PD-1 suppresses the maintenance of cell couples between cytotoxic T cells and target tumor cells within the tumor

Radiation Synergizes with IL2/IL15 Stimulation to Enhance Innate Immune Activation and Antitumor Immunity

Ionizing radiation is known to possess immune modulatory properties. However, how radiotherapy (RT) may complement with different types of immunotherapies to boost antitumor responses is unclear. In mice implanted with EO771 syngeneic tumors, NL-201 a stable, highly potent CD25-independent agonist to IL2 and IL15 receptors with enhanced affinity for IL2Rβγ was given with or without RT. Flow analysis and Western blot analysis was performed to determine the mechanisms involved. STING (-/-) and CD11c+ knockout mice were implanted with EO771 tumors to confirm the essential signaling and cell types required to mediate the effects seen. Combination of RT and NL-201 to enhance systemic immunotherapy with an anti-PD-1 checkpoint inhibitor was utilized to determine tumor growth inhibition and survival, along characterization of tumor microenvironment as compared with all other treatment groups. Here, we showed that RT, synergizing with NL-201 produced enhanced antitumor immune responses in murine breast cancer models. When given together, RT and NL-201 enhanced activation of the cytosolic DNA sensor cyclic GMP-AMP synthase-stimulator of IFN genes (cGAS-STING) pathway, resulting in increased type I IFN production in dendritic cells (DC), and consequently greater tumor infiltration and more efficient priming of antigen-specific T cells. The immune stimulatory mechanisms triggered by NL-201 and RT resulted in superior tumor growth inhibition and survival benefit in both localized and metastatic cancers. Our results support further preclinical and clinical investigation of this novel synergism regimen in locally advanced and metastatic settings.

Five Inhibitory Receptors Display Distinct Vesicular Distributions in Murine T Cells

T cells can express multiple inhibitory receptors. Upon induction of T cell exhaustion in response to a persistent antigen, prominently in the anti-tumor immune response, many are expressed simultaneously. Key inhibitory receptors are CTLA-4, PD-1, LAG3, TIM3, and TIGIT, as investigated here. These receptors are important as central therapeutic targets in cancer immunotherapy. Inhibitory receptors are not constitutively expressed on the cell surface, but substantial fractions reside in intracellular vesicular structures. It remains unresolved to which extent the subcellular localization of different inhibitory receptors is distinct. Using quantitative imaging of subcellular distributions and plasma membrane insertion as complemented by proximity proteomics and biochemical analysis of the association of the inhibitory receptors with trafficking adaptors, the subcellular distributions of the five inhibitory receptors were discrete. The distribution of CTLA-4 was most distinct, with preferential association with lysosomal-derived vesicles and the sorting nexin 1/2/5/6 transport machinery. With a lack of evidence for the existence of specific vesicle subtypes to explain divergent inhibitory receptor distributions, we suggest that such distributions are driven by divergent trafficking through an overlapping joint set of vesicular structures. This extensive characterization of the subcellular localization of five inhibitory receptors in relation to each other lays the foundation for the molecular investigation of their trafficking and its therapeutic exploitation.

Five inhibitory receptors display distinct vesicular distributions in T cells

T cells can express multiple inhibitory receptors. Upon induction of T cell exhaustion in response to persistent antigen, prominently in the anti-tumor immune response, many are expressed simultaneously. Key inhibitory receptors are CTLA-4, PD-1, LAG3, TIM3 and TIGIT, as investigated here. These receptors are important as central therapeutic targets in cancer immunotherapy. Inhibitory receptors are not constitutively expressed on the cell surface, but substantial fractions reside in intracellular vesicular structures. It remains unresolved to which extent the subcellular localization of different inhibitory receptors is distinct. Using quantitative imaging of subcellular distributions and plasma membrane insertion as complemented by proximity proteomics and a biochemical analysis of the association of the inhibitory receptors with trafficking adaptors, the subcellular distributions of the five inhibitory receptors were discrete. The distribution of CTLA-4 was most distinct with preferential association with lysosomal-derived vesicles and the sorting nexin 1/2/5/6 transport machinery. With a lack of evidence for the existence of specific vesicle subtypes to explain divergent inhibitory receptor distributions, we suggest that such distributions are driven by divergent trafficking through an overlapping joint set of vesicular structures. This extensive characterization of the subcellular localization of five inhibitory receptors in relation to each other lays the foundation for the molecular investigation of their trafficking and its therapeutic exploitation.

