The clinical relevance of T cells in the control of a diverse set of human cancers is now beyond doubt. However, the nature of the antigens that allow the immune system to distinguish cancer cells ...from noncancer cells has long remained obscure. Recent technological innovations have made it possible to dissect the immune response to patient-specific neoantigens that arise as a consequence of tumor-specific mutations, and emorging data suggest that recognition of such neoantigens is a major factor in the activity of clinical immunotherapies. These observations indicate that neoantigen load may form a biomarker in cancer immunotherapy and provide an incentive for the development of novel therapeutic approaches that selectively enhance T cell reactivity against this class of antigens.
Failure of T cells to protect against cancer is thought to result from lack of antigen recognition, chronic activation, and/or suppression by other cells. Using a mouse sarcoma model, we show that ...glucose consumption by tumors metabolically restricts T cells, leading to their dampened mTOR activity, glycolytic capacity, and IFN-γ production, thereby allowing tumor progression. We show that enhancing glycolysis in an antigenic “regressor” tumor is sufficient to override the protective ability of T cells to control tumor growth. We also show that checkpoint blockade antibodies against CTLA-4, PD-1, and PD-L1, which are used clinically, restore glucose in tumor microenvironment, permitting T cell glycolysis and IFN-γ production. Furthermore, we found that blocking PD-L1 directly on tumors dampens glycolysis by inhibiting mTOR activity and decreasing expression of glycolysis enzymes, reflecting a role for PD-L1 in tumor glucose utilization. Our results establish that tumor-imposed metabolic restrictions can mediate T cell hyporesponsiveness during cancer.
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•Tumor cells and TILs compete for glucose within the tumor niche•Metabolic competition can drive cancer progression•Checkpoint blockade antibodies alter the metabolic balance in a tumor•PD-L1 promotes Akt/mTOR activation and glycolysis in tumor cells
Glucose consumption by antigenic tumors can metabolically restrict T cells, directly dampening their effector function and allowing tumor progression. Checkpoint blockade therapy may correct this resource imbalance through a direct effect in the tumor cells.
Accumulated data from animal models and human cancer patients strongly support the concept that the immune system can identify and control nascent tumor cells in a process called cancer ...immunosurveillance. In addition, the immune system can also promote tumor progression through chronic inflammation, immunoselection of poorly immunogenic variants, and suppressing antitumor immunity. Together, the dual host‐protective and tumor‐promoting actions of immunity are referred to as cancer immunoediting. The current framework of cancer immunoediting is a dynamic process comprised of three distinct phases: elimination, equilibrium, and escape. Recently, we demonstrated that immunoselection by CD8+ T cells of tumor variants lacking strong tumor‐specific antigens represents one mechanism by which cancer cells escape tumor immunity and points toward the future of personalized cancer therapy.
Understanding how the immune system affects cancer development and progression has been one of the most challenging questions in immunology. Research over the past two decades has helped explain why ...the answer to this question has evaded us for so long. We now appreciate that the immune system plays a dual role in cancer: It can not only suppress tumor growth by destroying cancer cells or inhibiting their outgrowth but also promote tumor progression either by selecting for tumor cells that are more fit to survive in an immunocompetent host or by establishing conditions within the tumor microenvironment that facilitate tumor outgrowth. Here, we discuss a unifying conceptual framework called "cancer immunoediting," which integrates the immune system's dual host-protective and tumor-promoting roles.
Originally identified in studies of cellular resistance to viral infection, interferon (IFN)-γ is now known to represent a distinct member of the IFN family and plays critical roles not only in ...orchestrating both innate and adaptive immune responses against viruses, bacteria, and tumors, but also in promoting pathologic inflammatory processes. IFN-γ production is largely restricted to T lymphocytes and natural killer (NK) cells and can ultimately lead to the generation of a polarized immune response composed of T helper (Th)1 CD4
T cells and CD8
cytolytic T cells. In contrast, the temporally distinct elaboration of IFN-γ in progressively growing tumors also promotes a state of adaptive resistance caused by the up-regulation of inhibitory molecules, such as programmed-death ligand 1 (PD-L1) on tumor cell targets, and additional host cells within the tumor microenvironment. This review focuses on the diverse positive and negative roles of IFN-γ in immune cell activation and differentiation leading to protective immune responses, as well as the paradoxical effects of IFN-γ within the tumor microenvironment that determine the ultimate fate of that tumor in a cancer-bearing individual.
The immune system can identify and destroy nascent tumor cells in a process termed cancer immunosurveillance, which functions as an important defense against cancer. Recently, data obtained from ...numerous investigations in mouse models of cancer and in humans with cancer offer compelling evidence that particular innate and adaptive immune cell types, effector molecules, and pathways can sometimes collectively function as extrinsic tumor-suppressor mechanisms. However, the immune system can also promote tumor progression. Together, the dual host-protective and tumor-promoting actions of immunity are referred to as cancer immunoediting. In this review, we discuss the current experimental and human clinical data supporting a cancer immunoediting process that provide the fundamental basis for further study of immunity to cancer and for the rational design of immunotherapies against cancer.
