γδ T cells for cancer immunotherapy: A systematic review of clinical trials

Gamma delta T cells in acute myeloid leukemia: biology and emerging therapeutic strategies

γδ T cells play an important role in disease control in acute myeloid leukemia (AML) and have become an emerging area of therapeutic interest. These cells represent a minor population of T lymphocytes with intrinsic abilities to recognize antigens in a major histocompatibility complex-independent manner and functionally straddle the innate and adaptive immunity interface. AML shows high expression of phosphoantigens and UL-16 binding proteins that activate the Vδ2 and Vδ1 subtypes of γδ T cells, respectively, leading to γδ T cell-mediated cytotoxicity. Insights from murine models and clinical data in humans show improved overall survival, leukemia-free survival, reduced risk of relapse, enhanced graft-versus-leukemia effect, and decreased graft-versus-host disease in patients with AML who have higher reconstitution of γδ T cells following allogeneic hematopoietic stem cell transplantation. Clinical trials leveraging γδ T cell biology have used unmodified and modified allogeneic cells as well as bispecific engagers and monoclonal antibodies. In this review, we discuss γδ T cells' biology, roles in cancer and AML, and mechanisms of immune escape and antileukemia effect; we also discuss recent clinical advances related to γδ T cells in the field of AML therapeutics.

Immunotherapy Innovations in the Fight against Osteosarcoma: Emerging Strategies and Promising Progress

Immunosuppressive elements within the tumor microenvironment are the primary drivers of tumorigenesis and malignant advancement. The presence, as well as the crosstalk between myeloid-derived suppressor cells (MDSCs), osteosarcoma-associated macrophages (OS-Ms), regulatory T cells (Tregs), and endothelial cells (ECs) with osteosarcoma cells cause the poor prognosis of OS. In addition, the consequent immunosuppressive factors favor the loss of treatment potential. Nanoparticles offer a means to dynamically and locally manipulate immuno-nanoparticles, which present a promising strategy for transforming OS-TME. Additionally, chimeric antigen receptor (CAR) technology is effective in combating OS. This review summarizes the essential mechanisms of immunosuppressive cells in the OS-TME and the current immune-associated strategies. The last part highlights the limitations of existing therapies and offers insights into future research directions.

γδ T cells mediate robust anti-HIV functions during antiretroviral therapy regardless of immune checkpoint expression

Objectives

Although antiretroviral therapy (ART) efficiently suppresses HIV viral load, immune dysregulation and dysfunction persist in people living with HIV (PLWH). γδ T cells are functionally impaired during untreated HIV infection, but the extent to which they are reconstituted upon ART is currently unclear.

Methods

Utilising a cohort of ART-treated PLWH, we assessed the frequency and phenotype, characterised in vitro functional responses and defined the impact of immune checkpoint marker expression on effector functions of both Vδ1 and Vδ2 T cells. We additionally explore the in vitro expansion of Vδ2 T cells from PLWH on ART and the mechanisms by which such expanded cells may sense and kill HIV-infected targets.

Results

A matured NK cell-like phenotype was observed for Vδ1 T cells among 25 ART-treated individuals (PLWH/ART) studied compared to 17 HIV-uninfected controls, with heightened expression of 2B4, CD160, TIGIT and Tim-3. Despite persistent phenotypic perturbations, Vδ1 T cells from PLWH/ART exhibited strong CD16-mediated activation and degranulation, which were suppressed upon Tim-3 and TIGIT crosslinking. Vδ2 T cell degranulation responses to the phosphoantigen (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate at concentrations up to 2 ng mL-1 were significantly impaired in an immune checkpoint-independent manner among ART-treated participants. Nonetheless, expanded Vδ2 T cells from PLWH/ART retained potent anti-HIV effector functions, with the NKG2D receptor contributing substantially to the elimination of infected cells.

Conclusion

Our findings highlight that although significant perturbations remain within the γδ T cell compartment throughout ART-treated HIV, both subsets retain the capacity for robust anti-HIV effector functions.

Gamma/delta T cells as cellular vehicles for anti-tumor immunity

Adoptive cellular immunotherapy as a new paradigm to treat cancers is exemplified by the FDA approval of six chimeric antigen receptor-T cell therapies targeting hematological malignancies in recent years. Conventional αβ T cells applied in these therapies have proven efficacy but are confined almost exclusively to autologous use. When infused into patients with mismatched human leukocyte antigen, αβ T cells recognize tissues of such patients as foreign and elicit devastating graft-versus-host disease. Therefore, one way to overcome this challenge is to use naturally allogeneic immune cell types, such as γδ T cells. γδ T cells occupy the interface between innate and adaptive immunity and possess the capacity to detect a wide variety of ligands on transformed host cells. In this article, we review the fundamental biology of γδ T cells, including their subtypes, expression of ligands, contrasting roles in and association with cancer prognosis or survival, as well as discuss the gaps in knowledge pertaining to this cell type which we currently endeavor to elucidate. In addition, we propose how to harness the unique properties of γδ T cells for cellular immunotherapy based on lessons gleaned from past clinical trials and provide an update on ongoing trials involving these cells. Lastly, we elaborate strategies that have been tested or can be explored to improve the anti-tumor activity and durability of γδ T cells in vivo.

A retrospective cohort study of the impact of peripheral blood gamma- delta T cells to prognosis of nonmetastatic renal cell cancer after curative resection

AIM

Gamma-delta-T cells (γδT) have potential antitumor roles and have recently been applied in adoptive immunotherapy. In the present study, we focused on the proportion of γδT cells in the peripheral blood just before surgery for renal cell cancer (RCC) and investigated whether their proportion affected recurrence-free survival (RFS) and overall survival (OS) retrospectively.

PATIENTS AND METHODS

A total of 137 patients with localized, non-metastatic RCC who received surgery at our institutes were analyzed retrospectively. The patients were divided into 2 groups: normal and low γδT cell groups based on the proportion of peripheral blood γδT cells. Kaplan-Meier curves were constructed to access the association of the proportion of peripheral blood γδT cells to RFS and OS. Cox regression were also constructed to access the risks to prognosis. Uni- and multivariate logistic regressions were performed to access associations between risk factors and, RFS and OS.

RESULTS

Among 137 patients, 40 had a proportion of γδT cells in peripheral blood of less than 1%, which was below the normal range. The remaining 97 patients had these cells in peripheral blood at 1% or higher. In the groups with low γδT cells, 13 patients had recurrences, and 9 patients dies during the observation period. In the groups with normal γδT cells, 16 patients had recurrences, and 8 patients died. The normal γδT cell group demonstrated significantly better prognosis in terms of RFS and OS. Multivariate analysis revealed that a low hemoglobin level, a low proportion of γδT cells, and a high pathological T stage (pT) were statistically independent risk factors for RFS. Age, albumin, C-reactive protein (CRP), % γδT cells, and pT were statistically significant factors affecting OS and only pT was an independent risk factor by multivariate analysis.

CONCLUSION

A low proportion of γδT cells was identified as one of the risk factors for RFS. Our findings will provide clues to develop strategies for early intervention in preventing recurrence even after complete resection of RCC and, such as adoptive immunotherapy using autologous γδT cells in patients with a low proportion of γδT cells.

Adoptive cell therapy in paediatric extracranial solid tumours: current approaches and future challenges

Immunotherapy has ignited hope to cure paediatric solid tumours that resist traditional therapies. Among the most promising methods is adoptive cell therapy (ACT). Particularly, ACT using T cells equipped with chimeric antigen receptors (CARs) has moved into the spotlight in clinical studies. However, the efficacy of ACT is challenged by ACT-intrinsic factors, like lack of activation or T cell exhaustion, as well as immune evasion strategies of paediatric solid tumours, such as their highly immunosuppressive microenvironment. Novel strategies, including ACT using innate-like lymphocytes, innovative cell engineering techniques, and ACT combination therapies, are being developed and will be crucial to overcome these challenges. Here, we discuss the main classes of ACT for the treatment of paediatric extracranial solid tumours, reflect on the available preclinical and clinical evidence supporting promising strategies, and address the challenges that ACT is still facing. Ultimately, we highlight state-of-the-art developments and opportunities for new therapeutic options, which hold great potential for improving outcomes in this challenging patient population.

CD4-/CD8- double-negative tumor-infiltrating lymphocytes expanded from solid tumor tissue suppress the proliferation of tumor cells in an MHC-independent way

PURPOSE

Tumor-infiltrating lymphocytes (TILs) have shown remarkable clinical responses in some patients with advanced solid tumors. As a rare subset of TILs, CD4^-/CD8^- double-negative T cells (DNTs) were poorly known. This study aims to investigate the characteristics and function of CD3⁺CD4^-CD8^- TILs (double-negative TIL, DN-TILs) derived from solid tumor.

