Blockade Of Inhibitory Receptors Research Articles

A novel bioinformatics pipeline for the identification of immune inhibitory receptors as potential therapeutic targets.

Despite major successes with inhibitory receptor blockade in cancer, the identification of novel inhibitory receptors as putative drug targets is needed due to lack of durable responses, therapy resistance, and side effects. Most inhibitory receptors signal via immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and previous studies estimated that our genome contains over 1600 ITIM-bearing transmembrane proteins. However, testing and development of these candidates requires increased understanding of their expression patterns and likelihood to function as inhibitory receptor. Therefore, we designed a novel bioinformatics pipeline integrating machine learning-guided structural predictions and sequence-based likelihood models to identify putative inhibitory receptors. Using transcriptomics data of immune cells, we determined the expression of these novel inhibitory receptors, and classified them into previously proposed functional categories. Known and putative inhibitory receptors were expressed across different immune cell subsets with cell type-specific expression patterns. Furthermore, putative immune inhibitory receptors were differentially expressed in subsets of tumour infiltrating T cells. In conclusion, we present an inhibitory receptor pipeline that identifies 51 known and 390 novel human inhibitory receptors. This pipeline will support future drug target selection across diseases where therapeutic targeting of immune inhibitory receptors is warranted.

A novel bioinformatics pipeline for the identification of immune inhibitory receptors as potential therapeutic targets

Despite major successes with inhibitory receptor blockade in cancer, the identification of novel inhibitory receptors as putative drug targets is needed due to lack of durable responses, therapy resistance, and side effects. Most inhibitory receptors signal via immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and previous studies estimated that our genome contains over 1600 ITIM-bearing transmembrane proteins. However, testing and development of these candidates requires increased understanding of their expression patterns and likelihood to function as inhibitory receptor. Therefore, we designed a novel bioinformatics pipeline integrating machine learning-guided structural predictions and sequence-based likelihood models to identify putative inhibitory receptors. Using transcriptomics data of immune cells, we determined the expression of these novel inhibitory receptors, and classified them into previously proposed functional categories. Known and putative inhibitory receptors were expressed across different immune cell subsets with cell type-specific expression patterns. Furthermore, putative immune inhibitory receptors were differentially expressed in subsets of tumour infiltrating T cells. In conclusion, we present an inhibitory receptor pipeline that identifies 51 known and 390 novel human inhibitory receptors. This pipeline will support future drug target selection across diseases where therapeutic targeting of immune inhibitory receptors is warranted.

Harnessing the Power of NK Cell Receptor Engineering as a New Prospect in Cancer Immunotherapy.

Natural killer (NK) cells have recently gained popularity as an alternative for cancer immunotherapy. Adoptive cell transfer employing NK cells offers a safer therapeutic option compared to T-cell-based therapies, due to their significantly lower toxicity and the availability of diverse autologous and allogeneic NK cell sources. However, several challenges are associated with NK cell therapies, including limited in vivo persistence, the immunosuppressive and hostile tumor microenvironment (TME), and the lack of effective treatments for solid tumors. To address these limitations, the modification of NK cells to stably produce cytokines has been proposed as a strategy to enhance their persistence and proliferation. Additionally, the overexpression of activating receptors and the blockade of inhibitory receptors can restore the NK cell functions hindered by the TME. To further improve tumor infiltration and the elimination of solid tumors, innovative approaches focusing on the enhancement of NK cell chemotaxis through the overexpression of chemotactic receptors have been introduced. This review highlights the latest advancements in preclinical and clinical studies investigating the engineering of activating, inhibitory, and chemotactic NK cell receptors; discusses recent progress in cytokine manipulation; and explores the potential of combining the chimeric antigen receptor (CAR) technology with NK cell receptors engineering.

