Interleukin-15-armored GPC3-CAR T cells for patients with solid cancers

Interleukin-15 (IL15) promotes the survival of T lymphocytes and enhances the antitumor properties of CAR T cells in preclinical models of solid neoplasms in which CAR T cells have limited efficacy1-4. Glypican-3 (GPC3) is expressed in a group of solid cancers5-10, and here we report the first evaluation in humans of the effects of IL15 co-expression on GPC3-CAR T cells. Cohort 1 patients (NCT02905188/NCT02932956) received GPC3-CAR T cells, which were safe but produced no objective antitumor responses and reached peak expansion at two weeks. Cohort 2 patients (NCT05103631/NCT04377932) received GPC3-CAR T cells that co-expressed IL15 (15.CAR), which mediated significantly increased cell expansion and induced a disease control rate of 66% and antitumor response rate of 33%. Infusion of 15.CAR T cells was associated with increased incidence of cytokine release syndrome, which was rapidly ameliorated by activation of the inducible caspase 9 safety switch. Compared to non-responders, tumor-infiltrating 15.CAR T cells from responders showed repression of SWI/SNF epigenetic regulators and upregulation of FOS and JUN family members as well as genes related to type I interferon signaling. Collectively, these results demonstrate that IL15 increases the expansion, intratumoral survival, and antitumor activity of GPC3-CAR T cells in patients.

Anti-GD2 CAR-NKT cells in relapsed or refractory neuroblastoma: updated phase 1 trial interim results

Vα24-invariant natural killer T cells (NKTs) have anti-tumor properties that can be enhanced by chimeric antigen receptors (CARs). Here we report updated interim results from the first-in-human phase 1 evaluation of autologous NKTs co-expressing a GD2-specific CAR with interleukin 15 (IL15) (GD2-CAR.15) in 12 children with neuroblastoma (NB). The primary objectives were safety and determination of maximum tolerated dose (MTD). The anti-tumor activity of GD2-CAR.15 NKTs was assessed as a secondary objective. Immune response evaluation was an additional objective. No dose-limiting toxicities occurred; one patient experienced grade 2 cytokine release syndrome that was resolved by tocilizumab. The MTD was not reached. The objective response rate was 25% (3/12), including two partial responses and one complete response. The frequency of CD62L+NKTs in products correlated with CAR-NKT expansion in patients and was higher in responders (n = 5; objective response or stable disease with reduction in tumor burden) than non-responders (n = 7). BTG1 (BTG anti-proliferation factor 1) expression was upregulated in peripheral GD2-CAR.15 NKTs and is a key driver of hyporesponsiveness in exhausted NKT and T cells. GD2-CAR.15 NKTs with BTG1 knockdown eliminated metastatic NB in a mouse model. We conclude that GD2-CAR.15 NKTs are safe and can mediate objective responses in patients with NB. Additionally, their anti-tumor activity may be enhanced by targeting BTG1. ClinicalTrials.gov registration: NCT03294954 .

Interaction between tumor cell TNFR2 and monocyte membrane-bound TNF-α triggers tumorigenic inflammation in neuroblastoma

BACKGROUND

Tumor progression and resistance to therapy in children with neuroblastoma (NB), a common childhood cancer, are often associated with infiltration of monocytes and macrophages that produce inflammatory cytokines. However, the mechanism by which tumor-supportive inflammation is initiated and propagated remains unknown. Here, we describe a novel protumorigenic circuit between NB cells and monocytes that is triggered and sustained by tumor necrosis factor alpha (TNF-α).

METHODS

We used NB knockouts (KOs) of TNF-α and TNFRSF1A mRNA (TNFR1)/TNFRSF1B mRNA (TNFR2) and TNF-α protease inbitor (TAPI), a drug that modulates TNF-α isoform expression, to assess the role of each component in monocyte-associated protumorigenic inflammation. Additionally, we employed NB-monocyte cocultures and treated these with clinical-grade etanercept, an Fc-TNFR2 fusion protein, to neutralize signaling by both membrane-bound (m) and soluble (s)TNF-α isoforms. Further, we treated NOD/SCID/IL2Rγ(null) mice carrying subcutaneous NB/human monocyte xenografts with etanercept and evaluated the impact on tumor growth and angiogenesis. Gene set enrichment analysis (GSEA) was used to determine whether TNF-α signaling correlates with clinical outcomes in patients with NB.

RESULTS

We found that NB expression of TNFR2 and monocyte membrane-bound tumor necrosis factor alpha is required for monocyte activation and interleukin (IL)-6 production, while NB TNFR1 and monocyte soluble TNF-α are required for NB nuclear factor kappa B subunit 1 (NF-κB) activation. Treatment of NB-monocyte cocultures with clinical-grade etanercept completely abrogated release of IL-6, granulocyte colony-stimulating factor (G-CSF), IL-1α, and IL-1β and eliminated monocyte-induced enhancement of NB cell proliferation in vitro. Furthermore, etanercept treatment inhibited tumor growth, ablated tumor angiogenesis, and suppressed oncogenic signaling in mice with subcutaneous NB/human monocyte xenografts. Finally, GSEA revealed significant enrichment for TNF-α signaling in patients with NB that relapsed.

CONCLUSIONS

We have described a novel mechanism of tumor-promoting inflammation in NB that is strongly associated with patient outcome and could be targeted with therapy.

