Targeting human {gamma}delta} T cells with zoledronate and interleukin-2 for immunotherapy of hormone-refractory prostate cancer

Single-cell transcriptomic analysis of the immune microenvironment in pediatric acute leukemia

Relapse and treatment resistance pose significant challenges in the management of pediatric B cell acute lymphoblastic leukemia (B-ALL) and acute myeloid leukemia (AML). The efficacy of immunotherapy in leukemia remains limited due to factors such as the immunosuppressive tumor microenvironment (TME) and lack of suitable immunotherapeutic targets. Thus, an in-depth characterization of the TME in pediatric leukemia is warranted to improve the efficacy of immunotherapy. Here, we used single-cell RNA sequencing (scRNA-seq) to characterize the TME of pediatric B-ALL and AML, focusing specifically on bone-marrow-derived T cells. Moreover, we investigated the transcriptome changes during the initiation, remission, and relapse stages of pediatric AML. Our findings revealed that specific functional expression programs correlated with fluctuations in various T cell subsets, which may be associated with AML progression and relapse. Furthermore, our analysis of cellular communication networks led to the identification of VISTA, CD244, and TIM3 as potential immunotherapeutic targets in pediatric AML. Finally, we detected elevated proportions of γδ T cells and associated functional genes in samples from pediatric patients diagnosed with B-ALL and AML, which could inform the development of novel therapeutic approaches, potentially focusing on γδ T cells.

Beyond CAR T cells: exploring alternative cell sources for CAR-like cellular therapies

Chimeric antigen receptor (CAR)-T cell therapy has led to remarkable clinical outcomes in the treatment of hematological malignancies. However, challenges remain, such as limited infiltration into solid tumors, inadequate persistence, systemic toxicities, and manufacturing insufficiencies. The use of alternative cell sources for CAR-based therapies, such as natural killer cells (NK), macrophages (MΦ), invariant Natural Killer T (iNKT) cells, γδT cells, neutrophils, and induced pluripotent stem cells (iPSC), has emerged as a promising avenue. By harnessing these cells' inherent cytotoxic mechanisms and incorporating CAR technology, common CAR-T cell-related limitations can be effectively mitigated. We herein present an overview of the tumoricidal mechanisms, CAR designs, and manufacturing processes of CAR-NK cells, CAR-MΦ, CAR-iNKT cells, CAR-γδT cells, CAR-neutrophils, and iPSC-derived CAR-cells, outlining the advantages, limitations, and potential solutions of these therapeutic strategies.

Immunocytes interact directly with cancer cells in the tumor microenvironment: one coin with two sides and future perspectives

The tumor microenvironment is closely linked to the initiation, promotion, and progression of solid tumors. Among its constitutions, immunologic cells emerge as critical players, facilitating immune evasion and tumor progression. Apart from their indirect impact on anti-tumor immunity, immunocytes directly influence neoplastic cells, either bolstering or impeding tumor advancement. However, current therapeutic modalities aimed at alleviating immunosuppression from regulatory cells on effector immune cell populations may not consistently yield satisfactory results in various solid tumors, such as breast carcinoma, colorectal cancer, etc. Therefore, this review outlines and summarizes the direct, dualistic effects of immunocytes such as T cells, innate lymphoid cells, B cells, eosinophils, and tumor-associated macrophages on tumor cells within the tumor microenvironment. The review also delves into the underlying mechanisms involved and presents the outcomes of clinical trials based on these direct effects, aiming to propose innovative and efficacious therapeutic strategies for addressing solid tumors.

Exercise-induced β2-adrenergic Receptor Activation Enhances the Antileukemic Activity of Expanded γδ T-Cells via DNAM-1 Upregulation and PVR/Nectin-2 Recognition

Exercise mobilizes cytotoxic lymphocytes to blood which may allow superior cell products to be harvested and manufactured for cancer therapy. Gamma-Delta (γδ) T-cells have shown promise for treating solid tumors, but there is a need to increase their potency against hematologic malignancies. Here, we show that human γδ T-cells mobilized to blood in response to just 20 minutes of graded exercise have surface phenotypes and transcriptomic profiles associated with cytotoxicity, adhesion, migration, and cytokine signaling. Following 14 days ex vivo expansion with zoledronic acid and IL2, exercise mobilized γδ T-cells had surface phenotypes and transcriptomic profiles associated with enhanced effector functions and demonstrated superior cytotoxic activity against multiple hematologic tumors in vitro and in vivo in leukemia-bearing xenogeneic mice. Infusing humans with the β1+β2-agonist isoproterenol and administering β1 or β1+β2 antagonists prior to exercise revealed these effects to be β2-adrenergic receptor (AR) dependent. Antibody blocking of DNAM-1 on expanded γδ T-cells, as well as the DNAM-1 ligands PVR and Nectin-2 on leukemic targets, abolished the enhanced antileukemic effects of exercise. These findings provide a mechanistic link between exercise, β2-AR activation, and the manufacture of superior γδ T-cell products for adoptive cell therapy against hematologic malignancies.

SIGNIFICANCE

Exercise mobilizes effector γδ T-cells to blood via β2-adrenergic signaling which allows for generation of a potent expanded γδ T-cell product that is highly cytotoxic against hematologic malignancies.

Favorable impact of PD1/PD-L1 antagonists on bone remodeling: an exploratory prospective clinical study and ex vivo validation

BACKGROUND

Skeletal morbidity in patients with cancer has a major impact on the quality of life, and preserving bone health while improving outcomes is an important goal of modern antitumor treatment strategies. Despite their widespread use in early disease stages, the effects of immune checkpoint inhibitors (ICIs) on the skeleton are still poorly defined. Here, we initiated a comprehensive investigation of the impact of ICIs on bone health by longitudinal assessment of bone turnover markers in patients with cancer and by validation in a novel bioengineered 3D model of bone remodeling.

METHODS

An exploratory longitudinal study was conducted to assess serum markers of bone resorption (C-terminal telopeptide, CTX) and formation (procollagen type I N-terminal propeptide, PINP, and osteocalcin, OCN) before each ICI application (programmed cell death 1 (PD1) inhibitor or programmed death-ligand 1 (PD-L1) inhibitor) for 6 months or until disease progression in patients with advanced cancer and no evidence of bone metastases. To validate the in vivo results, we evaluated osteoclast (OC) and osteoblast (OB) differentiation on treatment with ICIs. In addition, their effect on bone remodeling was assessed by immunohistochemistry, confocal microscopy, and proteomics analysis in a dynamic 3D bone model.

RESULTS

During the first month of treatment, CTX levels decreased sharply but transiently. In contrast, we observed a delayed increase of serum levels of PINP and OCN after 4 months of therapy. In vitro, ICIs impaired the maturation of preosteoclasts by inhibiting STAT3/NFATc1 signaling but not JNK, ERK, and AKT while lacking any direct effect on osteogenesis. However, using our bioengineered 3D bone model, which enables the simultaneous differentiation of OB and OC precursor cells, we confirmed the uncoupling of the OC/OB activity on exposure to ICIs by demonstrating impaired OC maturation along with increased OB differentiation.

