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

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Sustained Ca signaling, known as store-operated calcium entry (SOCE), occurs downstream of immunoreceptor engagement and is critical for cytotoxic lymphocyte signaling and effector function. CD8 T cells require sustained Ca signaling for inflammatory cytokine production and the killing of target cells; however, much less is known about its role in NK cells. In this study, we use mice deficient in stromal interacting molecules 1 and 2, which are required for SOCE, to examine the contribution of sustained Ca signaling to murine NK cell function. Surprisingly, we found that, although SOCE is required for NK cell IFN-γ production in an NFAT-dependent manner, NK cell degranulation/cytotoxicity and tumor rejection in vivo remained intact in the absence of sustained Ca signaling. Our data suggest that mouse NK cells use different signaling mechanisms for cytotoxicity compared with other cytotoxic lymphocytes.

Gamma delta lymphocytes (γδ T) sit at the interface between innate and adaptive immunity. They have the capacity to recognize cancer cells by interaction of their surface receptors with an array of cancer cell surface target antigens. Interactions include the binding of γδ T cell receptors, the ligands for which are diverse and do not involve classical major histocompatibility complex (MHC) molecules. Moreover, a variety of natural killer-like and fragment crystallizable gamma (Fcγ) receptors confer additional cancer reactivity. Given this innate capacity to recognize and kill cancer cells, there appears less rationale for redirecting specific to cancer cell surface antigens through chimeric antigen receptor (CAR) expression. Several groups have however reported research findings that expression of CARs in γδ T cells can confer additional specificity or functionality. Though limited in number, these studies collectively identify the potential of CAR-T engineering to augment and fine tune anti-cancer responses. Together with the lack of graft versus host disease induced by allogeneic γδ T cells, these insights should encourage researchers to explore additional γδ T-CAR refinements for the development of off-the-shelf anti-cancer cell therapies.

Neuroblastoma (NB) accounts for a considerable portion of childhood cancer-related mortalities. Despite improvements in therapy over the last few decades, 5-year survival rates in patients with high-risk disease remain poor (40-50%). High-risk disease results from amplification of MYCN and dysregulation in downstream Myc-related pathways. Polyamine (PA) synthesis is one such pathway, as MYCN-amplified high-risk NBs have elevated polyamine levels, and the gate-keeper enzyme in this pathway, ornithine decarboxylase (ODC1), is a direct target of Myc. In a mouse model of MYCN-driven NB (TH-MYCN+/+ transgenic mice), inhibition of PA synthesis with an irreversible inhibitor of ODC1, difluoromethylornithine (DFMO), led to reductions in NB burden that seemed out of proportion to DFMO's ability to limit tumor growth in vitro, suggesting that PA blockade may result in additional tumor cell-extrinsic effects. Consistent with this possibility, PAs have been shown to favor the differentiation and function of suppressive, tumor-supportive cell types, while PA depletion results in reversal of immune suppression via increased number and function of tumor-infiltrating leukocytes (TILs) and concomitant inhibition of infiltration and differentiation of suppressive cell types. However, these previous studies focused on investigating the effects of PA depletion in vitro or in vivo in tumor-induction models or immune-deficient mice. We therefore sought to characterize the tumor microenvironment of NB in TH-MYCN+/+ mice in the presence or absence of DFMO-mediated PA blockade. Tumors at terminal disease were dissected, mechanically and enzymatically dissociated, and the number and frequencies of various TIL subsets were assessed using an optimized flow cytometry-based protocol. Results indicate that DFMO therapy reduces tumor growth and results in distinct and reproducible alterations in the cellular composition of the NB tumor microenvironment at terminal disease. Specifically, we found an increased frequency of dendritic cells, natural killer cells, and a late accumulation of CD4-negative invariant natural killer T cells and granulocytic tumor-associated myeloid cells. Increases in these specific TIL subsets are consistent with the hypothesis that polyamine blockade induces distinct tumor cell-extrinsic changes in the microenvironment that allow for more efficient immune control of NB. We hope that these studies will complement the data being accrued from phase I/II clinical studies using DFMO in various therapeutic strategies for NB and will allow for an increased understanding of how to employ PA blockade in the immunotherapy of this disease. Citation Format: Adriana D. Benavides, Annette T. Vu, Jennie B. Altman, Gabrielle M. Ferry, Michael D. Hogarty, Hamid Bassiri. Polyamine blockade modulates the neuroblastoma microenvironment. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B203.