METHODS

DN-TILs were derived and expanded ex vivo from resected gastric carcinoma tissue and phenotyped by flow cytometry. The cytotoxicity of DN-TILs was determined against established tumor cell lines in vitro or through in vivo adoptive transfer into xenograft models. K562 cells were transferred with the HLA gene to verify whether the cytotoxicity of DN-TILs was MHC-independent.

RESULTS

Flow cytometric analysis revealed a high-purity population of DN-TILs (> 97%) within CD3⁺ TILs, which expanded more than 800-folds in 2 weeks, consisting of a mixture of alpha-beta (αβ) and gamma-delta (γδ) T-cell receptor (TCR)-expressing cells (with the majority being αβ-TCR, > 95%). Using single-cell RNA sequencing, the expanded DN-TILs were categorized into four main subsets, Natural Killer T cells (approximately 80%, 5563 in 7028), Progenitor cells, Germ cells and T helper2 cells. DN-TILs exhibited a broad anticancer cytotoxicity in a donor-unrestricted manner against various cancer cell lines derived from pancreatic cancer (Panc-1), gastric cancer (HGC-27), ovarian cancer (SKOV-3), malignant melanoma (A375). The cytotoxicity was MHC-independent, which was not altered in K562 transferring with HLA gene or not. DN-TILs significantly reduced tumor volume in xenograft models with superior tumor-homing ability and low off-target toxicity.

CONCLUSION

Gastric carcinoma derived DN-TIL can target tumor cells in vitro and in vivo. DN-TILs have the potential to be used as a adoptive cell therapy for solid cancers with both the advantages of DNT and TIL.

New cell sources for CAR-based immunotherapy

Chimeric antigen receptor (CAR) T cell therapy, in which a patient's own T lymphocytes are engineered to recognize and kill cancer cells, has achieved striking success in some hematological malignancies in preclinical and clinical trials, resulting in six FDA-approved CAR-T products currently available in the market. Despite impressive clinical outcomes, concerns about treatment failure associated with low efficacy or high cytotoxicity of CAR-T cells remain. While the main focus has been on improving CAR-T cells, exploring alternative cellular sources for CAR generation has garnered growing interest. In the current review, we comprehensively evaluated other cell sources rather than conventional T cells for CAR generation.

A Phase I Trial of Allogeneic γδ T Lymphocytes From Haploidentical Donors in Patients With Refractory or Relapsed Acute Myeloid Leukemia

Introduction We report the results of a phase I clinical trial NCT03790072 of an adoptive transfer of γδ T lymphocytes from haploidentical donors in patients with refractory/relapsed acute myeloid leukemia after lymphodepletion regimen. Patients and methods Healthy donor mononuclear cells collected by leukapheresis were consistently expanded to generate products of 10⁹ to 10¹⁰ γδ T cells. Seven patients received donor-derived T cell product at doses of 10⁶/kg (n = 3), 10⁷/kg (n = 3), and 10⁸/kg (n = 1). Results Four patients had bone marrow evaluation at day 28. One patient had a complete remission, one was classified as morphologic leukemia-free state, one had stable disease and one had no evidence of response. In one patient, there was evidence of disease control with repeat infusions up to 100 days after first dosing. There were no treatment-related serious adverse events or treatment-related Common Terminology Criteria for Adverse Events grade 3 or greater toxicities at any dose level. Allogeneic Vγ9Vδ2 T cell infusion was shown to be safe and feasible up to a cell dose of 10⁸/kg. Discussion In agreement with previously published studies, the infusion of allogeneic Vγ9Vδ2 cells was safe. The contribution of lymphodepleting chemotherapy to responses seen cannot be ruled out. Main limitation of the study is the low number of patients and interruption due to COVID-19 pandemic. Conclusion These positive Phase 1 results support progression to phase II clinical trials.

Large Scale Ex Vivo Expansion of γδ T cells Using Artificial Antigen-presenting Cells

Higher γδ T cell counts in patients with malignancies are associated with better survival. However, γδ T cells are rare in the blood and functionally impaired in patients with malignancies. Promising results are reported on the treatment of various malignancies with in vivo expansion of autologous γδ T cells using zoledronic acid (zol) and interleukin-2 (IL-2). Here we demonstrated that zol and IL-2, in combination with a novel genetically engineered K-562 CD3scFv/CD137L/CD28scFv/IL15RA quadruplet artificial antigen-presenting cell (aAPC), efficiently expand allogeneic donor-derived γδ T cells using a Good Manufacturing Practice (GMP) compliant protocol sufficient to achieve cell doses for future clinical use. We achieved a 633-fold expansion of γδ T cells after day 10 of coculture with aAPC, which exhibited central (47%) and effector (43%) memory phenotypes. In addition, >90% of the expanded γδ T cells expressed NKG2D, although they have low cell surface expression of PD1 and LAG3 inhibitory checkpoint receptors. In vitro real-time cytotoxicity analysis showed that expanded γδ T cells were effective in killing target cells. Our results demonstrate that large-scale ex vivo expansion of donor-derived γδ T cells in a GMP-like setting can be achieved with the use of quadruplet aAPC and zol/IL-2 for clinical application.

Increased PD-1+Foxp3+ γδ T cells associate with poor overall survival for patients with acute myeloid leukemia

Problems

γδ T cells are essential for anti-leukemia function in immunotherapy, however, γδ T cells have different functional subsets, including regulatory cell subsets expressing the Foxp3. Whether they are correlated with immune-checkpoint mediated T cell immune dysfunction remains unknown in patients with acute myeloid leukemia (AML).

Methods

In this study, we used RNA-seq data from 167 patients in TCGA dataset to analyze the correlation between PD-1 and FOXP3 genes and these two genes' association with the prognosis of AML patients. The expression proportion of Foxp3⁺/PD-1⁺ cells in γδ T cells and two subgroups Vδ1 and Vδ2 T cells were performed by flow cytometry. The expression level of FOXP3 and PD-1 genes in γδ T cells were sorted from peripheral blood by MACS magnetic cell sorting technique were analyzed by quantitative real-time PCR.

Results

We found that PD-1 gene was positively correlated with FOXP3 gene and highly co-expressed PD-1 and FOXP3 genes were associated with poor overall survival (OS) from TCGA database. Then, we detected a skewed distribution of γδ T cells with increased Vδ1 and decreased Vδ2 T cell subsets in AML. Moreover, significantly higher percentages of PD-1⁺ γδ, Foxp3⁺ γδ, and PD-1⁺Foxp3⁺ γδ T cells were detected in de novo AML patients compared with healthy individuals. More importantly, AML patients containing higher PD-1⁺Foxp3⁺ γδ T cells had lower OS, which might be a potential therapeutic target for leukemia immunotherapy.

Conclusion

A significant increase in the PD-1⁺Foxp3⁺ γδ T cell subset in AML was associated with poor clinical outcome, which provides predictive value for the study of AML patients.

Positron Emission Tomography Probes for Imaging Cytotoxic Immune Cells

Non-invasive positron emission tomography (PET) imaging of immune cells is a powerful approach for monitoring the dynamics of immune cells in response to immunotherapy. Despite the clinical success of many immunotherapeutic agents, their clinical efficacy is limited to a subgroup of patients. Conventional imaging, as well as analysis of tissue biopsies and blood samples do not reflect the complex interaction between tumour and immune cells. Consequently, PET probes are being developed to capture the dynamics of such interactions, which may improve patient stratification and treatment evaluation. The clinical efficacy of cancer immunotherapy relies on both the infiltration and function of cytotoxic immune cells at the tumour site. Thus, various immune biomarkers have been investigated as potential targets for PET imaging of immune response. Herein, we provide an overview of the most recent developments in PET imaging of immune response, including the radiosynthesis approaches employed in their development.

Correlation Between Immune-Related Genes and Tumor-Infiltrating Immune Cells With the Efficacy of Neoadjuvant Chemotherapy for Breast Cancer

Background: In the absence of targeted therapy or clear clinically relevant biomarkers, neoadjuvant chemotherapy (NAC) is still the standard neoadjuvant systemic therapy for breast cancer. Among the many biomarkers predicting the efficacy of NAC, immune-related biomarkers, such as immune-related genes and tumor-infiltrating lymphocytes (TILs), play a key role.

Methods: We analyzed gene expression from several datasets in the Gene Expression Omnibus (GEO) database and evaluated the relative proportion of immune cells using the CIBERSORT method. In addition, mIHC/IF detection was performed on clinical surgical specimens of triple-negative breast cancer patients after NAC.

