RASA2 ablation in T cells boosts antigen sensitivity and long-term function

The efficacy of adoptive T cell therapies for cancer treatment can be limited by suppressive signals from both extrinsic factors and intrinsic inhibitory checkpoints1,2. Targeted gene editing has the potential to overcome these limitations and enhance T cell therapeutic function3-10. Here we performed multiple genome-wide CRISPR knock-out screens under different immunosuppressive conditions to identify genes that can be targeted to prevent T cell dysfunction. These screens converged on RASA2, a RAS GTPase-activating protein (RasGAP) that we identify as a signalling checkpoint in human T cells, which is downregulated upon acute T cell receptor stimulation and can increase gradually with chronic antigen exposure. RASA2 ablation enhanced MAPK signalling and chimeric antigen receptor (CAR) T cell cytolytic activity in response to target antigen. Repeated tumour antigen stimulations in vitro revealed that RASA2-deficient T cells show increased activation, cytokine production and metabolic activity compared with control cells, and show a marked advantage in persistent cancer cell killing. RASA2-knockout CAR T cells had a competitive fitness advantage over control cells in the bone marrow in a mouse model of leukaemia. Ablation of RASA2 in multiple preclinical models of T cell receptor and CAR T cell therapies prolonged survival in mice xenografted with either liquid or solid tumours. Together, our findings highlight RASA2 as a promising target to enhance both persistence and effector function in T cell therapies for cancer treatment.

Abstract 578: A functional approach to identifying and engineering TCRs results in highly-potent and specific TCRs for TCR-T cell therapy

Peptide-HLA (pHLA)- targeting therapeutics, such as T cell receptor-engineered T cells (TCR-T), have had clinical success in treating solid tumors. However, challenges related to safety exist: major concerns remain surrounding the cross-reactivity of T cell receptors (TCRs) as well as the ability of therapeutics to discriminate between on-target vs off-target pHLAs while maintaining high potency. Therefore, approaches that survey the diversity of the T cell repertoire to discover optimal TCRs, as well as platforms to comprehensively identify potential off-target liabilities, are critical to de-risking and accelerating the development of this promising class of pHLA-targeting therapeutics. We have developed a strategy that (1) queries the TCR repertoire to enrich and identify multiple active, sequence-distinct endogenous TCRs; (2) uses 3T-TRACE, a high-diversity pHLA library, to screen for cross-reactivity; and (3) exploits functional selections to simultaneously optimize for TCR potency and specificity. We applied this approach to identify TCRs of optimal specificity and potency targeting a peptide derived from the cancer-testis antigen NY-ESO-1 (SLLMWITQC) displayed by HLA-A2. We profiled 6 sequence-distinct TCRs using 3T-TRACE and validated potential endogenous off-target cross-reactivities. Many of the identified off-targets exhibited little to no sequence homology to the NY-ESO-1 epitope, highlighting the importance of diverse combinatorial libraries in identifying unexpected cross-reactivities. Leveraging the off-target liabilities identified by 3T-TRACE, we designed a functional library and selection scheme that enabled the identification of TCRs with increased potency and specificity. Optimized TCRs exhibited enhanced killing activity and improved safety against an NY-ESO-1-expressing melanoma cell line compared to benchmark TCRs, indicating that this approach has potential to improve clinical safety and efficacy. Using this multi-faceted and comprehensive approach we rapidly identified highly potent and specific TCRs against NY-ESO-1. Identifying cross-reactivities using 3T-TRACE proved to be critical in selecting TCRs suitable for engineering and functional selections. This approach can be extended to any pHLA target to create safe and effective TCR-Ts for clinical development.

Citation Format: John D. Leonard, Alejandro Ramirez, Jason Romero, Jake Kleiner, Joanna Dreux, Bindu Hegde, Bryan Xie, Akshay Sharathchandra, Nathan Katz, Venita I. DeAlmeida, Hans-Peter Gerber, Marvin H. Gee, Leah V. Sibener. A functional approach to identifying and engineering TCRs results in highly-potent and specific TCRs for TCR-T cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 578.