Natural killer T cells and other innate-like T lymphocytes as emerging platforms for allogeneic cancer cell therapy

T cells expressing chimeric antigen receptors (CARs) have achieved major clinical success in patients with hematologic malignancies. However, these treatments remain largely ineffective for solid cancers and require significant time and resources to be manufactured in an autologous setting. Developing alternative immune effector cells as cancer immunotherapy agents that can be employed in allogeneic settings is crucial for the advancement of cell therapy. Unlike T cells, Vα24-invariant natural killer T cells (NKTs) are not alloreactive and can therefore be generated from allogeneic donors for rapid infusion into numerous patients without the risk of graft-versus-host disease. Additionally, NKT cells demonstrate inherent advantages over T-cell products, including the ability to traffic to tumor tissues, target tumor-associated macrophages, transactivate NK cells, and cross-prime tumor-specific CD8 T cells. Both unmodified NKTs, which specifically recognize CD1d-bound glycolipid antigens expressed by certain types of tumors, and CAR-redirected NKTs are being developed as the next generation of allogeneic cell therapy products. In this review, we describe studies on the biology of NKTs and other types of innate-like T cells and summarize the clinical experiences of unmodified and CAR-redirected NKTs, including recent interim reports on allogeneic NKTs.

LEF1 Drives a Central Memory Program and Supports Antitumor Activity of Natural Killer T Cells

Vα24-invariant natural killer T cells (NKT) possess innate antitumor properties that can be exploited for cancer immunotherapy. We have shown previously that the CD62L+ central memory-like subset of these cells drives the in vivo antitumor activity of NKTs, but molecular mediators of NKT central memory differentiation remain unknown. Here, we demonstrate that relative to CD62L- cells, CD62L+ NKTs express a higher level of the gene encoding the Wnt/β-catenin transcription factor lymphoid enhancer binding factor 1 (LEF1) and maintain active Wnt/β-catenin signaling. CRISPR/Cas9-mediated LEF1 knockout reduced CD62L+ frequency after antigenic stimulation, whereas Wnt/β-catenin activator Wnt3a ligand increased CD62L+ frequency. LEF1 overexpression promoted NKT expansion and limited exhaustion following serial tumor challenge and was sufficient to induce a central memory-like transcriptional program in NKTs. In mice, NKTs expressing a GD2-specific chimeric-antigen receptor (CAR) with LEF1 demonstrated superior control of neuroblastoma xenograft tumors compared with control CAR-NKTs. These results identify LEF1 as a transcriptional activator of the NKT central memory program and advance development of NKT cell-based immunotherapy. See related Spotlight by Van Kaer, p. 144.

A Nanoradiomics Approach for Differentiation of Tumors Based on Tumor-Associated Macrophage Burden

Objective

Tumor-associated macrophages (TAMs) within the tumor immune microenvironment (TiME) of solid tumors play an important role in treatment resistance and disease recurrence. The purpose of this study was to investigate if nanoradiomics (radiomic analysis of nanoparticle contrast-enhanced images) can differentiate tumors based on TAM burden.

Materials and Methods

In vivo studies were performed in transgenic mouse models of neuroblastoma with low (N = 11) and high (N = 10) tumor-associated macrophage (TAM) burden. Animals underwent delayed nanoparticle contrast-enhanced CT (n-CECT) imaging at 4 days after intravenous administration of liposomal-iodine agent (1.1 g/kg). CT imaging-derived conventional tumor metrics (tumor volume and CT attenuation) were computed for segmented tumor CT datasets. Nanoradiomic analysis was performed using a PyRadiomics workflow implemented in the quantitative image feature pipeline (QIFP) server containing 900 radiomic features (RFs). RF selection was performed under supervised machine learning using a nonparametric neighborhood component method. A 5-fold validation was performed using a set of linear and nonlinear classifiers for group separation. Statistical analysis was performed using the Kruskal-Wallis test.

Results

N-CECT imaging demonstrated heterogeneous patterns of signal enhancement in low and high TAM tumors. CT imaging-derived conventional tumor metrics showed no significant differences (p > 0.05) in tumor volume between low and high TAM tumors. Tumor CT attenuation was not significantly different (p > 0.05) between low and high TAM tumors. Machine learning-augmented nanoradiomic analysis revealed two RFs that differentiated (p < 0.002) low TAM and high TAM tumors. The RFs were used to build a linear classifier that demonstrated very high accuracy and further confirmed by 5-fold cross-validation.

Conclusions

Imaging-derived conventional tumor metrics were unable to differentiate tumors with varying TAM burden; however, nanoradiomic analysis revealed texture differences and enabled differentiation of low and high TAM tumors.

Anti-GD2 CAR-NKT cells in patients with relapsed or refractory neuroblastoma: an interim analysis

Vα24-invariant natural killer T (NKT) cells have shown potent anti-tumor properties in murine tumor models and have been linked to favorable outcomes in patients with cancer. However, low numbers of these cells in humans have hindered their clinical applications. Here we report interim results from all three patients enrolled on dose level 1 in a phase 1 dose-escalation trial of autologous NKT cells engineered to co-express a GD2-specific chimeric antigen receptor (CAR) with interleukin-15 in children with relapsed or resistant neuroblastoma (NCT03294954). Primary and secondary objectives were to assess safety and anti-tumor responses, respectively, with immune response evaluation as an additional objective. We ex vivo expanded highly pure NKT cells (mean ± s.d., 94.7 ± 3.8%) and treated patients with 3 × 10⁶ CAR-NKT cells per square meter of body surface area after lymphodepleting conditioning with cyclophosphamide/fludarabine (Cy/Flu). Cy/Flu conditioning was the probable cause for grade 3-4 hematologic adverse events, as they occurred before CAR-NKT cell infusion, and no dose-limiting toxicities were observed. CAR-NKT cells expanded in vivo, localized to tumors and, in one patient, induced an objective response with regression of bone metastatic lesions. These initial results suggest that CAR-NKT cells can be expanded to clinical scale and safely applied to treat patients with cancer.