Results: We obtained seven immune-related genes, namely, CXCL1, CXCL9, CXCL10, CXCL11, IDO1, IFNG, and ORM1 with higher expression in the pathological complete response (pCR) group than in the non-pCR group. In the pCR group, the levels of M1 and γδT macrophages were higher, while those of the M2 macrophages and mast cells were lower. After NAC, the proportions of M1, γδT cells, and resting CD4 memory T cells were increased, while the proportions of natural killer cells and dendritic cells were decreased with downregulated immune-related genes. The results of mIHC/IF detection and the prognostic information of corresponding clinical surgical specimens showed the correlation of proportions of natural killer cells, CD8-positive T cells, and macrophages with different disease-free survival outcomes.

Conclusion: The immune-related genes and immune cells of different subtypes in the tumor microenvironment are correlated with the response to NAC in breast cancer, and the interaction between TILs and NAC highlights the significance of combining NAC with immunotherapy to achieve better clinical benefits.

A Simple and Robust Single-Step Method for CAR-Vδ1 γδT Cell Expansion and Transduction for Cancer Immunotherapy

The γδT cell subset of peripheral lymphocytes exhibits potent cancer antigen recognition independent of classical peptide MHC complexes, making it an attractive candidate for allogeneic cancer adoptive immunotherapy. The Vδ1-T cell receptor (TCR)-expressing subset of peripheral γδT cells has remained enigmatic compared to its more prevalent Vγ9Vδ2-TCR and αβ-TCR-expressing counterparts. It took until 2021 before a first patient was dosed with an allogeneic adoptive Vδ1 cell product despite pre-clinical promise for oncology indications stretching back to the 1980s. A contributing factor to the paucity of clinical progress with Vδ1 cells is the lack of robust, consistent and GMP-compatible expansion protocols. Herein we describe a reproducible one-step, clinically translatable protocol for Vδ1-γδT cell expansion from peripheral blood mononuclear cells (PBMCs), that is further compatible with high-efficiency gene engineering for immunotherapy purposes. Briefly, αβTCR- and CD56-depleted PBMC stimulation with known-in-the-art T cell stimulators, anti-CD3 mAb (clone: OKT-3) and IL-15, leads to robust Vδ1 cell expansion of high purity and innate-like anti-tumor efficacy. These Vδ1 cells can be virally transduced to express chimeric antigen receptors (CARs) using standard techniques, and the CAR-Vδ1 exhibit antigen-specific persistence, cytotoxicity and produce IFN-γ. Practicable, GMP-compatible engineered Vδ1 cell expansion methods will be crucial to the wide-spread clinical testing of these cells for oncology indications.

Hypoxia as a Modulator of Inflammation and Immune Response in Cancer

A clear association between hypoxia and cancer has heretofore been established; however, it has not been completely developed. In this sense, the understanding of the tumoral microenvironment is critical to dissect the complexity of cancer, including the reduction in oxygen distribution inside the tumoral mass, defined as tumoral hypoxia. Moreover, hypoxia not only influences the tumoral cells but also the surrounding cells, including those related to the inflammatory processes. In this review, we analyze the participation of HIF, NF-κB, and STAT signaling pathways as the main components that interconnect hypoxia and immune response and how they modulate tumoral growth. In addition, we closely examine the participation of the immune cells and how they are affected by hypoxia, the effects of the progression of cancer, and some innovative applications that take advantage of this knowledge, to suggest potential therapies. Therefore, we contribute to the understanding of the complexity of cancer to propose innovative therapeutic strategies in the future.

Characterisation and induction of tissue-resident gamma delta T-cells to target hepatocellular carcinoma

Immunotherapy is now the standard of care for advanced hepatocellular carcinoma (HCC), yet many patients fail to respond. A major unmet goal is the boosting of T-cells with both strong HCC reactivity and the protective advantages of tissue-resident memory T-cells (T_RM). Here, we show that higher intratumoural frequencies of γδ T-cells, which have potential for HLA-unrestricted tumour reactivity, associate with enhanced HCC patient survival. We demonstrate that γδ T-cells exhibit bona fide tissue-residency in human liver and HCC, with γδT_RM showing no egress from hepatic vasculature, persistence for >10 years and superior anti-tumour cytokine production. The Vγ9Vδ2 T-cell subset is selectively depleted in HCC but can efficiently target HCC cell lines sensitised to accumulate isopentenyl-pyrophosphate by the aminobisphosphonate Zoledronic acid. Aminobisphosphonate-based expansion of peripheral Vγ9Vδ2 T-cells recapitulates a T_RM phenotype and boosts cytotoxic potential. Thus, our data suggest more universally effective HCC immunotherapy may be achieved by combining aminobisphosphonates to induce Vγ9Vδ2T_RM capable of replenishing the depleted pool, with additional intratumoural delivery to sensitise HCC to Vγ9Vδ2T_RM-based targeting.

γδ T cell costimulatory ligands in antitumor immunity

Antitumor immunity relies on the ability of T cells to recognize and kill tumor targets. γδ T cells are a specialized subset of T cells that predominantly localizes to non-lymphoid tissue such as the skin, gut, and lung where they are actively involved in tumor immunosurveillance. γδ T cells respond to self-stress ligands that are increased on many tumor cells, and these interactions provide costimulatory signals that promote their activation and cytotoxicity. This review will cover costimulatory molecules that are known to be critical for the function of γδ T cells with a specific focus on mouse dendritic epidermal T cells (DETC). DETC are a prototypic tissue-resident γδ T cell population with known roles in antitumor immunity and are therefore useful for identifying mechanisms that may control activation of other γδ T cell subsets within non-lymphoid tissues. This review concludes with a brief discussion on how γδ T cell costimulatory molecules can be targeted for improved cancer immunotherapy.

Gastric cancer-derived exosomal miR-135b-5p impairs the function of Vγ9Vδ2 T cells by targeting specificity protein 1

Recent studies have shown that tumor-derived exosomes participate in the communication between tumor cells and their microenvironment and mediate malignant biological behaviors including immune escape. In this study, we found that gastric cancer (GC) cell-derived exosomes could be effectively uptaken by Vγ9Vδ2 T cells, decrease the cell viability of Vγ9Vδ2 T cells, induce apoptosis, and reduce the production of cytotoxic cytokines IFN-γ and TNF-α. Furthermore, we demonstrated that exosomal miR-135b-5p was delivered into Vγ9Vδ2 T cells. Exosomal miR-135b-5p impaired the function of Vγ9Vδ2 T cells by targeting specificity protein 1 (SP1). More importantly, blocking the SP1 function by Plicamycin, an SP1 inhibitor, abolished the effect of stable miR-135b-5p knockdown GC cell-derived exosomes on Vγ9Vδ2 T cell function. Collectively, our results suggest that GC cell-derived exosomes impair the function of Vγ9Vδ2 T cells via miR-135b-5p/SP1 pathway, and targeting exosomal miR-135b-5p/SP1 axis may improve the efficiency of GC immunotherapy based on Vγ9Vδ2 T cells.

The evolving role of immune cells in prostate cancer

Prostate cancer is the most commonly diagnosed cancer and the second leading cause of cancer-related death among men in western countries. Androgen deprivation therapy (ADT) is considered the standard therapy for recurrent prostate cancer; however, this therapy may lead to ADT resistance and tumor progression, which seems to be regulated by epithelial-mesenchymal transition (EMT) and/or neuroendocrine differentiation (NED). In addition, recent data suggested the involvement of either adaptive or innate infiltrated immune cells in the initiation, progression, metastasis, and treatment of prostate cancer. In this review, we outlined the characteristics and roles of these immune cells in the initiation, progression, metastasis, and treatments of prostate cancer. We also summarized the current therapeutic strategies in targeting immune cells of the prostate tumor microenvironment.

Potentiating Vγ9Vδ2 T cell proliferation and assessing their cytotoxicity towards adherent cancer cells at the single cell level

Vγ9Vδ2 T cells is the dominant γδ T cell subset in human blood. They are cytotoxic and activated by phosphoantigens whose concentrations are increased in cancer cells, making the cancer cells targets for Vγ9Vδ2 T cell immunotherapy. For successful immunotherapy, it is important both to characterise Vγ9Vδ2 T cell proliferation and optimise the assessment of their cytotoxic potential, which is the aim of this study. We found that supplementation with freshly-thawed human serum potentiated Vγ9Vδ2 T cell proliferation from peripheral mononuclear cells (PBMCs) stimulated with (E)-4-Hydroxy-3-methyl-but-2-enyl diphosphate (HMBPP) and consistently enabled Vγ9Vδ2 T cell proliferation from cryopreserved PBMCs. In cryopreserved PBMCs the proliferation was higher than in freshly prepared PBMCs. In a panel of short-chain prenyl alcohols, monophosphates and diphosphates, most diphosphates and also dimethylallyl monophosphate stimulated Vγ9Vδ2 T cell proliferation. We developed a method where the cytotoxicity of Vγ9Vδ2 T cells towards adherent cells is assessed at the single cell level using flow cytometry, which gives more clear-cut results than the traditional bulk release assays. Moreover, we found that HMBPP enhances the Vγ9Vδ2 T cell cytotoxicity towards colon cancer cells. In summary we have developed an easily interpretable method to assess the cytotoxicity of Vγ9Vδ2 T cells towards adherent cells, found that Vγ9Vδ2 T cell proliferation can be potentiated media-supplementation and how misclassification of non-responders may be avoided. Our findings will be useful in the further development of Vγ9Vδ2 T cell immunotherapy.

