when stimulated with a CD3xCEA TCE. Furthermore, restricting the activation of fresh human peripheral T cells to Vγ9Vδ2 T cells limited the production of protumor factors and proinflammatory cytokines, commonly associated with toxicity in patients. Taken together, our findings provide further insights that γδ T cell-specific TCEs hold promise as specific, effective, and potentially safe molecules to improve antitumor immunotherapies.

From immunomodulation to therapeutic prospects: Unveiling the biology of butyrophilins in cancer

Butyrophilin (BTN) proteins are a type of membrane protein that belongs to the Ig superfamily. They exhibit a high degree of structural similarity to molecules in the B7 family. They fulfill a complex function in regulating immune responses, including immunomodulatory roles, as they influence γδ T cells. The biology of BTN molecules indicates that they are capable of inhibiting the immune system's ability to detect antigens within tumors. A dynamic association between BTN molecules and cellular surfaces is also recognized in specific contexts, influencing their biology. Notably, the dynamism of BTN3A1 is associated with the immunosuppression of T cells or the activation of Vγ9Vδ2 T cells. Cancer immunotherapy relies heavily on T cells to modulate immune function within the intricate interaction of the tumor microenvironment (TME). A significant interaction between the TME and antitumor immunity involves the presence of BTN, which should be taken into account when developing immunotherapy. This review explores potential therapeutic applications of BTN molecules, based on the current understanding of their biology.

Controversial role of γδ T cells in colorectal cancer

Colorectal cancer (CRC) is the third most frequent type of cancer, and the second leading cause of cancer-related deaths worldwide. Current treatments for patients with CRC do not substantially improve the survival and quality of life of patients with advanced CRC, thus necessitating the development of new treatment strategies. The emergence of immunotherapy has revitalized the field, showing great potential in advanced CRC treatment. Owing to the ability of tumor cells to evade the immune system through major histocompatibility complex shedding and heterogeneous and low antigen spreading, only a few patients respond to immunotherapy. γδ T cells have heterogeneous structures and functions, and their key roles in immune regulation, tumor immunosurveillance, and specific primary immune responses have increasingly been recognized. γδ T cells recognize and kill CRC cells efficiently, thus inhibiting tumor progress through various mechanisms. However, γδ T cells can potentially promote tumor development and metastasis. Thus, given this dual role in prognosis, these cells can act as either a "friend" or "foe" of CRC. In this review, we explore the characteristics of γδ T cells and their functions in CRC, highlighting their application in immunotherapy.

Immune Regulatory Networks and Therapy of γδ T Cells in Liver Cancer: Recent Trends and Advancements

The roles of γδ T cells in liver cancer, especially in the potential function of immunotherapy due to their direct cytotoxic effects on tumor cells and secretion of important cytokines and chemokines, have aroused research interest. This review briefly describes the basic characteristics of γδ T cells, focusing on their diverse effects on liver cancer. In particular, different subtypes of γδ T cells have diverse or even opposite effects on liver cancer. We provide a detailed description of the immune regulatory network of γδ T cells in liver cancer from two aspects: immune components and nonimmune components. The interactions between various components in this immune regulatory network are dynamic and pluralistic, ultimately determining the biological effects of γδ T cells in liver cancer. We also integrate the current knowledge of γδ T-cell immunotherapy for liver cancer treatment, emphasizing the potential of these cells in liver cancer immunotherapy.

γδ T cells: Major advances in basic and clinical research in tumor immunotherapy

ABSTRACT

γδ T cells are a kind of innate immune T cell. They have not attracted sufficient attention because they account for only a small proportion of all immune cells, and many basic factors related to these cells remain unclear. However, in recent years, with the rapid development of tumor immunotherapy, γδ T cells have attracted increasing attention because of their ability to exert cytotoxic effects on most tumor cells without major histocompatibility complex (MHC) restriction. An increasing number of basic studies have focused on the development, antigen recognition, activation, and antitumor immune response of γδ T cells. Additionally, γδ T cell-based immunotherapeutic strategies are being developed, and the number of clinical trials investigating such strategies is increasing. This review mainly summarizes the progress of basic research and the clinical application of γδ T cells in tumor immunotherapy to provide a theoretical basis for further the development of γδ T cell-based strategies in the future.

A Bispecific γδ T-cell Engager Targeting EGFR Activates a Potent Vγ9Vδ2 T cell-Mediated Immune Response against EGFR-Expressing Tumors

Vγ9Vδ2 T cells are effector cells with proven antitumor efficacy against a broad range of cancers. This study aimed to assess the antitumor activity and safety of a bispecific antibody directing Vγ9Vδ2 T cells to EGFR-expressing tumors. An EGFR-Vδ2 bispecific T-cell engager (bsTCE) was generated, and its capacity to activate Vγ9Vδ2 T cells and trigger antitumor activity was tested in multiple in vitro, in vivo, and ex vivo models. Studies to explore safety were conducted using cross-reactive surrogate engagers in nonhuman primates (NHP). We found that Vγ9Vδ2 T cells from peripheral blood and tumor specimens of patients with EGFR+ cancers had a distinct immune checkpoint expression profile characterized by low levels of PD-1, LAG-3, and TIM-3. Vγ9Vδ2 T cells could be activated by EGFR-Vδ2 bsTCEs to mediate lysis of various EGFR+ patient-derived tumor samples, and substantial tumor growth inhibition and improved survival were observed in in vivo xenograft mouse models using peripheral blood mononuclear cells (PBMC) as effector cells. EGFR-Vδ2 bsTCEs exerted preferential activity toward EGFR+ tumor cells and induced downstream activation of CD4+ and CD8+ T cells and natural killer (NK) cells without concomitant activation of suppressive regulatory T cells observed with EGFR-CD3 bsTCEs. Administration of fully cross-reactive and half-life extended surrogate engagers to NHPs did not trigger signals in the safety parameters that were assessed. Considering the effector and immune-activating properties of Vγ9Vδ2 T cells, the preclinical efficacy data and acceptable safety profile reported here provide a solid basis for testing EGFR-Vδ2 bsTCEs in patients with EGFR+ malignancies.

Biological characteristics of γδT cells and application in tumor immunotherapy

Human γδT cells are a special immune cell type which exist in small quantities in the body, do not require processing and presentation for antigen recognition, and have non-major histocompatibility complex (MHC)-restricted immune response. They play an important role in the body's anti-tumor, anti-infection, immune regulation, immune surveillance and maintenance of immune tolerance. This article reviews the generation and development of human γδT cells, genetic characteristics, classification, recognition and role of antigens, and research progress in tumor immunotherapy.

Gamma Delta T Cells: Role in Immunotherapy of Hepatocellular Carcinoma

The most typical type of liver cancer or hepatocellular carcinoma (HCC) develops from hepatocyte loss. Non-alcoholic fatty liver disease (NAFLD), viral hepatitis C and cirrhosis are the leading causes of HCC. With the Hepatitis B vaccine and medicines, there are several treatments for HCC, including liver resection, ablation, transplantation, immunotherapy, gene therapy, radiation embolization, and targeted therapy. Currently, a wide range of studies are carried out on gene therapy to identify biomarkers and pathways, which help us identify the exact stage of the disorder and reduce its effects. γδT cells have recently received much interest as a potential cancer treatment method in adaptive immunotherapy. γδT cells can quickly form connections between receptor and ligand activation. They can clonally expand and are a significant source of cytokines and chemokines. The present review provides a comprehensive understanding on the function of γδT cells in immunotherapies and how they are used to treat HCC.