LEF1 activates a central memory-like program in human NKT cells

Vα24-invariant natural killer T cells (NKTs) possess potent antitumor activity that can be exploited for use in cancer immunotherapy. We recently demonstrated that the CD62L+ NKT subset persists longer and mediates more potent antitumor activity in vivo than its CD62L− counterpart; as such, CD62L+ NKTs are crucial to maximizing the therapeutic efficacy of NKTs. Key factors involved in transcriptional control of the CD62L+ central memory-like program in NKTs remain largely undefined. To address this gap, we performed comparative gene expression analysis in CD62L+ and CD62L− NKTs and found that LEF1, which encodes a mediator of Wnt/β-catenin signaling, was the top overexpressed gene in the positive subset. We also found that LEF1 protein expression was largely restricted to CD62L+ primary human NKTs and was associated with increased expression of Wnt target genes. While CRISPR-Cas9-mediated knockout of LEF1 expression did not impact CD62L+ cell numbers after initial ex vivo expansion, it did significantly reduce the frequency of these cells after antigenic restimulation. On the other hand, treatment with Wnt/β-catenin signaling activator TWS119 or Wnt3a ligand increased CD62L+ NKT cell frequency. Combined treatment of TWS119 with IL-21, which selectively protects the CD62L+ subset from apoptosis, resulted in significantly higher CD62L+ cell numbers than each single agent alone. These results identify LEF1 as a key transcriptional activator of the central memory-like program in CD62L+ NKTs and pave the way for targeted pharmacological enhancement of NKT cell-based cancer immunotherapy.

Glypican-3-Specific CAR T Cells Coexpressing IL15 and IL21 Have Superior Expansion and Antitumor Activity against Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the fourth most common cause of cancer-related death in the world, and curative systemic therapies are lacking. Chimeric antigen receptor (CAR)-expressing T cells induce robust antitumor responses in patients with hematologic malignancies but have limited efficacy in patients with solid tumors, including HCC. IL15 and IL21 promote T-cell expansion, survival, and function and can improve the antitumor properties of T cells. We explored whether transgenic expression of IL15 and/or IL21 enhanced glypican-3-CAR (GPC3-CAR) T cells' antitumor properties against HCC. We previously optimized the costimulation in GPC3-CARs and selected a second-generation GPC3-CAR incorporating a 4-1BB costimulatory endodomain (GBBz) for development. Here, we generated constructs encoding IL15, IL21, or both with GBBz (15.GBBz, 21.GBBz, and 21.15.GBBz, respectively) and examined the ability of transduced T cells to kill, produce effector cytokines, and expand in an antigen-dependent manner. We performed gene-expression and phenotypic analyses of GPC3-CAR T cells and CRISPR-Cas9 knockout of the TCF7 gene. Finally, we measured GPC3-CAR T-cell antitumor activity in murine xenograft models of GPC3+ tumors. The increased proliferation of 21.15.GBBz T cells was at least in part dependent on the upregulation and maintenance of TCF-1 (encoded by TCF7) and associated with a higher percentage of stem cell memory and central memory populations after manufacturing. T cells expressing 21.15.GBBz had superior in vitro and in vivo expansion and persistence, and the most robust antitumor activity in vivo These results provided preclinical evidence to support the clinical evaluation of 21.15.GPC3-CAR T cells in patients with HCC.

NKT Cells Coexpressing a GD2-Specific Chimeric Antigen Receptor and IL15 Show Enhanced In Vivo Persistence and Antitumor Activity against Neuroblastoma

PURPOSE

Vα24-invariant natural killer T cells (NKT) are attractive carriers for chimeric antigen receptors (CAR) due to their inherent antitumor properties and preferential localization to tumor sites. However, limited persistence of CAR-NKTs in tumor-bearing mice is associated with tumor recurrence. Here, we evaluated whether coexpression of the NKT homeostatic cytokine IL15 with a CAR enhances the in vivo persistence and therapeutic efficacy of CAR-NKTs.

EXPERIMENTAL DESIGN

Human primary NKTs were ex vivo expanded and transduced with CAR constructs containing an optimized GD2-specific single-chain variable fragment and either the CD28 or 4-1BB costimulatory endodomain, each with or without IL15 (GD2.CAR or GD2.CAR.15). Constructs that mediated robust CAR-NKT cell expansion were selected for further functional evaluation in vitro and in xenogeneic mouse models of neuroblastoma.

RESULTS

Coexpression of IL15 with either costimulatory domain increased CAR-NKT absolute numbers. However, constructs containing 4-1BB induced excessive activation-induced cell death and reduced numeric expansion of NKTs compared with respective CD28-based constructs. Further evaluation of CD28-based GD2.CAR and GD2.CAR.15 showed that coexpression of IL15 led to reduced expression levels of exhaustion markers in NKTs and increased multiround in vitro tumor cell killing. Following transfer into mice bearing neuroblastoma xenografts, GD2.CAR.15 NKTs demonstrated enhanced in vivo persistence, increased localization to tumor sites, and improved tumor control compared with GD2.CAR NKTs. Importantly, GD2.CAR.15 NKTs did not produce significant toxicity as determined by histopathologic analysis.

CONCLUSIONS

Our results informed selection of the CD28-based GD2.CAR.15 construct for clinical testing and led to initiation of a first-in-human CAR-NKT cell clinical trial (NCT03294954).