Targeting the extracellular matrix for immunomodulation: applications in drug delivery and cell therapies

Host immune cells interact bi-directionally with their extracellular matrix (ECM) to receive and deposit molecular signals, which orchestrate cellular activation, proliferation, differentiation, and function to maintain healthy tissue homeostasis. In response to pathogens or damage, immune cells infiltrate diseased sites and synthesize critical ECM molecules such as glycoproteins, proteoglycans, and glycosaminoglycans to promote healing. When the immune system misidentifies pathogens or fails to survey damaged cells effectively, maladies such as chronic inflammation, autoimmune diseases, and cancer can develop. In these conditions, it is essential to restore balance to the body through modulation of the immune system and the ECM. This review details the components of dysregulated ECM implicated in pathogenic environments and therapeutic approaches to restore tissue homeostasis. We evaluate emerging strategies to overcome inflamed, immune inhibitory, and otherwise diseased microenvironments, including mechanical stimulation, targeted proteases, adoptive cell therapy, mechanomedicine, and biomaterial-based cell therapeutics. We highlight various strategies that have produced efficacious responses in both pre-clinical and human trials and identify additional opportunities to develop next-generation interventions. Significantly, we identify a need for therapies to address dense or fibrotic tissue for the treatment of organ tissue damage and various cancer subtypes. Finally, we conclude that therapeutic techniques that disrupt, evade, or specifically target the pathogenic microenvironment have a high potential for improving therapeutic outcomes and should be considered a priority for immediate exploration. A schematic showing the various methods of extracellular matrix disruption/targeting in both fibrotic and cancerous environments. a Biomaterial-based cell therapy can be used to deliver anti-inflammatory cytokines, chemotherapeutics, or other factors for localized, slow release of therapeutics. b Mechanotherapeutics can be used to inhibit the deposition of molecules such as collagen that affect stiffness. c Ablation of the ECM and target tissue can be accomplished via mechanical degradation such as focused ultrasound. d Proteases can be used to improve the distribution of therapies such as oncolytic virus. e Localization of therapeutics such as checkpoint inhibitors can be improved with the targeting of specific ECM components, reducing off-target effects and toxicity.

Unconventional T cells and kidney disease

Unconventional T cells are a diverse and underappreciated group of relatively rare lymphocytes that are distinct from conventional CD4⁺ and CD8⁺ T cells, and that mainly recognize antigens in the absence of classical restriction through the major histocompatibility complex (MHC). These non-MHC-restricted T cells include mucosal-associated invariant T (MAIT) cells, natural killer T (NKT) cells, γδ T cells and other, often poorly defined, subsets. Depending on the physiological context, unconventional T cells may assume either protective or pathogenic roles in a range of inflammatory and autoimmune responses in the kidney. Accordingly, experimental models and clinical studies have revealed that certain unconventional T cells are potential therapeutic targets, as well as prognostic and diagnostic biomarkers. The responsiveness of human Vγ9Vδ2 T cells and MAIT cells to many microbial pathogens, for example, has implications for early diagnosis, risk stratification and targeted treatment of peritoneal dialysis-related peritonitis. The expansion of non-Vγ9Vδ2 γδ T cells during cytomegalovirus infection and their contribution to viral clearance suggest that these cells can be harnessed for immune monitoring and adoptive immunotherapy in kidney transplant recipients. In addition, populations of NKT, MAIT or γδ T cells are involved in the immunopathology of IgA nephropathy and in models of glomerulonephritis, ischaemia-reperfusion injury and kidney transplantation.

Dysfunctional BTN3A together with deregulated immune checkpoints and type I/II IFN dictate defective interplay between pDCs and γδ T cells in melanoma patients, which impacts clinical outcomes

Objectives

pDCs and γδ T cells emerge as potent immune players participating in the pathophysiology of cancers, yet still remaining enigmatic while harbouring a promising potential for clinical translations. Despite strategic and closed missions, crosstalk between pDCs and γδ T cells has not been deciphered yet in cancers, especially in melanoma where the long‐term control of the tumor still remains a challenge.

Methods

This prompted us to explore the interplay between pDCs and γδ T cells in the context of melanoma, investigating the reciprocal features of pDCs or γδ T cells, the underlying molecular mechanisms and its impact on clinical outcomes.

Results

TLRL‐activated pDCs from the blood and tumor infiltrate of melanoma patients displayed an impaired ability to activate, to modulate immune checkpoints and trigger the functionality of γδ T cells. Conversely, γδ T cells from the blood or tumor infiltrate of melanoma patients activated by PAg were defective in triggering pDCs’ activation and modulation of immune checkpoints, and failed to elicit the functionality of pDCs. Reversion of the dysfunctional cross‐talks could be achieved by specific cytokine administration and immune checkpoint targeting. Strikingly, we revealed an increased expression of BTN3A on circulating and tumor‐infiltrating pDCs and γδ T cells from melanoma patients, but stressed out the potential impairment of this molecule.

Conclusion

Our study uncovered that melanoma hijacked the bidirectional interplay between pDCs and γδ T cells to escape from immune control, and revealed BTN3A dysfunction. Such understanding will help harness and synergise the power of these potent immune cells to design new therapeutic approaches exploiting their antitumor potential while counteracting their skewing by tumors to improve patient outcomes.

Gamma Delta T Cells and Their Involvement in COVID-19 Virus Infections

The global outbreak of the SARS-Cov-2 virus in 2020 has killed millions of people worldwide and forced large parts of the world into lockdowns. While multiple vaccine programs are starting to immunize the global population, there is no direct cure for COVID-19, the disease caused by the SARS-Cov-2 infection. A common symptom in patients is a decrease in T cells, called lymphopenia. It is as of yet unclear what the exact role of T cells are in the immune response to COVID-19. The research so far has mainly focused on the involvement of classical αβ T cells. However, another subset of T cells called γδ T cells could have an important role to play. As part of the innate immune system, γδ T cells respond to inflammation and stressed or infected cells. The γδ T cell subset appears to be particularly affected by lymphopenia in COVID-19 patients and commonly express activation and exhaustion markers. Particularly in children, this subset of T cells seems to be most affected. This is interesting and relevant because γδ T cells are more prominent and active in early life. Their specific involvement in this group of patients could indicate a significant role for γδ T cells in this disease. Furthermore, they seem to be involved in other viral infections and were able to kill SARS infected cells in vitro. γδ T cells can take up, process and present antigens from microbes and human cells. As e.g. tumour-associated antigens are presented by MHC on γδ T cells to classical T-cells, we argue here that it stands to reason that also viral antigens, such as SARS-Cov-2-derived peptides, can be presented in the same way. γδ T cells are already used for medical purposes in oncology and have potential in cancer therapy. As γδ T cells are not necessarily able to distinguish between a transformed and a virally infected cell it could therefore be of great interest to investigate further the relationship between COVID-19 and γδ T cells.

αβ-T Cells Engineered to Express γδ-T Cell Receptors Can Kill Neuroblastoma Organoids Independent of MHC-I Expression

Currently ~50% of patients with a diagnosis of high-risk neuroblastoma will not survive due to relapsing or refractory disease. Recent innovations in immunotherapy for solid tumors are highly promising, but the low MHC-I expression of neuroblastoma represents a major challenge for T cell-mediated immunotherapy. Here, we propose a novel T cell-based immunotherapy approach for neuroblastoma, based on the use of TEG002, αβ-T cells engineered to express a defined γδ-T cell receptor, which can recognize and kill target cells independent of MHC-I. In a co-culture killing assay, we showed that 3 out of 6 neuroblastoma organoids could activate TEG002 as measured by IFNγ production. Transcriptional profiling showed this effect correlates with an increased activity of processes involved in interferon signaling and extracellular matrix organization. Analysis of the dynamics of organoid killing by TEG002 over time confirmed that organoids which induced TEG002 activation were efficiently killed independent of their MHC-I expression. Of note, efficacy of TEG002 treatment was superior to donor-matched untransduced αβ-T cells or endogenous γδ-T cells. Our data suggest that TEG002 may be a promising novel treatment option for a subset of neuroblastoma patients.