Abstract 74: Engineering tertiary lymphoid structures for glioblastoma: A novel gene combination promotes therapeutic TLS formation in an immune-competent mouse model of GBM

The absence of conventional lymphatic access to the brain parenchyma restricts the capacity of the peripheral immune system to recognize and elicit durable responses against glioma antigens. In some peripheral solid tumor types and autoimmune diseases such as multiple sclerosis, the spontaneous development of tertiary lymphoid structures (TLS) with varying degrees of organization have been observed in human patients and mice experiencing chronic inflammation. The presence of TLS in the context of cancer is generally associated with improved prognosis, particularly when these TLS are characterized by intratumoral infiltration of CD8+ T-cells and B-cells. We sought to engineer the development of TLS in the brain tumor setting, utilizing our SB28 glioblastoma (GBM) model which is sparsely infiltrated by lymphocytes and characterized by a significant myeloid-derived suppressor cell population. To determine the most critical chemokines and cytokines required to elicit TLS formation in the murine GBM context, we stably transduced SB28 with a combination of TLS-stimulating factors that we identified and injected these cells into the brain parenchyma of syngeneic C57BL/6J mice. A combination of the chemoattractant and lymphoid follicle-stimulating cytokines interleukin (IL)-7, LIGHT (TNFSF14), CCL21, and IL-17 promoted infiltration of CD8+CD3+ T-cells into the tumor and nearby parenchyma, but it also promoted enhanced tumor proliferation. A modified gene combination including IL-7, LIGHT, and CCL21 promoted CD8+ T-cell infiltration and clustering by immunofluorescence analysis. This combination also significantly decreased tumor burden as measured by bioluminescent imaging, resulting in complete tumor rejection in a subset of mice. Finally, modifying this combination to include CXCL13 promoted the infiltration and clustering of B-cells along with the observed CD8+ T-cell infiltration. This combination elicited the formation of vascular structures that stained for PNAd (MECA-79) and LYVE-1, markers for high endothelial venules (HEV) and lymphatic endothelium, respectively. Taken together, these analyses suggest that these factors are sufficient to stimulate the formation of TLS in the GBM setting. Future studies will evaluate a replication competent viral vector based approach for gene delivery and whether TLS formation can promote tumor specific T-cell memory and persistence in GBM. Ultimately, we aim to promote therapeutic TLS in a manner that is highly translational to brain tumor patients and complementary to existing T-cell therapies.

Citation Format: Kira Morgan Downey, Bindu Hegde, Zinal Chheda, Jason Zhang, Hideho Okada. Engineering tertiary lymphoid structures for glioblastoma: A novel gene combination promotes therapeutic TLS formation in an immune-competent mouse model of GBM [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 74.

Considerations when treating high-grade pediatric glioma patients with immunotherapy

INTRODUCTION

Children with high-grade gliomas (pHGGs) represent a clinical population in substantial need of new therapeutic options given the inefficacy and toxicity of current standard-of-care modalities. Although immunotherapy has emerged as a promising modality, it has yet to elicit a significant survival benefit for pHGG patients. While preclinical studies address a variety of underlying challenges, translational clinical trial design and management also need to reflect the most updated progress and lessons from the field.

AREAS COVERED

The authors will focus our discussion on the design of clinical trials, the management of potential toxicities, immune monitoring, and novel biomarkers. Clinical trial design should integrate appropriate patient populations, novel, and preclinically optimized trial design, and logical treatment combinations, particularly those which synergize with standard of care modalities. However, there are caveats due to the nature of immunotherapy trials, such as patient selection bias, evidenced by the frequent exclusion of patients on high-dose corticosteroids. Robust immune-modulating effects of modern immunotherapy can have toxicities. As such, it is important to understand and manage these, especially in pHGG patients.

EXPERT OPINION

Adequate integration of these considerations should allow us to effectively gain insights on biological activity, safety, and biomarkers associated with benefits for patients.