It is now well established that the immune system can recognize developing cancers and that therapeutic manipulation of immunity can induce tumor regression. The capacity to manifest remarkably ...durable responses in some patients has been ascribed in part to T cells that can (a) kill tumor cells directly, (b) orchestrate diverse antitumor immune responses, (c) manifest long-lasting memory, and (d) display remarkable specificity for tumor-derived proteins. This specificity stems from fundamental differences between cancer cells and their normal counterparts in that the former develop protein-altering mutations and undergo epigenetic and genetic alterations, resulting in aberrant protein expression. These events can result in formation of tumor antigens. The identification of mutated and aberrantly expressed self-tumor antigens has historically been time consuming and laborious. While mutant antigens are usually expressed in a tumor-specific manner, aberrantly expressed antigens are often shared between cancers and, therefore, in the past, have been the major focus of therapeutic cancer vaccines. However, advances in next-generation sequencing and epitope prediction now permit the rapid identification of mutant tumor neoantigens. This review focuses on a discussion of mutant tumor neoantigens and their use in personalizing cancer immunotherapies.
Highlights • Genomics analyses to identify the targets of cancer immunoediting and design personalized cancer immunotherapy. • Emerging role of innate immune cells (NK, DC, macrophages) in cancer ...immune surveillance. • Equilibrium is a prolonged and depends on adaptive immune system and cytokines such as IL-12 and IL-23. • Tumour cells modulate intrinsic and extrinsic pathways to escape host tumour immunity. • Recent advances in immunotherapy based on targeting of immune escape checkpoints and tumour metabolism.
Although current immune-checkpoint therapy (ICT) mainly targets lymphoid cells, it is associated with a broader remodeling of the tumor micro-environment. Here, using complementary forms of ...high-dimensional profiling, we define differences across all hematopoietic cells from syngeneic mouse tumors during unrestrained tumor growth or effective ICT. Unbiased assessment of gene expression of tumor-infiltrating cells by single-cell RNA sequencing (scRNAseq) and longitudinal assessment of cellular protein expression by mass cytometry (CyTOF) revealed significant remodeling of both the lymphoid and myeloid intratumoral compartments. Surprisingly, we observed multiple subpopulations of monocytes/macrophages, distinguishable by the markers CD206, CX3CR1, CD1d, and iNOS, that change over time during ICT in a manner partially dependent on IFNγ. Our data support the hypothesis that this macrophage polarization/activation results from effects on circulatory monocytes and early macrophages entering tumors, rather than on pre-polarized mature intratumoral macrophages.
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•High-dimensional analyses of successful ICT in tumor-bearing mice•ICT induces changes in intratumoral myeloid and lymphoid cells•Tumor-associated monocytes/macrophages display complex cytokine-driven phenotypes•Different cytokines act on tumor-infiltrating monocytes to drive macrophage polarization
Comprehensive changes in the tumor microenvironment during successful immune-checkpoint therapy are profiled, implicating a key role for polarization of infiltrating macrophages in the anti-tumor immune milieu.
Checkpoint immunotherapy unleashes T cell control of tumors, but is undermined by immunosuppressive myeloid cells. TREM2 is a myeloid receptor that transmits intracellular signals that sustain ...microglial responses during Alzheimer’s disease. TREM2 is also expressed by tumor-infiltrating macrophages. Here, we found that Trem2–/– mice are more resistant to growth of various cancers than wild-type mice and are more responsive to anti-PD-1 immunotherapy. Furthermore, treatment with anti-TREM2 mAb curbed tumor growth and fostered regression when combined with anti-PD-1. scRNA-seq revealed that both TREM2 deletion and anti-TREM2 are associated with scant MRC1+ and CX3CR1+ macrophages in the tumor infiltrate, paralleled by expansion of myeloid subsets expressing immunostimulatory molecules that promote improved T cell responses. TREM2 was expressed in tumor macrophages in over 200 human cancer cases and inversely correlated with prolonged survival for two types of cancer. Thus, TREM2 might be targeted to modify tumor myeloid infiltrates and augment checkpoint immunotherapy.
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•TREM2 is expressed by tumor-associated macrophages in different types of tumors•TREM2 deficiency and anti-TREM2 mAb treatment both curb tumor growth in mice•Anti-PD-1 treatment is more efficacious when TREM2 is either absent or engaged by a mAb•Modulation of TREM2 remodels the tumor macrophage landscape
TREM2 is a pro-tumorigenic marker of tumor-infiltrating macrophages in mouse models and human tumors that can be targeted to curb tumor growth and improve the efficacy of checkpoint blockade therapy while remodeling the landscape of tumor-infiltrating macrophages.
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