Induction of gammadelta T-lymphocyte effector functions by bisphosphonate zoledronic acid in cancer patients in vivo

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.

Targeting Melanoma-Associated Fibroblasts (MAFs) with Activated γδ (Vδ2) T Cells: An In Vitro Cytotoxicity Model

The tumor microenvironment (TME) has gained considerable scientific attention by playing a role in immunosuppression and tumorigenesis. Besides tumor cells, TME is composed of various other cell types, including cancer-associated fibroblasts (CAFs or MAFs when referring to melanoma-derived CAFs) and tumor-infiltrating lymphocytes (TILs), a subpopulation of which is labeled as γδ T cells. Since the current anti-cancer therapies using γδ T cells in various cancers have exhibited mixed treatment responses, to better understand the γδ T cell biology in melanoma, our research group aimed to investigate whether activated γδ T cells are capable of killing MAFs. To answer this question, we set up an in vitro platform using freshly isolated Vδ2-type γδ T cells and cultured MAFs that were biobanked from our melanoma patients. This study proved that the addition of zoledronic acid (1-2.5 µM) to the γδ T cells was necessary to drive MAFs into apoptosis. The MAF cytotoxicity of γδ T cells was further enhanced by using the stimulatory clone 20.1 of anti-BTN3A1 antibody but was reduced when anti-TCR γδ or anti-BTN2A1 antibodies were used. Since the administration of zoledronic acid is safe and tolerable in humans, our results provide further data for future clinical studies on the treatment of melanoma.

CD73 regulates zoledronate-induced lymphocyte infiltration in triple-negative breast cancer tumors and lung metastases

Introduction

Bisphosphonates (BPs) are bone-protecting osteoclast inhibitors, typically used in the treatment of osteoporosis and skeletal complications of malignancies. When given in the adjuvant setting, these drugs may also prevent relapses and prolong overall survival in early breast cancer (EBC), specifically among postmenopausal patients. Because of these findings, adjuvant nitrogen-containing BPs (N-BPs), such as zoledronate (ZOL), are now the standard of care for high-risk EBC patients, but there are no benefit-associated biomarkers, and the efficacy remains low. BPs have been demonstrated to possess anti-tumor activities, but the mechanisms by which they provide the beneficial effects in EBC are not known.

Methods

We used stably transfected 4T1 breast cancer cells together with suppression of CD73 (sh-CD73) or control cells (sh-NT). We compared ZOL effects on tumor growth and infiltrating lymphocytes (TILs) into tumors and lung metastases using two mouse models. B cell depletion was performed using anti-CD20 antibody.

Results

Sh-CD73 4T1 cells were significantly more sensitive to the growth inhibitory effects of n-BPs in vitro. However, while ZOL-induced growth inhibition was similar between the tumor groups in vivo, ZOL enhanced B and T lymphocyte infiltration into the orthotopic tumors with down-regulated CD73. A similar trend was detected in lung metastases. ZOL-induced tumor growth inhibition was found to be augmented with B cell depletion in sh-NT tumors, but not in sh-CD73 tumors. As an internal control, ZOL effects on bone were similar in mice bearing both tumor groups.

Discussion

Taken together, these results indicate that ZOL modifies TILs in breast cancer, both in primary tumors and metastases. Our results further demonstrate that B cells may counteract the growth inhibitory effects of ZOL. However, all ZOL-induced TIL effects may be influenced by immunomodulatory characteristics of the tumor.

Phenotypic and functional characterization of pharmacologically expanded Vγ9Vδ2 T cells in pigtail macaques

While gaining interest as treatment for cancer and infectious disease, the clinical efficacy of Vγ9Vδ2 T cell-based immunotherapeutics has to date been limited. An improved understanding of γδ T cell heterogeneity across lymphoid and non-lymphoid tissues, before and after pharmacological expansion, is required. Here, we describe the phenotype and tissue distribution of Vγ9Vδ2 T cells at steady state and following in vivo pharmacological expansion in pigtail macaques. Intravenous phosphoantigen administration with subcutaneous rhIL-2 drove robust expansion of Vγ9Vδ2 T cells in blood and pulmonary mucosa, while expansion was confined to the pulmonary mucosa following intratracheal antigen administration. Peripheral blood Vγ9Vδ2 T cell expansion was polyclonal, and associated with a significant loss of CCR6 expression due to IL-2-mediated receptor downregulation. Overall, we show the tissue distribution and phenotype of in vivo pharmacologically expanded Vγ9Vδ2 T cells can be altered based on the antigen administration route, with implications for tissue trafficking and the clinical efficacy of Vγ9Vδ2 T cell immunotherapeutics.

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.

Evaluation of intravenous zoledronic acid-induced acute-phase response in the emergency department

Background/Aim: A temporary influenza-like condition, called acute-phase reaction (APR), is commonly observed with intravenous (IV) administration of nitrogen-containing amino bisphosphonates, such as zoledronic acid (ZOL). This single-center study aimed to evaluate the incidence of APR symptoms after intravenous (IV) ZOL administration in patients with postmenopausal osteoporosis who were admitted to emergency department (ED). Methods: In this cross-sectional study, 107 osteoporotic patients who were diagnosed with post-menopausal osteoporosis (bone mineral density T-score equal to or below −2.5 with/without prevalent fractures) and who had an ED admission in the first 72 h after intravenous injection of ZOL were included in the study. The patient’s pre-treatment blood sample measurements, presenting symptoms (such as fever, fatigue, hyperpyrexia, headache), family history, previous medical treatment, and adverse effects caused by osteoporosis drugs, in addition to information on co-morbidities and comedications were obtained from clinical records. Results: One-hundred seven osteoporotic patients (19.56%) patients experienced APR and were admitted to the ED after IV-ZOL administration. The mean age was 64.58 (11.15) years (n = 107). The three most commonly reported symptoms were diffuse musculoskeletal symptoms, influenza-like illness, and gastrointestinal symptoms (34.5%, 21.5%, and 18.5%, respectively). Seventy percent of the patients who presented to the ED with APR symptoms were prescribed drugs only, and 30% of the patients received treatment specific for their symptoms in the ED. Most of the diffuse musculoskeletal symptoms consisted of myalgia (22.4%). A positive correlation between the onset time of APR symptoms and the number of IV bisphosphonate (BP) doses was found (r = 0.597; P = 0.032). Conclusion: Our study indicates that as the number of IV-ZOL administrations increase yearly in patients with osteoporosis, symptom onset time occurs later. A linear relationship was found between the number of drug applications and the duration of symptoms. Also, the incidence of APR following IV-ZOL administration was 19% in the osteoporotic patient population who presented to the ED or to other clinics according to the symptoms.

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.

