Targeting myeloma-osteoclast interaction with Vγ9Vδ2 T cells

Ex vivo expansion and activation of Vγ9Vδ2 T cells by CELMoDs in combination with zoledronic acid

As multiple myeloma (MM) progresses, immune effector cells decrease in number and function and become exhausted. This remains an insurmountable clinical issue that must be addressed by development of novel modalities to revitalize anti-MM immunity. Human Vγ9Vδ2 T (Vδ2+ γδ T) cells serve as the first line of defense against pathogens as well as tumors and can be expanded ex vivo from peripheral blood mononuclear cells (PBMCs) upon treatment with amino-bisphosphonates in combination with IL-2. Here, we demonstrated that next-generation immunomodulators called cereblon E3 ligase modulators (CELMoDs), as well as lenalidomide and pomalidomide, expanded Th1-like Vδ2+ γδ T cells from PBMCs in the presence of zoledronic acid (ZA). However, the expansion of Th1-like Vδ2+ γδ T cells by these immunomodulatory drugs was abolished under IL-2 blockade, although IL-2 production was induced in PBMCs. BTN3A1 triggers phosphoantigen presentation to γδ T-cell receptors and is required for γδ T-cell expansion and activation. ZA but not these immunomodulatory drugs upregulated BTN3A1 in monocytes. These results suggest that immunomodulatory drugs and ZA have cooperative roles in expansion of Th1-like Vδ2+ γδ T cells, and provide the important knowledge for clinical application of human Vδ2+ γδ T cells as effector cells.

CD155 and CD112 as possible therapeutic targets of FLT3 inhibitors for acute myeloid leukemia

Acute myeloid leukemia (AML) relapse is considered to be related to escape from antitumor immunity. Changes in the expression of immune checkpoints, including B7 homolog (H)1 and B7-H2, have been reported to contribute to AML progression. Binding of T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain (TIGIT) among other immune checkpoints on natural killer (NK) and T cells to CD155/CD112 in tumors is supposed to be inhibitory; however, the mechanism by which changes in CD155 and CD112 expression affect tumor immunity remains unclear. When the increased expression of CD155 and CD112 activates Raf-MEK-ERK pathway and Raf-MEK-ERK pathway is one of the targets of FMS-like tyrosine kinase 3 (FLT3) inhibition. The present study investigated the alterations in CD155 and CD112 expression under FLT3 inhibition (quizartinib and gilteritinib) and studied its effect on NK and T cell cytotoxicity. CD155 and CD112 expression was analyzed using flow cytometry and reverse transcription-quantitative PCR in AML cell lines with or without FLT3 mutation using FLT3 inhibitors. CD155 and CD112 expression was specifically downregulated by FLT3 inhibition in FLT3-mutated cell lines. Direct cytotoxicity and antibody-dependent cellular cytotoxicity against these cells by NK cells were enhanced. However, the cytotoxicity of γδ T cells with low TIGIT expression compared with NK cells was not enhanced in direct cytotoxicity assay using luciferase luminescence. The analysis of clinical trials from The Cancer Genome Atlas (TCGA) revealed that high CD155 and CD112 expression is associated with poor overall survival. The enhanced cytotoxicity of NK cells against CD155- and CD112-downregulated cells following FLT3 inhibition indicated CD155 and CD112 as possible targets of immunotherapy for AML using FLT3 inhibitors.

A Bispecific Antibody Antagonizes Prosurvival CD40 Signaling and Promotes Vγ9Vδ2 T cell-Mediated Antitumor Responses in Human B-cell Malignancies

Novel T cell-based therapies for the treatment of B-cell malignancies, such as chronic lymphocytic leukemia (CLL) and multiple myeloma (MM), are thought to have strong potential. Progress, however, has been hampered by low efficacy and high toxicity. Tumor targeting by Vγ9Vδ2 T cells, a conserved T-cell subset with potent intrinsic antitumor properties, mediated by a bispecific antibody represents a novel approach promising high efficacy with limited toxicity. Here, we describe the generation of a bispecific Vγ9Vδ2 T-cell engager directed against CD40, which, due to its overexpression and biological footprint in malignant B cells, represents an attractive target. The CD40-targeting moiety of the bispecific antibody was selected because it can prevent CD40L-induced prosurvival signaling and reduce CD40-mediated resistance of CLL cells to venetoclax. Selective activation of Vγ9Vδ2 T cells in the presence of CD40⁺ tumor cells induced potent Vγ9Vδ2 T-cell degranulation, cytotoxicity against CLL and MM cells in vitro, and in vivo control of MM in a xenograft model. The CD40-bispecific γδ T-cell engager demonstrated lysis of leukemic cells by autologous Vγ9Vδ2 T cells present in patient-derived samples. Taken together, our CD40 bispecific γδ T-cell engager increased the sensitivity of leukemic cells to apoptosis and induced a potent Vγ9Vδ2 T cell-dependent antileukemic response. It may, therefore, represent a potential candidate for the development of novel treatments for B-cell malignancies.