Vγ9γδ T Cell Induction by Human Umbilical Cord Blood Monocytes-Derived, Interferon-α-Stimulated Dendritic Cells

Dendritic cells (DC) are professional antigen-presenting cells that activate T cells to kill cancer cells. The extracellular products of DCs have also been reported to perform the same function. In this study, we examined the in vitro differentiation of umbilical cord blood monocytes into DCs in the presence of GM-CSF, and interferon (IFN)-α. The resulting DC population (called IFN-DCs) were then matured in the presence of TNF-α, and pulsed with total protein extracted from A549 cancer cell line. The pulsed DCs and their conditioned medium were then used to stimulate allogeneic lymphocytes (alloLym). The proliferation and cytotoxicity of alloLym were then determined. The results showed that after 5 days of differentiation, the stimulated monocytes had the typical morphology and characteristic surface markers of DCs. Both unpulsed and pulsed IFN-DCs can induce the proliferation of alloLym, especially Vγ9γδ T cells. The conditioned medium from pulsed and unpulsed IFN-DCs culture also prompted the growth of Vγ9γδ T cells. Moreover, alloLym stimulated with pulsed DCs and their conditioned medium had a greater cytotoxic effect on A549 cells than the ones that were not stimulated. Our results indicated that IFN-DCs and their conditioned medium could induce the anti-tumor immunity in vitro, providing evidence for application of cord blood monocytes-derived, interferon-α- stimulated dendritic cells and their extracellular products in anti-cancer therapy.

Interplay between γδT-Cell Metabolism and Tumour Microenvironment Offers Opportunities for Therapeutic Intervention

Solid tumour targeting using adoptive cell therapy has failed to reproduce the spectacular clinical successes seen with chimeric antigen receptor T cell therapies and B cell malignancies. Low in glucose, oxygen, pH and populated with suppressive cells, the solid tumour microenvironment (TME) remains a formidable obstacle to successful immune targeting. The use of atypical, tissue-tropic lymphocytes, such as γδT cells, may offer enhanced tumour trafficking over canonical αβT cells. Nonetheless, γδT cells too interact with the TME. The consequences of this interaction are poorly understood and of high translational relevance. Lopes and colleagues show that, in a murine context, low glucose environments preferentially retained pro-tumorigenic IL-17-producing γδT cells. Anti-tumorigenic IFN-γ-producing γδT cells, meanwhile, required high ambient glucose to survive and exert effector function. Unexpectedly, this metabolic imprinting was evident in the murine thymus, suggesting that the ontological separation of these functional subsets occurs early in their development. Elucidation of this relationship between TME glucose levels and γδT cell functionality in a human context is likely to carry significant implications for the development of γδT cell-based oncoimmunotherapeutics.

γδ T cells cultured with artificial antigen-presenting cells and IL-2 show long-term proliferation and enhanced effector functions compared with γδ T cells cultured with only IL-2 after stimulation with zoledronic acid

BACKGROUND AIMS

Immunotherapeutic approaches using γδ T cells have emerged as the function of γδ T cells in tumor surveillance and clearance has been discovered. In vitro expansion methods of γ9δ2 T cells have been based on phosphoantigens and cytokines, but expansion methods using feeder cells to generate larger numbers of γδ T cells have also been studied recently. However, there are no studies that directly compare γδ T cells cultured with phosphoantigens with those cultured with feeder cells. Therefore, this study aimed to compare the expansion, characteristics and effector functions of γδ T cells stimulated with K562-based artificial antigen-presenting cells (aAPCs) (aAPC-γδ T cells) and γδ T cells stimulated with only zoledronic acid (ZA) (ZA-γδ T cells).

METHODS

Peripheral blood mononuclear cells were stimulated with ZA for 7 days, and aAPC-γδ T cells were stimulated weekly with K562-based aAPCs expressing CD32, CD80, CD83, 4-1BBL, CD40L and CD70, whereas ZA-γδ T cells were stimulated with only IL-2. Cultured γδ T cells were analyzed by flow cytometry for the expression of co-stimulatory molecules, activating receptors and checkpoint inhibitors. Differentially expressed gene (DEG) analysis was also performed to determine the difference in gene expression between aAPC-γδ T cells and ZA-γδ T cells. In vitro cytotoxicity assay was performed with calcein AM release assay, and in vivo anti-tumor effect was compared using a U937 xenograft model.

RESULTS

Fold expansion on day 21 was 690.7 ± 413.1 for ZA-γδ T cells and 1415.2 ± 1016.8 for aAPC- γδ T cells. Moreover, aAPC-γδ T cells showed continuous growth, whereas ZA-γδ T cells showed a decline in growth after day 21. The T-cell receptor Vγ9⁺δ2⁺ percentages (mean ± standard deviation) on day 21 were 90.0 ± 2.7% and 87.0 ± 4.5% for ZA-γδ T cells and aAPC-γδ T cells, respectively. CD25 and CD86 expression was significantly higher in aAPC-γδ T cells. In DEG analysis, aAPC-γδ T cells and ZA-γδ T cells formed distinct clusters, and aAPC-γδ T cells showed upregulation of genes associated with metabolism and cytokine pathways. In vitro cytotoxicity revealed superior anti-tumor effects of aAPC-γδ T cells compared with ZA-γδ T cells on Daudi, Raji and U937 cell lines. In addition, in the U937 xenograft model, aAPC-γδ T-cell treatment increased survival, and a higher frequency of aAPC-γδ T cells was shown in bone marrow compared with ZA-γδ T cells.

CONCLUSIONS

Overall, this study demonstrates that aAPC-γδ T cells show long-term proliferation, enhanced activation and anti-tumor effects compared with ZA-γδ T cells and provides a basis for using aAPC-γδ T cells in further studies, including clinical applications and genetic engineering of γδ T cells.

Identification of new potential antigen recognized by γδT cells in hepatocellular carcinoma

In recent years, the application of chimeric antigen receptor T-cell (CAR-T) therapy based on gamma delta T (γδT) cells in hepatocellular carcinoma (HCC) immunotherapy has attracted more and more attention. However, specific antigens recognized by γδT cells are rarely identified, which has become the main restriction on such therapeutic application of γδT cells. In this report, we identified a new peptide and protein antigen recognized by γδT cells in HCC using our previous established strategy. First, we investigated the diversity of the γ9/δ2 T-cell immunorepertoire by sequence analyses of the expressed complementarity-determining region 3 (CDR3) in HCC patients. Then, we constructed γ9/δ2 T-cell receptor (TCR)-transfected cell lines expressing significant HCC CDR3 sequence and identified a series of peptides capable of binding to γδT cells specifically. Next, we identified, further tested and verified the biological functions of these peptides and their matched protein by bioinformatics analysis. We identified that the new protein hepatocyte growth factor-like protein, also called as macrophage-stimulating protein (MSP), and peptide HP1, not only bound to HCC-predominant γδTCR but also effectively activated γδT cells isolated from HCC patients. Moreover, they could stimulate γδT cells in peripheral blood from HCC patients to produce cytokines, which contributed to inhibiting HCC and played an important role in mediating cytotoxicity to HCC cell lines. In conclusion, we identified MSP and HP1, which showed potential as candidates for antigens recognized by γδT cells in HCC.

Glioblastoma cells potentiate the induction of the Th1-like profile in phosphoantigen-stimulated γδ T lymphocytes

PURPOSE

γδ T lymphocytes are non-conventional T cells that participate in protective immunity and tumor surveillance. In healthy humans, the main subset of circulating γδ T cells express the TCRVγ9Vδ2. This subset responds to non-peptide prenyl-pyrophosphate antigens such as (E)-4-hydroxy-3-methyl-but-enyl pyrophosphate (HMBPP). This unique feature of Vγ9Vδ2 T cells makes them a candidate for anti-tumor immunotherapy. In this study, we investigated the response of HMBPP-activated Vγ9Vδ2 T lymphocytes to glioblastoma multiforme (GBM) cells.

METHODS

Human purified γδ T cells were stimulated with HMBPP (1 µM) and incubated with GBM cells (U251, U373 and primary GBM cultures) or their conditioned medium. After overnight incubation, expression of CD69 and perforin was evaluated by flow cytometry and cytokines production by ELISA. As well, we performed a meta-analysis of transcriptomic data obtained from The Cancer Genome Atlas.

RESULTS

HMBPP-stimulated γδ T cells cultured with GBM or its conditioned medium increased CD69, intracellular perforin, IFN-γ, and TNF-α production. A meta-analysis of transcriptomic data showed that GBM patients display better overall survival when mRNA TRGV9, the Vγ9 chain-encoding gene, was expressed in high levels. Moreover, its expression was higher in low-grade GBM compared to GBM. Interestingly, there was an association between γδ T cell infiltrates and TNF-α expression in the tumor microenvironment.

CONCLUSION

GBM cells enhanced Th1-like profile differentiation in phosphoantigen-stimulated γδ T cells. Our results reinforce data that have demonstrated the implication of Vγ9Vδ2 T cells in the control of GBM, and this knowledge is fundamental to the development of immunotherapeutic protocols to treat GBM based on γδ T cells.

