Therapeutic antibodies that block the programmed death-ligand 1 (PD-L1)/programmed death-1 (PD-1) pathway can induce robust and durable responses in patients with various cancers, including metastatic urothelial cancer (mUC)1–5. However, these responses only occur in a subset of patients. Elucidating the determinants of response and resistance is key to improving outcomes and developing new treatment strategies. Here, we examined tumours from a large cohort of mUC patients treated with an anti–PD-L1 agent (atezolizumab) and identified major determinants of clinical outcome. Response was associated with CD8+ T-effector cell phenotype and, to an even greater extent, high neoantigen or tumour mutation burden (TMB). Lack of response was associated with a signature of transforming growth factor β (TGF-β) signalling in fibroblasts, particularly in patients with CD8+ T cells that were excluded from the tumour parenchyma and instead found in the fibroblast- and collagen-rich peritumoural stroma—a common phenotype among patients with mUC. Using a mouse model that recapitulates this immune excluded phenotype, we found that therapeutic administration of a TGF-β blocking antibody together with anti–PD-L1 reduced TGF-β signalling in stromal cells, facilitated T cell penetration into the centre of the tumour, and provoked vigorous anti-tumour immunity and tumour regression. Integration of these three independent biological features provides the best basis for understanding outcome in this setting and suggests that TGF-β shapes the tumour microenvironment to restrain anti-tumour immunity by restricting T cell infiltration.
Tumors constitute highly suppressive microenvironments in which infiltrating T cells are "exhausted" by inhibitory receptors such as PD-1. Here we identify TIGIT as a coinhibitory receptor that critically limits antitumor and other CD8(+) T cell-dependent chronic immune responses. TIGIT is highly expressed on human and murine tumor-infiltrating T cells, and, in models of both cancer and chronic viral infection, antibody coblockade of TIGIT and PD-L1 synergistically and specifically enhanced CD8(+) T cell effector function, resulting in significant tumor and viral clearance, respectively. This effect was abrogated by blockade of TIGIT's complementary costimulatory receptor, CD226, whose dimerization is disrupted upon direct interaction with TIGIT in cis. These results define a key role for TIGIT in inhibiting chronic CD8(+) T cell-dependent responses.
Targeted inhibition of mitogen-activated protein kinase (MAPK) kinase (MEK) can induce regression of tumors bearing activating mutations in the Ras pathway but rarely leads to tumor eradication. Although combining MEK inhibition with T-cell-directed immunotherapy might lead to more durable efficacy, T cell responses are themselves at least partially dependent on MEK activity. We show here that MEK inhibition did profoundly block naive CD8(+) T cell priming in tumor-bearing mice, but actually increased the number of effector-phenotype antigen-specific CD8(+) T cells within the tumor. MEK inhibition protected tumor-infiltrating CD8(+) T cells from death driven by chronic TCR stimulation while sparing cytotoxic activity. Combining MEK inhibition with anti-programmed death-ligand 1 (PD-L1) resulted in synergistic and durable tumor regression even where either agent alone was only modestly effective. Thus, despite the central importance of the MAP kinase pathway in some aspects of T cell function, MEK-targeted agents can be compatible with T-cell-dependent immunotherapy.
© 2019 American Association for Cancer Research T cells T cells aPDL1 MHCI and MHCII ARGI iNOS CD40 CD86 proinflammatory cytokines Phagocytosis pathways Proinflammatory Suppressive MacrophageWithout treatment, tumor macrophages maintain a suppressive phenotype.Following anti-PD-L1 treatment, increased IFN signaling remodels the macrophage compartment towards a more proinflammatory phenotype, which can enhance T-cell responses.Remodeling of the macrophage compartment is driven by IFN following anti-PD-L1 treatment. Macrophage Cancer cells ARGI IFNγIFNγ Checkpoint inhibitors like anti-PD1/PD-L1 have demonstrated significant therapeutic efficacy in a subset of patients partly through reinvigoration of CD8 T cells. However, their impact on myeloid cells remains largely unknown. Here, we report that anti-PD-L1 treatment favorably impacts the phenotype and function of tumor macrophages by polarizing the macrophage compartment toward a more proinflammatory phenotype. This phenotype was characterized by a decrease in Arginase-I (ARG1) expression and an increase in iNOS, MHCII, and CD40 expression. Whole-transcriptome profiling further confirmed extensive polarization of both tumor monocytes and macrophages from a suppressive to a proinflammatory, immunostimulatory phenotype. This polarization was driven mainly through IFNg and was associated with enhanced T-cell activity. Transfer of monocytes into anti-PD-L1treated tumor-bearing mice led to macrophage differentiation into a more proinflammatory phenotype, with an increase in CD8 T cells expressing granzyme-B and an increase in the CD8/Treg ratio compared with control-treated mice. Although in responsive tumor models, anti-PD-L1 treatment remodeled the macrophage compartment with beneficial effects on T cells, both macrophage reprogramming and depletion were needed to maximize anti-PD-L1 responses in a tumor immune contexture with high macrophage burden. Our results demonstrate that anti-PD-L1 treatment can favorably remodel the macrophage compartment in responsive tumor models toward a more proinflammatory phenotype, mainly through increased IFNg levels. They also suggest that directly targeting these cells with reprogramming and depleting agents may further augment the breadth and depth of response to anti-PD-L1 treatment in less responsive or more macrophage-dense tumor microenvironments.