A phase I clinical trial using armored GPC3 CAR T cells for children with relapsed/refractory liver tumors

TPS2647

Background: CAR T therapies have been successful against hematologic malignancies, but have benefited only a handful of patients with solid cancers. Glypican 3 (GPC3) is an attractive immunotherapeutic target due to its preferential expression on multiple pediatric and adult solid cancers and lack of expression on non-malignant tissues. GPC3-CAR T cells were tested preclinically and inclusion of the 4-1BB costimulatory endodomain with IL-15 and IL-21 co-expression enabled CAR T cells to expand and persist the most in vitro and in vivo and led to robust antitumor activity in vivo. We are now testing GPC3-CAR T cells with IL15 and IL-21 for the first time in children with relapsed/refractory liver tumors. Methods: In this Phase 1 trial (GAP, NCT02932956), we are evaluating patients in 3 cohorts: 1) GPC3-CAR alone; 2) GPC3-CAR and IL-15; 3) GPC3-CAR with IL-15 and IL-21. We will 1) define the safety and establish the Recommended Phase 2 Dose (RP2D) of GPC3-CAR T cells co-expressing IL-15 and IL-21; 2) determine persistence and anti-tumor activity of GPC3-CAR T cells; 3) examine changes in gene and protein expression in the tumor microenvironment associated with potential immune escape mechanisms. Inclusion criteria are the following: age ≤18; histology proven, GPC3-positive tumor; life expectancy>12 weeks; Child-Pugh-Turcotte score<7; serum AST<5 times ULN; total bilirubin<3 times ULN for age; INR ≤1.7; absolute neutrophil count>500/μl; platelet count>20,000/μl; Hgb≥9.0 g/dl. Toxicity will be monitored using the Common Terminology Criteria of Adverse Events v4. The RP2D will be determined by the standard 3+3 dose escalation method using 5 dose levels. Persistence will be quantified using RT-PCR and flow cytometry. Antitumor activity will be defined by 3D imaging using RECIST 1.1 criteria and the immune-related response criteria. Immune-escape will be examined using single cell RNA sequencing and imaging of paraffin-embedded tissues using codetection by indexing to evaluate candidate proteins. Data will be analyzed via descriptive statistics. Cohort 1 of this study is now open for enrollment. Clinical trial information: NCT02932956.

Abstract IA09: Harnessing natural and engineered properties of NKT cells for cancer immunotherapy

Due to their natural anti-tumor properties and ability to preferentially localize to the neuroblastoma (NB) tumor site, Vα24-invariant natural killer T cells (NKTs) are promising candidate immune effectors for chimeric antigen receptor (CAR)-based immunotherapies targeting NB and other solid tumors. We have previously demonstrated that human NKTs expressing a CAR specific for ganglioside GD2 (CAR.GD2) mediated potent anti-tumor activity in a xenogeneic NB model in NOD/SCID/IL-2Rγnull mice. In comparison with CAR.GD2 T cells, CAR.GD2 NKTs localized more effectively to the tumor tissues and did not induce graft-versus-host disease (GvHD). Clinical development of NKT cell-based therapeutics requires overcoming two fundamental challenges: 1) the low frequency of NKTs in human peripheral blood, and 2) the limited ability of adoptively transfered NKTs/CAR-NKTs to persist in tumor-bearing animals. To address the first limitation, we have developed a cGMP protocol to isolate NKT cells from leukapheresis products using NKT-specific magnetic beads with the CliniMAX® system (Miltenyi). Isolated NKTs then undergo stimulation with CD1d-expressing antigen-presenting cells pulsed with α-galactosylceramide, retroviral transduction with a CAR-expressing vector, and rapid numeric expansion in cytokine-supplemented culture. This protocol routinely produces more than 109 CAR-NKTs within 17 days with average NKT cell purity and CAR expression of 96% and 54%, respectively. To overcome the second limitation, we incorporated the primary NKT homeostatic cytokine, IL-15, into the CAR.GD2 construct and evaluated its ability to enhance NKT cell in vivo persistence and therapeutic efficacy. Following adoptive transfer into mice bearing human NB xenografts, NKTs expressing CAR.GD2 were undetectable by three weeks whereas CAR.GD2/IL-15 NKTs underwent progressive expansion at sites of NB metastasis, reaching 32% of bone marrow cells two months after a single injection. Treatment with CAR.GD2/IL-15 NKTs resulted in a median survival of 70 days versus 48 days for mice treated with CAR.GD2 NKTs (P &lt; 0.001). Importantly, the robust in vivo expansion and potent anti-tumor activity of CAR.GD2/IL-15 NKTs did not produce off-target toxicity or induce GvHD based on detailed pathological analysis of mouse tissues. These results have enabled the initiation of a first-in-human CAR-NKT clinical trial evaluating the safety of autologous NKTs expressing the GD2-specific CAR with IL-15 in children with relapsed or refractory neuroblastoma (NCT03294954).

Citation Format: Andras Heczey, Amy N. Courtney, Ho Ngai, Gengwen Tian, Simon N. Robinson, Gianpietro Dotti, Leonid S. Metelitsa. Harnessing natural and engineered properties of NKT cells for cancer immunotherapy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr IA09.

IL-21 Selectively Protects CD62L+ NKT Cells and Enhances Their Effector Functions for Adoptive Immunotherapy

T cells expressing CD19-specific chimeric Ag receptors (CARs) produce high remission rates in B cell lymphoma, but frequent disease recurrence and challenges in generating sufficient numbers of autologous CAR T cells necessitate the development of alternative therapeutic effectors. Vα24-invariant NKTs have intrinsic antitumor properties and are not alloreactive, allowing for off-the-shelf use of CAR-NKTs from healthy donors. We recently reported that CD62L⁺ NKTs persist longer and have more potent antilymphoma activity than CD62L^- cells. However, the conditions governing preservation of CD62L⁺ cells during NKT cell expansion remain largely unknown. In this study, we demonstrate that IL-21 preserves this crucial central memory-like NKT subset and enhances its antitumor effector functionality. We found that following antigenic stimulation with α-galactosylceramide, CD62L⁺ NKTs both expressed IL-21R and secreted IL-21, each at significantly higher levels than CD62L^- cells. Although IL-21 alone failed to expand stimulated NKTs, combined IL-2/IL-21 treatment produced more NKTs and increased the frequency of CD62L⁺ cells versus IL-2 alone. Gene expression analysis comparing CD62L⁺ and CD62L^- cells treated with IL-2 alone or IL-2/IL-21 revealed that the latter condition downregulated the proapoptotic protein BIM selectively in CD62L⁺ NKTs, protecting them from activation-induced cell death. Moreover, IL-2/IL-21-expanded NKTs upregulated granzyme B expression and produced more T_H1 cytokines, leading to enhanced in vitro cytotoxicity of nontransduced and anti-CD19-CAR-transduced NKTs against CD1d⁺ and CD19⁺ lymphoma cells, respectively. Further, IL-2/IL-21-expanded CAR-NKTs dramatically increased the survival of lymphoma-bearing NSG mice compared with IL-2-expanded CAR-NKTs. These findings have immediate translational implications for the development of NKT cell-based immunotherapies targeting lymphoma and other malignancies.