CONCLUSION

Our study indicates that the inhibition of the PD1/PD-L1 signaling axis interferes with bone turnover and may exert a protective effect on bone by indirectly promoting osteogenesis.

Phase I study of zoledronic acid combined with escalated doses of interleukine-2 for early in vivo generation of Vγ9Vδ2 T-cells after haploidentical stem cell transplant with posttransplant cyclophosphamide

The presence of donor Vγ9Vδ2 T-cells after haploidentical hematopoietic stem cell transplant (h-HSCT) has been associated with improved disease-free survival. These cells kill tumor cells in a non-MHC restricted manner, do not induce graft-versus-host disease (GVHD), and can be generated by stimulation with zoledronic acid (ZA) in combination with interleukin-2 (IL-2). This monocentric phase I, open-label, dose-escalating study (ClinicalTrials.gov: NCT03862833) aimed at evaluating the safety and possibility to generate Vγ9Vδ2 T-cells early after h-HSCT. It applied a standard 3 + 3 protocol to determine the maximum tolerated dose (MTD) of increasing low-doses of IL-2 (5 days [d] per week, 4 weeks) in combination with a single dose of ZA, starting both the first Monday after d + 15 posttransplant. Vγ9Vδ2 T-cell monitoring was performed by multiparameter flow cytometry on blood samples and compared with a control cohort of h-HSCT recipients. Twenty-six patients were included between April 2019 and September 2022, 16 of whom being ultimately treated and seven being controls who received h-HSCT only. At the three dose levels tested, 1, 0, and 1 dose-limiting toxicities were observed. MTD was not reached. A significantly higher number of Vγ9Vδ2 T-cells was observed during IL-2 treatment compared with controls. In conclusion, early in vivo generation of Vγ9Vδ2 T-cells is feasible after h-HSCT by using a combination of ZA and repeated IL-2 infusions. This study paves the way to a future phase 2 study, with the hope to document lesser posttransplant relapse with this particular adaptive immunotherapy.

Effective γδ T-cell clinical therapies: current limitations and future perspectives for cancer immunotherapy

γδ T cells are a unique subset of T lymphocytes, exhibiting features of both innate and adaptive immune cells and are involved with cancer immunosurveillance. They present an attractive alternative to conventional T cell-based immunotherapy due, in large part, to their lack of major histocompatibility (MHC) restriction and ability to secrete high levels of cytokines with well-known anti-tumour functions. To date, clinical trials using γδ T cell-based immunotherapy for a range of haematological and solid cancers have yielded limited success compared with in vitro studies. This inability to translate the efficacy of γδ T-cell therapies from preclinical to clinical trials is attributed to a combination of several factors, e.g. γδ T-cell agonists that are commonly used to stimulate populations of these cells have limited cellular uptake yet rely on intracellular mechanisms; administered γδ T cells display low levels of tumour-infiltration; and there is a gap in the understanding of γδ T-cell inhibitory receptors. This review explores the discrepancy between γδ T-cell clinical and preclinical performance and offers viable avenues to overcome these obstacles. Using more direct γδ T-cell agonists, encapsulating these agonists into lipid nanocarriers to improve their pharmacokinetic and pharmacodynamic profiles and the use of combination therapies to overcome checkpoint inhibition and T-cell exhaustion are ways to bridge the gap between preclinical and clinical success. Given the ability to overcome these limitations, the development of a more targeted γδ T-cell agonist-checkpoint blockade combination therapy has the potential for success in clinical trials which has to date remained elusive.

Adoptive cell therapy for high grade gliomas using simultaneous temozolomide and intracranial mgmt-modified γδ t cells following standard post-resection chemotherapy and radiotherapy: current strategy and future directions

Cellular therapies, including chimeric antigen receptor T cell therapies (CAR-T), while generally successful in hematologic malignancies, face substantial challenges against solid tumors such as glioblastoma (GBM) due to rapid growth, antigen heterogeneity, and inadequate depth of response to cytoreductive and immune therapies, We have previously shown that GBM constitutively express stress associated NKG2D ligands (NKG2DL) recognized by gamma delta (γδ) T cells, a minor lymphocyte subset that innately recognize target molecules via the γδ T cell receptor (TCR), NKG2D, and multiple other mechanisms. Given that NKG2DL expression is often insufficient on GBM cells to elicit a meaningful response to γδ T cell immunotherapy, we then demonstrated that NKG2DL expression can be transiently upregulated by activation of the DNA damage response (DDR) pathway using alkylating agents such as Temozolomide (TMZ). TMZ, however, is also toxic to γδ T cells. Using a p140K/MGMT lentivector, which confers resistance to TMZ by expression of O(6)-methylguanine-DNA-methyltransferase (MGMT), we genetically engineered γδ T cells that maintain full effector function in the presence of therapeutic doses of TMZ. We then validated a therapeutic system that we termed Drug Resistance Immunotherapy (DRI) that combines a standard regimen of TMZ concomitantly with simultaneous intracranial infusion of TMZ-resistant γδ T cells in a first-in-human Phase I clinical trial (NCT04165941). This manuscript will discuss DRI as a rational therapeutic approach to newly diagnosed GBM and the importance of repeated administration of DRI in combination with the standard-of-care Stupp regimen in patients with stable minimal residual disease.

The 29th Annual Prostate Cancer Foundation Scientific Retreat Report

BACKGROUND

The 29th Annual Prostate Cancer Foundation (PCF) Scientific Retreat was held from October 27 to 29, 2022, at the Omni La Costa Resort in Carlsbad, CA. This was the first-ever hybrid PCF Retreat.

METHODS

The Annual PCF Scientific Retreat is a prominent international scientific gathering centered on groundbreaking, unpublished, and influential studies in basic, translational, and clinical prostate cancer research. It also covers research from related fields with a strong potential for influencing prostate cancer research and patient care.

RESULTS

Key areas of research that were focused on at the 2022 PCF Retreat included: (i) the contributions of molecular and genomic factors to prostate cancer disparities; (ii) novel clinical trial updates; (iii) lessons from primary prostate cancer; (iv) lessons from single-cell studies; (v) genetic, epigenetic, epitranscriptomic and posttranslational mechanisms and clinical heterogeneity in prostate cancer; (vi) biology of neuroendocrine and lineage-plastic prostate cancer; (vii) next generation prostate cancer theranostics and combination therapies; (viii) the biology and therapeutic potential of targeting phosphoinositide 3-kinases pathways; (ix) combining immunomodulatory treatments for prostate cancer; (x) novel gamma delta (γδ) T-cell therapy platforms for oncology; and (xi) lessons from other cancers.