PD-1Hi CAR-T cells provide superior protection against solid tumors

Chimeric antigen receptor (CAR)-T cell therapy has emerged as a promising treatment option for several hematologic cancers. However, efforts to achieve the same level of therapeutic success in solid tumors have largely failed mainly due to CAR-T cell exhaustion and poor persistence at the tumor site. Although immunosuppression mediated by augmented programmed cell death protein-1 (PD-1) expression has been proposed to cause CAR-T cell hypofunction and limited clinical efficacy, little is known about the underlying mechanisms and immunological consequences of PD-1 expression on CAR-T cells. With flow cytometry analyses and in vitro and in vivo anti-cancer T cell function assays, we found that both manufactured murine and human CAR-T cell products displayed phenotypic signs of T cell exhaustion and heterogeneous expression levels of PD-1. Unexpectedly, PD-1high CAR-T cells outperformed PD-1low CAR-T cells in multiple T cell functions both in vitro and in vivo. Despite the achievement of superior persistence at the tumor site in vivo, adoptive transfer of PD-1high CAR-T cells alone failed to control tumor growth. Instead, a PD-1 blockade combination therapy significantly delayed tumor progression in mice infused with PD-1high CAR-T cells. Therefore, our data demonstrate that robust T cell activation during the ex vivo CAR-T cell manufacturing process generates a PD-1high CAR-T cell subset with improved persistence and enhanced anti-cancer functions. However, these cells may be vulnerable to the immunosuppressive microenvironment and require combination with PD-1 inhibition to maximize therapeutic functions in solid tumors.

The impact of hypoxia on tumor-mediated bypassing anti-PD-(L)1 therapy

Extending the durability of response is the current focus in cancer immunotherapy with immune checkpoint inhibitors (ICIs). However, factors like non-immunogenic tumor microenvironment (TME) along with aberrant angiogenesis and dysregulated metabolic systems are negative contributors. Hypoxia is a key TME condition and a critical promoter of tumor hallmarks. It acts on immune and non-immune cells within TME in order for promoting immune evasion and therapy resistance. Extreme hypoxia is a major promoter of resistance to the programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitor therapy. Hypoxia inducible factor-1 (HIF-1) acts as a key mediator of hypoxia and a critical promoter of resistance to the anti-PD-(L)1. Targeting hypoxia or HIF-1 can thus be an effective strategy for reinvigoration of cellular immunity against cancer. Among various strategies presented so far, the key focus is over vascular normalization, which is an approach highly effective for reducing the rate of hypoxia, increasing drug delivery into the tumor area, and boosting the efficacy of anti-PD-(L)1.

Computational immune synapse analysis reveals T-cell interactions in distinct tumor microenvironments

The tumor microenvironment (TME) and the cellular interactions within it can be critical to tumor progression and treatment response. Although technologies to generate multiplex images of the TME are advancing, the many ways in which TME imaging data can be mined to elucidate cellular interactions are only beginning to be realized. Here, we present a novel approach for multipronged computational immune synapse analysis (CISA) that reveals T-cell synaptic interactions from multiplex images. CISA enables automated discovery and quantification of immune synapse interactions based on the localization of proteins on cell membranes. We first demonstrate the ability of CISA to detect T-cell:APC (antigen presenting cell) synaptic interactions in two independent human melanoma imaging mass cytometry (IMC) tissue microarray datasets. We then generate melanoma histocytometry whole slide images and verify that CISA can detect similar interactions across data modalities. Interestingly, CISA histoctyometry analysis also reveals that T-cell:macrophage synapse formation is associated with T-cell proliferation. We next show the generality of CISA by extending it to breast cancer IMC images, finding that CISA quantifications of T-cell:B-cell synapses are predictive of improved patient survival. Our work demonstrates the biological and clinical significance of spatially resolving cell-cell synaptic interactions in the TME and provides a robust method to do so across imaging modalities and cancer types.