Advancing Treatment of Bone Metastases through Novel Translational Approaches Targeting the Bone Microenvironment

Bone metastases represent a lethal condition that frequently occurs in solid tumors such as prostate, breast, lung, and renal cell carcinomas, and increase the risk of skeletal-related events (SREs) including pain, pathologic fractures, and spinal cord compression. This unique metastatic niche consists of a multicellular complex that cancer cells co-opt to engender bone remodeling, immune suppression, and stromal-mediated therapeutic resistance. This review comprehensively discusses clinical challenges of bone metastases, novel preclinical models of the bone and bone marrow microenviroment, and crucial signaling pathways active in bone homeostasis and metastatic niche. These studies establish the context to summarize the current state of investigational agents targeting BM, and approaches to improve BM-targeting therapies. Finally, we discuss opportunities to advance research in bone and bone marrow microenvironments by increasing complexity of humanized preclinical models and fostering interdisciplinary collaborations to translational research in this challenging metastatic niche.

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.

The Functional Role of Lactoferrin in Intestine Mucosal Immune System and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing ulcerative colitis (UC) and Crohn's disease (CD), is one of the main types of intestinal inflammatory diseases with intestine mucosal immune disorder. Intestine mucosal immune system plays a remarkable and important role in the etiology and pathogenesis of IBD. Therefore, understanding the intestine mucosal immune mechanism is a key step to develop therapeutic interventions for IBD. Intestine mucosal immune system and IBD are influenced by various factors, such as inflammation, gut permeability, gut microbiota, and nutrients. Among these factors, emerging evidence show that nutrients play a key role in inflammation activation, integrity of intestinal barrier, and immune cell modulation. Lactoferrin (LF), an iron-binding glycoprotein belonging to transferrin family, is a dietary bioactive component abundantly found in mammalian milk. Notably, LF has been reported to perform diverse biological functions including antibacterial activity, anti-inflammatory activity, intestinal barrier protection, and immune cell modulation, and is involved in maintaining intestine mucosal immune homeostasis. The improved understanding of the properties of LF in intestine mucosal immune system and IBD will facilitate its application in nutrition, clinical medicine, and health. Herein, this review outlines the recent advancements on LF as a potential therapeutic intervention for IBD associated with intestine mucosal immune system dysfunction. We hope this review will provide a reference for future studies and lay a theoretical foundation for LF-based therapeutic interventions for IBD by understanding the particular effects of LF on intestine mucosal immune system.

Activated naïve γδ T cells accelerate deep molecular response to BCR-ABL inhibitors in patients with chronic myeloid leukemia

Tyrosine kinase inhibitors (TKIs) that target BCR-ABL are the frontline treatments in chronic myeloid leukemia (CML). Growing evidence has shown that TKIs also enhance immunity. Since gamma-delta T (γδT) cells possess the potent anticancer capability, here we investigated the potential involvement of γδT cells in TKI treatments for CML. We characterized γδT cells isolated from chronic-phase CML patients before and during TKI treatments. γδT expression increased significantly in CML patients who achieved major molecular response (MMR) and deep molecular response (DMR). Their Vδ2 subset of γδT also expanded, and increased expression of activating molecules, namely IFN-γ, perforin, and CD107a, as well as γδT cytotoxicity. Mechanistically, TKIs augmented the efflux of isopentenyl pyrophosphate (IPP) from CML cells, which stimulated IFN-γ production and γδT expansion. Notably, the size of the IFN-γ⁺ naïve γδT population in TKI-treated CML patients was strongly correlated with their rates to reach DMR and with the duration on DMR. Statistical analysis suggests that a cutoff of 7.5% IFN-γ⁺ naïve subpopulation of γδT in CML patients could serve as a determinant for MR^4.0 sustainability. Our results highlight γδT cells as a positive regulator for TKI responses in CML patients.

Strategies to Improve the Antitumor Effect of γδ T Cell Immunotherapy for Clinical Application

Human γδ T cells show potent cytotoxicity against various types of cancer cells in a major histocompatibility complex unrestricted manner. Phosphoantigens and nitrogen-containing bisphosphonates (N-bis) stimulate γδ T cells via interaction between the γδ T cell receptor (TCR) and butyrophilin subfamily 3 member A1 (BTN3A1) expressed on target cells. γδ T cell immunotherapy is classified as either in vivo or ex vivo according to the method of activation. Immunotherapy with activated γδ T cells is well tolerated; however, the clinical benefits are unsatisfactory. Therefore, the antitumor effects need to be increased. Administration of γδ T cells into local cavities might improve antitumor effects by increasing the effector-to-target cell ratio. Some anticancer and molecularly targeted agents increase the cytotoxicity of γδ T cells via mechanisms involving natural killer group 2 member D (NKG2D)-mediated recognition of target cells. Both the tumor microenvironment and cancer stem cells exert immunosuppressive effects via mechanisms that include inhibitory immune checkpoint molecules. Therefore, co-immunotherapy with γδ T cells plus immune checkpoint inhibitors is a strategy that may improve cytotoxicity. The use of a bispecific antibody and chimeric antigen receptor might be effective to overcome current therapeutic limitations. Such strategies should be tested in a clinical research setting.

Listeria monocytogenes-infected human monocytic derived dendritic cells activate Vγ9Vδ2 T cells independently of HMBPP production

Gamma-delta (γδ) T cells express T cell receptors (TCR) that are preconfigured to recognize signs of pathogen infection. In primates, γδ T cells expressing the Vγ9Vδ2 TCR innately recognize (E)-4-hydroxy-3-methyl-but- 2-enyl pyrophosphate (HMBPP), a product of the 2-C-methyl-D-erythritol 4- phosphate (MEP) pathway in bacteria that is presented in infected cells via interaction with members of the B7 family of costimulatory molecules butyrophilin (BTN) 3A1 and BTN2A1. In humans, Listeria monocytogenes (Lm) vaccine platforms have the potential to generate potent Vγ9Vδ2 T cell recognition. To evaluate the activation of Vγ9Vδ2 T cells by Lm-infected human monocyte-derived dendritic cells (Mo-DC) we engineered Lm strains that lack components of the MEP pathway. Direct infection of Mo-DC with these bacteria were unchanged in their ability to activate CD107a expression in Vγ9Vδ2 T cells despite an inability to synthesize HMBPP. Importantly, functional BTN3A1 was essential for this activation. Unexpectedly, we found that cytoplasmic entry of Lm into human dendritic cells resulted in upregulation of cholesterol metabolism in these cells, and the effect of pathway regulatory drugs suggest this occurs via increased synthesis of the alternative endogenous Vγ9Vδ2 ligand isoprenyl pyrophosphate (IPP) and/or its isomer dimethylallyl pyrophosphate (DMAPP). Thus, following direct infection, host pathways regulated by cytoplasmic entry of Lm can trigger Vγ9Vδ2 T cell recognition of infected cells without production of the unique bacterial ligand HMBPP.