CONCLUSIONS

This article provides a summary of the presentations from the 2022 PCF Scientific Retreat. By disseminating this knowledge, we hope to enhance our understanding of the present research landscape and guide future strides in both prostate cancer research and patient care.

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.

Vdelta1 T cells are more resistant than Vdelta2 T cells to the immunosuppressive properties of galectin-3

Ovarian carcinomas have the highest lethality amongst gynecological tumors. A problem after primary resection is the recurrence of epithelial ovarian carcinomas which is often associated with chemotherapy resistance. To improve the clinical outcome, it is of high interest to consider alternative therapy strategies. Due to their pronounced plasticity, γδ T cells are attractive for T-cell-based immunotherapy. However, tumors might escape by the release of lectin galectin-3, which impairs γδ T-cell function. Hence, we tested the effect of galectin-3 on the different γδ T-cell subsets. After coculture between ovarian tumor cells and Vδ1 or Vδ2 T cells enhanced levels of galectin-3 were released. This protein did not affect the cytotoxicity of both γδ T-cell subsets, but differentially influenced the proliferation of the two γδ T-cell subsets. While increased galectin-3 levels and recombinant galectin-3 inhibited the proliferation of Vδ2 T cells, Vδ1 T cells were unaffected. In contrast to Vδ1 T cells, the Vδ2 T cells strongly upregulated the galectin-3 binding partner α3β1-integrin after their activation correlating with the immunosuppressive properties of galectin-3. In addition, galectin-3 reduced the effector memory compartment of zoledronate-activated Vδ2 T cells. Therefore, our data suggest that an activation of Vδ1 T-cell proliferation as part of a T-cell-based immunotherapy can be of advantage.

γδ T cell-mediated cytotoxicity against patient-derived healthy and cancer cervical organoids

Cervical cancer is a leading cause of death among women globally, primarily driven by high-risk papillomaviruses. However, the effectiveness of chemotherapy is limited, underscoring the potential of personalized immunotherapies. Patient-derived organoids, which possess cellular heterogeneity, proper epithelial architecture and functionality, and long-term propagation capabilities offer a promising platform for developing viable strategies. In addition to αβ T cells and natural killer (NK) cells, γδ T cells represent an immune cell population with significant therapeutic potential against both hematologic and solid tumours. To evaluate the efficacy of γδ T cells in cervical cancer treatment, we generated patient-derived healthy and cancer ectocervical organoids. Furthermore, we examined transformed healthy organoids, expressing HPV16 oncogenes E6 and E7. We analysed the effector function of in vitro expanded γδ T cells upon co-culture with organoids. Our findings demonstrated that healthy cervical organoids were less susceptible to γδ T cell-mediated cytotoxicity compared to HPV-transformed organoids and cancerous organoids. To identify the underlying pathways involved in this observed cytotoxicity, we performed bulk-RNA sequencing on the organoid lines, revealing differences in DNA-damage and cell cycle checkpoint pathways, as well as transcription of potential γδ T cell ligands. We validated these results using immunoblotting and flow cytometry. We also demonstrated the involvement of BTN3A1 and BTN2A1, crucial molecules for γδ T cell activation, as well as differential expression of PDL1/CD274 in cancer, E6/E7+ and healthy organoids. Interestingly, we observed a significant reduction in cytotoxicity upon blocking MSH2, a protein involved in DNA mismatch-repair. In summary, we established a co-culture system of γδ T cells with cervical cancer organoids, providing a novel in vitro model to optimize innovative patient-specific immunotherapies for cervical cancer.

γδ T cells: origin and fate, subsets, diseases and immunotherapy

The intricacy of diseases, shaped by intrinsic processes like immune system exhaustion and hyperactivation, highlights the potential of immune renormalization as a promising strategy in disease treatment. In recent years, our primary focus has centered on γδ T cell-based immunotherapy, particularly pioneering the use of allogeneic Vδ2+ γδ T cells for treating late-stage solid tumors and tuberculosis patients. However, we recognize untapped potential and optimization opportunities to fully harness γδ T cell effector functions in immunotherapy. This review aims to thoroughly examine γδ T cell immunology and its role in diseases. Initially, we elucidate functional differences between γδ T cells and their αβ T cell counterparts. We also provide an overview of major milestones in γδ T cell research since their discovery in 1984. Furthermore, we delve into the intricate biological processes governing their origin, development, fate decisions, and T cell receptor (TCR) rearrangement within the thymus. By examining the mechanisms underlying the anti-tumor functions of distinct γδ T cell subtypes based on γδTCR structure or cytokine release, we emphasize the importance of accurate subtyping in understanding γδ T cell function. We also explore the microenvironment-dependent functions of γδ T cell subsets, particularly in infectious diseases, autoimmune conditions, hematological malignancies, and solid tumors. Finally, we propose future strategies for utilizing allogeneic γδ T cells in tumor immunotherapy. Through this comprehensive review, we aim to provide readers with a holistic understanding of the molecular fundamentals and translational research frontiers of γδ T cells, ultimately contributing to further advancements in harnessing the therapeutic potential of γδ T cells.

Modulation of lytic molecules restrain serial killing in γδ T lymphocytes

γδ T cells play a pivotal role in protection against various types of infections and tumours, from early childhood on and throughout life. They consist of several subsets characterised by adaptive and innate-like functions, with Vγ9Vδ2 being the largest subset in human peripheral blood. Although these cells show signs of cytotoxicity, their modus operandi remains poorly understood. Here we explore, using live single-cell imaging, the cytotoxic functions of γδ T cells upon interactions with tumour target cells with high temporal and spatial resolution. While γδ T cell killing is dominated by degranulation, the availability of lytic molecules appears tightly regulated in time and space. In particular, the limited co-occurrence of granzyme B and perforin restrains serial killing of tumour cells by γδ T cells. Thus, our data provide new insights into the cytotoxic arsenal and functions of γδ T cells, which may guide the development of more efficient γδ T cell based adoptive immunotherapies.

Human gamma-delta (γδ) T cell therapy for glioblastoma: A novel alternative to overcome challenges of adoptive immune cell therapy

Glioblastoma is the most common brain malignancy with devastating prognosis. Numerous clinical trials using various target therapeutic agents have failed and recent clinical trials using check point inhibitors also failed to provide survival benefits for glioblastoma patients. Adoptive T cell transfer is suggested as a novel therapeutic approach that has exhibited promise in preliminary clinical studies. However, the clinical outcomes are inconsistent, and there are several limitations of current adoptive T cell transfer strategies for glioblastoma treatment. As an alternative cell therapy, gamma-delta (γδ) T cells have been recently introduced for several cancers including glioblastoma. Since the leading role of γδ T cells is immune surveillance by recognizing a broad range of ligands including stress molecules, phosphoantigens, or lipid antigens, recent studies have suggested the potential benefits of γδ T cell transfer against glioblastomas. However, γδ T cells, as a small subset (1-5%) of T cells in human peripheral blood, are relatively unknown compared to conventional alpha-beta (αβ) T cells. In this context, our study introduced γδ T cells as an alternative and novel option to overcome several challenges regarding immune cell therapy in glioblastoma treatment. We described the unique characteristics and advantages of γδ T cells compared to conventional αβ T cells and summarize several recent preclinical studies using human gamma-delta T cell therapy for glioblastomas. Finally, we suggested future direction of human γδ T cell therapy for glioblastomas.