IL-21 selectively protects CD62L+ NKTs from activation-induced cell death during ex vivo expansion and enhances antitumor activity of NKT cell therapy in vivo

Vα24-invariant natural killer T cells (NKTs) have potent antitumor properties that can be exploited for use in cancer immunotherapy. This requires rigorous protocols for ex vivo expansion of primary NKTs that preserve their longevity and function. We recently reported that CD62L+ NKTs persist longer and have better antitumor activity in vivo than CD62L− counterparts. However, the conditions governing preservation of CD62L expression in NKTs during expansion remain largely unknown. Comparative gene expression analysis of CD62L+ and CD62L− NKTs revealed significantly higher IL-21R expression in the former subset, which was confirmed at the protein level by flow cytometry. Hence, we hypothesized that IL-21 preferentially supports CD62L+ NKTs. We expanded primary human peripheral blood NKTs by stimulating in vitro with cognate antigen, α-galactosylceramide, and supplemented the culture with IL-2, IL-21, or both cytokines. In contrast to IL-2, IL-21 alone failed to support NKT cell expansion, but combined treatment with IL-2 and IL-21 produced more NKTs and preserved a significantly higher frequency of CD62L+ cells. We further demonstrated that IL-21 selectively downregulates BIM in CD62L+ NKTs and protects the subset from activation-induced cell death. Functionally, IL-2/IL-21-expanded NKTs secreted more TH1 cytokines and were more cytotoxic against lymphoma cells, which was associated with granzyme B upregulation by IL-21. Following adoptive transfer to NSG mice, IL-2/IL-21-expanded NKTs persisted significantly longer and had higher therapeutic efficacy in a lymphoma model compared with IL-2-expanded NKTs. Our results instruct inclusion of IL-21 in NKT-cell expansion protocols for cancer immunotherapy applications.

NKT cells control tumor associated macrophages and metastatic growth in neuroblastoma

Va24-invariant NKT cells (NKTs) control tumor growth via poorly understood interactions with CD1d-positive tumor-associated macrophages (TAMs). TAMs comprise M1- and M2-like subsets, but only CD163high M2-like TAMs are associated with poor outcome in neuroblastoma (NB) patients. Here, we demonstrate that NKTs selectively target M2-like TAMs via contact-dependent and independent mechanisms. Upon direct contact with antigen-pulsed M1 or M2, NKTs selectively kill the latter. Additionally, we found that antigen-activated NKTs could reprogram M2 into functional M1-like macrophages via GM-CSF production. Furthermore, adoptive transfer of human NKTs resulted in M1-like polarization of TAMs in metastatic NB xenografts in humanized NSG mice. To further explore the role of NKT–TAM axis in tumor immune surveillance, we examined the effect of NKT deficiency on tumor progression and TAM accumulation in NB-Tag transgenic model of NB. Mice lacking either type I (Jα18−/−NB-Tag) or all (CD1d−/−NB-Tag) NKTs had shortened survival compared with NB-Tag mice (P &lt; 0.0002). At four month of age we observed an increase of CD11b+Ly6G-Ly6C-F4/80+ TAMs in primary tumors of NKT deficient groups compared with NB-Tag mice. Despite no difference in the size of primary adrenal tumors between groups, the increase of TAM frequency coincided with metastatic spread in NKT deficient groups as detected by CT imaging and confirmed by pathological analysis. By five months, nearly all mice in NKT deficient groups had distant metastases in liver and lungs but none of the NKT replete mice had detectable distant metastases. Thus, our results reveal a novel mechanism of immune regulation, in which NKTs selectively control M2-like TAMs and suppress tumor metastasis.

IL-21 maintains CD62L expression during NKT-cell ex vivo expansion and enhances antitumor activity of NKT cell therapy in vivo

Vα24-invariant Natural Killer T cells (NKTs) have potent antitumor properties and are being developed for cellular immunotherapy of cancer. Such therapy requires extensive ex vivo expansion of NKTs while preserving their longevity and function. In a recent report from our group, CD62L+ subset of NKTs has been shown to have longer persistence in vivo and stronger antitumor activity than CD62L− counterpart. However, the requirements for the preservation of CD62L+ NKTs during ex vivo expansion remain largely unknown. The gene expression analysis comparing CD62L+ and CD62L− NKTs revealed a significantly higher expression level of IL-21R mRNA in the former. FACS analysis confirmed the finding at the cell surface protein level. These led us to hypothesize that IL-21 preferentially supports CD62L+ NKTs. To test this hypothesis, we expanded primary human peripheral blood NKTs using in vitro stimulation with their cognate antigen, α-galactosylceramide. The culture was supplemented with IL-2, IL-21, or both cytokines. We found that in contrast to IL-2, IL-21 alone failed to support NKT-cell expansion. A combination of IL-2 and IL-21 led to similar absolute numbers of NKTs compared with IL-2 alone. However, the proportion of CD62L+ NKT-cell subset was significantly higher in the culture with IL-2/IL-21 combination compared with IL-2 alone after both primary and secondary expansions. Furthermore, after transfer to NSG mice, IL2/IL-21-expanded NKTs persisted significantly longer and had higher therapeutic efficacy in a lymphoma model compared with IL-2-expanded NKTs. Our results suggest that inclusion of IL-21 in the NKT-cell expansion protocol, which currently uses IL-2 alone, would increase antitumor potential of NKT cell therapy.