Identification and characterization of PD-1 agonists for the treatment of autoimmune and inflammatory diseases

Abstract The development of autoimmune diseases is the result of a dysregulated immune response against self-antigens, resulting in cell dysregulation and tissue damage. Upon chronic exposure to antigens, inhibitory receptors (IR) are upregulated as a feedback mechanism to limit T-cell effector activity. IR deficiency is associated with autoimmunity in mice and humans. Similarly, blockade of IR is efficacious for the treatment of cancer but is often associated with new onset of immune-related adverse events. Therefore, if loss or blocking of IR pathways can result in autoimmunity, agonism of these pathways should restore normal immune homeostasis. However, the generation of agonistic antibodies present some challenges. For instance, to elicit strong receptor agonism, super-clustering mediated by the binding of the constant region (Fc) of an antibody to FcgRs, must occur. However, while FcgRs are widely expressed on antigen-presenting cells (APCs), they are not the same and are classified, based on their function, as activating or inhibitory. Of note, FcgRIIb is the only inhibitory Fc receptor, and APCs derived from mice deficient in this receptor exhibited exaggerated cytokine release. Most PD-1 agonist antibodies in clinical development contain a wild-type Fc and can trigger unwanted production of pro-inflammatory cytokines by engaging activating FcgRs. To mitigate such liability, we designed novel PD-1 agonistic antibodies that selectively bind FcgRIIb and prevent APC activation.

The Accelerator and Brake Modulatory System of Carotid Body Sensitivity

The carotid body (CB) is the primary sensor of arterial gases in the human body that through reflex pathways maintains cardiovascular homeostasis. It is known that CB chemosensitivity increases upon repeated stimulation as well as disease states; however, the molecular basis for this remains elusive. Objectives: To investigate the effect of excitatory and inhibitory amino acids in mediating CB afferent activity. Hypothesis: We hypothesised that glutamate and γ-aminobutyric acid (GABA) act to modulate CB sensitivity. Methods: Electrophysiological recordings of carotid sinus nerve (CSN) afferent discharge were made from an ex vivo arterially perfused common carotid artery bifurcation preparation. Effects of agents on CB sensitivity were assessed from responses evoked by cyanide (CN−) (1.23 μmol bolus). Results: The CSN response to CN− consisted of a rapid high amplitude discharge that was quenched abruptly, leading to a low amplitude tail. Glutamate administration augmented the CSN response to CN− by 2-fold compared to baseline ( p=0.0005). In contrast, GABA administration suppressed the CN− response by 2-fold ( p = 3.71 x 10−5). An N-methyl-D-aspartic acid (NMDA) receptor antagonist (MK801; 100 μM) increased the response amplitude resulting in one single high amplitude discharge (160% increase from baseline), abolishing the low amplitude tail. Such an effect was also observed following GABAA receptor blockade with bicuculline (500 μM), when an 80% increase was observed. The CN− response was blocked by PPADS (a P2X receptor antagonist; 100 μM) (242 ± 154 vs 4.82 ± 2.23 % change from baseline; p=0.03), suggesting it to be solely mediated by purinergic transmission. Summary of the data: We propose that CN-evoked excitation of CB chemosensory cells leads to the co-release of ATP and glutamate. ATP activates directly P2X receptors on petrosal chemosensory afferents, while glutamate acting via NMDA receptors on chemosensory cells leads to activity-induced potentiation of ATP release and co-release of GABA to quench ATP-mediated CSN discharge in a time-controlled manner. This is supported by our finding that blockade of either excitatory (NMDAR) or inhibitory (GABAA) receptors both heighten the CN− evoked CB response. A statement of the conclusions: Our results suggest an intrinsic ‘accelerator and brake’ paracrine mechanism within the CB involving glutamate and GABA controlling CB afferent sensitivity. Research was supported by the Health Research Council of New Zealand and the Sidney Taylor Trust. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Absence of Toll-like receptor 5 confers survival in mice bearing ovarian tumors treated with anti-PD-L1