Reducing farnesyl diphosphate synthase levels activates Vγ9Vδ2 T cells and improves tumor suppression in murine xenograft cancer models

Human Vγ9Vδ2 T cells are attractive candidates for cancer immunotherapy due to their potent capacity for tumor recognition and cytolysis of many tumor cell types. However, efforts to deploy clinical strategies for Vγ9Vδ2 T cell cancer therapy are hampered by insufficient potency. We are pursuing an alternate strategy of modifying tumors to increase the capacity for Vγ9Vδ2 T cell activation, as a means for strengthening the anti-tumor response by resident or ex vivo manufactured Vγ9Vδ2 T cells. Vγ9Vδ2 T cells are activated in vitro by non-peptidic antigens including isopentenyl pyrophosphate (IPP), a substrate of farnesyl diphosphate synthase (FDPS) in the pathway for biosynthesis of isoprenoids. In an effort to improve in vivo potency of Vγ9Vδ2 T cells, we reduced FDPS expression in tumor cells using a lentivirus vector encoding a short-hairpin RNA that targets FDPS mRNA (LV-shFDPS). Prostate (PC3) or hepatocellular carcinoma (Huh-7) cells transduced with LV-shFDPS induced Vγ9Vδ2 T cell stimulation in vitro, resulting in increased cytokine expression and tumor cell cytotoxicity. Immune deficient mice implanted with LV-shFDPS transduced tumor cells showed dramatic responses to intraperitoneal injection of Vγ9Vδ2 T cells with strong suppression of tumor growth. In vivo potency was increased by transducing tumor cells with a vector expressing both shFDPS and human IL-2. Tumor suppression by Vγ9Vδ2 T cells was dose-dependent with greater effects observed in mice injected with 100% LV-shFDPS transduced cells compared to mice injected with a mixture of 50% LV-shFDPS transduced cells and 50% control (no vector) tumor cells. Delivery of LV-shFDPS by intratumoral injection was insufficient to knockdown FDPS in the majority of tumor cells, resulting in insignificant tumor suppression by Vγ9Vδ2 T cells. Thus, Vγ9Vδ2 T cells efficiently targeted and suppressed tumors expressing shFDPS in mouse xenotransplant models. This proof-of-concept study demonstrates the potential for suppression of genetically modified tumors by human Vγ9Vδ2 T cells and indicates that co-expression of cytokines may boost the anti-tumor effect.

γδ T Cells in the Tumor Microenvironment-Interactions With Other Immune Cells

A growing number of studies have shown that γδ T cells play a pivotal role in mediating the clearance of tumors and pathogen-infected cells with their potent cytotoxic, cytolytic, and unique immune-modulating functions. Unlike the more abundant αβ T cells, γδ T cells can recognize a broad range of tumors and infected cells without the requirement of antigen presentation via major histocompatibility complex (MHC) molecules. Our group has recently demonstrated parts of the mechanisms of T-cell receptor (TCR)-dependent activation of Vγ9Vδ2+ T cells by tumors following the presentation of phosphoantigens, intermediates of the mevalonate pathway. This process is mediated through the B7 immunoglobulin family-like butyrophilin 2A1 (BTN2A1) and BTN3A1 complexes. Such recognition results in activation, a robust immunosurveillance process, and elicits rapid γδ T-cell immune responses. These include targeted cell killing, and the ability to produce copious quantities of cytokines and chemokines to exert immune-modulating properties and to interact with other immune cells. This immune cell network includes αβ T cells, B cells, dendritic cells, macrophages, monocytes, natural killer cells, and neutrophils, hence heavily influencing the outcome of immune responses. This key role in orchestrating immune cells and their natural tropism for tumor microenvironment makes γδ T cells an attractive target for cancer immunotherapy. Here, we review the current understanding of these important interactions and highlight the implications of the crosstalk between γδ T cells and other immune cells in the context of anti-tumor immunity.

TCR engineered T cells for solid tumor immunotherapy

T cell immunotherapy remains an attractive approach for cancer immunotherapy. T cell immunotherapy mainly employs chimeric antigen receptor (CAR)- and T cell receptor (TCR)-engineered T cells. CAR-T cell therapy has been an essential breakthrough in treating hematological malignancies. TCR-T cells can recognize antigens expressed both on cell surfaces and in intracellular compartments. Although TCR-T cells have not been approved for clinical application, a number of clinical trials have been performed, particularly for solid tumors. In this article, we summarized current TCR-T cell advances and their potential advantages for solid tumor immunotherapy.

Local Ablative Therapy Associated with Immunotherapy in Locally Advanced Pancreatic Cancer: A Solution to Overcome the Double Trouble?-A Comprehensive Review

Pancreatic ductal adenocarcinoma (PDAC) remains a major killer and is a challenging clinical research issue with abysmal survival due to unsatisfactory therapeutic efficacy. Two major issues thwart the treatment of locally advanced nonresectable pancreatic cancer (LAPC): high micrometastasis rate and surgical inaccessibility. Local ablative therapies induce a systemic antitumor response (i.e., abscopal effect) in addition to local effects. Thus, the incorporation of additional therapies could be key to improving immunotherapy's clinical efficacy. In this systematic review, we explore recent applications of local ablative therapies combined with immunotherapy to overcome immune resistance in PDAC and discuss future perspectives and challenges. Particularly, we describe four chemoradiation studies and nine reports on irreversible electroporation (IRE). Clinically, IRE is the ablative therapy of choice, utilized in all but two clinical trials, and may create a favorable microenvironment for immunotherapy. Various immunotherapies have been used in combination with IRE, such as NK cell- or γδ T cell-based therapy, as well as immune checkpoint inhibitors. The results of the clinical trials presented in this review and the advancement potential of these therapies to phase II/III trials remain unknown. A multiple treatment approach involving chemotherapy, local ablation, and immunotherapy holds promise in overcoming the double trouble of LAPC.

When Onco-Immunotherapy Meets Cold Atmospheric Plasma: Implications on CAR-T Therapies

T cells engineered with chimeric antigen receptors (CAR) have demonstrated its widespread efficacy as a targeted immunotherapeutic modality. Yet, concerns on its specificity, efficacy and generalization prevented it from being established into a first-line approach against cancers. By reviewing challenges limiting its clinical application, ongoing efforts trying to resolve them, and opportunities that emerging oncotherapeutic modalities may bring to temper these challenges, we conclude that careful CAR design should be done to avoid the off-tumor effect, enhance the efficacy of solid tumor treatment, improve product comparability, and resolve problems such as differential efficacies of co-stimulatory molecules, cytokine storm, tumor lysis syndrome, myelosuppression and severe hepatotoxicity. As a promising solution, we propose potential synergies between CAR-T therapies and cold atmospheric plasma, an emerging onco-therapeutic strategy relying on reactive species, towards improved therapeutic efficacies and enhanced safety that deserve extensive investigations.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Advances of Tumorigenesis, Diagnosis at Early Stage, and Cellular Immunotherapy in Gastrointestinal Malignancies

Globally, in 2018, 4.8 million new patients have a diagnosis of gastrointestinal (GI) cancers, while 3.4 million people died of such disorders. GI malignancies are tightly relevant to 26% of the world-wide cancer incidence and occupies 35% of all cancer-associated deaths. In this article, we principally investigated molecular and cellular mechanisms of tumorigenesis in five major GI cancers occurring at esophagus, stomach, liver, pancreas, and colorectal region that illustrate high morbidity in Eastern and Western countries. Moreover, through this investigation, we not only emphasize importance of the tumor microenvironment in development and treatment of malignant tumors but also identify significance of M2PK, miRNAs, ctDNAs, circRNAs, and CTCs in early detection of GI cancers, as well as systematically evaluate contribution of personalized precision medicine including cellular immunotherapy, new antigen and vaccine therapy, and oncolytic virotherapy in treatment of GI cancers.