IMMU-28. INDUCTION OF TERTIARY LYMPHOID STRUCTURE-LIKE T-CELL CLUSTERS BY DELIVERY OF A NOVEL GENE COMBINATION INTO AN IMMUNOCOMPETENT MOUSE MODEL OF GLIOBLASTOMA

The lack of conventional lymphatic drainage to and from the brain parenchyma restricts the capacity of the peripheral immune system to recognize and respond to glioma antigens. In some peripheral solid tumor types and central nervous system autoimmunity, the spontaneous development of tertiary lymphoid structures (TLS) with varying degrees of organization have been observed in human patients and mice following chronic inflammation. In the cancer setting, presence of TLS are generally associated with improved prognosis, especially when they are characterized by intratumoral infiltration of CD8+ T-cells. We aimed to induce the development of TLS in vivo, utilizing our SB28 glioblastoma model which is sparsely infiltrated by lymphocytes. As a proof-of-concept study, we stably transduced SB28 with a combination of several TLS-stimulating factors that we’ve identified and injected these cells into the brain parenchyma of syngeneic C57BL/6J mice. A combination of the chemoattractant and lymphoid follicle-stimulating cytokines LIGHT, CCL21, IL-7, and IL-17 produced substantial infiltration of CD8+CD3+ T-cells into the tumor and nearby parenchyma. However, this combination was also associated with accelerated tumor growth. A modified gene combination including LIGHT, CCL21, and IL-7 promoted CD8+CD3+ T-cell infiltration by flow cytometry, T-cell clustering by immunofluorescence analysis, and inhibited tumor burden compared with the control as measured by bioluminescent imaging. There was also evidence of increased lymphatic vasculature around the margins of T-cell clustering as demonstrated by LYVE-1 staining. Together, these analyses highlight a role for these factors in stimulating the recruitment and clustering of T-cell to the glioblastoma microenvironment in a TLS-like phenomenon. Future studies will evaluate whether the recruitment of other lymphocytes and stromal cells to these TLS-like clusters can promote T-cell memory and persistence. Ultimately, we aim to provide these factors utilizing a gene delivery method that will prove translatable to the clinic and complementary to existing T-cell therapies.

IMMU-38. CRISPR BASED GENOME EDITING OF HUMAN T CELLS TO TARGET H3.3K27M MUTATION IN GLIOMAS

We recently identified an HLA-A*02:01-restricted CD8 T cell epitope encompassing the H3.3K27M mutation, which is common in diffuse midline glioma, and a corresponding high-affinity T cell receptor (TCR) that recognizes the epitope. While recombinant viral vectors have been widely used for genetic reprogramming of T cells, viral vectors are far from ideal as they typically integrate randomly into the genome and are not governed by the molecular regulatory mechanisms of the cell. We used a non-viral, CRISPR-Cas9-based approach to replace the endogenous TCR with H3.3K27M TCR at the TCR a constant region (TRAC) in human T cells. Co-electroporation of healthy donor-derived T cells with homology-directed repair (HDR) templates encoding the full-length sequence of H3.3K27M TCR along with CRISPR-Cas9 ribonucleoprotein (RNP) resulted in the integration of the new TCR into the TRAC locus by HDR. Antibody staining of TCR α/β and H3.3K27M dextramer showed replacement of endogenous TCR with H.3.3K27M TCR in ~5–10% of TCR+ CD8 T cells. Modifying the HDR template to include a binding site for Cas9, which contains the nuclear localization signal that acts as a “shuttle”, further enhanced the integration efficiency (~15% of TCR+ CD8 T cells). Furthermore, HLA-A2+ H3.3K27M TCR-engineered T cells selectively killed U87 glioma cells expressing the H3.3K27M epitope. In addition, the engineered T cells exhibited a stem memory-like phenotype when expanded in the presence of a cocktail of IL-2, IL-7 and IL-15. Taken together, these data provide evidence for non-viral genome editing as a strategy to engineer T cells with specific TCR for cancer immunotherapy.