Bisphosphonate-Based Conjugates and Derivatives as Potential Therapeutic Agents in Osteoporosis, Bone Cancer and Metastatic Bone Cancer

Metastatic bone cancer occurs in every type of cancer but is prevalent in lung, breast, and prostate cancers. These metastases can cause extensive morbidity, including a range of skeletal-related events, often painful and linked with substantial hospital resource usage. The treatment used is a combination of chemotherapy and surgery. However, anticancer drugs are still limited due to severe side effects, drug resistance, poor blood supply, and non-specific drug uptake, necessitating high toxic doses. Bisphosphonates are the main class of drugs utilized to inhibit metastatic bone cancer. It is also used for the treatment of osteoporosis and other bone diseases. However, bisphosphonate also suffers from serious side effects. Thus, there is a serious need to develop bisphosphonate conjugates with promising therapeutic outcomes for treating metastatic bone cancer and osteoporosis. This review article focuses on the biological outcomes of designed bisphosphonate-based conjugates for the treatment of metastatic bone cancer and osteoporosis.

Prognostic effects of cytokine levels on patients treated with taxane and zoledronic acid for metastatic breast cancer in bone (BEAT-ZO) (KCSG BR 10-13)

Advanced breast cancer frequently metastasizes to the skeleton causing major mobility issues and hazards to quality of life. To manage osteolytic bone metastasis, bone-modifying agents and chemotherapy are recommended as the standard of care. Here, we investigated serologic biomarkers that might be associated with prognosis in breast cancer patients treated with zoledronic acid (ZA) and taxane-based chemotherapy. We collected serum samples from breast cancer patients with bone metastasis who received taxane plus ZA as palliative treatment. Fourteen biomarkers of angiogenesis, immunogenicity, and apoptosis were assessed, and the correlation between serum cytokine levels and patient's prognosis was statistically analyzed. Sixty-six patients were enrolled, and samples from 40 patients were analyzed after laboratory quality control. Patients with low baseline PDGF-AA, high IFN-γ, low MCP-2, low TGF-β1, and low TNF-α were significantly associated with longer progression-free survival (PFS). Decreasing VEGF and TNF-α and increasing FGF-2 and PDGF-AA in the early treatment phase indicated longer PFS. In univariate and multivariate analyses, low TGF-β1 and TNF-α and high IFN-γ at baseline were associated with a significantly low hazard ratio for disease progression. Further, we designed a risk score with TGF-β1, TNF-α, and IFN-γ levels, which could prognosticate patients for PFS. In conclusion, serum cytokine level, such as TGF-β1, TNF-α, and IFN-γ, could be a potential prognostic biomarker for breast cancer patients with bone metastasis treated with ZA and taxane-based chemotherapy.

The role of the thymus in allogeneic bone marrow transplantation and the recovery of the peripheral T-cell compartment

As the thymus represents the primary site of T-cell development, optimal thymic function is of paramount importance for the successful reconstitution of the adaptive immunity after allogeneic hematopoietic stem cell transplantation. Thymus involutes as part of the aging process and several factors, including previous chemotherapy treatments, conditioning regimen used in preparation to the allograft, occurrence of graft-versus-host disease, and steroid therapy that impair the integrity of the thymus, thus affecting its role in supporting T-cell neogenesis. Although the pathways governing its regeneration are still poorly understood, the thymus has a remarkable capacity to recover its function after damage. Measurement of both recent thymic emigrants and T-cell receptor excision circles is valuable tools to assess thymic output and gain insights on its function. In this review, we will extensively discuss available data on factors regulating thymic function after allogeneic hematopoietic stem cell transplantation, as well as the strategies and therapeutic approaches under investigation to promote thymic reconstitution and accelerate immune recovery in transplanted patients, including the use of cytokines, sex-steroid ablation, precursor T-cells, and thymus bioengineering. Although none of them is routinely used in the clinic, these approaches have the potential to enhance thymic function and immune recovery, not only in patients given an allograft but also in other conditions characterized by immune deficiencies related to a defective function of the thymus.

Comparable Vδ2 Cell Functional Characteristics in Virally Suppressed People Living with HIV and Uninfected Individuals

Crosstalk between innate and adaptive pathways is a critical component to developing an effective, lasting immune response. Among natural effector cells, innate-like γδ T cells promote immunity by facilitating communication between the two compartments and exerting cytotoxic effector functions. Dysregulation of γδ T cell populations is a byproduct of primary human immunodeficiency virus (HIV) infection. This is most pronounced in the depletion and loss of function within cells expressing a Vγ9Vδ2 TCR (Vδ2 cells). Whether or not prolonged viral suppression mediated by antiretroviral therapy (ART) can reverse these effects has yet to be determined. In this study, we present evidence of similar Vδ2 cell functional responses within a cohort of people living with HIV (PLWH) that has been stably suppressed for >1 year and uninfected donors. Through the use of aminobisphosphonate drugs, we were able to generate a comprehensive comparison between ex vivo and expanded Vδ2 cells within each group. Both groups had largely similar compositions of memory and effector phenotypes, post-expansion TCR repertoire diversity, and cytotoxic capabilities. Our findings support the notion that ART promotes the recovery of Vδ2 polyfunctionality and provides insight for strategies aiming to reconstitute the full immune response after infection with HIV.

Adoptive transfer of zoledronate-expanded autologous Vγ9Vδ2 T-cells in patients with treatment-refractory non-small-cell lung cancer: a multicenter, open-label, single-arm, phase 2 study

BACKGROUND

Not all non-small cell lung cancer (NSCLC) patients possess drug-targetable driver mutations, and response rates to immune checkpoint blockade therapies also remain unsatisfactory. Therefore, more effective treatments are still needed. Here, we report the results of a phase 2 clinical trial of adoptive cell therapy using zoledronate-expanded autologous Vγ9Vδ2 T-cells for treatment-refractory NSCLC.

METHODS

NSCLC patients who had undergone at least two regimens of standard chemotherapy for unresectable disease or had had at least one treatment including chemotherapy or radiation for recurrent disease after surgery were enrolled in this open-label, single-arm, multicenter, phase 2 study. After preliminary testing of Vγ9Vδ2 T-cell proliferation, autologous peripheral blood mononuclear cells were cultured with zoledronate and IL-2 to expand the Vγ9Vδ2 T-cells. Cultured cells (>1×10⁹) were intravenously administered every 2 weeks for six injections. The primary endpoint of this study was progression-free survival (PFS), and secondary endpoints included overall survival (OS), best objective response rate (ORR), disease control rate (DCR), safety and immunomonitoring. Clinical efficacy was defined as median PFS significantly >4 months.