Next Generation Sequencing-Based Identification of T-Cell Receptors for Immunotherapy Against Hepatocellular Carcinoma

Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) remains a global health concern, and HBV proteins may be ideal targets for T cell-based immunotherapy for HCC. There is a need for fast and efficient identification of HBV-specific T cell receptors (TCRs) for the development of TCR-transduced T (TCR-T) cell-based immunotherapy. Two widely employed TCR identification approaches, T cell clonal expansion and single-cell sequencing, involve a TCR singularization process for the direct identification of Vα and Vβ pairs of TCR chains. Clonal expansion of T cells is well known to have tedious time and effort requirements due to the use of T cell cultures, whereas single-cell sequencing is limited by the requirements of cell sorting and the preparation of a single-cell immune-transcriptome library as well as the massive cost of the whole procedure. Here, we present a next-generation sequencing (NGS)-based HBV-specific TCR identification that does not require the TCR singularization process. Conclusion: Two pairing strategies, ranking-based strategy and α-β chain mixture-based strategy, have proved to be useful for NGS-based TCR identification, particularly for polyclonal T cells purified by a peptide-major histocompatibility complex (pMHC) multimer-based approach. Functional evaluation confirmed the specificity and avidity of two identified HBV-specific TCRs, which may potentially be used to produce TCR-T cells to treat patients with HBV-related HCC.

Clinicopathological Correlates of γδ T Cell Infiltration in Triple-Negative Breast Cancer

Simple Summary

The prognostic impact of the different tumor-infiltrating lymphocyte (TIL) subpopulations remains debated in solid cancers. We investigated the clinicopathological correlates and prognostic impact of TILs, particularly of γδ T cells, in 162 triple-negative breast cancer (TNBC) patients. A high γδ T cell density was significantly associated with younger age, higher tumor histological grade, adjuvant chemotherapy, BRCA1 promoter methylation, TIL density, and PD-L1 and PD-1 expression. In multivariate analyses, γδ T cell infiltration was an independent prognostic factor. However, this prognostic impact varied according to the tumor PIK3CA mutational status. High γδ T cell infiltration was associated with better survival in patients with PIK3CA wild-type tumors, without significant difference in the PIK3CA-mutated tumor subgroup. Altogether, these data suggest that high γδ T cell infiltrate is correlated with immune infiltration and might represent a prognostic tool in TNBC patients.

Abstract

The prognostic impact of the different tumor-infiltrating lymphocyte (TIL) subpopulations in solid cancers is still debated. Here, we investigated the clinicopathological correlates and prognostic impact of TILs, particularly of γδ T cells, in 162 patients with triple-negative breast cancer (TNBC). A high γδ T cell density (>6.625 γδ T cells/mm²) was associated with younger age (p = 0.008), higher tumor histological grade (p = 0.002), adjuvant chemotherapy (p = 0.010), BRCA1 promoter methylation (p = 0.010), TIL density (p < 0.001), and PD-L1 (p < 0.001) and PD-1 expression (p = 0.040). In multivariate analyses, γδ T cell infiltration (cutoff = 6.625 γδ T cells/mm²) was an independent prognostic factor (5-year relapse-free survival: 63.3% vs. 89.8%, p = 0.027; 5-year overall survival: 73.8% vs. 89.9%, p = 0.031, for low vs. high infiltration). This prognostic impact varied according to the tumor PIK3CA mutational status. High γδ T cell infiltration was associated with better survival in patients with PIK3CA wild-type tumors, but the difference was not significant in the subgroup with PIK3CA-mutated tumors. Altogether, these data suggest that high γδ T cell infiltrate is correlated with immune infiltration and might represent a candidate prognostic tool in patients with TNBC.

Gut γδ T cells as guardians, disruptors, and instigators of cancer

Colorectal cancer is the third most common cancer worldwide with nearly 2 million cases per year. Immune cells and inflammation are a critical component of colorectal cancer progression, and they are used as reliable prognostic indicators of patient outcome. With the growing appreciation for immunology in colorectal cancer, interest is growing on the role γδ T cells have to play, as they represent one of the most prominent immune cell populations in gut tissue. This group of cells consists of both resident populations-γδ intraepithelial lymphocytes (γδ IELs)-and transient populations that each has unique functions. The homeostatic role of these γδ T cell subsets is to maintain barrier integrity and prevent microorganisms from breaching the mucosal layer, which is accomplished through crosstalk with enterocytes and other immune cells. Recent years have seen a surge in discoveries regarding the regulation of γδ IELs in the intestine and the colon with particular new insights into the butyrophilin family. In this review, we discuss the development, specialities, and functions of γδ T cell subsets during cancer progression. We discuss how these cells may be used to predict patient outcome, as well as how to exploit their behavior for cancer immunotherapy.

Irreversible electroporation plus allogenic Vγ9Vδ2 T cells enhances antitumor effect for locally advanced pancreatic cancer patients

Immunotherapy has limited efficacy against locally advanced pancreatic cancer (LAPC) due to the presence of an immunosuppressive microenvironment (ISM). Irreversible electroporation (IRE) can not only induce immunogenic cell death, but also alleviate immunosuppression. This study aimed to investigate the antitumor efficacy of IRE plus allogeneic γδ T cells in LAPC patients. A total of 62 patients who met the eligibility criteria were enrolled in this trial, then randomized into two groups (A: n = 30 and B: n = 32). All patients received IRE therapy and after receiving IRE, the group A patients received at least two cycles of γδ T-cell infusion as one course continuously. Group A patients had better survival than group B patients (median OS: 14.5 months vs. 11 months; median PFS: 11 months vs. 8.5 months). Moreover, the group A patients treated with multiple courses of γδ T-cell infusion had longer OS (17 months) than those who received a single course (13.5 months). IRE combined with allogeneic γδ T-cell infusion is a promising strategy to enhance the antitumor efficacy in LAPC patients, yielding extended survival benefits.

ClinicalTrials.gov ID: NCT03180437.

Immune Effects of γδ T Cells in Colorectal Cancer: A Review

Gamma delta (γδ) T cells can effectively recognize and kill colorectal cancer (CRC) cells, thereby suppressing tumor progression via multiple mechanisms. They also have abilities to exert a protumor effect via secreting interleukin-17 (IL-17). γδ T cells have been selected as potential immunocytes for antitumor treatment because of their significant cytotoxic activity. Immunotherapy is another potential anti-CRC strategy after an operation, chemotherapy, and radiotherapy. γδ T cell-based immunotherapy for CRC shows fewer side effects and better toleration. This review will outline the immune functions and the mechanisms of γδ T cells in the growth and progression of CRC in recent years, and summarize the immunotherapies based on γδ T cells, thus providing a direction for future γδ T cells in CRC research.