Abstract Ovarian cancer accounts for more deaths than any other cancer of the female reproductive system. Patients bearing ovarian tumors infiltrated with high frequencies of T cells associate with a greater survival probability. However, therapies targeting T cells in ovarian cancers are ineffective. We observed in models of late-stage murine ovarian cancer that in absence of Toll-Like Receptor 5 (TLR5) signaling, anti-PD-L1 promotes significant survival and protection against tumor rechallenge. Ovarian tumors from rechallenged TLR5KO mice exhibited significantly higher frequency/number of CD8 T cells expressing functional and activation markers. Thus, in the absence of TLR5 signaling, T cells mount/maintain a stronger response to ovarian tumors after inhibitory receptor blockade. Furthermore, protection against tumor progression in TLR5KO mice corresponds with a significant increase in tumor infiltrating cross presenting and IL-12 producing Dendritic cells (DCs). Additionally, in CD11c Cre x TLR5 fl/fl mice, whose DCs lack TLR5 expression, PD-L1-blockade mediated extended survival in ovarian tumor-bearing mice. Using a mixed bone marrow chimera approach, we demonstrate that direct TLR5 signaling functionally alters DCs to become more suppressive in the tumor microenvironment, impacting T cell differentiation and anti-tumor activity, thereby reducing survival during aPD-L1 therapy. Clinically, roughly 7.5% of the general population harbor a TLR5 SNP that diminishes TLR5 signaling and is associated with increased long-term survival for ovarian cancer patients. Therefore, patients who express the TLR5 SNP may immediately benefit from anti-PDL1 therapy and those without the SNP, TLR5 antagonism. NIH/NCI 1R01CA253285 UVA Farrow Fellowship

Abstract PL04-05: LAG3: The third checkpoint inhibitor

Abstract Immunotherapies targeting the PD1/PDL1 pathway have had a major impact on cancer treatment. However, only a proportion of patients respond, and an even smaller proportion exhibit a long-term, durable cure. Several mechanisms of resistance and potential combinatorial approaches will be discussed. Lack of response to inhibitory receptor (IR) blockade therapy and increased disease burden has been associated with circulating, peripheral CD8+ T cell exhaustion, which is defined by poor T cell function linked to increased IR expression (eg: PD1, LAG3, neuropilin-1 [NRP1]). LAG3 is the third IR to be targeted in the clinic, consequently garnering considerable interest and scrutiny. However, persistent antigen exposure in the tumor microenvironment results in sustained PD1/LAG3 expression, contributing to a state of exhaustion manifest in impaired proliferation and cytokine production. This presentation will include a brief introduction LAG3, discussion of the signaling mechanism used by LAG3, and assessment of new insight in to the function of LAG3, alone and in combination with PD1, from mouse models of cancer and analysis of samples from patients treated with LAG3/PD1 therapeutics. Citation Format: Dario A. Vignali. LAG3: The third checkpoint inhibitor. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr PL04-05.

Combined PD-L1 and TIM3 blockade improves expansion of fit human CD8+ antigen-specific T cells for adoptive immunotherapy

Antigen-specific Tcell expansion exvivo followed by adoptive transfer enables targeting of a multitude of microbial and cancer antigens. However, clinical-scale Tcell expansion from rare precursors requires repeated stimulation, which may lead toTcell dysfunction and limited therapeutic potential. We useda clinically compliant protocol to expand Epstein-Barr virus (EBV) and Wilms tumor 1 (WT1) antigen-specific CD8+ Tcells, and leveraged Tcell exhaustion-associated inhibitory receptor blockade to improve Tcell expansion. Several inhibitory receptors were expressed early by exvivo-expanded antigen-specific CD8+ Tcells, including PD-1 and TIM3, with co-expression matching evidence of Tcell dysfunction as the cultures progressed. Introduction of anti-PD-L1 and anti-TIM3 blockade in combination (but not individually) to the culture led to markedly improved antigen-specific Tcell expansion without inducing Tcell dysfunction. Single-cell RNA sequencing (RNA-seq) and Tcell receptor (TCR) repertoire profiling revealed that double blockade does not impart specific transcriptional programs in Tcells or alterations in TCR repertoires. However, combined blockade may affect gene expression in a minority of clonotypes in a donor-specific fashion. We conclude that antigen-specific CD8+ Tcell manufacturing can be improved by using TIM3 and PD-L1/PD-1 axis blockade in combination. This approach is readily applicable to several adoptive immunotherapy strategies.