RESULTS

Twenty-five patients (20 adenocarcinoma, 4 squamous cell carcinoma and 1 large cell carcinoma) were enrolled. Autologous Vγ9Vδ2 T-cell therapy was administered to all 25 patients, of which 16 completed the foreseen course of 6 injections of cultured cells. Median PFS was 95.0 days (95% CI 73.0 to 132.0 days); median OS was 418.0 days (179.0-479.0 days), and best overall responses were 1 partial response, 16 stable disease (SD) and 8 progressive disease. ORR and DCR were 4.0% (0.1%-20.4%) and 68.0% (46.5%-85.1%), respectively. Severe adverse events developed in nine patients, mostly associated with disease progression. In one patient, pneumonitis and inflammatory responses resulted from Vγ9Vδ2 T-cell infusions, together with the disappearance of a massive tumor.

CONCLUSIONS

Although autologous Vγ9Vδ2 T-cell therapy was well tolerated and may have an acceptable DCR, this trial did not meet its primary efficacy endpoint.

TRIAL REGISTRATION NUMBER

UMIN000006128.

Zoledronic Acid Inhibits the RhoA-mediated Amoeboid Motility of Prostate Cancer Cells

BACKGROUND

The bisphosphonate Zoledronic acid (ZA) is a potent osteoclast inhibitor currently used in the clinic to reduce osteoporosis and cancer-induced osteolysis. Moreover, ZA exerts an anti-tumor effect in several tumors. Despite this evidence, the relevance of ZA in prostate cancer (PCa) is not completely understood.

OBJECTIVE

To investigate the effect of ZA administration on the invasive properties of PC3 cells, which are characterised by RhoA-dependent amoeboid motility.

METHODS

The effect of ZA administration on the in vitro invasive properties of PC3 cells was evaluated by cell migration in 3D collagen matrices, immunofluorescence and Boyden assays or transendothelial migration. Lung retention and colonization assays were performed to assess the efficacy of ZA administration in vivo.

RESULTS

PC3 cells are characterised by RhoA-dependent amoeboid motility. We now report a clear inhibition of in vitro PC3 cell invasion and RhoA activity upon ZA treatment. Moreover, to confirm a specific role of ZA in the inhibition of amoeboid motility of PC3 cells, we demonstrate that ZA interferes only partially with PC3 cells showing a mesenchymal phenotype due to both treatment with conditioned medium of cancer associated fibroblasts or to the acquisition of chemoresistance. Furthermore, we demonstrate that ZA impairs adhesion to endothelial cells and the trans-endothelial cell migration, two essential properties characterising amoeboid motility and PC3 metastatic dissemination. In vivo experiments prove the ability of ZA to inhibit the metastatic process of PC3 cells as shown by the decrease in lung colonization.

CONCLUSION

This study demonstrates that ZA inhibits Rho-dependent amoeboid motility of PC3 cells, thus suggesting ZA as a potential therapy to impede the metastatic dissemination of PC3 cells.

Deciphering human γδ T cell response in cancer: Lessons from tumor-infiltrating γδ T cells

The finding that γδ T cells are present among tumor-infiltrating lymphocytes in humans suggests they participate in tumor immune surveillance, but their relevance is unclear because the relative abundance of tumor-infiltrating γδ T cells correlates with positive or negative, or even do not correlate with prognosis. This likely depends on the fact that tumor-infiltrating γδ T cells may play substantially different effector or regulatory functions, and correlation with patient's prognosis relies on distinct γδ T cell subsets in the context of the tumor. There is interest to exploit γδ T cells in tumor immunotherapy, but to make this approach successful there is urgent need to fully understand the biological functions of γδ T cells and of how they can be manipulated in vivo and ex vivo to safely provide benefit to the host. This review focuses on our previous and ongoing studies of tumor-infiltrating γδ T lymphocytes in different types of human cancer. Moreover, we discuss the interaction of tumor-infiltrating γδ T cells with other cells and molecules present in the tumor microenvironment, and their clinical relevance on the ground, that deep knowledge in this field can be used further for better immunotherapeutic intervention in cancer.

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.

CAR-T Engineering: Optimizing Signal Transduction and Effector Mechanisms

The adoptive transfer of genetically engineered T cells expressing a chimeric antigen receptor (CAR) has shown remarkable results against B cell malignancies. This immunotherapeutic approach has advanced and expanded rapidly from preclinical models to the recent approval of CAR-T cells to treat lymphomas and leukemia by the Food and Drug Administration (FDA). Ongoing research efforts are focused on employing CAR-T cells as a therapy for other cancers, and enhancing their efficacy and safety by optimizing their design. Here we summarize modifications in the intracellular domain of the CAR that gave rise to first-, second-, third- and next-generation CAR-T cells, together with the impact that these different designs have on CAR-T cell biology and function. Further, we describe how the structure of the antigen-sensing ectodomain can be enhanced, leading to superior CAR-T cell signaling and/or function. Finally we discuss how tissue-specific factors may impact the clinical efficacy of CAR-T cells for bone and the central nervous system, as examples of specific indications that may require further CAR signaling optimization to perform in such inhospitable microenvironments.

Analysis of colon-infiltrating γδ T cells in chronic inflammatory bowel disease and in colitis-associated cancer

Inflammatory bowel disease (IBD) remains a global health problem with a significant percentage of patients progressing to chronic inflammation and colitis-associated cancer (CAC). Whether or not γδ T cells contribute to initiation and maintenance of inflammation in IBD and in the development of CAC is not known. We have evaluated the frequency, phenotype, and functions of γδ T cells among tissue-infiltrating lymphocytes in healthy donors and IBD and CAC patients. Results show that Vδ1 T cells are the dominant γδ T-cell population in healthy tissue, whereas Vδ2 T significantly abound in chronic IBD. Vδ2 T cells produce more IFN-γ, TNF-α, and IL-17 than Vδ1 T cells in chronic inflamed IBD. In CAC patients no significant cytokine production was detected in tissue-resident Vδ1 T cells, but Vδ2 T cells produced remarkable amounts of IFN-γ and TNF-α; these data were confirmed by the analysis of an independent cohort of IBD transcriptomes. Moreover, transcriptomes of IBD patients revealed a clear-cut clusterization of genes related with the maintenance of the inflammatory status. In conclusion, our results demonstrating that Vδ2 T cells have a proinflammatory profile in chronic IBD are suggestive of their participation in IBD and CAC pathogenesis.