CD62L+ NKT cells have prolonged persistence and antitumor activity in vivo

Vα24-invariant natural killer T cells (NKTs) localize to tumors and have inherent antitumor properties, making them attractive chimeric antigen receptor (CAR) carriers for redirected cancer immunotherapy. However, clinical application of CAR-NKTs has been impeded, as mechanisms responsible for NKT expansion and the in vivo persistence of these cells are unknown. Here, we demonstrated that antigen-induced expansion of primary NKTs in vitro associates with the accumulation of a CD62L+ subset and exhaustion of CD62L- cells. Only CD62L+ NKTs survived and proliferated in response to secondary stimulation. When transferred to immune-deficient NSG mice, CD62L+ NKTs persisted 5 times longer than CD62L- NKTs. Moreover, CD62L+ cells transduced with a CD19-specific CAR achieved sustained tumor regression in a B cell lymphoma model. Proliferating CD62L+ cells downregulated or maintained CD62L expression when activated via T cell receptor alone or in combination with costimulatory receptors. We generated HLAnull K562 cell clones that were engineered to express CD1d and costimulatory ligands. Clone B-8-2 (HLAnullCD1dmedCD86high4-1BBLmedOX40Lhigh) induced the highest rates of NKT expansion and CD62L expression. B-8-2-expanded CAR-NKTs exhibited prolonged in vivo persistence and superior therapeutic activities in models of lymphoma and neuroblastoma. Therefore, we have identified CD62L as a marker of a distinct NKT subset endowed with high proliferative potential and have developed artificial antigen-presenting cells that generate CD62L-enriched NKTs for effective cancer immunotherapy.

CD62L+ NKT cells have superior in vivo persistence and anti-tumor activity

Va24-invariant Natural Killer T cells (NKTs) have potent antitumor properties and are being developed for cellular immunotherapy of cancer. Such therapy requires extensive ex vivo expansion of primary NKTs while preserving their longevity and function. However, the mechanism responsible for NKT-cell maintenance remains poorly understood. In this study we analyzed the proliferative potential of human NKT-cell subsets and found that antigen-induced in vitro expansion of primary NKTs is associated with the accumulation of a CD62L-positive subset. Following magnetic sorting, only CD62L-positive cells survived and proliferated in response to TCR-stimulation in vitro. After transfer to NSG mice, CD62L-positive NKTs persisted 5 times longer and had higher therapeutic efficacy in a lymphoma model compared with CD62L-negative NKTs. Proliferating CD62L-positive cells downregulated or maintained CD62L expression when they were activated via TCR alone or in combination with co-stimulatory receptors, respectively. After testing 161 clones of K562 cells, genetically modified to express CD1d and various combinations of co-stimulatory molecules, we selected the B-8-2 clone (HLAnullCD1dmedCD86high4-1BBmedOX40Lmed) which induced the highest rate of NKT-cell expansion with the preservation of CD62L-positive cells. Compared with NKTs expanded with autologous PBMC, those expanded with B-8-2 exhibited a prolonged in vivo persistence and superior antitumor activity. Thus, our results reveal a previously unanticipated functional hierarchy in human NKTs that can be exploited for cancer immunotherapy.

Cross-talk between NKT cells and tumor associated macrophages in the tumor microenvironment

CD1d-reactive Va24-invariant NKT cells (NKTs) control tumor growth via yet poorly understood interactions with tumor-associated macrophages (TAMs) and other myeloid cells. TAMs comprise M1- and M2-like subsets, but only CD163high M2-like TAMs are associated with poor outcome in neuroblastoma (NB) and other tumors. Here, we demonstrate that NKTs selectively target M2-like TAMs via contact-dependent and independent mechanisms. Upon direct contact with antigen-pulsed M1 or M2 macrophages, NKTs selectively killed the latter. Although the killing was strictly CD1d-dependent, CD1d expression between macrophage subsets was equivalent. In contrast, only M2-polarized macrophages expressed CD204, a scavenger receptor responsible for cellular uptake of CD1d ligands. Anti-CD204 blocking mAb inhibited NKT-cell cytotoxicity against M2 in vitro while lentiviral transduction with CD204 cDNA rendered M1 sensitive to NKT cytotoxicity. We also found that antigen-activated NKTs could reprogram M2- into functional M1-like macrophages via GM-CSF production. Furthermore, adoptive transfer of human NKTs resulted in a M1-like polarization of TAMs in metastatic NB xenografts in humanized NSG mice. However, tumors progressed even after NKT cell treatment, suggesting a tumor escape mechanism. Indeed, we found that exposure to activated NKTs resulted in rapid up-regulation of PD-L1 on both M2 and M1 subsets, which correlated with suppressed NKT proliferation and cytokine production. Thus, our results reveal a novel mechanism of immune regulation, in which NKTs control tumor-supportive inflammation via killing or reprogramming of M2-like TAMs. However NKT function is negatively regulated by TAMs at least in part in a PD-1-dependent manner.