Introduction Most current animal models of hindlimb ischemia use acute arterial occlusion that does not accurately reflect the pathogenesis of gradual arterial occlusion in humans. We therefore developed the first mouse model of gradual arterial occlusion and tested the hypothesis that the mechanisms regulating blood flow recovery are critically dependent on the rate of arterial occlusion. Methods Gradual arterial occlusion was induced by placing ameroid constrictors on the proximal and distal left femoral artery, and ligating the femoral arterial branches (n=36). Acute arterial occlusion was accomplished by excising the left femoral artery (n=36). The blood flow recovery was studied by laser Doppler imaging. Differential gene expression between these two models was assessed by quantitative real time PCR. Inflammatory and progenitor cells recruitment were determined by immunohistochemistry. Results We found that hypoxia-related genes increased significantly in the calf, but not in the thigh, after gradual and acute femoral arterial occlusion (p<0.05). Shear-stress dependent genes and inflammatory genes were upregulated immediately in the thigh only after acute femoral arterial occlusion (p<0.05). These differences in gene expression were consistent with increased SDF-1α expression, recruitment of macrophages and hemangiocytes, and higher blood flow recovery after acute arterial occlusion than after gradual arterial occlusion (p<0.05). Conclusion This is the first study to show the mechanisms that regulate blood flow recovery are critically dependent on the rate of arterial occlusion. This novel model of gradual arterial occlusion may more closely resemble the human diseases, and may provide more accurate mechanistic insights for creating novel molecular therapies.
We tested the hypothesis that oxidized low-density lipoprotein (oxLDL)-induced inactivation of Akt within endothelial progenitor cells (EPCs) is mediated at the level of Phosphoinositide 3-kinase (PI3K), specifically by nitrosylation of the p85 subunit of PI3K, and that this action is critical in provoking oxLDL-induced EPC apoptosis. Hypercholesterolemic ApoE null mice had a significant reduction of the phosphorylated Akt (p-Akt)/Akt ratio in EPCs, as well as a greater percentage of apoptosis in these cells than EPCs isolated from wild-type (WT) C57Bl/6 mice. EPCs were isolated from WT spleen and exposed to oxLDL in vitro. oxLDL increased O2– and H2O2 in these cells and induced a dose- and time-dependent reduction in the p-Akt/Akt ratio and increase in EPC apoptosis. These effects were significantly reduced by the antioxidants superoxide dismutase, L-NAME, epicatechin and FeTPPs. oxLDL also induced nitrosylation of the p85 subunit of PI3K and subsequent dissociation of the p85 and p110 subunits, an effect significantly reduced by all the antioxidant agents tested. EPC transfection with a constitutively active Akt isoform (Ad-myrAkt) significantly reduced oxLDL-induced apoptosis of WT EPCs. The present findings indicate that oxLDL disrupts the PI3K/Akt signaling pathway at the level of p85 in EPCs. This dysfunction can be reversed by ex vivo antioxidant therapy.
Exhausted T cells have been described in cancer patients and murine tumor models largely based on their expression of various inhibitory receptors. Understanding of the functional attributes of these cells is limited. Here, we report that among CD8+ T cells in commonly used syngeneic tumor models, the coexpression of inhibitory receptors PD-1, LAG3, and TIM3 defined a group of highly activated and functional effector cells. Coexpression of these receptors further enriched for antigen-specific cells with increased T-cell receptor clonality. Anti–PD-L1 treatment increased the number and activation of these triple-positive CD8+ T cells without affecting the density of PD-1− cells. The intratumoral density of CD8+ T cells coexpressing inhibitory receptors negatively correlated with tumor burden. The density ratio and pretreatment phenotype of CD8+ T cells coexpressing inhibitory receptors was positively correlated with response across a variety of tumor models. Our results demonstrate that coexpression of inhibitory receptors is not a signifier of exhausted T cells, but rather can define a group of activated and functional effector cells in syngeneic tumor models. In the cancer setting, these cells could represent a heterogeneous population of not only exhausted but also highly activated cells responsive to treatment.
Objective The goals of this study were to determine if endothelial nitric oxide synthase (eNOS) affects both early and late collateral arterial adaptation and blood flow recovery after severe limb ischemia, and to determine if eNOS-derived NO was necessary for recruitment of CXCR4+ VEGFR1+ hemangiocytes to the site of ischemia. Methods and Results Two studies were carried out. In the first study, hindlimb ischemia was induced by unilateral femoral artery excision in 3 groups: C57Bl6 (wild type), eNOS-/-, and C57Bl/6 mice treated with L-NAME from 1 day prior to excision through day 3 after excision (early L-NAME group). These 3 groups were studied on the 3rd day after induction of ischemia. In the second study, hindlimb ischemia was induced in 2 groups: C57Bl/6 mice (wild type) and C57Bl/6 mice treated with L-NAME from the 3rd through the 28th day after induction of ischemia. These 2 groups were studied on the 28th day after induction of ischemia. Dependent variables included hindlimb perfusion, collateral artery diameter, and the number and location of hemangiocytes within the ischemic hindlimb. Results In the first study, the eNOS-/- and early L-NAME treatment groups developed toe gangrene by the 2nd day of ischemia. These groups demonstrated less blood flow recovery and smaller collateral artery diameter than the wild type group. Hemangiocytes were present within the adventitia of collateral arteries in the wild type group, but were only sparsely present, in a random pattern, in the eNOS-/- and early L-NAME treatment groups. In the second study, the late L-NAME group showed less blood flow recovery and smaller collateral artery diameter on the 28th day of ischemia than the wild type group. Hemangiocytes were present in a peri-capillary distribution in the wild type group, but present only sparsely in the late L-NAME treatment group. Conclusion eNOS-derived NO is necessary for both the early (day 3) and late (day 28) adaptive responses to hindlimb ischemia. NO is necessary for normal hemangiocyte recruitment to the ischemic tissue.
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