Expansion With IL-15 Increases Cytotoxicity of Vγ9Vδ2 T Cells and Is Associated With Higher Levels of Cytotoxic Molecules and T-bet

Cancer immunotherapy has shown great advances during recent years, but it has yet to reach its full potential in all cancer types. Adoptive cell therapy (ACT) is now an approved treatment option for certain hematological cancers and has also shown success for some solid cancers. Still, benefit and eligibility do not extend to all patients. ACT with Vγ9Vδ2 T cells is a promising approach to overcome this hurdle. In this study, we aimed to explore the effect of different cytokine conditions on the expansion of Vγ9Vδ2 T cells in vitro. We could show that Vγ9Vδ2 T cell expansion is feasible with two different cytokine conditions: (a) 1,000 U/ml interleukin (IL)-2 and (b) 100 U/ml IL-2 + 100 U/ml IL-15. We did not observe differences in expansion rate or Vγ9Vδ2 T cell purity between the conditions; however, IL-2/IL-15-expanded Vγ9Vδ2 T cells displayed enhanced cytotoxicity against tumor cells, also in hypoxia. While this increase in killing capacity was not reflected in natural killer (NK) cell marker or activation marker expression, we demonstrated that IL-2/IL-15-expanded Vγ9Vδ2 T cells were characterized by an increased expression of perforin, granzyme B, and granulysin compared to IL-2-expanded cells. These cytotoxic molecules were not only increased in a resting state, but also released to a greater extent upon target recognition. In contrast, CD107a and cytokine expression did not differ between expansion conditions. However, IL-2/IL-15-expanded Vγ9Vδ2 T cells showed higher levels of transcription factor T-bet expression, which could indicate that T-bet and cytotoxic molecule levels confer the increased cytotoxicity. These results advocate the inclusion of IL-15 into ex vivo Vγ9Vδ2 T cell expansion protocols in future clinical studies.

Beneficial Effect of Antibiotics and Microbial Metabolites on Expanded Vδ2Vγ9 T Cells in Hepatocellular Carcinoma Immunotherapy

Animal experiments and clinical trials have shown that the gut microbiota modulates host immunity and immune checkpoint-mediated responses to tumor cells. However, it remains unclear whether microbiota can also play a role in the tumor immune response of γδT cells, a kind of cell that targets cancer directly. Here, we report that microbiota dysbiosis induced by antibiotics enhanced γδT cell efficacy during tumor therapy in a mouse model. Further microbiota and metabolite analysis revealed that the alteration of γδT cell cytotoxicity might be closely associated with specific metabolites, which are produced by intestinal bacteria and stimulate γδT cells to release more cytotoxic cytokines, such as granzyme B and perforin. Among the metabolites that we analyzed, 3-indopropionic acid (IPA) showed the highest concentration in antibiotic-treated mice and can improve the cytotoxic ability of γδT cells both in vitro and in vivo. Our research determined how the gut microbiota can influence the antitumor ability of γδT cells and identified potential intermediate molecules that connect the gut microbiota and γδT cells.

TIM-3 blockade combined with bispecific antibody MT110 enhances the anti-tumor effect of γδ T cells

As ideal cells that can be used for adoptive cell therapy, γδ T cells are a group of homogeneous cells with high proliferative and tumor killing ability. However, γδ T cells are apt to apoptosis and show decreased cytotoxicity under persistent stimulation in vitro and cannot aggregate at tumor sites efficiently in vivo, both of which are two main obstacles to tumor adoptive immunotherapy. In this study, we found that the immune checkpoint T-cell immunoglobulin domain and mucin domain 3 (TIM-3) were up-regulated significantly on γδ T cells during their ex vivo expansion and this up-regulation contributed to the dysfunction of γδ T cells. Although the killing ability of γδ T cells against breast cancer cells which exhibited a high level of epithelial cell adhesion molecule (EpCAM) was enhanced, the level of TIM-3 on γδ T cells was also further up-regulated under the application of the bispecific antibody MT110 (anti-CD3 × anti-EpCAM) which can redirect T cells to target cells. Besides, these γδ T cells with up-regulated TIM-3 exhibited an increased susceptibility to apoptosis. By reinvigorating dysfunctional γδ T cells and promoting them to accumulate at tumor sites, the combined use of TIM-3 inhibitor and MT110 could further enhance the anti-tumor effect of the adoptively transfused γδ T cells. These results may have clinical implications for the design of new translational anti-tumor regimens aimed at combining checkpoint blockade and immune cell redirection.

Diversity of Tumor-Infiltrating, γδ T-Cell Abundance in Solid Cancers

γδ T-cells contribute to the immune response against many tumor types through their direct cytolytic functions and their capacity to recruit and regulate the biological functions of other immune cells. As potent effectors of the anti-tumor immune response, they are considered an attractive therapeutic target for immunotherapies, but their presence and abundance in the tumor microenvironment are not routinely assessed in patients with cancer. Here, we validated an antibody for immunohistochemistry analysis that specifically detects all γδ T-cell subpopulations in healthy tissues and in the microenvironment of different cancer types. Tissue microarray analysis of breast, colon, ovarian, and pancreatic tumors showed that γδ T-cell density varies among cancer types. Moreover, the abundance of γδ tumor-infiltrating lymphocytes was variably associated with the outcome depending on the cancer type, suggesting that γδ T-cell recruitment is influenced by the context. These findings also suggest that γδ T-cell detection and analysis might represent a new and interesting diagnostic or prognostic marker.

Identification of a regulatory Vδ1 gamma delta T cell subpopulation expressing CD73 in human breast cancer

γδ T cells contribute to the immune response against many cancers, notably through their powerful effector functions that lead to the elimination of tumor cells and the recruitment of other immune cells. However, their presence in the tumor microenvironment has been associated with poor prognosis in breast, colon, and pancreatic cancer, suggesting that γδ T cells may also display pro-tumor activities. Here, we identified in blood from healthy donors a subpopulation of Vδ1T cells that represents around 20% of the whole Vδ1 population, expresses CD73, and displays immunosuppressive phenotype and functions (i.e., production of immunosuppressive molecules, such as IL-10, adenosine, and the chemotactic factor IL-8, and inhibition of αβ T cell proliferation). We then found that in human breast tumors, γδ T cells were present particularly in late stage breast cancer samples, and that ∼20% of tumor-infiltrating γδ T cells expressed CD73. Taken together, these results suggest that regulatory γδ T cells are present in the breast cancer microenvironment and may display immunosuppressive functions through the production of immunosuppressive molecules, such as IL-10, IL-8, and adenosine, thus promoting tumor growth.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Preferential Infiltration of Unique Vγ9Jγ2-Vδ2 T Cells Into Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is clinically highly aggressive as a result of evolutionary dynamics induced by cross-talk between cancer cells and a heterogeneous group of immune cells in tumor microenvironment. The brain harbors limited numbers of immune cells with few lymphocytes and macrophages; thus, innate-like lymphocytes, such as γδ T cells, have important roles in antitumor immunity. Here, we characterized GBM-infiltrating γδ T cells, which may have roles in regulating the GBM tumor microenvironment and cancer cell gene expression. V(D)J repertoires of tumor-infiltrating and blood-circulating γδ T cells from four patients were analyzed by next-generation sequencing-based T-cell receptor (TCR) sequencing in addition to mutation and immune profiles in four GBM cases. In all tumor tissues, abundant innate and effector/memory lymphocytes were detected, accompanied by large numbers of tumor-associated macrophages and closely located tumor-infiltrating γδ T cells, which appear to have anti-tumor activity. The immune-related gene expression analysis using the TCGA database showed that the signature gene expression extent of γδ T cells were more associated with those of cytotoxic T and Th1 cells and M1 macrophages than those of Th2 cells and M2 macrophages. Although the most abundant γδ T cells were Vγ9Vδ2 T cells in both tumor tissues and blood, the repertoire of intratumoral Vγ9Vδ2 T cells was distinct from that of peripheral blood Vγ9Vδ2 T cells and was dominated by Vγ9Jγ2 sequences, not by canonical Vγ9JγP sequences that are mostly commonly found in blood γδ T cells. Collectively, unique GBM-specific TCR clonotypes were identified by comparing TCR repertoires of peripheral blood and intra-tumoral γδ T cells. These findings will be helpful for the elucidation of tumor-specific antigens and development of anticancer immunotherapies using tumor-infiltrating γδ T cells.