Local γδ T cells: translating promise to practice in cancer immunotherapy

Rapid bench-to-bedside translation of basic immunology to cancer immunotherapy has revolutionised the clinical practice of oncology over the last decade. Immune checkpoint inhibitors targeting αβ T cells now offer durable remissions and even cures for some patients with hitherto treatment-refractory metastatic cancers. Unfortunately, these treatments only benefit a minority of patients and efforts to improve efficacy through combination therapies utilising αβ T cells have seen diminishing returns. Alongside αβ T cells and B cells, γδ T cells are a third lineage of adaptive lymphocytes. Less is known about these cells, and they remain relatively untested in cancer immunotherapy. Whilst preclinical evidence supports their utility, the few early-phase trials involving γδ T cells have failed to demonstrate convincing efficacy in solid cancers. Here we review recent progress in our understanding of how these cells are regulated, especially locally within tissues, and the potential for translation. In particular, we focus on the latest advances in the field of butyrophilin (BTN) and BTN-like (BTNL) regulation of γδ T cells and speculate on how these advances may address the limitations of historical approaches in utilising these cells, as well as how they may inform novel approaches in deploying these cells for cancer immunotherapy.

Insight into Cancer Immunity: MHCs, Immune Cells and Commensal Microbiota

Cancer cells circumvent immune surveillance via diverse strategies. In accordance, a large number of complex studies of the immune system focusing on tumor cell recognition have revealed new insights and strategies developed, largely through major histocompatibility complexes (MHCs). As one of them, tumor-specific MHC-II expression (tsMHC-II) can facilitate immune surveillance to detect tumor antigens, and thereby has been used in immunotherapy, including superior cancer prognosis, clinical sensitivity to immune checkpoint inhibition (ICI) therapy and tumor-bearing rejection in mice. NK cells play a unique role in enhancing innate immune responses, accounting for part of the response including immunosurveillance and immunoregulation. NK cells are also capable of initiating the response of the adaptive immune system to cancer immunotherapy independent of cytotoxic T cells, clearly demonstrating a link between NK cell function and the efficacy of cancer immunotherapies. Eosinophils were shown to feature pleiotropic activities against a variety of solid tumor types, including direct interactions with tumor cells, and accessorily affect immunotherapeutic response through intricating cross-talk with lymphocytes. Additionally, microbial sequencing and reconstitution revealed that commensal microbiota might be involved in the modulation of cancer progression, including positive and negative regulatory bacteria. They may play functional roles in not only mucosal modulation, but also systemic immune responses. Here, we present a panorama of the cancer immune network mediated by MHCI/II molecules, immune cells and commensal microbiota and a discussion of prospective relevant intervening mechanisms involved in cancer immunotherapies.

New insights and options into the mechanisms and effects of combined targeted therapy and immunotherapy in prostate cancer

Chronic inflammation is believed to drive prostate carcinogenesis by producing reactive oxygen species or reactive nitrogen species to induce DNA damage. This effect might subsequently cause epigenetic and genomic alterations, leading to malignant transformation. Although established therapeutic advances have extended overall survival, tumors in patients with advanced prostate cancer are prone to metastasis, transformation into metastatic castration-resistant prostate cancer, and therapeutic resistance. The tumor microenvironment (TME) of prostate cancer is involved in carcinogenesis, invasion and drug resistance. A plethora of preclinical studies have focused on immune-based therapies. Understanding the intricate TME system in prostate cancer may hold much promise for developing novel therapies, designing combinational therapeutic strategies, and further overcoming resistance to established treatments to improve the lives of prostate cancer patients. In this review, we discuss nonimmune components and various immune cells within the TME and their putative roles during prostate cancer initiation, progression, and metastasis. We also outline the updated fundamental research focusing on therapeutic advances of targeted therapy as well as combinational options for prostate cancer.

A close look at current γδ T-cell immunotherapy

Owing to their antitumor and major histocompatibility complex (MHC)-independent capacities, γδ T cells have gained popularity in adoptive T-cell immunotherapy in recent years. However, many unknowns still exist regarding γδ T cells, and few clinical data have been collected. Therefore, this review aims to describe all the main features of the applications of γδ T cells and provide a systematic view of current γδ T-cell immunotherapy. Specifically, this review will focus on how γδ T cells performed in treating cancers in clinics, on the γδ T-cell clinical trials that have been conducted to date, and the role of γδ T cells in the pharmaceutical industry.

The emerging roles of γδ T cells in cancer immunotherapy

Current cancer immunotherapies are primarily predicated on αβ T cells, with a stringent dependence on MHC-mediated presentation of tumour-enriched peptides or unique neoantigens that can limit their efficacy and applicability in various contexts. After two decades of preclinical research and preliminary clinical studies involving very small numbers of patients, γδ T cells are now being explored as a viable and promising approach for cancer immunotherapy. The unique features of γδ T cells, including their tissue tropisms, antitumour activity that is independent of neoantigen burden and conventional MHC-dependent antigen presentation, and combination of typical properties of T cells and natural killer cells, make them very appealing effectors in multiple cancer settings. Herein, we review the main functions of γδ T cells in antitumour immunity, focusing on human γδ T cell subsets, with a particular emphasis on the differences between Vδ1⁺ and Vδ2⁺ γδ T cells, to discuss their prognostic value in patients with cancer and the key therapeutic strategies that are being developed in an attempt to improve the outcomes of these patients.

NKG2A Immune Checkpoint in Vδ2 T Cells: Emerging Application in Cancer Immunotherapy

Immune regulation has revolutionized cancer treatment with the introduction of T-cell-targeted immune checkpoint inhibitors (ICIs). This successful immunotherapy has led to a more complete view of cancer that now considers not only the cancer cells to be targeted and destroyed but also the immune environment of the cancer cells. Current challenges associated with the enhancement of ICI effects are increasing the fraction of responding patients through personalized combinations of multiple ICIs and overcoming acquired resistance. This requires a complete overview of the anti-tumor immune response, which depends on a complex interplay between innate and adaptive immune cells with the tumor microenvironment. The NKG2A was revealed to be a key immune checkpoint for both Natural Killer (NK) cells and T cells. Monalizumab, a humanized anti-NKG2A antibody, enhances NK cell activity against various tumor cells and rescues CD8 αβ T cell function in combination with PD-1/PD-L1 blockade. In this review, we discuss the potential for targeting NKG2A expressed on tumor-sensing human γδ T cells, mostly on the specific Vδ2 T cell subset, in order to emphasize its importance and potential in the development of new ICI-based therapeutic approaches.