Abstract 5571: Disruption of cell-intrinsic checkpoint regulator CTLA-4 in CD19 directed CAR T cells provides clinical efficacy in CLL patients

Abstract The field of cancer immunotherapy has led to successful treatments such as monoclonal antibodies (MAb), inhibitory receptor (IR) blockade, and adoptive cell transfer (ACT). ACT modified to express chimeric antigen receptors (CARs) can redirect T cells to tumor antigens and has shown remarkable clinical efficacy in patients with relapse and refractory leukemia and lymphoma. 90% of pediatric patients with acute lymphoblastic leukemia (ALL) respond to CD19 CAR T cell therapy (CAR T19), although only 26-35% of patients with chronic lymphocytic leukemia (CLL) show complete responses (CR). It is unclear why responses are less frequent in CLL compared to ALL. The heavy pre-treatment received by CLL patients likely contributes to lower response rates with CAR T cell therapy, and disease progression is worsened due to profound T cell defects characterized by elevated expression of IRs such as PD-1 and CTLA-4. Fraietta et. al. assessed CLL patient apheresis samples and CART19 products to show that CR was associated with elevated levels of CD27+PD1-CD8+ T memory cells whereas the non-responders (NR) showed an exhausted phenotype with high levels of multiple IRs. We studied 14 patients with advanced, heavily pretreated CLL who received at least one dose of CART19. Patients with CRs exhibited high in vivo expansion and persistence of infused CAR T cells, as opposed to NR’s. Importantly, at peak levels of in vivo CAR expansion, NR’s had elevated levels of CTLA-4 expression which correlated with poor CLL patient responses to CART19 therapy. In summary, these data suggest that eliminating CTLA-4 mediated T cell inhibition can be clinically beneficial. Thus, we tested the hypothesis that disruption of CTLA4 would improve CAR T cell efficacy in CLL based on numerous observations. Our data demonstrate that knockout (KO) of CTLA-4 in T cells from healthy donors using CRISPR Cas9 technology leads to maintenance of surface CAR expression and higher tumor clearance in a chronic re-stimulation model using CART19 cells against NALM6 tumor cells. In xenograft models of ALL, KO of CTLA-4 increases the anti-tumor efficacy of CART19 cells. We then performed CTLA4 disruption in T cells banked from CLL patients that did not respond to CAR T cell therapy to determine whether dysfunctional CAR T infusion products can be invigorated by CTLA-4 KO. In both chronic re-stimulation model and xenograft models of NALM6, CTLA-4 KO CD19 CAR T cells from CLL patients maintained surface CAR expression, exhibited enhanced tumor clearance, and higher survival rates relative to subject-matched unedited CAR T cells. Thus, suggesting that CTLA4 disrupted CAR T cell products may enhance the success rate of CAR T cell therapy for CLL patients. This technology can be feasibly expanded to other tumor indications to increase the overall efficacy of CAR T cells. These IND-enabling studies will support the translation of this therapy to the clinic. Citation Format: Sangya Agarwal, Angela Aznar Gomez, Tong Da, Shunichiro Kuramitsu, Weimin Kong, Pranali Ravikumar, Mercy Gohil, Megan M. Davis, Joseph A. Fraietta, Gabriela Plesa, David L. Porter, Regina M. Young, Carl H. June. Disruption of cell-intrinsic checkpoint regulator CTLA-4 in CD19 directed CAR T cells provides clinical efficacy in CLL patients [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 5571.

Autoreactive CD8+ T cells are restrained by an exhaustion-like program that is maintained by LAG3.

Impaired chronic viral and tumor clearance has been attributed to CD8+ T cell exhaustion, a differentiation state in which T cells have reduced and altered effector function that can be partially reversed upon blockade of inhibitory receptors. The role of the exhaustion program and transcriptional networks that control CD8+ T cell function and fate in autoimmunity is not clear. Here we show that intra-islet CD8+ T cells phenotypically, transcriptionally, epigenetically and metabolically possess features of canonically exhausted T cells, yet maintain important differences. This 'restrained' phenotype can be perturbed and disease accelerated by CD8+ T cell-restricted deletion of the inhibitory receptor lymphocyte activating gene 3 (LAG3). Mechanistically, LAG3-deficient CD8+ T cells have enhanced effector-like functions, trafficking to the islets, and have a diminished exhausted phenotype, highlighting a physiological role for an exhaustion program in limiting autoimmunity and implicating LAG3 as a target for autoimmune therapy.

Systemic Immune Dysfunction in Cancer Patients Driven by IL6 Induction of LAG3 in Peripheral CD8+ T Cells.