In Vivo PET Tracking of 89Zr-Labeled Vγ9Vδ2 T Cells to Mouse Xenograft Breast Tumors Activated with Liposomal Alendronate

Gammadelta T (γδ-T) cells are strong candidates for adoptive immunotherapy in oncology due to their cytotoxicity, ease of expansion, and favorable safety profile. The development of γδ-T cell therapies would benefit from non-invasive cell-tracking methods and increased targeting to tumor sites. Here we report the use of [89Zr]Zr(oxinate)4 to track Vγ9Vδ2 T cells in vivo by positron emission tomography (PET). In vitro, we showed that 89Zr-labeled Vγ9Vδ2 T cells retained their viability, proliferative capacity, and anti-cancer cytotoxicity with minimal DNA damage for amounts of 89Zr ≤20 mBq/cell. Using a mouse xenograft model of human breast cancer, 89Zr-labeled γδ-T cells were tracked by PET imaging over 1 week. To increase tumor antigen expression, the mice were pre-treated with PEGylated liposomal alendronate. Liposomal alendronate, but not placebo liposomes or non-liposomal alendronate, significantly increased the 89Zr signal in the tumors, suggesting increased homing of γδ-T cells to the tumors. γδ-T cell trafficking to tumors occurred within 48 hr of administration. The presence of γδ-T cells in tumors, liver, and spleen was confirmed by histology. Our results demonstrate the suitability of [89Zr]Zr(oxinate)4 as a cell-labeling agent for therapeutic T cells and the potential benefits of liposomal bisphosphonate treatment before γδ-T cell administration.

Allogenic γδ T cell and tumor cell fused vaccine for enhanced immunotherapeutic efficacy of osteosarcoma

Human γδ T cells have displayed their potential in cancer immunity through efficient tumor killing activities. Besides, they are also known for their capacity of antigen presentation. How to improve γδ T cells' immunotherapeutic effect as the cell vaccine is still a great challenge. Herein, we explore the human γδ T cells and tumor cell fused vaccine for enhanced immunotherapeutic efficacy of osteosarcoma. The fusion cell vaccine was prepared by chemical fusion between human γδ T cells and inactive osteosarcoma Saos-2 cells. The fusion process was confirmed by microscopy observation, and flow cytometry analysis further validated the antigen presenting functions of the fusion cells. Moreover, the immunotherapeutic potential of the fusion cells was then verified via cytotoxicity assay and cytokine release detection. Our study provided novel immunotherapeutic strategy for patients with osteosarcoma, which merits further practice in the near future.

Unconventional T Cell Targets for Cancer Immunotherapy

Most studies on the immunotherapeutic potential of T cells have focused on CD8 and CD4 T cells that recognize peptide antigens (Ag) presented by polymorphic major histocompatibility complex (MHC) class I and MHC class II molecules, respectively. However, unconventional T cells, which interact with MHC class Ib and MHC-I like molecules, are also implicated in tumor immunity, although their role therein is unclear. These include unconventional T cells targeting MHC class Ib molecules such as HLA-E and its murine ortholog Qa-1b, natural killer T (NKT) cells, mucosal associated invariant T (MAIT) cells, and γδ T cells. Here, we review the current understanding of the roles of these unconventional T cells in tumor immunity and discuss why further studies into the immunotherapeutic potential of these cells is warranted.

The portal vein as a distinct immunological compartment - A comprehensive immune phenotyping study

Advanced liver diseases are associated with impaired intestinal barrier function, which results in bacterial influx via the portal vein to the liver, causing hepatic and systemic inflammation. Little is known about possible concomitant trafficking of immune cells from the intestines to the liver. We therefore performed a comprehensive immunophenotyping study of the portal venous versus peripheral blood compartment in patients with liver cirrhosis who received a transjugular intrahepatic portosystemic stent shunt (TIPS). Our analysis suggests that the portal vein constitutes a distinct immunological compartment resembling that of the intestines, at least in patients with advanced liver cirrhosis. In detail, significantly lower frequencies of naïve CD4⁺ T cells, monocytes, dendritic cells and Vδ2 T cells were observed in the portal vein, whereas frequencies of activated CD4⁺ and CD8⁺ T cells, as well as of mucosa-associated Vδ1 T cells were significantly higher in portal venous compared to peripheral blood. In conclusion, our data raises interesting questions, e.g. whether liver cirrhosis-associated chronic inflammation of the intestines and portal hypertension promote an influx of activated intestinal immune cells like γδ T cells into the liver.

Checkpoint Blockade Rescues the Repressive Effect of Histone Deacetylases Inhibitors on γδ T Cell Function

Histone deacetylases (HDAC) are one of the key epigenetic modifiers that control chromatin accessibility and gene expression. Their role in tumorigenesis is well established and HDAC inhibitors have emerged as an effective treatment modality. HDAC inhibitors have been investigated for their specific antitumor activities and also clinically evaluated in treatment of various malignancies. In the present study, we have investigated the effect of HDAC inhibitors on the effector functions of human γδ T cells. HDAC inhibitors inhibit the antigen-specific proliferative response of γδ T cells and cell cycle progression. In antigen-activated γδ T cells, the expression of transcription factors (Eomes and Tbet) and effector molecules (perforin and granzyme B) were decreased upon treatment with HDAC inhibitors. Treatment with HDAC inhibitors attenuated the antitumor cytotoxic potential of γδ T cells, which correlated with the enhanced expression of immune checkpoints programmed death-1 (PD-1) and programmed death ligand-1 in γδ T cells. Interestingly, PD-1 blockade improves the antitumor effector functions of HDAC inhibitor-treated γδ T cells, which is reflected in the increased expression of Granzyme B and Lamp-1. This study provides a rationale for designing HDAC inhibitor and immune check point blockade as a combinatorial treatment modality for cancer.

γδ T cells in cancer immunotherapy

γδ T cells are one of the three immune cell types that express antigen receptors. They contribute to lymphoid antitumor surveillance and bridge the gap between innate and adaptive immunity. γδ T cells have the capacity of secreting abundant cytokines and exerting potent cytotoxicity against a wide range of cancer cells. γδ T cells exhibit important roles in immune-surveillance and immune defense against tumors and have become attractive effector cells for cancer immunotherapy. γδ T cells mediate anti-tumor therapy mainly by secreting pro-apoptotic molecules and inflammatory cytokines, or through a TCR-dependent pathway. Recently, γδ T cells are making their way into clinical trials. Some clinical trials demonstrated that γδ T cell-based immunotherapy is well tolerated and efficient. Despite the advantages that could be exploited, there are obstacles have to be addressed for the development of γδ T cell immunotherapies. Future direction for immunotherapy using γδ T cells should focus on overcoming the side effects of γδ T cells and exploring better antigens that help stimulating γδ T cell expansion in vitro.