Approaches for refining and furthering the development of CAR-based T cell therapies for solid malignancies

Introduction: Chimeric antigen receptor-engineered T-cells typically use the binding domains of antibodies to target cytotoxicity toward tumors. This approach has produced great efficacy against selected hematological cancers, but benefit in solid tumors has been limited. Characteristically, the microenvironment in solid tumors restricts CAR T cell function, thereby limiting success. Enhancing efficacy will depend on novel target discovery to refine specificity and reduce toxicity. Additionally, overcoming immunosuppressive mechanisms may be achieved by altering the structure of the CAR itself, together with ancillary gene expression or additional therapeutic interventions.Areas covered: Herein, the authors discuss approaches for refining and further developing CAR T cell therapies specifically for use with solid malignancies. The authors survey the existing literature and provide perspectives for the future.Expert opinion: Pronounced efficacy in solid tumors will likely require combination therapies, targeting both the tumor itself and associated immunosuppressive mechanisms. Future exploration of CAR T cell therapies for solid tumors is likely to incorporate next-generation designs that couple more precise targeting of cancer-associated targets with enhanced potency and resistance to exhaustion.

Dichotomous and stable gamma delta T-cell number and function in healthy individuals

BACKGROUND

Gamma-delta (γδ) T lymphocytes are primed to potently respond to pathogens and transformed cells by recognizing a broad range of antigens. However, adoptive immunotherapy with γδT cells has exhibited mixed treatment responses. Better understanding of γδT cell biology and stratifying healthy donors for allogeneic adoptive therapy is clinically needed to fully realize the therapeutic potential of γδT cells.

METHODS

We examine 98 blood samples from healthy donors and measure their expansion capacity after zoledronate stimulation, and test the migration and cytotoxic effector function of expanded γδT cells in 2D culture, 3D tumor spheroid and patient-derived melanoma organoid assays.

RESULTS

We find that γδT cell expansion capacity is independent of expansion methods, gender, age and HLA type. Basal γδT cell levels in Peripheral blood mononuclear cell (PBMC) correlate well with their expansion, migration and cytotoxic effector capacity in vitro. Circulating γδT cells with lower expression of PD-1, CTLA-4, Eomes, T-bet and CD69, or higher IFN-γ production expand better. γδT cells with central memory and effector memory phenotypes are significantly more abundant in good expanders. A cut-off level of 0.82% γδT cells in PBMC stratifies good versus poor γδT cell expansion with a sensitivity of 97.78%, specificity of 90.48% and area under the curve of 0.968 in a healthy individual. Donors with higher Vδ2 Index Score in PBMC have greater anti-tumor functions including migratory function and cytotoxicity.

CONCLUSIONS

Our results demonstrate that the interindividual γδT cell functions correlate with their circulating levels in healthy donors. Examination of circulating γδT cell level may be used to select healthy donors to participate in γδT-based immunotherapies.

Epigenetic modulation of immune synaptic-cytoskeletal networks potentiates γδ T cell-mediated cytotoxicity in lung cancer

γδ T cells are a distinct subgroup of T cells that bridge the innate and adaptive immune system and can attack cancer cells in an MHC-unrestricted manner. Trials of adoptive γδ T cell transfer in solid tumors have had limited success. Here, we show that DNA methyltransferase inhibitors (DNMTis) upregulate surface molecules on cancer cells related to γδ T cell activation using quantitative surface proteomics. DNMTi treatment of human lung cancer potentiates tumor lysis by ex vivo-expanded Vδ1-enriched γδ T cells. Mechanistically, DNMTi enhances immune synapse formation and mediates cytoskeletal reorganization via coordinated alterations of DNA methylation and chromatin accessibility. Genetic depletion of adhesion molecules or pharmacological inhibition of actin polymerization abolishes the potentiating effect of DNMTi. Clinically, the DNMTi-associated cytoskeleton signature stratifies lung cancer patients prognostically. These results support a combinatorial strategy of DNMTis and γδ T cell-based immunotherapy in lung cancer management.

Vγ9Vδ2 T cells strengthen cisplatin inhibition activity against breast cancer MDA-MB-231 cells by disrupting mitochondrial function and cell ultrastructure

BACKGROUND

Breast cancer ranks second of new cases and fifth of death in 2018 worldwide. Cis-platinum (CDDP) has been used as a chemotherapy to treat breast cancer for years. However, CDDP can adversely disrupt immune function of host. Thus, development of new protocol that can minimize side effect and meanwhile elevate clinical efficacy of CDDP will eventually benefit cancer patients. Since Vγ9Vδ2 T cells can up-regulate immune function of cancer patients, therefore, our hypothesis is that introduction of Vγ9Vδ2 T cells could potentiate CDDP efficacy against breast cancer.

METHODS

We used breast cancer cell line MDA-MB-231 as model cell to test our hypothesis. The cancer cell viability in vitro in the context of different dose of CDDP was analyzed by flow cytometry. The cytoskeleton alteration was visualized by confocal microscopy, and the ultrastructure of cell membrane was observed by atomic force microscopy. The mitochondrial function of MDA-MB-231 cells was detected as well by flow cytometry.

RESULTS

Comparing to either Vγ9Vδ2 T cells or CDDP alone, Vγ9Vδ2 T cells plus CDDP could more strikingly induce MDA-MB-231 cell membrane ultrastructure disruption and cytoskeleton disorder, and more significantly enhance the inhibition of CDDP on proliferation of MDA-MB-231 cells. At the same time, Vγ9Vδ2 T cells strengthened CDDP-induced mitochondrial dysfunction of cancer cells.

CONCLUSION

This work revealed that Vγ9Vδ2 T cells could synergistically enhance the inhibition activity of CDDP against breast cancer cells. Meanwhile, this in vitro proof-of-concept study implied the clinical prospect of the combining application of Vγ9Vδ2 T cells and CDDP in breast cancer therapy.

Advances in identification and selection of personalized neoantigen/T-cell pairs for autologous adoptive T cell therapies

Based on the success of tumor-infiltrating lymphocytes (TIL)-based therapies, personalized adoptive cell therapies (ACT) targeting neoantigens have the potential to become a disruptive technology and lead to highly effective treatments for cancer patients for whom no other options exist. ACT of TIL, peripheral blood or gene-engineered peripheral blood lymphocytes (PBLs) targeting neoantigens is a highly personalized intervention that requires three discrete steps: i) Identification of suitable personal targets (neoantigens), ii) selection of T cells or their T cell receptors (TCRs) that are specific for the identified neoantigens and iii) expansion of the selected T cell population or generation of sufficient number of TCR modified T cells. In this review, we provide an introduction into challenges and approaches to identify neoantigens and to select the Adoptive Cell Therapy, ACT, Neoantigen, T cell, Cancer respective neoantigen-reactive T cells for use in ACT.

Differences in circulating γδ T cells in patients with primary colon cancer and relation with prognostic factors

Downregulation of the T cell system has been proposed as a mechanism to block immunity in colonic cancer (CC). However, little has been studied about circulating αβ and γδ T cells and their immunological status in newly diagnosed patients. The aim of this study was to characterize the αβ and γδ T cell subsets in peripheral blood of patients with CC matched with healthy volunteers. In this prospective case-control study, blood samples were obtained from 96 patients with newly diagnosed treatment-naïve infiltrating colonic adenocarcinoma and 48 healthy volunteers. Pathological report at surgery was obtained from all CC patients. A significant decrease in CD3+ γδ T cells and CD3+CD8+ γδ T cells (p<0.001) were observed in CC patients. Apoptosis was significantly increased in all conventional and both αβ and γδ T cell subsets in patients with CC vs healthy subjects. γδ T cells were decreased in peripheral blood of patients with microscopic infiltration in tissues, history of cancer and synchronous colon cancer (p < 0.05). IFN-γ was significantly reduced in CC patients compared to controls. Cytotoxic effector γδ T cells TEMRA (CD8 and CD56) are the proportionally most abundant T cells in peripheral blood of CC patients. Patients with CC present a deep downregulation in the systemic T-cell immunity. These variations are evident through all tumor stages and suggest that a deficiency in γδ T cell populations could be preventing control of tumor progression. This fact prove the role of immunomodulation on CC carcinogenesis.

Strategies to Improve Chimeric Antigen Receptor Therapies for Neuroblastoma

Chimeric antigen receptors (CARs) are among the curative immunotherapeutic approaches that exploit the antigen specificity and cytotoxicity function of potent immune cells against cancers. Neuroblastomas, the most common extracranial pediatric solid tumors with diverse characteristics, could be a promising candidate for using CAR therapies. Several methods harness CAR-modified cells in neuroblastoma to increase therapeutic efficiency, although the assessment has been less successful. Regarding the improvement of CARs, various trials have been launched to overcome insufficient capacity. However, the reasons behind the inadequate response against neuroblastoma of CAR-modified cells are still not well understood. It is essential to update the present state of comprehension of CARs to improve the efficiency of CAR therapies. This review summarizes the crucial features of CARs and their design for neuroblastoma, discusses challenges that impact the outcomes of the immunotherapeutic competence, and focuses on devising strategies currently being investigated to improve the efficacy of CARs for neuroblastoma immunotherapy.