Many cancer patients do not develop a durable response to the current standard-of-care immunotherapies, despite substantial advances in targeting immune inhibitory receptors. A potential compounding issue, which may serve as an unappreciated, dominant resistance mechanism, is an inherent systemic immune dysfunction that is often associated with advanced cancer. Minimal response to inhibitory receptor (IR) blockade therapy and increased disease burden have been associated with peripheral CD8+ T-cell dysfunction, characterized by suboptimal T-cell proliferation and chronic expression of IRs (e.g., PD1 and LAG3). Here, we demonstrated that approximately a third of cancer patients analyzed in this study have peripheral CD8+ T cells that expressed robust intracellular LAG3 (LAG3IC), but not surface LAG3 (LAG3SUR) due to a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10) cleavage. This is associated with poor disease prognosis and decreased CD8+ T-cell function, which could be partially reversed by anti-LAG3. Systemic immune dysfunction was restricted to CD8+ T cells, including, in some cases, a high percentage of peripheral naïve CD8+ T cells, and was driven by the cytokine IL6 via STAT3. These data suggest that additional studies are warranted to determine if the combination of increased LAG3IC in peripheral CD8+ T cells and elevated systemic IL6 can serve as predictive biomarkers and identify which cancer patients may benefit from LAG3 blockade.

Absence of Toll-like receptor 5 confers survival in mice bearing ovarian tumors treated with anti-PD-L1

Abstract Ovarian cancer accounts for more deaths than any other cancer of the female reproductive system. Patients bearing ovarian tumors infiltrated with high frequencies of T cells associate with a greater survival probability. However, therapeutic strategies targeting T cells in ovarian cancers are largely ineffective. We have observed in our models of late-stage murine ovarian cancer that in the absence of Toll-Like Receptor 5 (TLR5) signaling, anti-PD-L1 therapy promotes significant survival and subsequent protection against tumor rechallenge. Ovarian tumors from rechallenged TLR5KO mice exhibited significantly higher frequency/number of both CD4 and CD8 effector memory T cell subsets and greater numbers of antigen experienced T cells. Thus, in the absence of TLR5 signaling, T cells are better able to mount/maintain a response to ovarian tumors after inhibitory receptor blockade. Furthermore, protection against tumor progression in TLR5KO mice corresponds with a significant increase in tumor infiltrating cross presenting and IL-12 producing Dendritic cells (DCs) which could account for the differences in T cell infiltrates. We hypothesize that TLR5 signaling functionally alters DCs to become more suppressive in the tumor microenvironment, impacting T cell differentiation and anti-tumor activity, thereby reducing survival during ovarian tumor progression with aPD-L1 therapy. Clinical implications are already present, as roughly 7.5% of the general population harbor a TLR5 SNP that diminishes TLR5 signaling and is associated with increased long-term survival for ovarian cancer patients. Therefore, patients who express the TLR5 SNP may immediately benefit from anti-PDL1 therapy and those without the SNP, TLR5 antagonism. Supported by NIH/NCI 1R01CA253285 UVA CIC Collaborative Grant

Blockade of inhibitory killer cell immunoglobulin-like receptors and IL-2 triggering reverses the functional hypoactivity of tumor-derived NK-cells in glioblastomas

Killer cell immunoglobulin-like receptors (KIRs) comprise a group of highly polymorphic inhibitory receptors which are specific for classical HLA class-I molecules. Peripheral blood and freshly prepared tumor cell suspensions (n = 60) as well as control samples (n = 32) were investigated for the distribution, phenotype, and functional relevance of CD158ab/KIR2DL1,-2/3 expressing NK-cells in glioblastoma (GBM) patients. We found that GBM were scarcely infiltrated by NK-cells that preferentially expressed CD158ab/KIR2DL1,-2/3 as inhibitory receptors, displayed reduced levels of the activating receptors CD335/NKp46, CD226/DNAM-1, CD159c/NKG2C, and showed diminished capacity to produce IFN-γ and perforin. Functional hypoactivity of GBM-derived NK-cells persisted despite IL-2 preactivation. Blockade with a specific KIR2DL-1,2/3 monoclonal antibody reversed NK-cell inhibition and significantly enhanced degranulation and IFN-γ production of IL-2 preactivated NK-cells in the presence of primary GBM cells and HLA-C expressing but not HLA class-I deficient K562 cells. Additional analysis revealed that significant amounts of IL-2 could be produced by tumor-derived CD4+ and CD8+CD45RA- memory T-cells after combined anti-CD3/anti-CD28 stimulation. Our data indicate that both blockade of inhibitory KIR and IL-2 triggering of tumor-derived NK-cells are necessary to enhance NK-cell responsiveness in GBM.