γδ T cell-mediated individualized immunotherapy for hepatocellular carcinoma considering clinicopathological characteristics and immunosuppressive factors

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer. γδ T cells have been revealed to be promising candidates for immunotherapy in patients with HCC. However, the use of these cells in clinical practice has been demonstrated to be challenging. In the present study, γδ T cells isolated from the peripheral blood of patients with HCC (n=83) and healthy donors (n=15) were characterized. Flow cytometry was used to analyze the proportion, phenotype, tumor-killing capacity and cytokine secretion of regulatory T cells (Tregs) and γδ T17 cells in peripheral blood samples prior to and following amplification. Interleukin (IL)-17A levels in the supernatant was analyzed using an ELISA on days 3, 7, 10 and 14. The in vitro cytotoxicity of γδ T cells was measured using an MTT assay. It was revealed that zoledronate with IL-2 may efficiently expand γδ T cells sourced from the peripheral blood of patients with HCC. The amplification capacity of γδ T cells was associated with the clinicopathological characteristics of patients (clinical stage, levels of AFP and albumin, duration of disease, size and number of tumors, numbers of Tregs and γδ T17 cells, and levels of IL-17A). The proportion of γδ T cells positive for interferon-γ, tumor necrosis factor-α, granzyme B, perforin, and lysosome-associated membrane protein 1 was almost unchanged prior to and following amplification. Following amplification, the in vitro cytotoxicity of γδ T cells also remained unchanged. γδ T17 cells, Tregs and IL-17A levels were not altered during amplification. In summary, following in vitro amplification, circulating γδ T cells were revealed to possess features that may make them suitable for immunotherapy for HCC without increasing immunosuppressive factors. However, immunotherapy should be individualized according to the clinicopathological features of patients.

A bispecific nanobody approach to leverage the potent and widely applicable tumor cytolytic capacity of Vγ9Vδ2-T cells

Though Vγ9Vδ2-T cells constitute only a small fraction of the total T cell population in human peripheral blood, they play a vital role in tumor defense and are therefore of major interest to explore for cancer immunotherapy. Vγ9Vδ2-T cell-based cancer immunotherapeutic approaches developed so far have been generally well tolerated and were able to induce significant clinical responses. However, overall results were inconsistent, possibly due to the fact that these strategies induced systemic activation of Vγ9Vδ2-T cells without preferential accumulation and targeted activation in the tumor. Here we show that a novel bispecific nanobody-based construct targeting both Vγ9Vδ2-T cells and EGFR induced potent Vγ9Vδ2-T cell activation and subsequent tumor cell lysis both in vitro and in an in vivo mouse xenograft model. Tumor cell lysis was independent of KRAS and BRAF tumor mutation status and common Vγ9Vδ2-T cell receptor sequence variations. In combination with the conserved monomorphic nature of the Vγ9Vδ2-TCR and the facile replacement of the tumor-specific nanobody, this immunotherapeutic approach can be applied to a large group of cancer patients.

CD20-Specific Immunoligands Engaging NKG2D Enhance γδ T Cell-Mediated Lysis of Lymphoma Cells

Human γδ T cells are innate-like T cells which are able to kill a broad range of tumour cells and thus may have potential for cancer immunotherapy. The activating receptor natural killer group 2 member D (NKG2D) plays a key role in regulating immune responses driven by γδ T cells. Here, we explored whether recombinant immunoligands consisting of a CD20 single-chain fragment variable (scFv) linked to a NKG2D ligand, either MHC class I chain-related protein A (MICA) or UL16 binding protein 2 (ULBP2), could be employed to engage γδ T cells for tumour cell killing. The two immunoligands, designated MICA:7D8 and ULBP2:7D8, respectively, enhanced cytotoxicity of ex vivo-expanded γδ T cells against CD20-positive lymphoma cells. Both Vδ1 and Vδ2 γδ T cells were triggered by MICA:7D8 or ULBP2:7D8. Killing of CD20-negative tumour cells was not induced by the immunoligands, indicating their antigen specificity. MICA:7D8 and ULBP2:7D8 acted in a dose-dependent manner and induced cytotoxicity at nanomolar concentrations. Importantly, chronic lymphocytic leukaemia (CLL) cells isolated from patients were sensitized by the two immunoligands for γδ T cell cytotoxicity. In a combination approach, the immunoligands were combined with bromohydrin pyrophosphate (BrHPP), an agonist for Vδ2 γδ T cells, which further enhanced the efficacy in target cell killing. Thus, employing tumour-directed recombinant immunoligands which engage NKG2D may represent an attractive strategy to enhance antitumour cytotoxicity of γδ T cells.

The cholesterol metabolite 27 hydroxycholesterol facilitates breast cancer metastasis through its actions on immune cells

Obesity and elevated circulating cholesterol are risk factors for breast cancer recurrence, while the use of statins, cholesterol biosynthesis inhibitors widely used for treating hypercholesterolemia, is associated with improved disease-free survival. Here, we show that cholesterol mediates the metastatic effects of a high-fat diet via its oxysterol metabolite, 27-hydroxycholesterol. Ablation or inhibition of CYP27A1, the enzyme responsible for the rate-limiting step in 27-hydroxycholesterol biosynthesis, significantly reduces metastasis in relevant animal models of cancer. The robust effects of 27-hydroxycholesterol on metastasis requires myeloid immune cell function, and it was found that this oxysterol increases the number of polymorphonuclear-neutrophils and γδ-T cells at distal metastatic sites. The pro-metastatic actions of 27-hydroxycholesterol requires both polymorphonuclear-neutrophils and γδ-T cells, and 27-hydroxycholesterol treatment results in a decreased number of cytotoxic CD8⁺T lymphocytes. Therefore, through its actions on γδ-T cells and polymorphonuclear-neutrophils, 27-hydroxycholesterol functions as a biochemical mediator of the metastatic effects of hypercholesterolemia.High cholesterol is a risk factor for breast cancer recurrence. Here the authors show that cholesterol promotes breast cancer metastasis via its metabolite 27-hydroxycholesterol (27HC) that acts on immune myeloid cells residing at the distal metastatic sites, thus promoting an immune suppressive environment.

Dual Face of Vγ9Vδ2-T Cells in Tumor Immunology: Anti- versus Pro-Tumoral Activities

Vγ9Vδ2-T cells are considered as potent effector cells for tumor immunotherapy through directly killing tumor cells and indirectly regulating other innate and adaptive immune cells to establish antitumoral immunity. The antitumoral activity of Vγ9Vδ2-T cells is governed by a complicated set of activating and inhibitory cell receptors. In addition, cytokine milieu in tumor microenvironment can also induce the pro-tumoral activities and functional plasticity of Vγ9Vδ2-T cells. Here, we review the anti- versus pro-tumoral activities of Vγ9Vδ2-T cells and discuss the mechanisms underlying the recognition, activation, differentiation and regulation of Vγ9Vδ2-T cells in tumor immunosurveillance. The comprehensive understanding of the dual face of Vγ9Vδ2-T cells in tumor immunology may improve the therapeutic efficacy and clinical outcomes of Vγ9Vδ2-T cell-based tumor immunotherapy.

Zoledronic acid renders human M1 and M2 macrophages susceptible to Vδ2+ γδ T cell cytotoxicity in a perforin-dependent manner

Vδ2⁺ T cells are a subpopulation of γδ T cells in humans that are cytotoxic towards cells which accumulate isopentenyl pyrophosphate. The nitrogen-containing bisphosphonate, zoledronic acid (ZA), can induce tumour cell lines to accumulate isopentenyl pyrophosphate, thus rendering them more susceptible to Vδ2⁺ T cell cytotoxicity. However, little is known about whether ZA renders other, non-malignant cell types susceptible. In this study we focussed on macrophages (Mϕs), as these cells have been shown to take up ZA. We differentiated peripheral blood monocytes from healthy donors into Mϕs and then treated them with IFN-γ or IL-4 to generate M1 and M2 Mϕs, respectively. We characterised these Mϕs based on their phenotype and cytokine production and then tested whether ZA rendered them susceptible to Vδ2⁺ T cell cytotoxicity. Consistent with the literature, IFN-γ-treated Mϕs expressed higher levels of the M1 markers CD64 and IL-12p70, whereas IL-4-treated Mϕs expressed higher levels of the M2 markers CD206 and chemokine (C–C motif) ligand 18. When treated with ZA, both M1 and M2 Mϕs became susceptible to Vδ2⁺ T cell cytotoxicity. Vδ2⁺ T cells expressed perforin and degranulated in response to ZA-treated Mϕs as shown by mobilisation of CD107a and CD107b to the cell surface. Furthermore, cytotoxicity towards ZA-treated Mϕs was sensitive—at least in part—to the perforin inhibitor concanamycin A. These findings suggest that ZA can render M1 and M2 Mϕs susceptible to Vδ2⁺ T cell cytotoxicity in a perforin-dependent manner, which has important implications regarding the use of ZA in cancer immunotherapy.