Functional Phenotypes of Human Vγ9Vδ2 T Cells in Lymphoid Stress Surveillance

Butyrophilin and butyrophilin-like proteins select γδ T cells and direct the migration of γδ T cell subsets to distinct anatomical sites. γδ T cells expressing Vδ2 paired with Vγ9 (Vγ9Vδ2 T cells) are the predominant γδ T cell type in human peripheral blood. Vγ9Vδ2 T cells, which cannot be studied easily in vivo because they do not exist in rodents, are often referred to as innate-like T cells. The genetically recombined γδ T cell receptor (TCR) that responds to isoprenoid-derived pyrophosphates (phosphoantigens) produced by infected and malignant cells in a butyrophilin-dependent manner qualifies them as therapeutically relevant components of the adaptive immune system. On the other hand, cell-surface proteins such as the C-type lectin CD161 mark a functional phenotype of Vγ9Vδ2 T cells that mediates TCR-independent innate-like responses. Moreover, CD56 (neural cell adhesion molecule, NCAM) and the G protein-coupled receptor GPR56 define Vγ9Vδ2 T cells with increased cytolytic potential and, like CD161, may also be expressed by dendritic cells, principally facilitating the generation of an innate-like immunological synapse. In this review, we summarise current knowledge of Vγ9Vδ2 T cell functional phenotypes that are critical to lymphoid stress surveillance.

Degranulation of human cytotoxic lymphocytes is a major source of proteolytically active soluble CD26/DPP4

Dipeptidyl peptidase 4 (DPP4, CD26) is a serine protease detected on several immune cells and on epithelial cells of various organs. Besides the membrane-bound enzyme, a catalytically active soluble form (sCD26/DPP4) is detected in several body fluids. Both variants cleave off dipeptides from the N-termini of various chemokines, neuropeptides, and hormones. CD26/DPP4 plays a fundamental role in the regulation of blood glucose levels by inactivating insulinotropic incretins and CD26/DPP4 inhibitors are thus routinely used in diabetes mellitus type 2 therapy to improve glucose tolerance. Such inhibitors might also prevent the CD26/DPP4-mediated inactivation of the T-cell chemoattractant CXCL10 released by certain tumors and thus improve anti-tumor immunity and immunotherapy. Despite its implication in the regulation of many (patho-)physiological processes and its consideration as a biomarker and therapeutic target, the cellular source of sCD26/DPP4 remains highly debated and mechanisms of its release are so far unknown. In line with recent reports that activated T lymphocytes could be a major source of sCD26/DPP4, we now demonstrate that CD26/DPP4 is stored in secretory granules of several major human cytotoxic lymphocyte populations and co-localizes with effector proteins such as granzymes, perforin, and granulysin. Upon stimulation, vesicular CD26/DPP4 is rapidly translocated to the cell surface in a Ca2+-dependent manner. Importantly, activation-induced degranulation leads to a massive release of proteolytically active sCD26/DPP4. Since activated effector lymphocytes serve as a major source of sCD26/DPP4, these results might explain the observed disease-associated alterations of sCD26/DPP4 serum levels and also indicate a so far unknown role of CD26/DPP4 in lymphocyte-mediated cytotoxicity.

Cholesterol and beyond - The role of the mevalonate pathway in cancer biology

Cancer is a multifaceted global disease. Transformation of a normal to a malignant cell takes several steps, including somatic mutations, epigenetic alterations, metabolic reprogramming and loss of cell growth control. Recently, the mevalonate pathway has emerged as a crucial regulator of tumor biology and a potential therapeutic target. This pathway controls cholesterol production and posttranslational modifications of Rho-GTPases, both of which are linked to several key steps of tumor progression. Inhibitors of the mevalonate pathway induce pleiotropic antitumor-effects in several human malignancies, identifying the pathway as an attractive candidate for novel therapies. In this review, we will provide an overview about the role and regulation of the mevalonate pathway in certain aspects of cancer initiation and progression and its potential for therapeutic intervention in oncology.

Characterization of γδ T Cells in Intestinal Mucosa From Patients With Early-Onset or Long-Standing Inflammatory Bowel Disease and Their Correlation With Clinical Status

BACKGROUND AND AIMS

Inflammatory bowel disease [IBD] is a complex chronic inflammatory disease of the human gut with no clear aetiology. Traditionally, dysregulated adaptive immune responses play an important role even though accumulating evidence suggests a role also for innate immunity. Because of the well-known plasticity of γδ T cells, we investigated their percentage occurrence, phenotypic features and effector functions in the intestinal mucosa of early-onset and long-standing IBD patients, as compared to healthy subjects.

METHODS

Fresh biopsies from 30 Crohn's disease and ulcerative colitis patients were obtained and digested, and cells were analysed by flow cytometry.

RESULTS

We found a reduced frequency of Vδ1 T cells in tissue from early and late IBD patients (2.24% and 1.95%, respectively, vs 5.44% in healthy tissue) but an increased frequency of Vδ2 T cells in the gut of late IBD patients (3.19% in late patients vs 1.5% in early patients and 1.65% in healthy tissue). The infiltrating Vδ2 T cells had predominant effector memory and terminally differentiated phenotypes and produced elevated levels of tumour necrosis factor-α [TNF-α] and interleukin-17 [IL-17]. The frequency of tissue Vδ2 T cells correlated with the extent of the inflammatory response and the severity of IBD.

CONCLUSION

Our study shows that tissue Vδ1 T cells are decreased in IBD patients while Vδ2 T cells are increased in the gut of IBD patients and contribute to TNF-α production. Moreover, we identify an as yet unappreciated role of Vδ2 T cells in IL-17 production in the gut of long-standing IBD patients, suggesting that they also participate in the chronic inflammatory process.

Bisphosphonates and primary breast cancer risk: an updated systematic review and meta-analysis involving 963,995 women

Importance

Prevention of primary breast cancer (BCa) in women is of great public health importance. The existing results from observational epidemiologic studies focused on the association between bisphosphonates and primary BCa risk have been inconsistent.

Objective

To update this systematic review and meta-analysis to assess the effect of bisphosphonates on primary BCa risk.

Data sources

We comprehensively searched MEDLINE, EMBASE, Cochrane libraries, ProQuest, and Web of Science through June 25, 2018 for relevant studies.

Study selection

Epidemiological studies that assessed the effect of bisphosphonates on the risk of primary BCa in women.

Data extraction and synthesis

We reported this meta-analysis according to the PRISMA guidelines. Available multivariable-adjusted effect estimates and corresponding 95% CIs were pooled with a random-effects model.

Main outcomes and measures

The prespecified main outcome was the risk of primary BCa.