Intra-islet CD8+ T cells are restrained by an exhaustion program that can be reversed by LAG3 deletion

Abstract CD8+ T cell exhaustion or dysfunction is a differentiation state in which T cells become unresponsive to stimulation and lose effector function1. Impaired chronic viral and tumor clearance has been attributed to CD8+ T cell exhaustion and can be partially reversed upon blockade of inhibitory receptors (IR) such as programmed cell death protein 1 (PD1). Despite detailed analysis of CD8+T cell in tumors and chronic viral infection, the role of the exhaustion program and the transcriptional networks that control CD8+T cell function and fate in autoimmunity are still unknown. Here we show that intra-islet CD8+T cells phenotypically and transcriptionally possess features of exhausted T cells, yet maintain key differences, such as an expanded repertoire of effector mechanisms, that contribute to their persistent pathogenicity in autoimmune diabetes. This dual identity, which we refer to as a ‘divergent’ exhaustion program, can be perturbed substantively by CD8+ T cell-restricted deletion of the IR Lymphocyte Activating Gene 3 (LAG3), causing enhanced effector-like function and pathogenicity. Understanding this divergent exhaustion program and its key mediators will guide future immunotherapeutic interventions by characterizing ways to promote exhaustion in autoimmunity and reversing exhaustion programs in chronic viral infections and tumors.

Peptide Blocking CTLA-4 and B7-1 Interaction.

Discovery of the B7 family immune checkpoints such as CTLA-4 (CD152), PD-1 (CD279), as well as their ligands B7-1 (CD80), B7-2 (CD86), B7-H1 (PD-L1, CD274), and B7-DC (PD-L2, CD273), has opened new possibilities for cancer immunotherapy using monoclonal antibodies (mAb). The blockade of inhibitory receptors (CTLA-4 and PD-1) with specific mAb results in the activation of cancer patients’ T lymphocytes and tumor rejection. However, the use of mAb in clinics has several limitations including side effects and cost of treatment. The development of new low-molecular compounds that block immune checkpoints’ functional activity can help to overcome some of these limitations. In this paper, we describe a synthetic peptide (p344) containing 14 amino acids that specifically interact with CTLA-4 protein. A 3D computer model suggests that this peptide binds to the 99MYPPPY104 loop of CTLA-4 protein and potentially blocks the contact of CTLA-4 receptor with B7-1 ligand. Experimental data confirm the peptide-specific interaction with CTLA-4 and its ability to partially block CTLA-4/B7-1 binding. The identified synthetic peptide can be used for the development of novel immune checkpoint inhibitors that can block CTLA-4 functional activity for cancer immunotherapy.

The NK cell-cancer cycle: advances and new challenges in NK cell-based immunotherapies.

Natural killer (NK) cells belong to the innate immune system and contribute to protecting the host through killing of infected, foreign, stressed or transformed cells. Additionally, via cellular cross-talk, NK cells orchestrate antitumor immune responses. Hence, significant efforts have been undertaken to exploit the therapeutic properties of NK cells in cancer. Current strategies in preclinical and clinical development include adoptive transfer therapies, direct stimulation, recruitment of NK cells into the tumor microenvironment (TME), blockade of inhibitory receptors that limit NK cell functions, and therapeutic modulation of the TME to enhance antitumor NK cell function. In this Review, we introduce the NK cell-cancer cycle to highlight recent advances in NK cell biology and to discuss the progress and problems of NK cell-based cancer immunotherapies.

Abstract IA17: Cellular interactions and regulatory mechanisms in head and neck cancer