Tuning cancer fate: the unremitting role of host immunity

Host immunity plays a central and complex role in dictating tumour progression. Solid tumours are commonly infiltrated by a large number of immune cells that dynamically interact with the surrounding microenvironment. At first, innate and adaptive immune cells successfully cooperate to eradicate microcolonies of transformed cells. Concomitantly, surviving tumour clones start to proliferate and harness immune responses by specifically hijacking anti-tumour effector mechanisms and fostering the accumulation of immunosuppressive immune cell subsets at the tumour site. This pliable interplay between immune and malignant cells is a relentless process that has been concisely organized in three different phases: elimination, equilibrium and escape. In this review, we aim to depict the distinct immune cell subsets and immune-mediated responses characterizing the tumour landscape throughout the three interconnected phases. Importantly, the identification of key immune players and molecules involved in the dynamic crosstalk between tumour and immune system has been crucial for the introduction of reliable prognostic factors and effective therapeutic protocols against cancers.

Enhancing adoptive cancer immunotherapy with Vγ2Vδ2 T cells through pulse zoledronate stimulation

Background

Human γδ T cells expressing Vγ2Vδ2 T cell receptors monitor foreign- and self-prenyl pyrophosphate metabolites in isoprenoid biosynthesis to mediate immunity to microbes and tumors. Adoptive immunotherapy with Vγ2Vδ2 T cells has been used to treat cancer patients with partial and complete remissions. Most clinical trials and preclinical studies have used continuous zoledronate exposure to expand Vγ2Vδ2 cells where zoledronate is slowly diluted over the course of the culture. Zoledronate inhibits farnesyl diphosphate synthase (FDPS) in monocytes causing isopentenyl pyrophosphate to accumulate that then stimulates Vγ2Vδ2 cells. Because zoledronate inhibition of FDPS is also toxic for T cells, we hypothesized that a short period of exposure would reduce T cell toxicity but still be sufficient for monocytes uptake. Additionally, IL-15 increases the anti-tumor activity of murine αβ T cells in mice but its effect on the in vivo anti-tumor activity of human Vγ2Vδ2 cells has not been assessed.

Methods

Human Vγ2Vδ2 T cells were expanded by pulse or continuous zoledronate stimulation with IL-2 or IL-15. Expanded Vγ2Vδ2 cells were tested for their expression of effector molecules and killing of tumor cells as well as their in vivo control of human prostate cancer tumors in immunodeficient NSG mice.

Results

Pulse zoledronate stimulation with either IL-2 or IL-15 resulted in more uniform expansion of Vγ2Vδ2 cells with higher purity and cell numbers as compared with continuous exposure. The Vγ2Vδ2 cells had higher levels of CD107a and perforin and increased tumor cytotoxicity. Adoptive immunotherapy with Vγ2Vδ2 cells derived by pulse stimulation controlled human PC-3 prostate cancer tumors in NSG mice significantly better than those derived by continuous stimulation, halting tumor growth. Although pulse zoledronate stimulation with IL-15 preserved early memory subsets, adoptive immunotherapy with IL-15-derived Vγ2Vδ2 cells equally inhibited PC-3 tumor growth as those derived with IL-2.

Conclusions

Pulse zoledronate stimulation maximizes the purity, quantity, and quality of expanded Vγ2Vδ2 cells for adoptive immunotherapy but there is no advantage to using IL-15 over IL-2 in our humanized mouse model. Pulse zoledronate stimulation is a simple modification to existing protocols that will enhance the effectiveness of adoptively transferred Vγ2Vδ2 cells by increasing their numbers and anti-tumor activity.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-017-0209-6) contains supplementary material, which is available to authorized users.

Zoledronate can induce colorectal cancer microenvironment expressing BTN3A1 to stimulate effector γδ T cells with antitumor activity

Amino-bis-phosphonates (N-BPs) such as zoledronate (Zol) have been used in anticancer clinical trials due to their ability to upregulate pyrophosphate accumulation promoting antitumor Vγ9Vδ2 T cells. The butyrophilin 3A (BTN3A, CD277) family, mainly the BTN3A1 isoform, has emerged as an important structure contributing to Vγ9Vδ2 T cells stimulation. It has been demonstrated that the B30.2 domain of BTN3A1 can bind phosphoantigens (PAg) and drive the activation of Vγ9Vδ2 T cells through conformational changes of the extracellular domains. Moreover, BTN3A1 binding to the cytoskeleton, and its consequent membrane stabilization, is crucial to stimulate the PAg-induced tumor cell reactivity by human Vγ9Vδ2 T cells. Aim of this study was to investigate the relevance of BTN3A1 in N-BPs-induced antitumor response in colorectal cancer (CRC) and the cell types involved in the tumor microenvironment. In this paper, we show that (i) CRC, exposed to Zol, stimulates the expansion of Vδ2 T lymphocytes with effector memory phenotype and antitumor cytotoxic activity, besides sensitizing cancer cells to γδ T cell-mediated cytotoxicity; (ii) this effect is partially related to BTN3A1 expression and in particular with its cellular re-distribution in the membrane and cytoskeleton-associated fraction; (iii) BTN3A1 is detected in CRC at the tumor site, both on epithelial cells and on tumor-associated fibroblasts (TAF), close to areas infiltrated by Vδ2 T lymphocytes; (iv) Zol is effective in stimulating antitumor effector Vδ2 T cells from ex-vivo CRC cell suspensions; and (v) both CRC cells and TAF can be primed by Zol to trigger Vδ2 T cells.

Prevention of Vγ9Vδ2 T Cell Activation by a Vγ9Vδ2 TCR Nanobody

Vγ9Vδ2 T cell activation plays an important role in antitumor and antimicrobial immune responses. However, there are conditions in which Vγ9Vδ2 T cell activation can be considered inappropriate for the host. Patients treated with aminobisphosphonates for hypercalcemia or metastatic bone disease often present with a debilitating acute phase response as a result of Vγ9Vδ2 T cell activation. To date, no agents are available that can clinically inhibit Vγ9Vδ2 T cell activation. In this study, we describe the identification of a single domain Ab fragment directed to the TCR of Vγ9Vδ2 T cells with neutralizing properties. This variable domain of an H chain-only Ab (VHH or nanobody) significantly inhibited both phosphoantigen-dependent and -independent activation of Vγ9Vδ2 T cells and, importantly, strongly reduced the production of inflammatory cytokines upon stimulation with aminobisphosphonate-treated cells. Additionally, in silico modeling suggests that the neutralizing VHH binds the same residues on the Vγ9Vδ2 TCR as the Vγ9Vδ2 T cell Ag-presenting transmembrane protein butyrophilin 3A1, providing information on critical residues involved in this interaction. The neutralizing Vγ9Vδ2 TCR VHH identified in this study might provide a novel approach to inhibit the unintentional Vγ9Vδ2 T cell activation as a consequence of aminobisphosphonate administration.