Vγ9Vδ2 T cells inhibit immature dendritic cell transdifferentiation into osteoclasts through downregulation of RANK, c‑Fos and ATP6V0D2

Osteoimmunological studies have revealed that T cells exert a powerful impact on the formation and activity of osteoclasts and bone remodeling. Evidence demonstrates that immature dendritic cells (iDCs) are more efficient transdifferentiating into osteoclasts (OCs) than monocytes. However, whether Vγ9Vδ2 T (γδ T) cells stimulate or inhibit iDC transdifferentiation into OCs has never been reported. The aim of the present study was to investigate the effects of γδ T cells on this transdifferentiation process. γδ T cells and iDCs were isolated from the peripheral blood of healthy volunteers separately and were co-cultured with Transwelll inserts, with γδ T cells in the upper chamber and iDCs in the lower chamber. IDCs were treated with macrophage-colony stimulating factor and receptor activator of nuclear factor-κB (RANK) ligand. Tartrate resistant acid phosphatase (TRAP) assay and dentine resorption assay were performed to detect OC formation and their resorption capacity, respectively. The mRNA expression of OCs was examined using a micro-array and real time-quantitative polymerase chain reaction to trace the changes during iDC transdifferentiation into OCs. The results demonstrated that γδ T cells significantly inhibited the generation of the TRAP-positive OCs from iDCs and their resorption capacity. The microarray analysis identified decreased expression level of Fos proto-oncogene AP-1 transcription factor subunit (c-Fos), ATPase H⁺ transporting V0 subunit d (ATP6V0D2) and cathepsin K when iDCs were co-cultured with γδ T cells. These genes are associated with OC differentiation, indicating that γδ T cells suppressed iDCs osteoclastogenesis by downregulation of the RANK/c-Fos/ATP6V0D2 signaling pathway. The present findings provide novel insights into the interactions between human γδ T cells and iDCs, and demonstrate that γδ T cells are capable of inhibiting OC formation and their activity via downregulation of genes associated with OC differentiation.

Adoptive transfer of ex vivo expanded Vγ9Vδ2 T cells in combination with zoledronic acid inhibits cancer growth and limits osteolysis in a murine model of osteolytic breast cancer

Bone metastases occur in over 75% of patients with advanced breast cancer and are responsible for high levels of morbidity and mortality. In this study, ex vivo expanded cytotoxic Vγ9Vδ2 T cells isolated from human peripheral blood were tested for their anti-cancer efficacy in combination with zoledronic acid (ZOL), using a mouse model of osteolytic breast cancer. In vitro, expanded Vγ9Vδ2 T cells were cytotoxic against a panel of human breast cancer cell lines, and ZOL pre-treatment further sensitised breast cancer cells to killing by Vγ9Vδ2 T cells. Vγ9Vδ2 T cells adoptively transferred into NOD/SCID mice localised to osteolytic breast cancer lesions in the bone, and multiple infusions of Vγ9Vδ2 T cells reduced tumour growth in the bone. ZOL pre-treatment potentiated the anti-cancer efficacy of Vγ9Vδ2 T cells, with mice showing further reductions in tumour burden. Mice treated with the combination also had reduced tumour burden of secondary pulmonary metastases, and decreased bone degradation. Our data suggests that adoptive transfer of Vγ9Vδ2 T cell in combination with ZOL may prove an effective immunotherapeutic approach for the treatment of breast cancer bone metastases.

A mathematical model of cell equilibrium and joint cell formation in multiple myeloma

In Multiple Myeloma Bone Disease healthy bone remodelling is affected by tumour cells by means of paracrine cytokinetic signalling in such a way that osteoclast formation is enhanced and the growth of osteoblast cells inhibited. The participating cytokines are described in the literature. Osteoclast-induced myeloma cell growth is also reported. Based on existing mathematical models for healthy bone remodelling a three-way equilibrium model is presented for osteoclasts, osteoblasts and myeloma cell populations to describe the progress of the illness in a scenario in which there is a secular increase in the cytokinetic interactive effectiveness of paracrine processes. The equilibrium state for the system is obtained. The paracrine interactive effectiveness is explored by parameter variation and the stable region in the parameter space is identified. Then recently-discovered joint myeloma-osteoclast cells are added to the model to describe the populations inside lytic lesions. It transpires that their presence expands the available parameter space for stable equilibrium, thus permitting a detrimental, larger population of osteoclasts and myeloma cells. A possible relapse mechanism for the illness is explored by letting joint cells dissociate. The mathematics then permits the evaluation of the evolution of the cell populations as a function of time during relapse.