Results

In total, five cohort studies involving 657,558 women and 12,991 primary BCa patients, three population-based case-control studies involving 54,701 primary BCa cases and 237,962 healthy controls and two randomized controlled trials (RCTs) involving 13,774 women and 165 primary BCa patients were included in this meta-analysis. Bisphosphonates were associated with a 12% decreased risk of primary BCa (RR, 0.88; 95% CI, 0.83–0.94). However, when we analyzed study designs separately, the pooled results from observational studies were inconsistent with that from RCTs. The observed association of primary BCa risk with long-term use (≥1 year) of bisphosphonates seemed to be more robust and stronger than that of short-term use (<1 year) (RR, 0.75; 95% CI, 0.66–0.84; and 0.90; 95% CI, 0.84–0.97; respectively).

Conclusion

This meta-analysis adds to the body of evidence for an association between bisphosphonates and a significantly decreased risk of primary BCa. However, future large-scale RCTs are required to validate this concern.

The emerging role of γδ T cells in cancer immunotherapy

The recent successes of chimeric antigen receptor T cells in the treatment of hematological malignancies have clearly led to an explosion in the field of adoptive cell therapy for cancer. Current efforts are focused on the translation of this exciting technology to the treatment of solid tumors and the development of allogeneic ‘off-the-shelf’ therapies. γδ T cells are currently gaining considerable attention in this field as their unique biology and established role in cancer immunosurveillance place them in a unique position to potentially overcome these challenges in adoptive cell therapy. Here, we review the relevant aspects of the function of γδ T cells in cancer immunity, and summarize clinical observations and clinical trial results that highlight their emerging role as a platform for the development of safe and effective cancer immunotherapies.

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γδ T cells are a unique subset of T cells combining innate and adaptive features.

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Tissue-resident γδ T cells have important functions in tissue and cancer immunosurveillance.

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γδ T cells are being exploited increasingly for cancer immunotherapy.

γδ cell-based immunotherapy for cancer

Introduction: Cancer immunotherapy relies on the development of an efficient and long-lasting anti-tumor response, generally mediated by cytotoxic T cells. γδ T cells possess distinctive features that justify their use in cancer immunotherapy. Areas covered: Here we will review our current knowledge on the functions of human γδ T cells that may be relevant in tumor immunity and the most recent advances in our understanding of how these functions are regulated in the tumor microenvironment. We will also discuss the major achievements and limitations of γδ T cell-based immunotherapy of cancer. Expert opinion: Several small-scale clinical trials have been conducted in cancer patients using either in vivo activation of γδ T cells or adoptive transfer of ex vivo-expanded γδ T cells. Both strategies are safe and give some clinical benefit to patients, thus providing a proof of principle for their utilization in addition to conventional therapies. However, low objective response rates have been obtained in both settings and therefore larger and well-controlled trials are needed. Discovering the factors which influence the success of γδ T cell-based immunotherapy will lead to a better understanding of their mechanism of action and to harness these cells for effective and durable anti-tumor responses.

Optimized protocols for γδ T cell expansion and lentiviral transduction

γδ T cells are a subset of unconventional T cells that serve a critical role in infectious diseases and various types of cancer. Cell therapy with genetically‑modified γδ T cells is regarded as a promising tool for tumor treatment. However, since γδ T cells constitute a minority of T cells, their large‑scale expansion is difficult to realize in an efficient and cost‑effective manner. In the present study, based on previous studies, culture protocols for γδ T cells were tested using different combinations of isopentenyl pyrophosphate and interleukin 2 in order to satisfy different experimental purposes. One protocol was demonstrated to be the most suitable for lentiviral transduction. These results greatly reinforce the promising prospects of using γδ T cells in basic research and for clinical applications.

Characterization of human infiltrating and circulating gamma-delta T cells in prostate cancer

Purpose

The aim of our study was to prospectively evaluate the distribution of gamma-delta (γδ)1 and γδ2 T cells and their phenotypes in peripheral blood and prostate samples of patients diagnosed with or without prostate cancer (PCa) at prostate biopsy.

Materials and Methods

A consecutive series of 43 outpatients underwent trans-rectal echo-guided prostate biopsy for suspected PCa. Flow cytometry analysis was used to identify and characterize the γδ T cells populations in peripheral blood and tissue samples. Patients were stratified according to the presence or not of PCa, and its International Society of Urological Pathology (ISUP) grade (1 vs. ≥2).

Results

The distribution of γδ T cells in peripheral blood and prostate tissue showed wide variability and non-significant differences. A slightly higher percentage of δ2 T cells and a slightly lower percentage of δ1 T cells were found in peripheral blood of cancer patients. A non-significantly higher percentage of both Vδ1 and Vδ2 was expressed in cancer tissues, but a trend for lower distribution of δ1 and δ2 T cells was observed in ISUP grade ≥2. The "central memory" and "effector memory" were the most expressed T cells phenotype in peripheral blood and tissue samples. However no substantial differences in T cells subtypes distribution between cancer and healthy tissue were observed.

Conclusions

No substantially different percentages of γδ T cells were found in peripheral blood and biopsy samples of healthy and PCa patients. However a non-significant trend for lower infiltrate in higher ISUP grade cancer tissue was observed, suggesting a possible role for the immunosurveillance of PCa.

Bisphosphonate conjugation for bone specific drug targeting

Bones provide essential functions and are sites of unique biochemistry and specialized cells, but can also be sites of disease. The treatment of bone disorders and neoplasia has presented difficulties in the past, and improved delivery of drugs to bone remains an important goal for achieving effective treatments. Drug targeting strategies have improved drug localization to bone by taking advantage of the high mineral concentration unique to the bone hydroxyapatite matrix, as well as tissue-specific cell types. The bisphosphonate molecule class binds specifically to hydroxyapatite and inhibits osteoclast resorption of bone, providing direct treatment for degenerative bone disorders, and as emerging evidence suggests, cancer. These bone-binding molecules also provide the opportunity to deliver other drugs specifically to bone by bisphosphonate conjugation. Bisphosphonate bone-targeted therapies have been successful in treatment of osteoporosis, primary and metastatic neoplasms of the bone, and other bone disorders, as well as refining bone imaging. In this review, we focus upon the use of bisphosphonate conjugates with antineoplastic agents, and overview bisphosphonate based imaging agents, nanoparticles, and other drugs. We also discuss linker design potential and the current state of bisphosphonate conjugate research progress. Ongoing investigations continue to expand the possibilities for bone-targeted therapeutics and for extending their reach into clinical practice.