Zinc Oxide Nanowires Exposure Induces a Distinct Inflammatory Response via CCL11-Mediated Eosinophil Recruitment

High aspect ratio zinc oxide nanowires (ZnONWs) have become one of the most important products in nanotechnology. The wide range applications of ZnONWs have heightened the need for evaluating the risks and biological consequences to these particles. In this study, we investigated inflammatory pathways activated by ZnONWs in cultured cells as well as the consequences of systemic exposure in mouse models. Confocal microscopy showed rapid phagocytic uptake of FITC-ZnONWs by macrophages. Exposure of macrophages or lung epithelial cells to ZnONWs induced the production of CCL2 and CCL11. Moreover, ZnONWs exposure induced both IL-6 and TNF-α production only in macrophages but not in LKR13 cells. Intratracheal instillation of ZnONWs in C57BL/6 mice induced a significant increase in the total numbers of immune cells in the broncho alveolar lavage fluid (BALFs) 2 days after instillation. Macrophages and eosinophils were the predominant cellular infiltrates of ZnONWs exposed mouse lungs. Similar cellular infiltrates were also observed in a mouse air-pouch model. Pro-inflammatory cytokines IL-6 and TNF-α as well as chemokines CCL11, and CCL2 were increased both in BALFs and air-pouch lavage fluids. These results suggest that exposure to ZnONWs may induce distinct inflammatory responses through phagocytic uptake and formation of soluble Zn²⁺ ions.

Enhancement of gut barrier function by microbial metabolite, urolithin A via AhR-Nrf2 dependent pathways in IBD

Inflammatory bowel diseases (IBD) consisting of Crohn’s and ulcerative colitis are resultant of dysregulation of the immune system leading to intestinal inflammation and microbial dysbiosis. Numerous studies in recent years highlighted the pivotal role of gut microbiota and their metabolites in host physiological processes including in IBD. Urolithin A (UroA) is a microbial metabolite derived from polyphenolics (e.g., ellagitannins/ellagic acid) of pomegranate and berries. We also synthesized a potent structural analogue of UroA (UAS03) and tested their efficacies in preventing and treating colitis in pre-clinical models. Our studies showed that UroA/UAS03 significantly enhance gut barrier function in addition to blocking unwarranted inflammation. We demonstrate that UroA and UAS03 exert their barrier functions through activation of aryl hydrocarbon receptor (AhR)- nuclear factor erythroid 2–related factor 2 (Nrf2)-dependent pathways to upregulate epithelial tight junction proteins. In addition, treatment with these compounds attenuated colitis in pre-clinical models by remedying barrier dysfunction and blocking increased inflammatory mediators such as IL-6, TNF-α and IL-1β. UroA/UAS03 failed to induce tight junction proteins and protect against 2,4,6-Trinitrobenzenesulfonic acid (TNBS)-induced colitis in AhR−/− and Nrf2−/− mice suggesting an obligatory requirement of AhR and Nrf2 pathways for UroA/UAS03 mediated beneficial activities. Overall, the results highlight how microbial metabolites provide two-pronged beneficial activities at gut epithelium by enhancing barrier functions and reducing systemic and local inflammation to protect from colonic diseases.

Genetically Engineered T-Cells for Malignant Glioma: Overcoming the Barriers to Effective Immunotherapy

Malignant gliomas carry a dismal prognosis. Conventional treatment using chemo- and radiotherapy has limited efficacy with adverse events. Therapy with genetically engineered T-cells, such as chimeric antigen receptor (CAR) T-cells, may represent a promising approach to improve patient outcomes owing to their potential ability to attack highly infiltrative tumors in a tumor-specific manner and possible persistence of the adaptive immune response. However, the unique anatomical features of the brain and susceptibility of this organ to irreversible tissue damage have made immunotherapy especially challenging in the setting of glioma. With safety concerns in mind, multiple teams have initiated clinical trials using CAR T-cells in glioma patients. The valuable lessons learnt from those trials highlight critical areas for further improvement: tackling the issues of the antigen presentation and T-cell homing in the brain, immunosuppression in the glioma microenvironment, antigen heterogeneity and off-tumor toxicity, and the adaptation of existing clinical therapies to reflect the intricacies of immune response in the brain. This review summarizes the up-to-date clinical outcomes of CAR T-cell clinical trials in glioma patients and examines the most pressing hurdles limiting the efficacy of these therapies. Furthermore, this review uses these hurdles as a framework upon which to evaluate cutting-edge pre-clinical strategies aiming to overcome those barriers.