Effective cancer vaccine platform based on attenuated salmonella and a type III secretion system

Vaccines explored for cancer therapy have been based generally on injectable vector systems used to control foreign infectious pathogens, to which the immune system evolved to respond naturally. However, these vectors may not be effective at presenting tumor-associated antigens (TAA) to the immune system in a manner that is sufficient to engender antitumor responses. We addressed this issue with a novel orally administered Salmonella-based vector that exploits a type III secretion system to deliver selected TAA in the cytosol of professional antigen-presenting cells in situ. A systematic comparison of candidate genes from the Salmonella Pathogenicity Island 2 (SPI2) locus was conducted in the vaccine design, using model antigens and a codon-optimized form of the human TAA survivin (coSVN), an oncoprotein that is overexpressed in most human cancers. In a screen of 20 SPI2 promoter:effector combinations, a PsifB::sseJ combination exhibited maximal potency for antigen translocation into the APC cytosol, presentation to CD8 T cells, and murine immunogenicity. In the CT26 mouse model of colon carcinoma, therapeutic vaccination with a lead PsifB::sseJ-coSVN construct (p8032) produced CXCR3-dependent infiltration of tumors by CD8 T cells, reversed the CD8:Treg ratio at the tumor site, and triggered potent antitumor activity. Vaccine immunogenicity and antitumor potency were enhanced by coadministration of the natural killer T-cell ligand 7DW8-5, which heightened the production of IL12 and IFNγ. Furthermore, combined treatment with p8032 and 7DW8-5 resulted in complete tumor regression in A20 lymphoma-bearing mice, where protective memory was demonstrated. Taken together, our results demonstrate how antigen delivery using an oral Salmonella vector can provide an effective platform for the development of cancer vaccines.

G-CSF receptor positive neuroblastoma subpopulations are enriched in chemotherapy-resistant or relapsed tumors and are highly tumorigenic

Neuroblastoma is a neural crest-derived embryonal malignancy, which accounts for 13% of all pediatric cancer mortality, primarily due to tumor recurrence. Therapy-resistant cancer stem cells are implicated in tumor relapse, but definitive phenotypic evidence of the existence of these cells has been lacking. In this study, we define a highly tumorigenic subpopulation in neuroblastoma with stem cell characteristics, based on the expression of CSF3R, which encodes the receptor for granulocyte colony-stimulating factor (G-CSF). G-CSF receptor positive (aka G-CSFr(+) or CD114(+)) cells isolated from a primary tumor and the NGP cell line by flow cytometry were highly tumorigenic and capable of both self-renewal and differentiation to progeny cells. CD114(+) cells closely resembled embryonic and induced pluripotent stem cells with respect to their profiles of cell cycle, miRNA, and gene expression. In addition, they reflect a primitive undifferentiated neuroectodermal/neural crest phenotype revealing a developmental hierarchy within neuroblastoma tumors. We detected this dedifferentiated neural crest subpopulation in all established neuroblastoma cell lines, xenograft tumors, and primary tumor specimens analyzed. Ligand activation of CD114 by the addition of exogenous G-CSF to CD114(+) cells confirmed intact STAT3 upregulation, characteristic of G-CSF receptor signaling. Together, our data describe a novel distinct subpopulation within neuroblastoma with enhanced tumorigenicity and a stem cell-like phenotype, further elucidating the complex heterogeneity of solid tumors such as neuroblastoma. We propose that this subpopulation may represent an additional target for novel therapeutic approaches to this aggressive pediatric malignancy.

IL-15 protects NKT cells from inhibition by tumor-associated macrophages and enhances antimetastatic activity

Vα24-invariant NKT cells inhibit tumor growth by targeting tumor-associated macrophages (TAMs). Tumor progression therefore requires that TAMs evade NKT cell activity through yet-unknown mechanisms. Here we report that a subset of cells in neuroblastoma (NB) cell lines and primary tumors expresses membrane-bound TNF-α (mbTNF-α). These proinflammatory tumor cells induced production of the chemokine CCL20 from TAMs via activation of the NF-κB signaling pathway, an effect that was amplified in hypoxia. Flow cytometry analyses of human primary NB tumors revealed selective accumulation of CCL20 in TAMs. Neutralization of the chemokine inhibited in vitro migration of NKT cells toward tumor-conditioned hypoxic monocytes and localization of NKT cells to NB grafts in mice. We also found that hypoxia impaired NKT cell viability and function. Thus, CCL20-producing TAMs served as a hypoxic trap for tumor-infiltrating NKT cells. IL-15 protected antigen-activated NKT cells from hypoxia, and transgenic expression of IL-15 in adoptively transferred NKT cells dramatically enhanced their antimetastatic activity in mice. Thus, tumor-induced chemokine production in hypoxic TAMs and consequent chemoattraction and inhibition of NKT cells represents a mechanism of immune escape that can be reversed by adoptive immunotherapy with IL-15-transduced NKT cells.

Intranasal but not intravenous delivery of the adjuvant α-galactosylceramide permits repeated stimulation of natural killer T cells in the lung

Efficient induction of antigen-specific immunity is achieved by delivering multiple doses of vaccine formulated with appropriate adjuvants that can harness the benefits of innate immune mediators. The synthetic glycolipid α-galactosylceramide (α-GalCer) is a potent activator of NKT cells, a major innate immune mediator cell type effective in inducing maturation of DCs for efficient presentation of co-administered antigens. However, systemic administration of α-GalCer results in NKT cell anergy in which the cells are unresponsive to subsequent doses of α-GalCer. We show here that α-GalCer delivered as an adjuvant by the intranasal route, as opposed to the intravenous route, enables repeated activation of NKT cells and DCs, resulting in efficient induction of cellular immune responses to co-administered antigens. We show evidence that after intranasal delivery,α-GalCer is selectively presented by DCs for the activation of NKT cells, not B cells. Furthermore, higher levels of PD-1 expression, a potential marker for functional exhaustion of the NKT cells when α-GalCer is delivered by the intravenous route, are not observed after intranasal delivery. These results support a mucosal route of delivery for the utility of α-GalCer as an adjuvant for vaccines, which often requires repeated dosing to achieve durable protective immunity.