Highly specific and potently activating Vγ9Vδ2-T cell specific nanobodies for diagnostic and therapeutic applications

Vγ9Vδ2-T cells constitute the predominant subset of γδ-T cells in human peripheral blood and have been shown to play an important role in antimicrobial and antitumor immune responses. Several efforts have been initiated to exploit these cells for cancer immunotherapy, e.g. by using phosphoantigens, adoptive cell transfer, and by a bispecific monoclonal antibody based approach. Here, we report the generation of a novel set of Vγ9Vδ2-T cell specific VHH (or nanobody). VHH have several advantages compared to conventional antibodies related to their small size, stability, ease of generating multispecific molecules and low immunogenicity. With high specificity and affinity, the anti-Vγ9Vδ2-T cell receptor VHHs are shown to be useful for FACS, MACS and immunocytochemistry. In addition, some VHH were found to specifically activate Vγ9Vδ2-T cells. Besides being of possible immunotherapeutic value, these single domain antibodies will be of great value in the further study of this important immune effector cell subset.

Regulatory and effector functions of gamma-delta (γδ) T cells and their therapeutic potential in adoptive cellular therapy for cancer

γδ T cells are an important innate immune component of the tumor microenvironment and are known to affect the immune response in a wide variety of tumors. Unlike αβ T cells, γδ T cells are capable of spontaneous secretion of IL-17A and IFN-γ without undergoing clonal expansion. Although γδ T cells do not require self-MHC-restricted priming, they can distinguish "foreign" or transformed cells from healthy self-cells by using activating and inhibitory killer Ig-like receptors. γδ T cells were used in several clinical trials to treat cancer patient due to their MHC-unrestricted cytotoxicity, ability to distinguish transformed cells from normal cells, the capacity to secrete inflammatory cytokines and also their ability to enhance the generation of antigen-specific CD8(+) and CD4(+) T cell response. In this review, we discuss the effector and regulatory function of γδ T cells in the tumor microenvironment with special emphasis on the potential for their use in adoptive cellular immunotherapy.

Hepatocellular carcinoma cell sensitivity to Vγ9Vδ2 T lymphocyte-mediated killing is increased by zoledronate

The limited efficacy of vaccines in hepatocellular carcinoma (HCC), due to the low frequency of tumor-infiltrating cytotoxic T lymphocytes (CTLs), indicates the importance of innate immune surveillance, which assists acquired immunity by directly recognizing and eliminating HCC. Innate Vγ9Vδ2 T cells have major histocompatibility complex-unrestricted antitumor activity and are activated by phosphoantigens, which are upregulated in cancer cells by the nitrogen-containing bisphosphonate, zoledronate (Zol). A better understanding of HCC susceptibility to Zol and downstream γδ T cell-mediated killing is essential to optimize γδ T cell-mediated immunotherapy. This study systematically examined the interactions between γδ T cells and Zol-treated HCC cell lines (HepG2, HLE, HLF, HuH-1, JHH5, JHH7, and Li-7) in vitro. All HCC cell lines expressed the DNAX accessory molecule-1 ligands, poliovirus receptor, and Nectin-2, and γδ T cell-mediated killing of these cells was significantly enhanced by Zol. Small interfering RNA-mediated knockdown of these ligands did not affect the susceptibility to γδ T cell lysis. This killing activity was partly inhibited by mevastatin, an inhibitor of the mevalonate pathway, and markedly reduced by a monoclonal antibody to γ- and δ-chain T cell receptor, indicating that this is crucial for Zol-induced HCC killing. In addition, Zol-treated HCC cell lines triggered γδ T cell proliferation and induced production of Th1 and Th2, but not Th17, cytokines. The Zol concentration that enhanced HCC cell susceptibility to γδ T cell killing was lower than that required to directly inhibit HCC proliferation. Thus, γδ T cells may be important effector cells in the presence of Zol, especially where there are insufficient number of cancer antigen-specific CTLs to eliminate HCC. Our in vitro data support the proposal that Zol-treatment, combined with adaptive γδ T cell immunotherapy, may provide a feasible and effective approach for treatment of HCC.

A promising sword of tomorrow: Human γδ T cell strategies reconcile allo-HSCT complications

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is potentially a curative therapeutic option for hematological malignancies. In clinical practice, transplantation associated complications greatly affected the final therapeutical outcomes. Currently, primary disease relapse, graft-versus-host disease (GVHD) and infections remain the three leading causes of a high morbidity and mortality in allo-HSCT patients. Various strategies have been investigated in the past several decades including human γδ T cell-based therapeutical regimens. In different microenvironments, human γδ T cells assume features reminiscent of classical Th1, Th2, Th17, NKT and regulatory T cells, showing diverse biological functions. The cytotoxic γδ T cells could be utilized to target relapsed malignancies, and recently regulatory γδ T cells are defined as a novel implement for GVHD management. In addition, human γδ Τ cells facilitate control of post-transplantation infections and participate in tissue regeneration and wound healing processes. These features potentiate γδ T cells a versatile therapeutical agent to target transplantation associated complications. This review focuses on insights of applicable potentials of human γδ T cells reconciling complications associated with allo-HSCT. We believe an improved understanding of pertinent γδ T cell functions would be further exploited in the design of innovative immunotherapeutic approaches in allo-HSCT, to reduce mortality and morbidity, as well as improve quality of life for patients after transplantation.

Immunity, tolerance and autoimmunity in the liver: A comprehensive review

The hepatic immune system is constantly exposed to a massive load of harmless dietary and commensal antigens, to which it must remain tolerant. Immune tolerance in the liver is mediated by a number of specialized antigen-presenting cells, including dendritic cells, Kupffer cells, liver sinusoidal endothelial cells and hepatic stellate cells. These cells are capable of presenting antigens to T cells leading to T cell apoptosis, anergy, or differentiation into regulatory T cells. However, the hepatic immune system must also be able to respond to pathogens and tumours and therefore must be equipped with mechanisms to override immune tolerance. The liver is a site of accumulation of a number of innate lymphocyte populations, including natural killer cells, CD56(+) T cells, natural killer T cells, γδ T cells, and mucosal-associated invariant T cells. Innate lymphocytes recognize conserved metabolites derived from microorganisms and host cells and respond by killing target cells or promoting the differentiation and/or activation of other cells of the immune system. Innate lymphocytes can promote the maturation of antigen-presenting cells from their precursors and thereby contribute to the generation of immunogenic T cell responses. These cells may be responsible for overriding hepatic immune tolerance to autoantigens, resulting in the induction and maintenance of autoreactive T cells that mediate liver injury causing autoimmune liver disease. Some innate lymphocyte populations can also directly mediate liver injury by killing hepatocytes or bile duct cells in murine models of hepatitis, whilst other populations may protect against liver disease. It is likely that innate lymphocyte populations can promote or protect against autoimmune liver disease in humans and that these cells can be targeted therapeutically. Here I review the cellular mechanisms by which hepatic antigen-presenting cells and innate lymphocytes control the balance between immunity, tolerance and autoimmunity in the liver.

γδ T cells as a potential tool in colon cancer immunotherapy

γδ T cells are capable of recognizing tumor cells and exert potent cellular cytotoxicity against a large range of tumors, including colon cancer. However, tumors utilize numerous strategies to escape recognition or killing by patrolling γδ T cells, such a downregulation of NKG2D ligands, MICA/B and ULBPs. Therefore, the combined upregulation of T-cell receptorand NKG2D ligands on tumor cells and induction of NKG2D expression on γδ T cells may greatly enhance tumor killing and unlock the functions of γδ T cells. Here, we briefly review current data on the mechanisms of γδ T-cell recognition and killing of colon cancer cells and propose that γδ T cells may represent a promising target for the design of novel and highly innovative immunotherapy in patients with colon cancer.