Development and Selection of the Human Vγ9Vδ2+ T-Cell Repertoire

Vγ9Vδ2⁺ lymphocytes are among the first T-cells to develop in the human fetus and are the predominant peripheral blood γδ T-cell population in most adults. Capable of broad polyclonal responses to pyrophosphate antigens (pAg), they are implicated in immunity to a diverse range of infections. Previously Vγ9Vδ2⁺ development was thought to involve postnatal selection and amplification of public Vγ9 clonotypes in response to microbial stimuli. However, recent data indicate the Vγ9Vδ2⁺ T-cell receptor (TCR) repertoire, which is generated early in gestation, is dominated by public Vγ9 clonotypes from birth. These chains bear highly distinct features compared to Vγ9 chains from Vδ1⁺ T-cells, due either to temporal differences in recombination of each subset and/or potentially prenatal selection of pAg-reactive clonotypes. While these processes result in a semi-invariant repertoire featuring Vγ9 sequences preconfigured for pAg recognition, alterations in TCRδ repertoires between neonate and adult suggest either peripheral selection of clonotypes responsive to microbial antigens or altered postnatal thymic output of Vγ9Vδ2⁺ T-cells. Interestingly, some individuals demonstrate private Vγ9Vδ2⁺ expansions with distinct effector phenotypes, suggestive of selective expansion in response to microbial stimulation. The Vγ9Vδ2⁺ T-cell subset, therefore, exhibits many features common to mouse γδ T-cell subsets, including early development, a semi-invariant TCR repertoire, and a reliance on butyrophilin-like molecules in antigen recognition. However, importantly Vγ9Vδ2⁺ T-cells retain TCR sensitivity after acquiring an effector phenotype. We outline a model for Vγ9Vδ2⁺ T-cell development and selection involving innate prenatal repertoire focusing, followed by postnatal repertoire shifts driven by microbial infection and/or altered thymic output.

γδ T cells: an immunotherapeutic approach for HIV cure strategies

Current strategies aimed to cure HIV infection are based on combined efforts to reactivate the virus from latency and improve immune effector cell function to clear infected cells. These strategies are primarily focused on CD8+ T cells and approaches are challenging due to insufficient HIV antigen production from infected cells and poor HIV-specific CD8+ T cells. γδ T cells represent a unique subset of effector T cells that can traffic to tissues, and selectively target cancer or virally infected cells without requiring MHC presentation. We analyzed whether γδ T cells represent a complementary/alternative immunotherapeutic approach towards HIV cure strategies. γδ T cells from HIV-infected virologically suppressed donors were expanded with bisphosphonate pamidronate (PAM) and cells were used in autologous cellular systems ex vivo. These cells (a) are potent cytotoxic effectors able to efficiently inhibit HIV replication ex vivo, (b) degranulate in the presence of autologous infected CD4+ T cells, and (c) specifically clear latently infected cells after latency reversal with vorinostat. This is the first proof of concept to our knowledge showing that γδ T cells target and clear autologous HIV reservoirs upon latency reversal. Our results open potentially new insights into the immunotherapeutic use of γδ T cells for current interventions in HIV eradication strategies.

Improving the Efficiency of Vγ9Vδ2 T-Cell Immunotherapy in Cancer

Increasing immunological knowledge and advances in techniques lay the ground for more efficient and broader application of immunotherapies. gamma delta (γδ) T-cells possess multiple favorable anti-tumor characteristics, making them promising candidates to be used in cellular and combination therapies of cancer. They recognize malignant cells, infiltrate tumors, and depict strong cytotoxic and pro-inflammatory activity. Here, we focus on human Vγ9Vδ2 T-cells, the most abundant γδ T-cell subpopulation in the blood, which are able to inhibit cancer progression in various models in vitro and in vivo. For therapeutic use they can be cultured and manipulated ex vivo and in the following adoptively transferred to patients, as well as directly stimulated to propagate in vivo. In clinical studies, Vγ9Vδ2 T-cells repeatedly demonstrated a low toxicity profile but hitherto only the modest therapeutic efficacy. This review provides a comprehensive summary of established and newer strategies for the enhancement of Vγ9Vδ2 T-cell anti-tumor functions. We discuss data of studies exploring methods for the sensitization of malignant cells, the improvement of recognition mechanisms and cytotoxic activity of Vγ9Vδ2 T-cells. Main aspects are the tumor cell metabolism, antibody-dependent cell-mediated cytotoxicity, antibody constructs, as well as activating and inhibitory receptors like NKG2D and immune checkpoint molecules. Several concepts show promising results in vitro, now awaiting translation to in vivo models and clinical studies. Given the array of research and encouraging findings in this area, this review aims at optimizing future investigations, specifically targeting the unanswered questions.

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

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

Enrichment of human Vγ9Vδ2 T lymphocytes by magnetic poly(divinylbenzene-co-glycidyl methacrylate) colloidal particles conjugated with specific antibody

γδ T cells play a significant role in protection against cancer. Purification of γδ T cells is needed for insight when studying their anti-cancer functionality and their utilization in adoptive cell therapy. To improve the purification of γδ T cells, in this work, a composite material based on magnetic nanoparticles was developed for purification of Vγ9Vδ2 T cells, the predominant subset of γδ T lymphocytes in human peripheral blood. The epoxy-functionalized magnetic poly(divinylbenzene-co-glycidyl methacrylate) particles (mPDGs) were bio-conjugated with anti-human Vδ2 antibody to provide specific recognition sites for T cell receptors of Vγ9Vδ2 T cells. Using fluorescence-activated cell sorting (FACS) analysis, separation of Vγ9Vδ2 T cells from peripheral blood mononuclear cells of healthy donors was confirmed with high purity [89.77% (range 87.00–91.80, n = 3)]. More interestingly, the immobilized particles did not affect the viability of purified cells as high cell viability was indicated (>90%). By combining the properties of magnetic nanoparticles with specific antibodies, these immobilized particles were shown to be used as a cell-friendly purification tool of Vγ9Vδ2 T lymphocytes without any limits for the further use of cells. The purified Vγ9Vδ2 T cells using the antibody-immobilized epoxy-functionalized mPDGs could be used directly without a detachment step for further cultivation and expansion. This highlights the advantages of this method in allowing the study of cell function and further investigation of such rare T cell populations in immunotherapy.

Schematic procedure of Vγ9Vδ2 T cell purification using antibody-immobilized epoxy-functionalized mPDGs.