Correlation analysis between immune-related genes and cell infiltration revealed prostate cancer immunotherapy biomarkers linked to T cells gamma delta

Prostate cancer (PCa) is a urological malignancy with poor prognosis. Immune-related genes are associated with immune infiltration in prostate cancer, but their role in immunogenic PCa is less well understood. We assessed the infiltration patterns of 22 immune cells in PCa and the relationship of immune-related differentially expressed genes (IDEGs) with them. The 87 IDEGs are involved in the interaction between the extracellular matrix and the tumor microenvironment. The model, including seven IDEGs (SLPI, DES, IAPP, NPY, ISG15, PLA2G2A, and HLA-DMB), showed a good predictive power. The SLPI expression is positively correlated with the infiltration level of T cells gamma delta. In addition, PCa has high infiltration levels in Macrophages M1 (18.07%) and Dendritic cells activated (17.64%). The correlation analysis between IDEGs and immune cell infiltration suggested that PCa immunotherapy biomarkers may be closely related to T cells gamma delta.

The way of interaction between Vγ9Vδ2 T cells and tumor cells

Immunotherapy has been a promising, emerging treatment for various cancers. Gamma delta (γδ) T cells own a T cell receptor composed of γ- and δ- chain and act as crucial players in the anti-tumor immune effect. Currently, Vγ9Vδ2 T cells, the predominate γδ T cell subset in human peripheral blood, has been shown to exert multiple biological functions. In addition, a growing body of evidence notes that Vγ9Vδ2 T cells interact with tumor cells in many ways, such as TCR-mediated nonpeptidic-phosphorylated phosphoantigens (pAgs) recognization, NKG2D/NKG2D ligand (NKG2DL) pathway, Fas-FasL axis and antibody-dependent cellular cytotoxicity (ADCC) as well as exosome. More importantly, clinical studies with Vγ9Vδ2 T cells in cancers have propelled several clinical applications to investigate their safety and efficacy. Herein, this review summarized the underlying ways and mechanisms of interplay cancer cells and Vγ9Vδ2 T cells, which may help us to generate new strategies for tumor immunotherapy in the future.

Releasing the restraints of Vγ9Vδ2 T-cells in cancer immunotherapy

Objectives

Vγ9Vδ2 T-cells are a subset of T-cells with a crucial role in immunosurveillance which can be activated and expanded by multiple means to stimulate effector responses. Little is known about the expression of checkpoint molecules on this cell population and whether the ligation of these molecules can regulate their activity. The aim of this study was to assess the expression of both activatory and inhibitory receptors on Vγ9Vδ2 T-cells to assess potential avenues of regulation to target with immunotherapy.

Methods

Expression of various activatory and inhibitory receptors was assessed on Vγ9Vδ2 T-cells by flow cytometry following activation and expansion using zoledronic acid (ZA) and Bacillus Calmette-Guérin (BCG). Expression of these markers and production of effector molecules was also examined following co-culture with various tumour cell targets. The effect of immune checkpoint blockade on Vγ9Vδ2 T-cells was also explored.

Results

Vγ9Vδ2 T-cells expressed high levels of activatory markers both at baseline and following stimulation. Vγ9Vδ2 T-cells expressed variable levels of inhibitory checkpoint receptors with many being upregulated following stimulation. Expression of these markers is further modulated upon co-culture with tumour cells with changes reflecting activation and effector functions. Despite their high expression of inhibitory receptors when cultured with tumour cells expressing cognate ligands there was no effect on Vδ2+ T-cell cytotoxic capacity or cytokine production with immune checkpoint blockade.

Conclusions

Our work suggests the expression of checkpoint receptors present on Vγ9Vδ2 T-cells which may provide a mechanism with the potential to be utilised by tumour cells to subvert Vγ9Vδ2 T-cell cytotoxicity. This work suggests important candidates for blockade by ICI therapy in order to increase the successful use of Vγ9Vδ2 T-cells in immunotherapy.

Immunological effects and activity of multiple doses of zolbetuximab in combination with zoledronic acid and interleukin-2 in a phase 1 study in patients with advanced gastric and gastroesophageal junction cancer

PURPOSE

Zolbetuximab (IMAB362) is engineered to induce antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity. We evaluated ADCC activity and the impact of the immune-modulating drugs zoledronic acid (ZA) and interleukin-2 (IL-2) as co-treatment with zolbetuximab on relevant immune cell populations and ADCC lysis activity.

METHODS

This phase 1, multicenter, open-label study investigated the immunological effects and activity, safety, tolerability, and antitumor activity of multiple doses of zolbetuximab alone (n = 5) or in combination with ZA (n = 7) or with ZA plus two different dose levels of IL-2 (low dose: 1 million international units [mIU] [n = 9]; intermediate dose: 3 mIU [n = 7]) in pretreated patients with advanced gastric and gastroesophageal junction (G/GEJ) adenocarcinoma.

RESULTS

Twenty-eight patients with previously treated advanced G/GEJ adenocarcinoma that was CLDN18.2-expressing were enrolled into four treatment arms. Treatment with zolbetuximab + ZA + IL-2 induced short-lived expansion and activation of ADCC-mediating cell populations, namely γ9δ2 T cells and natural killer cells, within 2 days after administration; this effect was more pronounced with intermediate-dose IL-2. Expansion and activation of regulatory T cells treated with either IL2 dose was moderate and short-lived. Strong ADCC activity was observed with zolbetuximab alone. Short-lived ADCC activity was observed in several patients treated with ZA + intermediate-dose IL-2, but not lower-dose IL-2. In the clinical efficacy population, the best confirmed response was stable disease (n = 11/19; 58%).

CONCLUSIONS

Zolbetuximab mediates proficient ADCC in patients with pretreated advanced G/GEJ cancers. Co-treatment with ZA + IL-2 did not further improve this effect.

TRIAL REGISTRATION

NCT01671774.

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.

γδ T cells and their clinical application in colon cancer

In recent years, research has focused on colorectal cancer to implement modern treatment approaches to improve patient survival. In this new era, γδ T cells constitute a new and promising candidate to treat many types of cancer because of their potent killing activity and their ability to recognize tumor antigens independently of HLA molecules. Here, we focus on the roles that γδ T cells play in antitumor immunity, especially in colorectal cancer. Furthermore, we provide an overview of small-scale clinical trials in patients with colorectal cancer employing either in vivo activation or adoptive transfer of ex vivo expanded γδ T cells and suggest possible combinatorial approaches to treat colon cancer.