Inflammasome-Independent Leukotriene B4 Production Drives Crystalline Silica-Induced Sterile Inflammation

Silicosis is a lung inflammatory disease caused by chronic exposure to crystalline silica (CS). Leukotriene B₄ (LTB₄) plays an important role in neutrophilic inflammation, which drives silicosis and promotes lung cancer. In this study, we examined the mechanisms involved in CS-induced inflammatory pathways. Phagocytosis of CS particles is essential for the production of LTB₄ and IL-1β in mouse macrophages, mast cells, and neutrophils. Phagosomes enclosing CS particles trigger the assembly of lipidosome in the cytoplasm, which is likely the primary source of CS-induced LTB₄ production. Activation of the JNK pathway is essential for both CS-induced LTB₄ and IL-1β production. Studies with bafilomycin-A1- and NLRP3-deficient mice revealed that LTB₄ synthesis in the lipidosome is independent of inflammasome activation. Small interfering RNA knockdown and confocal microscopy studies showed that GTPases Rab5c, Rab40c along with JNK1 are essential for lipidosome formation and LTB₄ production. BI-78D3, a JNK inhibitor, abrogated CS-induced neutrophilic inflammation in vivo in an air pouch model. These results highlight an inflammasome-independent and JNK activation-dependent lipidosome pathway as a regulator of LTB₄ synthesis and CS-induced sterile inflammation.

Targeted delivery of microbial metabolite, urolithin A protects from chemically (DSS or TNBS) induced colitis in pre-clinical models

Epidemiological data suggests that consumption of diets rich in phytochemicals are protective in inflammatory bowel diseases (IBDs). However, the beneficial effects are not uniform among individuals and attributed to variations in gut microbiota, and altered capacity to generate certain metabolites. Urolithin A (UroA) (3,8-dihydroxybenzo[c]chromen-6-one) is a microbial metabolite, derived from ellagic acid and ellagitannins, major poly phenolic components in berries and pomegranates. Here, we examined therapeutic applications of UroA and mechanisms of action in IBDs. Our studies suggested that UroA significantly reduced LPS induced inflammatory mediators (e.g., IL-6, TNF-alpha and IL-12) as well as ROS production in mouse bone marrow-derived macrophages (BMDMs), dendritic and THP1 cells. Most importantly, UroA also reduced LPS induced systemic inflammation in mouse models. Next, we examined therapeutic applications of UroA in dextran sodium sulphate (DSS)-induced, 2,4,6-Trinitrobenzenesulfonic acid (TNBS)-induced colitis models. Treatment with UroA significantly reduced both acute and chronic DSS-induced colitis as well as TNBS induced colitis in mouse models. Most importantly, delivery of UroA utilizing inflammation targeting oral nano-particles (single treatment regimen) effectively mitigated the colitis in both models. In summary, these results highlight even presence of single microbial metabolite at right location at right time will have significant beneficial effects to protect from adverse inflammatory activities.

Inflammasome Independent Leukotriene B4 Production Drives Crystalline Silica Induced Sterile Inflammation in Lungs

Occupational exposure to Crystalline Silica (CS) is a major public health concern with millions of workers continuously exposed to CS. Deposition of fine silica particles in the lungs can lead to severe lung inflammation and cancer. Lipid chemokine Leukotriene B4 (LTB4) and IL-1b that mediate leukocyte recruitment to the site of injury, are the key mediators of CS-induced sterile inflammation. Our previous studies have shown that CS exposure increases lung tumor burden in K-rasLA1 mice and that is abrogated in the LTB4 receptor, BLT1 deficient mice. Here, we show that phagocytosis of CS sequentially activates a series of pathways leading to LTB4, IL-1b and CXC chemokine production. CS uptake induces rapid formation of lipid bodies termed “lipidosome” independent of inflammasome activation. Studies with inhibitors suggested that CS-induced lipidosome formation and LTB4 production is linked to the phagocytosis pathway, an observation confirmed by confocal microscopy. We further demonstrated the SiRNA knockdown of cPla2, JNK or Rab40c prevents the formation of lipidosome and production of LTB4. Lastly, we demonstrate using an air pouch model in mice that JNK inhibitor, BI-78D3 is effective in reducing CS induced sterile-inflammation in-vivo. In summary, our studies highlight a novel inflammasome independent and JNK activation dependent lipidosome pathway leading to the production LTB4 as a major regulator of CS-induced sterile inflammation.