Navigating the bone marrow niche: translational insights and cancer-driven dysfunction

The bone marrow niche consists of stem and progenitor cells destined to become mature cells such as haematopoietic elements, osteoblasts or adipocytes. Marrow cells, influenced by endocrine, paracrine and autocrine factors, ultimately function as a unit to regulate bone remodelling and haematopoiesis. Current evidence highlights that the bone marrow niche is not merely an anatomic compartment; rather, it integrates the physiology of two distinct organ systems, the skeleton and the marrow. The niche has a hypoxic microenvironment that maintains quiescent haematopoietic stem cells (HSCs) and supports glycolytic metabolism. In response to biochemical cues and under the influence of neural, hormonal, and biochemical factors, marrow stromal elements, such as mesenchymal stromal cells (MSCs), differentiate into mature, functioning cells. However, disruption of the niche can affect cellular differentiation, resulting in disorders ranging from osteoporosis to malignancy. In this Review, we propose that the niche reflects the vitality of two tissues - bone and blood - by providing a unique environment for stem and stromal cells to flourish while simultaneously preventing disproportionate proliferation, malignant transformation or loss of the multipotent progenitors required for healing, functional immunity and growth throughout an organism's lifetime. Through a fuller understanding of the complexity of the niche in physiologic and pathologic states, the successful development of more-effective therapeutic approaches to target the niche and its cellular components for the treatment of rheumatic, endocrine, neoplastic and metabolic diseases becomes achievable.

Novel immunostimulatory effects of osteoclasts and macrophages on human γδ T cells

It has been widely reported that T cells are capable of influencing osteoclast formation and bone remodelling, yet relatively little is known of the reciprocal effects of osteoclasts for affecting T cell function and/or activity. In this study we investigated the effects of human osteoclasts on the function of γδ T cells, a subset of non-CD4(+) T cells implicated in a variety of inflammatory disease states. γδ T cells and CD4(+) T cells were isolated from peripheral blood of healthy volunteers and were co-cultured with autologous mature osteoclasts (generated by treatment with M-CSF and RANKL) before phenotypical and functional changes in the T cell populations were assessed. Macrophages, osteoclasts, and conditioned medium derived from macrophages or osteoclasts induced activation of γδ T cells, as determined by the expression of the early activation marker CD69. TNFα was a major mediator of this stimulatory effect on γδ T cells. Consistent with this stimulatory effect, osteoclasts augmented proliferation of IL-2-stimulated γδ T cells and also supported the survival of unstimulated γδ and CD4(+) T cells, although these effects required co-culture with osteoclasts. Co-culture with osteoclasts also increased the proportion of γδ T cells producing IFNγ, but did not modulate IFNγ or IL-17 production by CD4(+) T cells. We provide new insights into the in vitro interactions between human γδ T cells and osteoclasts/macrophages, and demonstrate that osteoclasts or their precursors are capable of influencing γδ T function both via the release of soluble factors and also through direct cell-cell interactions.

Zoledronic acid causes γδ T cells to target monocytes and down-modulate inflammatory homing

Zoledronic acid (ZA) is a potential immunotherapy for cancer because it can induce potent γδ T-cell-mediated anti-tumour responses. Clinical trials are testing the efficacy of intravenous ZA in cancer patients; however, the effects of systemic ZA on the activation and migration of peripheral γδ T cells remain poorly understood. We found that γδ T cells within ZA-treated peripheral blood mononuclear cells were degranulating, as shown by up-regulated expression of CD107a/b. Degranulation was monocyte dependent because CD107a/b expression was markedly reduced in the absence of CD14(+) cells. Consistent with monocyte-induced degranulation, we observed γδ T-cell-dependent induction of monocyte apoptosis, as shown by phosphatidylserine expression on monocytes and decreased percentages of monocytes in culture. Despite the prevailing paradigm that ZA promotes tumour homing in γδ T cells, we observed down-modulation of their tumour homing capacity, as shown by decreased expression of the inflammatory chemokine receptors CCR5 and CXCR3, and reduced migration towards the inflammatory chemokine CCL5. Taken together our data suggest that ZA causes γδ T cells to target monocytes and down-modulate the migratory programme required for inflammatory homing. This study provides novel insight into how γδ T cells interact with monocytes and the possible implications of systemic use of ZA in cancer.