Bibliometric analysis of single-cell sequencing researches on immune cells and their application of DNA damage repair in cancer immunotherapy

INTRODUCTION

In recent decades, single-cell sequencing technology has developed rapidly and used widely in various fields of life sciences, especially for the detection of immune cells. A bibliometric analysis of single-cell sequencing research work on immune cells published during the 2011-2021 period should provide new insight on the use of single-cell sequencing.

METHODS

We screened 1,460 publications on single-cell sequencing on immune cells according to the publication date, article type, language, and country.

REULTS

The United States published the first and largest number of articles, while China's research started relatively late, but ranked second in the number of publications. T cells were the most commonly studied immune cells by single-cell sequencing, followed by mononuclear macrophages. Cancer biology was the most common field of immune cell research by single-cell sequencing. Single-cell sequencing studies using γδ T cells were mainly in the fields of cancer biology and cell development, and focused over time from cell surface receptor to cell function. Through in-depth analysis of the articles on single-cell sequencing of T cells in the oncology field, our analysis found that immunotherapy and tumor microenvironment were the most popular research directions in recent years.

DISCUSSION

The combination of DNA damage repair and immunotherapy seems to provide a new strategy for cancer therapy.

Human Vδ2 T Cells and Their Versatility for Immunotherapeutic Approaches

Gamma/delta (γδ) T cells are innate-like immune effectors that are a critical component linking innate and adaptive immune responses. They are recognized for their contribution to tumor surveillance and fight against infectious diseases. γδ T cells are excellent candidates for cellular immunotherapy due to their unique properties to recognize and destroy tumors or infected cells. They do not depend on the recognition of a single antigen but rather a broad-spectrum of diverse ligands through expression of various cytotoxic receptors. In this manuscript, we review major characteristics of the most abundant circulating γδ subpopulation, Vδ2 T cells, their immunotherapeutic potential, recent advances in expansion protocols, their preclinical and clinical applications for several infectious diseases and malignancies, and how additional modulation could enhance their therapeutic potential.

Lymphoid Lineage γδ T Cells Were Successfully Generated from Human Pluripotent Stem Cells via Hemogenic Endothelium

γδ T cells are a rare and unique prototype of T cells that share properties with natural killer cells in secondary lymphoid organs. Although many studies have revealed the function and importance of adult-derived γδ T cells in cancer biology and regenerative medicine, the low numbers of these cells hamper their application as therapeutic cell sources in the clinic. To solve this problem, pluripotent stem cell-derived γδ T cells are considered alternative cell sources; however, few studies have reported the generation of human pluripotent stem cell-derived γδ T cells. In the present study, we investigated whether lymphoid lineage γδ T cells were successfully generated from human pluripotent stem cells via hemogenic endothelium under defined culture conditions. Our results revealed that pluripotent stem cells successfully generated γδ T cells with an overall increase in transcriptional activity of lymphoid lineage genes and cytolytic factors, indicating the importance of the optimization of culture conditions in generating lymphoid lineage γδ T cells. We uncovered an initial step in differentiating γδ T cells that could be applied to basic and translational investigations in the field of cancer biology. Based on our result, we will develop an appropriate method to purify γδ T cells with functionality and it helpful for the study of basic mechanism of γδ T cells in pathophysiologic condition as well as clinic application.

Identification of the immunosuppressive effect of γδ T cells correlated to bone morphogenetic protein 2 in acute myeloid leukemia

Description of immune landscapes in malignant microenvironment is critical to the improvement of therapeutic strategies for various tumors. Acute myeloid leukemia (AML) remains a severe life-threatening malignancy and often confronts treatment dilemma in clinic. Although γδ T cells exhibit independent and potent cytotoxicity against leukemic cells in vitro and in the mouse models, efficacy of γδ T cell-based immunotherapy on AML patients has seemed unsatisfying so far. How the anti-AML capacity of γδ T cells is suppressed in vivo remains elusive. Herein, we found an aberrant γδ T cells subset expressing CD25⁺CD127^lowVδ2⁺ in the bone marrows of patients with newly diagnosed AML. The emergence of this subset was significantly associated with disease status and risk stratification as well as with the abnormally increased bone morphogenetic protein 2 (BMP2). Mechanistically, BMP2 could directly induce CD25⁺CD127^lowVδ2⁺ γδ T cells (named as Reg-Vδ2) in vitro. The immunosuppressive features of Reg-Vδ2 cells were identified by combining immunophenotypical and functional data. Furthermore, inhibition of BMP2 pathway significantly blocked the emergence of Reg-Vδ2 cells and enhanced the anti-AML immunity in humanized mice. These findings not only provide a novel insight into the mechanisms of immunosuppression in the context of leukemia, but also suggest potential targets for the treatment of AML and other hematopoietic malignancies.

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.

Lipids in cancer: a global view of the contribution of lipid pathways to metastatic formation and treatment resistance

Lipids are essential constituents for malignant tumors, as they are absolutely required for tumor growth and dissemination. Provided by the tumor microenvironment (TME) or by cancer cells themselves through activation of de novo synthesis pathways, they orchestrate a large variety of pro-tumorigenic functions. Importantly, TME cells, especially immune cells, cancer-associated fibroblasts (CAFs) and cancer-associated adipocytes (CAAs), are also prone to changes in their lipid content, which hinder or promote tumor aggressiveness. In this review, we address the significant findings for lipid contribution in tumor progression towards a metastatic disease and in the poor response to therapeutic treatments. We also highlight the benefits of targeting lipid pathways in preclinical models to slow down metastasis development and overcome chemo-and immunotherapy resistance.

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.

Controversial role of γδ T cells in pancreatic cancer

γδ T cells are rare lymphocytes with cogent impact on immune responses. These cells are one of the earliest cells to be recruited in the sites of infection or tumors and play a critical role in coordinating innate and adaptive immune responses. The anti-tumor activity of γδ T cells have been numerously reported; nonetheless, there is controversy among published studies regarding their anti-tumor vs pro-tumor effect- especially in pancreatic cancer. A myriad of studies has confirmed that activated γδ T cells can potently lyse a broad variety of solid tumors and leukemia/lymphoma cells and produce an array of cytokines; however, early γδ T cell-based clinical trials did not lead to optimal efficacy, despite acceptable safety. Depending on the local micromilieu, γδ T cells can differentiate into tumor promoting or suppressing cells such as Th1-, Th2-, or Th17-like cells and produce prototypical cytokines such as interferon-γ (IFNγ) and interleukin (IL)-4/-10, IL-9, or IL-17. In an abstruse tumor such as pancreatic cancer- also known as immunologically cold tumor- γδ T cells are more likely to switch to their immunosuppressive phenotype. In this review we will adduce the accumulated knowledge on these two controversial aspects of γδ T cells in cancers- with a focus on solid tumors and pancreatic cancer. In addition, we propose strategies for enhancing the anti-tumor function of γδ T cells in cancers and discuss the potential future directions.