A semi-synthetic natural product blocks collagen induced arthritis by preferentially suppressing the production of IL-6

Rheumatoid arthritis (RA), an autoimmune-inflammatory disease is characterized by dysregulation of signal transduction pathways, increased production of pro-inflammatory cytokines, enhanced leukocyte infiltration into synovial microvascular endothelium, extensive formation of hyper proliferative pannus, degradation of cartilage and bone erosion. Several compounds that abrogate cytokine production demonstrate a therapeutic effect in experimental models of arthritis. In this study, we report that a novel semi-synthetic natural product (Compound A) being a preferential IL-6 inhibitor, is efficacious in a murine model of arthritis. In vitro evaluations of pro-inflammatory cytokine production reveal that Compound A preferentially inhibits induced production of IL-6 and not TNF-α from THP-1 cells and isolated human monocytes. Furthermore, Compound A robustly inhibits the spontaneous production of IL-6 from pathologically relevant synovial tissue cells isolated from patients with active RA. In a physiologically relevant assay, Compound A selectively inhibits the activated T cell contact-mediated production of IL-6 from human monocytes. Compound A, at pharmacologically efficacious concentrations, does not significantly curtail the LPS-induced activation of p38 MAPKs. In the collagen-induced arthritis (CIA) mouse model (i) macroscopic observations demonstrate that Compound A, administered subcutaneously in a therapeutic regimen, significantly and dose-dependently inhibits disease associated increases in articular index and paw thickness; (ii) histological analyses of paw tissues reveal that Compound A prominently diminishes joint destruction, hyperproliferative pannus formation and infiltration of inflammatory cells. Collectively, these results provide direct evidence that Compound A, a novel preferential IL-6 inhibitor, suppresses collagen-induced arthritis, and may be a potential therapeutic for treating patients with active RA.

NF-κB dependent anti-inflammatory activity of chlorojanerin isolated from Saussurea heteromalla

Medicinal plants have shown great promise as a source of novel drug compounds for the treatment of inflammatory disorders. In our search for new entities with anti-inflammatory potential, the extracts of the whole plant of Saussurea heteromalla (family-Asteraceae), collected from Himalayas, were evaluated in the high throughput screen for TNF-α and IL-6 inhibitors. The extract blocked TNF-α and IL-6 production in LPS stimulated THP-1 cells (human acute monocyte leukemia cell line) completely at 10 and 30 μg/ml. The plant has been found as a new source of chlorojanerin, a guaianolide type of sesquiterpene lactone. Chlorojanerin was shown to be significantly effective in inhibiting TNF-α and IL-6 production in LPS-stimulated THP-1 cells (IC(50)=2.3±0.2 μM and 1.8±0.7 μM respectively). The compound also blocked TNF-α and IL-6 production from LPS-stimulated human monocytes (IC(50)=1.5±0.4 and 0.7±0.2 μM respectively) and synovial cells from a patient with rheumatoid arthritis (IC(50)<0.03 and 0.5 μM respectively). Transcriptional profiling of the LPS stimulated THP-1 cells revealed that chlorojanerin exerted its anti-inflammatory effect by inhibiting the expression of 8 genes involved in activating the transcription factor - NF-κB. Real time analysis of these genes validated the effect of chlorojanerin on the classical downstream targets of NF-κB. Thus, this study clearly delineated 8 genes which were specifically mitigated due to the effect of chlorojanerin on NF-κB induced signaling at the mRNA level. Further, chlorojanerin at 5 μM also inhibited the binding of NF-κB in a GFP reporter assay system by 55.5% thus validating the microarray gene expression data. This work is a step towards the isolation and characterization of lead anti-inflammatory agents from the extract of Saussurea heteromalla, which can be developed into better therapeutic molecules targeted towards some specific inflammatory diseases.