Aiming for the Sweet Spot: Glyco-Immune Checkpoints and γδ T Cells in Targeted Immunotherapy

Though a healthy immune system is capable of recognizing and eliminating emergent cancerous cells, an established tumor is adept at escaping immune surveillance. Altered and tumor-specific expression of immunosuppressive cell surface carbohydrates, also termed the “tumor glycocode,” is a prominent mechanism by which tumors can escape anti-tumor immunity. Given their persistent and homogeneous expression, tumor-associated glycans are promising targets to be exploited as biomarkers and therapeutic targets. However, the exploitation of these glycans has been a challenge due to their low immunogenicity, immunosuppressive properties, and the inefficient presentation of glycolipids in a conventional major histocompatibility complex (MHC)-restricted manner. Despite this, a subset of T-cells expressing the gamma and delta chains of the T-cell receptor (γδ T cells) exist with a capacity for MHC-unrestricted antigen recognition and potent inherent anti-tumor properties. In this review, we discuss the role of tumor-associated glycans in anti-tumor immunity, with an emphasis on the potential of γδ T cells to target the tumor glycocode. Understanding the many facets of this interaction holds the potential to unlock new ways to use both tumor-associated glycans and γδ T cells in novel therapeutic interventions.

Aryloxy Diester Phosphonamidate Prodrugs of Phosphoantigens (ProPAgens) as Potent Activators of Vγ9/Vδ2 T-Cell Immune Responses

Vγ9/Vδ2 T-cells are activated by pyrophosphate-containing small molecules known as phosphoantigens (PAgs). The presence of the pyrophosphate group in these PAgs has limited their drug-like properties because of its instability and polar nature. In this work, we report a novel and short Grubbs olefin metathesis-mediated synthesis of methylene and difluoromethylene monophosphonate derivatives of the PAg (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBP) as well as their aryloxy diester phosphonamidate prodrugs, termed ProPAgens. These prodrugs showed excellent stability in human serum (t_1/2 > 12 h) and potent activation of Vγ9/Vδ2 T-cells (EC₅₀ ranging from 5 fM to 73 nM), which translated into sub-nanomolar γδ T-cell-mediated eradication of bladder cancer cells in vitro. Additionally, a combination of in silico and in vitro enzymatic assays demonstrated the metabolism of these phosphonamidates to release the unmasked PAg monophosphonate species. Collectively, this work establishes HMBP monophosphonate ProPAgens as ideal candidates for further investigation as novel cancer immunotherapeutic agents.

Higher TIGIT+CD226- γδ T cells in Patients with Acute Myeloid Leukemia

The diverse structural and functional heterogeneity of γδ T cells is related to their distinct role in cancer immunity. The different phenotypes of γδ T cells in patients with acute myeloid leukemia (AML) is far from clear. In particular, the expression pattern of co-inhibitory and co-stimulatory receptors on γδ T cells remains unknown. In this study, we analyzed the distribution of γδ T cell subsets by expression of the immune checkpoint co-inhibitor TIGIT (T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain) and its competing co-stimulatory receptor CD226 in AML patients of different clinical statuses (including de novo AML, AML in non-remission (NR), and AML in complete remission (CR)). Our data demonstrated an imbalanced distribution of TIGIT and CD226 on γδ T cells with a decrease in CD226⁺ γδ T cells and an increase in TIGIT⁺ γδ T cells in de novo AML patients, while TIGIT^-CD226⁺ γδ T cells were restored in AML patients who achieved CR after chemotherapy. Moreover, the patients who had higher TIGIT⁺CD226^- γδ T cells showed lower overall survival rate for non-M3 AML, which may be considered a novel prognostic immune biomarker. In conclusion, our study reveals for the first time that imbalance in the TIGIT/CD226 axis might be related to different clinical outcomes for AML patients.

ABBREVIATIONS

AML: acute myeloid leukemia; CR: complete remission; ICs: immune checkpoints; PD-1: programmed death-1; γδ T cells: gamma delta T cells; TCR: T cell receptor; MHC: major histocompatibility complex; TIGIT: T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain; NK: natural killer; PB: Peripheral blood; NR: non-remission; FAB: French-American-British; WHO: World Health Organization; HIs: healthy individuals; OS: overall survival.

HDAC Inhibitor LBH589 Suppresses the Proliferation but Enhances the Antileukemic Effect of Human γδT Cells

γδT cells have potent effects on hematological malignancies, and their functions can be regulated by anti-tumor agents. Histone deacetylase inhibitors (HDACis) not only have antileukemic activity on leukemia but also affect immune cells during therapeutic application. In this in vitro study, we showed that LBH589, a pan-HDACi, impaired the proliferation of human γδT cells, as well as their proportions in peripheral blood mononuclear cells (PBMCs). At the specific concentration, LBH589 induced significant antileukemic activity of γδT cells against the HL-60 cells and Kasumi cells in a dose-dependent manner. However, the expression levels of activating receptor and molecules, as well as interferon-γ (IFN-γ) expression on γδT cells, were not affected by LBH589. After treatment with LBH589 for indicated times, extracellular-regulated protein kinase (ERK), Akt, and c-Jun N-terminal kinase (JNK) signaling pathways in γδT cells were not activated. In contrast, a stronger expression of Notch was observed and sustained for 72 h. Inhibition of Notch signaling by FLI-06, the γ-secretase inhibitor, significantly reversed the enhanced antileukemic ability of γδT cells induced by LBH589. For the first time, our investigations demonstrate that LBH589 can inhibit proliferation of γδT cells but facilitate their antileukemic effects via activation of Notch signaling.

Targeting the interleukin-17 immune axis for cancer immunotherapy

IL-17 plays versatile roles during tumorigenesis. Here, Vitiello and Miller summarize current knowledge in harnessing IL-17–producing γδ and Th17 cells for successful cancer immunotherapy.

The role of IL-17 in cancer remains controversial. Emerging evidence suggests that during early oncogenesis IL-17 supports tumor growth, whereas in established tumors IL-17 production by γδ and Th17 cells potentiates antitumor immunity. Consequently, γδ and Th17 cells are attractive targets for immunotherapy in the IL-17 immune axis. To optimize IL-17–based immunotherapy, a deeper understanding of the cytokines dictating IL-17 production and the polarity of γδ and Th17 cells is critical. Here, we delve into the dichotomous roles of IL-17 in cancer and provide insight into the tumor microenvironment conducive for successful IL-17–based γδ and Th17 cell immunotherapy.

Aberrantly Expressed Embryonic Protein NODAL Alters Breast Cancer Cell Susceptibility to γδ T Cell Cytotoxicity

Gamma delta (γδ) T cells kill transformed cells, and increased circulating γδ T cells levels correlate with improved outcome in cancer patients; however, their function within the breast tumor microenvironment (TME) remains controversial. As tumors progress, they begin to express stem-cell associated proteins, concomitant with the emergence of therapy resistant metastatic disease. For example, invasive breast cancers often secrete the embryonic morphogen, NODAL. NODAL has been shown to promote angiogenesis, therapy resistance and metastasis in breast cancers. However, to date, little is known about how this secreted protein may interact with cells in the TME. Herein we explore how NODAL in the TME may influence γδ T cell function. We have assessed the proximity of γδ T cells to NODAL in a cohort of triple negative breast tumors. In all cases in which γδ T cells could be identified in these tumors, γδ T cells were found in close proximity to NODAL-expressing tumor cells. Migration of γδ and αβ T cells was similar toward MDA-MB-231 cells in which NODAL had been knocked down (shN) and MDA-MB-231 scrambled control cells (shC). Furthermore, Vδ1 γδ T cells did not migrate preferentially toward conditioned medium from these cell lines. While 24-h exposure to NODAL did not impact CD69, PD-1, or T cell antigen receptor (TCR) expression on γδ T cells, long term exposure resulted in decreased Vδ2 TCR expression. Maturation of γδ T cells was not significantly influenced by NODAL stimulation. While neither short- nor long-term NODAL stimulation impacted the ability of γδ T cells to kill MCF-7 breast cancer cells, the absence of NODAL resulted in greater sensitivity of targets to γδ T cell cytotoxicity, while overexpression of NODAL conferred resistance. This appeared to be at least in part due to an inverse correlation between NODAL and surface MICA/B expression on breast cancer target lines. As such, it appears that NODAL may play a role in strategies employed by breast cancer cells to evade γδ T cell targeting, and this should be considered in the development of safe and effective γδ T cell immunotherapies.