Cancer immunotherapy based on image-guided STING activation by nucleotide nanocomplex-decorated ultrasound microbubbles

The cytosolic innate immune sensor cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway is crucial for priming adaptive antitumour immunity through antigen-presenting cells (APCs). Natural agonists, such as cyclic dinucleotides (CDNs), activate the cGAS-STING pathway, but their clinical translation is impeded by poor cytosolic entry and serum stability, low specificity and rapid tissue clearance. Here we developed an ultrasound (US)-guided cancer immunotherapy platform using nanocomplexes composed of 2'3'-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) electrostatically bound to biocompatible branched cationic biopolymers that are conjugated onto APC-targeting microbubbles (MBs). The nanocomplex-conjugated MBs engaged with APCs and efficiently delivered cGAMP into the cytosol via sonoporation, resulting in activation of cGAS-STING and downstream proinflammatory pathways that efficiently prime antigen-specific T cells. This bridging of innate and adaptive immunity inhibited tumour growth in both localized and metastatic murine cancer models. Our findings demonstrate that targeted local activation of STING in APCs under spatiotemporal US stimulation results in systemic antitumour immunity and improves the therapeutic efficacy of checkpoint blockade, thus paving the way towards novel image-guided strategies for targeted immunotherapy of cancer.

Combined angiogenesis and PD-1 inhibition for immunomodulatory TNBC: concept exploration and biomarker analysis in the FUTURE-C-Plus trial

BACKGROUND

Immune checkpoint inhibitors had a great effect in triple-negative breast cancer (TNBC); however, they benefited only a subset of patients, underscoring the need to co-target alternative pathways and select optimal patients. Herein, we investigated patient subpopulations more likely to benefit from immunotherapy and inform more effective combination regimens for TNBC patients.

METHODS

We conducted exploratory analyses in the FUSCC cohort to characterize a novel patient selection method and actionable targets for TNBC immunotherapy. We investigated this in vivo and launched a phase 2 trial to assess the clinical value of such criteria and combination regimen. Furthermore, we collected clinicopathological and next-generation sequencing data to illustrate biomarkers for patient outcomes.

RESULTS

CD8-positivity could identify an immunomodulatory subpopulation of TNBCs with higher possibilities to benefit from immunotherapy, and angiogenesis was an actionable target to facilitate checkpoint blockade. We conducted the phase II FUTURE-C-Plus trial to assess the feasibility of combining famitinib (an angiogenesis inhibitor), camrelizumab (a PD-1 monoclonal antibody) and chemotherapy in advanced immunomodulatory TNBC patients. Within 48 enrolled patients, the objective response rate was 81.3% (95% CI, 70.2-92.3), and the median progression-free survival was 13.6 months (95% CI, 8.4-18.8). No treatment-related deaths were reported. Patients with CD8- and/or PD-L1- positive tumors benefit more from this regimen. PKD1 somatic mutation indicates worse progression-free and overall survival.

CONCLUSION

This study confirms the efficacy and safety of the triplet regimen in immunomodulatory TNBC and reveals the potential of combining CD8, PD-L1 and somatic mutations to guide clinical decision-making and treatments.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT04129996 . Registered 11 October 2019.

Adenosine 2A receptor and TIM3 suppress cytolytic killing of tumor cells via cytoskeletal polarization

Tumors generate an immune-suppressive environment that prevents effective killing of tumor cells by CD8⁺ cytotoxic T cells (CTL). It remains largely unclear upon which cell type and at which stage of the anti-tumor response mediators of suppression act. We have combined an in vivo tumor model with a matching in vitro reconstruction of the tumor microenvironment based on tumor spheroids to identify suppressors of anti-tumor immunity that directly act on interaction between CTL and tumor cells and to determine mechanisms of action. An adenosine 2A receptor antagonist, as enhanced by blockade of TIM3, slowed tumor growth in vivo. Engagement of the adenosine 2A receptor and TIM3 reduced tumor cell killing in spheroids, impaired CTL cytoskeletal polarization ex vivo and in vitro and inhibited CTL infiltration into tumors and spheroids. With this role in CTL killing, blocking A_2AR and TIM3 may complement therapies that enhance T cell priming, e.g. anti-PD-1 and anti-CTLA-4.