Multicolor flow cytometry analyses of cellular immune response in rhesus macaques

The rhesus macaque model is currently the best available model for HIV-AIDS with respect to understanding the pathogenesis as well as for the development of vaccines and therapeutics(1,2,3). Here, we describe a method for the detailed phenotypic and functional analyses of cellular immune responses, specifically intracellular cytokine production by CD4+ and CD8+ T cells as well as the individual memory subsets. We obtained precise quantitative and qualitative measures for the production of interferon gamma (INF-) and interleukin (IL) -2 in both CD4+ and CD8+ T cells from the rhesus macaque PBMC stimulated with PMA plus ionomycin (PMA+I). The cytokine profiles were different in the different subsets of memory cells. Furthermore, this protocol provided us the sensitivity to demonstrate even minor fractions of antigen specific CD4+ and CD8+ T cell subsets within the PBMC samples from rhesus macaques immunized with an HIV envelope peptide cocktail vaccine developed in our laboratory. The multicolor flow cytometry technique is a powerful tool to precisely identify different populations of T cells (4,5) with cytokine-producing capability(6) following non-specific or antigen-specific stimulation (5,7).

Alpha-galactosylceramide is an effective mucosal adjuvant for repeated intranasal or oral delivery of HIV peptide antigens

Mucosal delivery of vaccines against sexually transmitted pathogens is important to elicit strong immune responses at biologically relevant sites. However, inclusion of appropriate adjuvants is essential to overcome the inherent mucosal tolerance. We present evidence in support of the effectiveness of co-administering alpha-galactosylceramide (alpha-GalCer) as an adjuvant with a CTL-inducing HIV envelope peptide, via either oral or intranasal route, to prime antigen-specific immune responses in multiple systemic and mucosal compartments. Contrary to the known potential of repeated parenteral dosing with alpha-GalCer to induce NKT cell anergy that could compromise adoptive immunity development, we have observed that two and three doses delivered by the intranasal or oral route were more efficient in priming broader antigen-specific immune responses. These results demonstrate the effectiveness of alpha-GalCer as adjuvant for repeated intranasal or oral administration of vaccines for protection against mucosally transmitted pathogens.

α-GalCer is an effective mucosal adjuvant for repeated nasal or oral delivery of HIV peptide antigens (39.54)

Mucosal vaccine delivery is important for strong immune responses at biologically relevant sites, however weakly immunogenic antigens delivered by the mucosal route may induce tolerance. Therefore, appropriate adjuvants should be included for effective mucosal immunization. Mice were immunized by the oral or nasal route with alpha-Galactosylceramide (α-GalCer) as an adjuvant for co-administering with a CTL-inducing HIV envelope peptide (R15K). We observed antigen-specific cellular immune responses in multiple systemic and mucosal tissues. Contrary to the known potential of repeated parenteral dosing with α-GalCer to induce NKT cell anergy that could compromise adoptive immunity, we observed that multiple doses delivered by mucosal routes were more efficient in priming broader antigen-specific immune responses. We also obtained results showing that poly-lactic acid based nanoparticles conjugated with α-GalCer can repeatedly stimulate NKT cells both in vitro and in vivo without inducing anergy. Mechanistic studies showed that nanoparticle-formulated α-GalCer is efficiently presented by mouse CD11c+ dendritic cells and CD11b+ macrophages, but very poorly by B220+ B cells. These results demonstrate the effectiveness of α-GalCer as an adjuvant for repeated administration of vaccines for protection against mucosally transmitted pathogens.

Mucosal Epithelial Cells Provide the Critical Link for Dendritic Cell-mediated Amplification of HIV (45.19)

An estimated 30-40% of all new HIV-1 infections occur in women through the vaginal mucosa even though it carries a lower transmission probability per exposure rate (1/200 - 1/2,000) than both rectal and mother to child transmission (1/10 - 1/300). Paradoxically, the mucosal epithelial cells express low to negligible levels of the HIV receptors and the mucosal tissue microenvironment is laden with numerous antiviral factors. We obtained in vitro and in vivo evidence of HIV manipulating the mucosal microenvironment to sustain and increase infection by inducing genital mucosal epithelial cells to produce thymic stromal lymphopoietin (TSLP), a cytokine known to activate DC to induce robust CD4+ T cell homeostatic expansion. We provide molecular evidence for the involvement of NFκB signaling pathway in HIV-induced TSLP expression. In rhesus macaques we observed dramatic increases in TSLP expression concurrent with increases in DC and CD4+ T cell numbers, and viral replication in the vaginal tissues within the first two weeks after vaginal SIV exposure. Our studies demonstrate that HIV-mediated TSLP production by mucosal epithelial cells is a critical trigger for DC-mediated amplification of HIV-infection in activated CD4+ T cells. The cross talk between mucosal epithelial cells and DC, mediated by HIV induced TSLP, is a novel mechanism important for AIDS pathology that should be explored for therapeutic potential.

Intranasal immunization with synthetic peptides corresponding to the E6 and E7 oncoproteins of human papillomavirus type 16 induces systemic and mucosal cellular immune responses and tumor protection

The E6 and E7 oncoproteins of the high-risk HPV type16 represent ideal targets for HPV vaccine development, they being consistently expressed in cervical cancer lesions. Since HPV-16 is primarily transmitted through genital mucosal route, mucosal immune responses constitute an essential feature for vaccination strategies against HPV-associated lesions. We present here evidence showing that mucosal immunization of mice by the intranasal route with a mixture of peptides E7(44-62) and E6(43-57) from the E7 and E6 oncoproteins of HPV-16, respectively, using a mutant cholera toxin adjuvant (CT-2*), primed strong antigen-specific cellular immune responses in systemic and mucosal tissues. Significant levels of IFN-gamma production by both CD4 and CD8 cells were observed along with CTL responses that were effective against both peptide-pulsed targets as well as syngeneic tumor cells (TC-1) expressing the cognate E6 and E7 proteins. Furthermore, mice immunized with the peptide mixture and CT-2* effectively resisted TC-1 tumor challenge. These results together with our earlier observations that T cell responses to these peptides correlate with recurrence-free survival in women after ablative treatment for HPV-associated cervical intraepithelial neoplasia, support the potential of these E6 and E7 peptides for inclusion in vaccine formulations.