γδ T Cells: The Ideal Tool for Cancer Immunotherapy

γδ T cells have recently gained considerable attention as an attractive tool for cancer adoptive immunotherapy due to their potent anti-tumor activity and unique role in immunosurveillance. The remarkable success of engineered T cells for the treatment of hematological malignancies has revolutionized the field of adoptive cell immunotherapy. Accordingly, major efforts are underway to translate this exciting technology to the treatment of solid tumors and the development of allogeneic therapies. The unique features of γδ T cells, including their major histocompatibility complex (MHC)-independent anti-cancer activity, tissue tropism, and multivalent response against a broad spectrum of the tumors, render them ideal for designing universal 'third-party' cell products, with the potential to overcome the challenges of allogeneic cell therapy. In this review, we describe the crucial role of γδ T cells in anti-tumor immunosurveillance and we summarize the different approaches used for the ex vivo and in vivo expansion of γδ T cells suitable for the development of novel strategies for cancer therapy. We further discuss the different transduction strategies aiming at redirecting or improving the function of γδ T cells, as well as, the considerations for the clinical applications.

Emerging Challenges of Preclinical Models of Anti-tumor Immunotherapeutic Strategies Utilizing Vγ9Vδ2 T Cells

Despite recent advances, the eradication of cancers still represents a challenge which justifies the exploration of additional therapeutic strategies such as immunotherapies, including adoptive cell transfers. Human peripheral Vγ9Vδ2 T cells, which constitute a major transitional immunity lymphocyte subset, represent attractive candidates because of their broad and efficient anti-tumor functions, as well as their lack of alloreactivity and easy handling. Vγ9Vδ2 T cells act like immune cell stress sensors that can, in a tightly controlled manner but through yet incompletely understood mechanisms, detect subtle changes of levels of phosphorylated metabolites of isoprenoid synthesis pathways. Consequently, various anti-tumor immunotherapeutic strategies have been proposed to enhance their reactivity and cytotoxicity, as well as to reduce the deleterious events. In this review, we expose these advances based on different strategies and their validation in preclinical models. Importantly, we next discuss advantages and limits of each approach, by highlighting the importance of the use of relevant preclinical model for evaluation of safety and efficacy. Finally, we propose novel perspectives and strategies that should be explored using these models for therapeutic improvements.

Hypoxia regulates the differentiation and anti-tumor effector functions of γδT cells in oral cancer

Hypoxia within the tumor microenvironment (TME) is a key factor contributing to immunosuppression in tumors, co-relating with poor treatment outcome and decreased overall survival in advanced oral cancer (OC) patients. Vδ2 is a dominant subset of gamma delta T cells (γδT cells) present in the peripheral blood which exhibits potent anti-tumor cytotoxicity and is evolving as a key player of anti-cancer cellular therapy. However, the fate of γδT cells in hypoxic oral tumors remains elusive. In the present study, we compared the effect of hypoxia (1% O₂ ) and normoxia (21% O₂ ) on the expansion, proliferation, activation status, cytokine secretion and cytotoxicity of γδT cells isolated from OC patients and healthy individuals. Hypoxia-exposed γδT cells exhibited reduced cytotoxicity against oral tumor cells. Our data demonstrated that hypoxia reduces the calcium efflux and the expression of degranulation marker CD107a in γδT cells, which explains the decreased anti-tumor cytotoxicity of γδT cells observed under hypoxia. Hypoxia-exposed γδT cells differentiated to γδT17 [γδ T cells that produce interleukin (IL)-17] cells, which corroborated our observations of increased γδT17 cells observed in the oral tumors. Co-culture of γδT cells with CD8 T cells in the presence of hypoxia showed that programmed cell death ligand 1 (PD-L1)^high γδT cells brought about apoptosis of programmed cell death 1 (PD-1)^high CD8 T cells which could be significantly reversed upon blocking PD-1. Thus, future immunotherapeutic treatment modality for oral cancer may use a combined approach of blocking the PD-1/PD-L1 signaling and targeting hypoxia-inducible factor 1α, which may help in reversing hypoxia-induced immunosuppression.

Identification of prognostic factors for γδT cell immunotherapy in patients with solid tumor

BACKGROUND AIMS

Activated γδT cells have been shown to exhibit cytotoxicity against tumor cells. However, the efficacy of γδT cell immunotherapy for a large number of patients with solid tumors remains unclear. In this study, we examined the efficacy of γδT cell immunotherapy using in vitro-activated γδT lymphocytes in combination with standard therapies in terms of the survival of patients with solid tumors, and determined prognostic factor for γδT cell immunotherapy.

METHODS

131 patients enrolled in this study received γδT cell immunotherapy with or without standard therapies. Their overall survival was analyzed by the Kaplan-Meier with log-rank test and Cox regression methods. Immunological analysis was performed by flow cytometry (FCM) before and after six cycles of γδT cell immunotherapy.

RESULTS

Multivariable analysis revealed that patients who showed stable disease (SD) and partial response (PR) to γδT cell immunotherapy showed better prognosis than those with a progressive disease (PD) (P = 0.0269, hazard ratio [HR], 0.410, 95% confidence interval [CI], 0.190-0.901). Furthermore, when immunological parameters were examined by FCM, the high Vγ9/γδT ratio (i.e., the high purity of the Vγ9 cells within the adoptively transferred γδT cells) before treatment was found to be a good prognostic factor for γδT cell immunotherapy (P = 0.0142, HR, 0.328, 95% CI, 0.125-0.801). No serious adverse events were reported during γδT cell immunotherapy.

CONCLUSION

Thus, γδT cell immunotherapy might extend the survival of patients with solid tumors.

Induction of Antitumor Immunity by Exosomes Isolated from Cryopreserved Cord Blood Monocyte-Derived Dendritic Cells

(1) Background: Dendritic cell (DC) vaccination has shown outstanding achievements in cancer treatment, although it still has some adverse side effects. Vaccination with DC-derived exosomes has been thought to overcome the side effects of the parental DCs. (2) Method: We performed the experiments to check the ability of cryopreserved umbilical cord blood mononuclear cell-derived DCs (cryo CBMDCs) and their exosomes to prime allogeneic T cell proliferation and allogeneic peripheral blood mononuclear cell (alloPBMCs) cytotoxicity against A549 lung cancer cells. (3) Results: We found that both lung tumor cell lysate-pulsed DCs and their exosomes could induce allogeneic T cell proliferation. Moreover, alloPBMCs primed with tumor cell lysate-pulsed DCs and their exosomes have a greater cytotoxic activity against A549 cells compared to unprimed cells and cells primed with unpulsed DCs and their exosomes. (4) Conclusion: Tumor cell lysate-pulsed DCs and their exosomes should be considered to develop into a novel immunotherapeutic strategy-e.g., vaccines-for patients with lung cancer. Our results also suggested that cryo umbilical cord blood mononuclear cells source, which is a readily and available source, is effective for generation of allogeneic DCs and their exosomes will be material for vaccinating against cancer.

Alpaca (Vicugna pacos), the first nonprimate species with a phosphoantigen-reactive Vγ9Vδ2 T cell subset

Vγ9Vδ2 T cells are a major γδ T cell population in the human blood expressing a characteristic Vγ9JP rearrangement paired with Vδ2. This cell subset is activated in a TCR-dependent and MHC-unrestricted fashion by so-called phosphoantigens (PAgs). PAgs can be microbial [(E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate, HMBPP] or endogenous (isopentenyl pyrophosphate, IPP) and PAg sensing depends on the expression of B7-like butyrophilin (BTN3A, CD277) molecules. IPP increases in some transformed or aminobisphosphonate-treated cells, rendering those cells a target for Vγ9Vδ2 T cells in immunotherapy. Yet, functional Vγ9Vδ2 T cells have only been described in humans and higher primates. Using a genome-based study, we showed in silico translatable genes encoding Vγ9, Vδ2, and BTN3 in a few nonprimate mammalian species. Here, with the help of new monoclonal antibodies, we directly identified a T cell population in the alpaca (Vicugna pacos), which responds to PAgs in a BTN3-dependent fashion and shows typical TRGV9- and TRDV2-like rearrangements. T cell receptor (TCR) transductants and BTN3-deficient human 293T cells reconstituted with alpaca or human BTN3 or alpaca/human BTN3 chimeras showed that alpaca Vγ9Vδ2 TCRs recognize PAg in the context of human and alpaca BTN3. Furthermore, alpaca BTN3 mediates PAg recognition much better than human BTN3A1 alone and this improved functionality mapped to the transmembrane/cytoplasmic part of alpaca BTN3. In summary, we found remarkable similarities but also instructive differences of PAg-recognition by human and alpaca, which help in better understanding the molecular mechanisms controlling the activation of this prominent population of γδ T cells.