PD-1/PD-L1-Associated Immunoarchitectural Patterns Stratify Pancreatic Cancer Patients into Prognostic/Predictive Subgroups

Immunotherapy, including PD-1/PD-L1 agonists, has shown limited efficacy in pancreatic ductal adenocarcinoma (PDAC). We examined the PD-1/PD-L1 expression and immunoarchitectural features by automated morphometric analysis using multiplex immunofluorescence and 118 microsatellite-stable, treatment-naïve, surgically resected PDACs (study cohort). Five microsatellite-instable cases were stained in parallel (MSI cohort). Molecular analysis was additionally performed. An independent PDAC cohort (n = 226) was immunostained for PD-L1 and used as a validation cohort. PD-L1 expression on tumor cells (TC) and/or immune cells (IC) was present in 32% and 30% of the study and validation cohorts, respectively, and assigned into one of four patterns: "adaptive-1" (TC: 0, IC > 1%), "adaptive-2" (TC > 1% to < 25%, IC > 1%), "constitutive" (TC ≥ 25%, IC: 0), and "combined" (TC ≥ 25%, IC > 1%). "Constitutive" tumors were characterized by reduced numbers of all ICs and poor outcome. In contrast, "adaptive-1" tumors exhibited abundant T cells, including high counts of cytotoxic CD3+CD8+ and PD-1+CD3+CD8+ cells, but low counts of PD-L1+CD3+CD8+ cells and associated with the best outcome. "Adaptive-2" tumors displayed higher proportions of PD-L1+CD3+CD8+ T cells and tumor-associated macrophages (CD68+ and CD68+CD206+) compared with "adaptive-1" tumors. In the "combined" pattern, extensive PD-L1 expression on TCs was accompanied by increased numbers of T cells and improved overall survival. ICs were closer to PD-L1- than to PD-L1+ PDAC cells. TP53 and PIK3CA alterations tended to be more frequent in PD-L1+ tumors. The 5 MSI cases were PD-L1- The distinct PD-1/PD-L1-associated immunoarchitectural patterns underpin the heterogeneity of the immunologic responses and might be used to inform patient outcomes and therapeutic decisions in pancreatic cancer.

Actin Dynamics at the T Cell Synapse as Revealed by Immune-Related Actinopathies

The actin cytoskeleton is composed of dynamic filament networks that build adaptable local architectures to sustain nearly all cellular activities in response to a myriad of stimuli. Although the function of numerous players that tune actin remodeling is known, the coordinated molecular orchestration of the actin cytoskeleton to guide cellular decisions is still ill defined. T lymphocytes provide a prototypical example of how a complex program of actin cytoskeleton remodeling sustains the spatio-temporal control of key cellular activities, namely antigen scanning and sensing, as well as polarized delivery of effector molecules, via the immunological synapse. We here review the unique knowledge on actin dynamics at the T lymphocyte synapse gained through the study of primary immunodeficiences caused by mutations in genes encoding actin regulatory proteins. Beyond the specific roles of individual actin remodelers, we further develop the view that these operate in a coordinated manner and are an integral part of multiple signaling pathways in T lymphocytes.

A LAT-Based Signaling Complex in the Immunological Synapse as Determined with Live Cell Imaging Is Less Stable in T Cells with Regulatory Capability

Peripheral immune regulation is critical for the maintenance of self-tolerance. Here we have investigated signaling processes that distinguish T cells with regulatory capability from effector T cells. The murine Tg4 T cell receptor recognizes a peptide derived from the self-antigen myelin basic protein. T cells from Tg4 T cell receptor transgenic mice can be used to generate effector T cells and three types of T cells with regulatory capability, inducible regulatory T cells, T cells tolerized by repeated in vivo antigenic peptide exposure or T cells treated with the tolerogenic drug UCB9608 (a phosphatidylinositol 4 kinase IIIβ inhibitor). We comparatively studied signaling in all of these T cells by activating them with the same antigen presenting cells presenting the same myelin basic protein peptide. Supramolecular signaling structures, as efficiently detected by large-scale live cell imaging, are critical mediators of T cell activation. The formation of a supramolecular signaling complex anchored by the adaptor protein linker for activation of T cells (LAT) was consistently terminated more rapidly in Tg4 T cells with regulatory capability. Such termination could be partially reversed by blocking the inhibitory receptors CTLA-4 and PD-1. Our work suggests that attenuation of proximal signaling may favor regulatory over effector function in T cells.