Bacillus Calmette-Guerin (BCG) induces superior anti-tumour responses by Vδ2+ T cells compared with the aminobisphosphonate drug zoledronic acid

Vδ2⁺ T cells can recognize malignantly transformed cells as well as those infected with mycobacteria. This cross-reactivity supports the idea of using mycobacteria to manipulate Vδ2⁺ T cells in cancer immunotherapy. To date, therapeutic interventions using Vδ2⁺ T cells in cancer have involved expanding these cells in or ex vivo using zoledronic acid (ZA). Here, we show that the mycobacterium Bacillus Calmette–Guérin (BCG) also causes Vδ2⁺ T-cell expansion in vitro and that resulting Vδ2⁺ cell populations are cytotoxic toward tumour cell lines. We show that both ZA and BCG-expanded Vδ2+ cells effectively killed both Daudi and THP-1 cells. THP-1 cell killing by both ZA and BCG-expanded Vδ2+ cells was enhanced by treatment of targets cells with ZA. Although no difference in cytotoxic activity between ZA- and BCG-expanded Vδ2+ cells was observed, BCG-expanded cells degranulated more and produced a more diverse range of cytokines upon tumour cell recognition compared to ZA-expanded cells. ZA-expanded Vδ2+ cells were shown to upregulate exhaustion marker CD57 to a greater extent than BCG-expanded Vδ2+ cells. Furthermore, ZA expansion was associated with upregulation of inhibitory markers PD-1 and TIM3 in a dose-dependent manner whereas PD-1 expression was not increased following expansion using BCG. Intradermal BCG vaccination of rhesus macaques caused in vivo expansion of Vδ2⁺ cells. In combination with the aforementioned in vitro data, this finding suggests that BCG treatment could induce expansion of Vδ2⁺ T cells with enhanced anti-tumour potential compared to ZA treatment and that either ZA or BCG could be used intratumourally as a means to potentiate stronger anti-tumour Vδ2⁺ T-cell responses.

Human γδ T Cell Subsets and Their Clinical Applications for Cancer Immunotherapy

Simple Summary

Research into the immunotherapeutic potential of T cells has predominantly focused on conventional alpha beta (αβ) T cells, which recognize peptide antigens presented by polymorphic major histocompatibility complex (MHC) class I and class II molecules. However, innate-like T cells, such as gamma delta (γδ) T cells, also play important roles in antitumor immunity. Here, we review the current understanding of γδ T cells in antitumor immunity and discuss strategies that could potentially maximize their potential in cancer immunotherapy.

Abstract

Gamma delta (γδ) T cells are a minor population of T cells that share adaptive and innate immune properties. In contrast to MHC-restricted alpha beta (αβ) T cells, γδ T cells are activated in an MHC-independent manner, making them ideal candidates for developing allogeneic, off-the-shelf cell-based immunotherapies. As the field of cancer immunotherapy progresses rapidly, different subsets of γδ T cells have been explored. In addition, γδ T cells can be engineered using different gene editing technologies that augment their tumor recognition abilities and antitumor functions. In this review, we outline the unique features of different subsets of human γδ T cells and their antitumor properties. We also summarize the past and the ongoing pre-clinical studies and clinical trials utilizing γδ T cell-based cancer immunotherapy.

Gamma Delta T-Cell Based Cancer Immunotherapy: Past-Present-Future

γδ T-cells directly recognize and kill transformed cells independently of HLA-antigen presentation, which makes them a highly promising effector cell compartment for cancer immunotherapy. Novel γδ T-cell-based immunotherapies, primarily focusing on the two major γδ T-cell subtypes that infiltrate tumors (i.e. Vδ1 and Vδ2), are being developed. The Vδ1 T-cell subset is enriched in tissues and contains both effector T-cells as well as regulatory T-cells with tumor-promoting potential. Vδ2 T-cells, in contrast, are enriched in circulation and consist of a large, relatively homogeneous, pro-inflammatory effector T-cell subset. Healthy individuals typically harbor in the order of 50-500 million Vγ9Vδ2 T-cells in the peripheral blood alone (1-10% of the total CD3⁺ T-cell population), which can rapidly expand upon stimulation. The Vγ9Vδ2 T-cell receptor senses intracellular phosphorylated metabolites, which accumulate in cancer cells as a result of mevalonate pathway dysregulation or upon pharmaceutical intervention. Early clinical studies investigating the therapeutic potential of Vγ9Vδ2 T-cells were based on either ex vivo expansion and adoptive transfer or their systemic activation with aminobisphosphonates or synthetic phosphoantigens, either alone or combined with low dose IL-2. Immune-related adverse events (irAE) were generally \mild, but the clinical efficacy of these approaches provided overall limited benefit. In recent years, critical advances have renewed the excitement for the potential of Vγ9Vδ2 T-cells in cancer immunotherapy. Here, we review γδ T-cell-based therapeutic strategies and discuss the prospects of those currently evaluated in clinical studies in cancer patients as well as future therapies that might arise from current promising pre-clinical results.

Targeting Cytokine Signals to Enhance γδT Cell-Based Cancer Immunotherapy

γδT cells represent a small percentage of T cells in circulation but are found in large numbers in certain organs. They are considered to be innate immune cells that can exert cytotoxic functions on target cells without MHC restriction. Moreover, γδT cells contribute to adaptive immune response via regulating other immune cells. Under the influence of cytokines, γδT cells can be polarized to different subsets in the tumor microenvironment. In this review, we aimed to summarize the current understanding of antigen recognition by γδT cells, and the immune regulation mediated by γδT cells in the tumor microenvironment. More importantly, we depicted the polarization and plasticity of γδT cells in the presence of different cytokines and their combinations, which provided the basis for γδT cell-based cancer immunotherapy targeting cytokine signals.

Engineering γδ T Cells: Recognizing and Activating on Their Own Way

Adoptive cell therapy (ACT) with engineered T cells has emerged as a promising strategy for the treatment of malignant tumors. Among them, there is great interest in engineered γδ T cells for ACT. With both adaptive and innate immune characteristics, γδ T cells can be activated by γδ TCRs to recognize antigens in a MHC-independent manner, or by NK receptors to recognize stress-induced molecules. The dual recognition system enables γδ T cells with unique activation and cytotoxicity profiles, which should be considered for the design of engineered γδ T cells. However, the current designs of engineered γδ T cells mostly follow the strategies that used in αβ T cells, but not making good use of the specific characteristics of γδ T cells. Therefore, it is no surprising that current engineered γδ T cells in preclinical or clinical trials have limited efficacy. In this review, we summarized the patterns of antigen recognition of γδ T cells and the features of signaling pathways for the functions of γδ T cells. This review will additionally discuss current progress in engineered γδ T cells and provide insights in the design of engineered γδ T cells based on their specific characteristics.