Abstract Head and neck squamous cell carcinoma (HNSCC) arises through exposure to environment carcinogens or malignant transformation by human papilloma virus (HPV). Two studies will be discussed. First, we have performed transcriptional profiling of single cells from peripheral and intratumoral immune populations in HPV- and HPV+ HNSCC and healthy donors. We found a spectrum of transcriptional relationships from very similar to highly divergent between the tumor microenvironments (TME) in HPV- and HPV+ HNSCC. Our comprehensive survey of the TME in in HPV- and HPV+ HNSCC highlights the diversity of immune states and complexity of crosstalk between immune populations, and is a benchmark for analysis of the TME in human cancer. Second, many cancer patients do not develop a durable response to current standard of care immunotherapies despite substantial advances in targeting immune inhibitory receptors. A potentially important and unappreciated compounding issue, which may serve as a dominant resistance mechanism, is the inherent systemic immune dysfunction that is often associated with advanced cancer. Although this has been described for decades, primary mechanisms and drivers remain unknown. Lack of response to inhibitory receptor blockade therapy and increased disease burden has been associated with circulating, peripheral CD8+ T-cell exhaustion, which is defined by poor T-cell function linked to increased inhibitory receptor expression (PD1 or LAG3). Our recent studies have assessed if LAG3 and PD1 impact systemic T-cell function. Citation Format: Dario A.A. Vignali. Cellular interactions and regulatory mechanisms in head and neck cancer [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr IA17.

Inhibition-Resistant CARs for NK Cell Cancer Immunotherapy

The promise of natural killer (NK) cells as effectors in cancer cellular therapy is limited by their expression of dominant inhibitory receptors for human leukocyte antigen (HLA) class I. Here, we discuss how chimeric antigen receptors (CARs) engineered to override inhibitory signaling might boost NK cell antitumor responses, independently of blockade of NK cell inhibitory receptors.

MiR-149-3p reverses CD8+ T-cell exhaustion by reducing inhibitory receptors and promoting cytokine secretion in breast cancer cells.

Blockade of inhibitory receptors (IRs) is one of the most effective immunotherapeutic approaches to treat cancer. Dysfunction of miRNAs is a major cause of aberrant expression of IRs and contributes to the immune escape of cancer cells. How miRNAs regulate immune checkpoint proteins in breast cancer remains largely unknown. In this study, downregulation of miRNAs was observed in PD-1-overexpressing CD8+ T cells using miRNA array analysis of mouse breast cancer homografts. The data reveal that miR-149-3p was predicted to bind the 3'UTRs of mRNAs encoding T-cell inhibitor receptors PD-1, TIM-3, BTLA and Foxp1. Treatment of CD8+ T cells with an miR-149-3p mimic reduced apoptosis, attenuated changes in mRNA markers of T-cell exhaustion and downregulated mRNAs encoding PD-1, TIM-3, BTLA and Foxp1. On the other hand, T-cell proliferation and secretion of effector cytokines indicative of increased T-cell activation (IL-2, TNF-α, IFN-γ) were upregulated after miR-149-3p mimic treatment. Moreover, the treatment with a miR-149-3p mimic promoted the capacity of CD8+ T cells to kill targeted 4T1 mouse breast tumour cells. Collectively, these data show that miR-149-3p can reverse CD8+ T-cell exhaustion and reveal it to be a potential antitumour immunotherapeutic agent in breast cancer.

Chronic stimulation drives human NK cell dysfunction and epigenetic reprograming.

A population of Natural Killer (NK) cells expressing the activating receptor NKG2C and the maturation marker CD57 expands in response to human cytomegalovirus (HCMV) infection. CD3-CD56dimCD57+NKG2C+ NK cells are similar to CD8+ memory T cells with rapid and robust effector function upon re-stimulation, persistence, and epigenetic remodeling of the IFNG locus. Chronic antigen stimulation drives CD8+ memory T cell proliferation while also inducing genome-wide epigenetic reprograming and dysfunction. We hypothesized that chronic stimulation could similarly induce epigenetic reprograming and dysfunction in NK cells. Here we show that chronic stimulation of adaptive NK cells through NKG2C using plate-bound agonistic antibodies in combination with IL-15 drove robust proliferation and activation of CD3-CD56dimCD57+NKG2C+ NK cells while simultaneously inducing high expression of the checkpoint inhibitory receptors LAG-3 and PD-1. Marked induction of checkpoint inhibitory receptors was also observed on the surface of adaptive NK cells co-cultured with HCMV-infected endothelial cells. Chronically stimulated adaptive NK cells were dysfunctional when challenged with tumor targets. These cells exhibited a pattern of epigenetic reprograming, with genome-wide alterations in DNA methylation. Our study has important implications for cancer immunotherapy and suggest that exhausted NK cells could be targeted with inhibitory checkpoint receptor blockade.