Reconstitution of T and NK cells after haploidentical hematopoietic cell transplantation using αβ T cell-depleted grafts and the clinical implication of γδ T cells

To investigate reconstitution of T and NK cells after αβ T lymphocyte-depleted haploidentical hematopoietic cell transplantation (HHCT) and the clinical implications of γδ T cells, we analyzed 50 pediatric patients who received 55 HHCTs using αβ T cell-depleted grafts. The number of CD3+ T cells and CD8+ T cells recovered rapidly and reached donor levels at days 180 and 60, respectively. Recovery of NK cells was rapid, and the median of NK cells at day 14 was comparable to the donor level. At day 14, median percentage of γδ T lymphocytes was 70.5%. After day 14, the percentage of γδ T cells gradually decreased, while the percentage of αβ T cells gradually increased. Patients with a low percentage (≤21%) of γδ T cells at day 30 had significantly higher incidence of cytomegalovirus (CMV) reactivation compared to patients with a high percentage (>70%) of γδ T cells (P < .01). In patients with acute leukemia, patients with high percentage of γδ T cells at day 30 showed significantly higher relapse-free survival compared to those with low percentage of γδ T cells (P = .02). Data suggest that early recovery of γδ T cells decreases the risk of CMV reactivation and leukemia relapse.

Current Advances in γδ T Cell-Based Tumor Immunotherapy

γδ T cells are a minor population (~5%) of CD3 T cells in the peripheral blood, but abound in other anatomic sites such as the intestine or the skin. There are two major subsets of γδ T cells: those that express Vδ1 gene, paired with different Vγ elements, abound in the intestine and the skin, and recognize the major histocompatibility complex (MHC) class I-related molecules such as MHC class I-related molecule A, MHC class I-related molecule B, and UL16-binding protein expressed on many stressed and tumor cells. Conversely, γδ T cells expressing the Vδ2 gene paired with the Vγ9 chain are the predominant (50-90%) γδ T cell population in the peripheral blood and recognize phosphoantigens (PAgs) derived from the mevalonate pathway of mammalian cells, which is highly active upon infection or tumor transformation. Aminobisphosphonates (n-BPs), which inhibit farnesyl pyrophosphate synthase, a downstream enzyme of the mevalonate pathway, cause accumulation of upstream PAgs and therefore promote γδ T cell activation. γδ T cells have distinctive features that justify their utilization in antitumor immunotherapy: they do not require MHC restriction and are less dependent that αβ T cells on co-stimulatory signals, produce cytokines with known antitumor effects as interferon-γ and tumor necrosis factor-α and display cytotoxic and antitumor activities in vitro and in mouse models in vivo. Thus, there is interest in the potential application of γδ T cells in tumor immunotherapy, and several small-sized clinical trials have been conducted of γδ T cell-based immunotherapy in different types of cancer after the application of PAgs or n-BPs plus interleukin-2 in vivo or after adoptive transfer of ex vivo-expanded γδ T cells, particularly the Vγ9Vδ2 subset. Results from clinical trials testing the efficacy of any of these two strategies have shown that γδ T cell-based therapy is safe, but long-term clinical results to date are inconsistent. In this review, we will discuss the major achievements and pitfalls of the γδ T cell-based immunotherapy of cancer.

BTN3A1 Discriminates γδ T Cell Phosphoantigens from Nonantigenic Small Molecules via a Conformational Sensor in Its B30.2 Domain

Human Vγ9/Vδ2 T-cells detect tumor cells and microbial infections by recognizing small phosphorylated prenyl metabolites termed phosphoantigens (P-Ag). The type-1 transmembrane protein Butyrophilin 3A1 (BTN3A1) is critical to the P-Ag-mediated activation of Vγ9/Vδ2 T-cells; however, the molecular mechanisms involved in BTN3A1-mediated metabolite sensing are unclear, including how P-Ag's are discriminated from nonantigenic small molecules. Here, we utilized NMR and X-ray crystallography to probe P-Ag sensing by BTN3A1. Whereas the BTN3A1 immunoglobulin variable domain failed to bind P-Ag, the intracellular B30.2 domain bound a range of negatively charged small molecules, including P-Ag, in a positively charged surface pocket. However, NMR chemical shift perturbations indicated BTN3A1 discriminated P-Ag from nonantigenic small molecules by their ability to induce a specific conformational change in the B30.2 domain that propagated from the P-Ag binding site to distal parts of the domain. These results suggest BTN3A1 selectively detects P-Ag intracellularly via a conformational antigenic sensor in its B30.2 domain and have implications for rational design of antigens for Vγ9/Vδ2-based T-cell immunotherapies.

Distinctive features of tumor-infiltrating γδ T lymphocytes in human colorectal cancer

γδ T cells usually infiltrate many different types of cancer, but it is unclear whether they inhibit or promote tumor progression. Moreover, properties of tumor-infiltrating γδ T cells and those in the corresponding normal tissue remain largely unknown. Here we have studied features of γδ T cells in colorectal cancer, normal colon tissue and peripheral blood, and correlated their levels with clinicopathologic hallmarks. Flow cytometry and transcriptome analyses showed that the tumor comprised a highly variable rate of TILs (5-90%) and 4% γδ T cells on average, with the majority expressing Vδ1. Most Vδ1 and Vδ2 T cells showed a predominant effector memory phenotype and had reduced production of IFN- γ which was likely due to yet unidentified inhibitory molecules present in cancer stem cell secretome. Transcriptome analyses revealed that patients containing abundant γδ T cells had significantly longer 5-year disease free survival rate, suggesting their efficacy in controlling tumor at very early stage.

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

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

Zoledronic acid boosts γδ T-cell activity in children receiving αβ+ T and CD19+ cell-depleted grafts from an HLA-haplo-identical donor

We demonstrated that γδ T cells of patients given HLA-haploidentical HSCT after removal of αβ⁺ T cells and CD19⁺ B cells are endowed with the capacity of killing leukemia cells after ex vivo treatment with zoledronic acid (ZOL). Thus, we tested the hypothesis that infusion of ZOL in patients receiving this type of graft may enhance γδ T-cell cytotoxic activity against leukemia cells. ZOL was infused every 28 d in 43 patients; most were treated at least twice. γδ T cells before and after ZOL treatments were studied in 33 of these 43 patients, till at least 7 mo after HSCT by high-resolution mass spectrometry, flow-cytometry, and degranulation assay. An induction of Vδ2-cell differentiation, paralleled by increased cytotoxicity of both Vδ1 and Vδ2 cells against primary leukemia blasts was associated with ZOL treatment. Cytotoxic activity was further increased in Vδ2 cells, but not in Vδ1 lymphocytes in those patients given more than one treatment. Proteomic analysis of γδ T cells purified from patients showed upregulation of proteins involved in activation processes and immune response, paralleled by downregulation of proteins involved in proliferation. Moreover, a proteomic signature was identified for each ZOL treatment. Patients given three or more ZOL infusions had a better probability of survival in comparison to those given one or two treatments (86% vs. 54%, respectively, p = 0.008). Our data indicate that ZOL infusion in pediatric recipients of αβ T- and B-cell-depleted HLA-haploidentical HSCT promotes γδ T-cell differentiation and cytotoxicity and may influence the outcome of patients.