Anti-cancer γδ T lymphocytes: contradictory past and promising future

Recent anti-cancer strategies are based on the stimulation of anti-tumor immune reaction, exploiting distinct lymphocyte subsets. Among them, γδ T cells represent optimal anti-cancer candidates, especially in those tissues where they are highly localized, such as the respiratory or gastrointestinal tract. One important challenge has been the identification of stimulating drugs able to induce and maintain γδ T cell-mediated anti-cancer immune response. Amino-bisphosphonates (N-BPs) have been largely employed in anti-cancer clinical trials due to their ability to upregulate the accumulation of pyrophosphates that promote the activation of Vγ9Vδ2 T cells. This activation depends on the butyrophilin A family, which is crucial in contributing to Vγ9Vδ2 T cells stimulation but is not equally expressed in all cancer tissues. Thus, the clinical outcome of such treatments is still a challenge. In this viewpoint, a critical picture of γδ T cells as effective anti-cancer effectors is designed, with a specific focus on the best immune-stimulating therapeutic schemes involving this lymphocyte subset and the tools available to measure their efficacy and presence in tumor tissues. Some pre-clinical models, useful to measure γδ T cell anti-cancer potential and their response to stimulating drugs, therapeutic monoclonal antibodies, or bispecific antibodies are described. Computerized imaging and digital pathology are also proposed as a help in the identification of co-stimulatory molecules and localization of γδ T cell effectors. Finally, two types of novel drug preparation are proposed: nanoparticles loaded with N-BPs and pro-drug formulations that enhance the effectiveness of γδ T lymphocyte stimulation.

Analysis of the Seasonal Fluctuation of γδ T Cells and Its Potential Relation with Vitamin D3

In addition to its role in bone metabolism, vitamin D3 exerts immunomodulatory effects and has been proposed to contribute to seasonal variation of immune cells. This might be linked to higher vitamin D3 levels in summer than in winter due to differential sun exposure. γδ T cells comprise a numerically small subset of T cells in the blood, which contribute to anti-infective and antitumor immunity. We studied the seasonal fluctuation of γδ T cells, the possible influence of vitamin D3, and the effect of the active metabolite 1α,25(OH)2D3 on the in vitro activation of human γδ T cells. In a retrospective analysis with 2625 samples of random blood donors, we observed higher proportions of γδ T cells in winter when compared with summer. In a prospective study over one year with a small cohort of healthy adults who did or did not take oral vitamin D3 supplementation, higher proportions of γδ T cells were present in donors without oral vitamin D3 uptake, particularly in spring. However, γδ T cell frequency in blood did not directly correlate with serum levels of 25(OH)D3. The active metabolite 1α,25(OH)2D3 inhibited the in vitro activation of γδ T cells at the level of proliferation, cytotoxicity, and interferon-γ production. Our study reveals novel insights into the seasonal fluctuation of γδ T cells and the immunomodulatory effects of vitamin D3.

Mutation of the Polyproline Sequence in CD3ε Evidences TCR Signaling Requirements for Differentiation and Function of Pro-Inflammatory Tγδ17 Cells

Tγδ17 cells have emerged as a key population in the development of inflammatory and autoimmune conditions such as psoriasis. Thus, the therapeutic intervention of Tγδ17 cells can exert protective effects in this type of pathologies. Tγδ cells commit to IL-17 production during thymus development, and upon immune challenge, additional extrathymic signals induce the differentiation of uncommitted Tγδ cells into Tγδ17 effector cells. Despite the interest in Tγδ17 cells during the past 20 years, the role of TCR signaling in the generation and function of Tγδ17 cells has not been completely elucidated. While some studies point to the notion that Tγδ17 differentiation requires weak or no TCR signaling, other works suggest that Tγδ17 require the participation of specific kinases and adaptor molecules downstream of the TCR. Here we have examined the differentiation and pathogenic function of Tγδ17 cells in “knockin” mice bearing conservative mutations in the CD3ε polyproline rich sequence (KI-PRS) with attenuated TCR signaling due to lack of binding of the essential adaptor Nck. KI-PRS mice presented decreased frequency and numbers of Tγδ17 cells in adult thymus and lymph nodes. In the Imiquimod model of skin inflammation, KI-PRS presented attenuated skin inflammation parameters compared to wild-type littermates. Moreover, the generation, expansion and effector function Tγδ17 cells were impaired in KI-PRS mice upon Imiquimod challenge. Thus, we conclude that an intact CD3ε-PRS sequence is required for optimal differentiation and pathogenic function of Tγδ17 cells. These data open new opportunities for therapeutic targeting of specific TCR downstream effectors for treatment of Tγδ17-mediated diseases.

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.

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.

γδ T Cell-Based Adoptive Cell Therapies Against Solid Epithelial Tumors

ABSTRACT

Conventionally, adoptive cell therapies have been developed and optimized using αβ T cells. However, the understudied and less abundant γδ T cells offer unique advantages to the immunotherapy field especially for therapies against solid tumors. Recently, γδ T-cell potential against a broad spectrum of malignant cells has been demonstrated in the preclinical setting. In the clinic, γδ T-cell-based immunotherapies have proven to be safe; however, their efficacy needs improvement. Considering the growing body of literature reflecting the increasing interest in γδ T cells, we sought to capture the current topics of discussion in the field, pertaining to their use in adoptive immunotherapy. We aimed to compile information about γδ T-cell enhancement in terms of expansion, phenotype, and inhibitory receptors, in addition to the latest advances in preclinical and clinical research using γδ T cells specifically against solid epithelial tumors.

γδ T Cells Support Antigen-Specific αβ T cell-Mediated Antitumor Responses during BCG Treatment for Bladder Cancer

Bacillus Calmette-Guérin (BCG) is the most effective intravesical agent at reducing recurrence for patients with high-grade, non-muscle-invasive bladder cancer. Nevertheless, response to BCG is variable and strategies to boost BCG efficacy have not materialized. Prior work demonstrated a requirement for either conventional αβ or nonconventional γδ T cells in mediating BCG treatment efficacy, yet the importance of T-cell antigen specificity for BCG's treatment effect is unclear. Here, we provide direct evidence to show that BCG increases the number of tumor antigen-specific αβ T cells in patients with bladder cancer and protects mice from subsequent same-tumor challenge, supporting BCG induction of tumor-specific memory and protection. Adoptive T-cell transfers of antigen-specific αβ T cells into immunodeficient mice challenged with syngeneic MB49 bladder tumors showed that both tumor and BCG antigen-specific αβ T cells contributed to BCG efficacy. BCG-specific antitumor immunity, however, also required nonconventional γδ T cells. Prior work shows that the mTOR inhibitor rapamycin induces the proliferation and effector function of γδ T cells. Here, rapamycin increased BCG efficacy against both mouse and human bladder cancer in vivo in a γδ T cell-dependent manner. Thus, γδ T cells augment antitumor adaptive immune effects of BCG and support rapamycin as a promising approach to boost BCG efficacy in the treatment of non-muscle-invasive bladder cancer.

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.