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Cancer-specific TCF1 + stem-like CD8 + T cells can drive protective anticancer immunity through expansion and effector cell differentiation 1-4 ; however, this response is dysfunctional in tumours. Current cancer immunotherapies 2,5-9 can promote anticancer responses through TCF1 + stem-like CD8 + T cells in some but not all patients. This variation points towards currently ill-defined mechanisms that limit TCF1 + CD8 + T cell-mediated anticancer immunity. Here we demonstrate that tumour-derived prostaglandin E2 (PGE 2 ) restricts the proliferative expansion and effector differentiation of TCF1 + CD8 + T cells within tumours, which promotes cancer immune escape. PGE 2 does not affect the priming of TCF1 + CD8 + T cells in draining lymph nodes. PGE 2 acts through EP 2 and EP 4 (EP 2 /EP 4 ) receptor signalling in CD8 + T cells to limit the intratumoural generation of early and late effector T cell populations that originate from TCF1 + tumour-infiltrating CD8 + T lymphocytes (TILs). Ablation of EP 2 /EP 4 signalling in cancer-specific CD8 + T cells rescues their expansion and effector differentiation within tumours and leads to tumour elimination in multiple mouse cancer models. Mechanistically, suppression of the interleukin-2 (IL-2) signalling pathway underlies the PGE 2 -mediated inhibition of TCF1 + TIL responses. Altogether, we uncover a key mechanism that restricts the IL-2 responsiveness of TCF1 + TILs and prevents anticancer T cell responses that originate from these cells. This study identifies the PGE 2 -EP 2 /EP 4 axis as a molecular target to restore IL-2 responsiveness in anticancer TILs to achieve cancer immune control., (© 2024. The Author(s).)

This article is part of the Dendritic Cell Guidelines article series, which provides a collection of state-of-the-art protocols for the preparation, phenotype analysis by flow cytometry, generation, fluorescence microscopy, and functional characterization of mouse and human dendritic cells (DC) from lymphoid organs and various non-lymphoid tissues. Here, we provide detailed procedures for a variety of multiparameter fluorescence microscopy imaging methods to explore the spatial organization of DC in tissues and to dissect how DC migrate, communicate, and mediate their multiple functional roles in immunity in a variety of tissue settings. The protocols presented here entail approaches to study DC dynamics and T cell cross-talk by intravital microscopy, large-scale visualization, identification, and quantitative analysis of DC subsets and their functions by multiparameter fluorescence microscopy of fixed tissue sections, and an approach to study DC interactions with tissue cells in a 3D cell culture model. While all protocols were written by experienced scientists who routinely use them in their work, this article was also peer-reviewed by leading experts and approved by all co-authors, making it an essential resource for basic and clinical DC immunologists., (© 2023 The Authors. European Journal of Immunology published by Wiley-VCH GmbH.)

Type 1 conventional dendritic cells (cDC1) can support T cell responses within tumors but whether this determines protective versus ineffective anti-cancer immunity is poorly understood. Here, we use imaging-based deep learning to identify intratumoral cDC1-CD8 + T cell clustering as a unique feature of protective anti-cancer immunity. These clusters form selectively in stromal tumor regions and constitute niches in which cDC1 activate TCF1 + stem-like CD8 + T cells. We identify a distinct population of immunostimulatory CCR7 neg cDC1 that produce CXCL9 to promote cluster formation and cross-present tumor antigens within these niches, which is required for intratumoral CD8 + T cell differentiation and expansion and promotes cancer immune control. Similarly, in human cancers, CCR7 neg cDC1 interact with CD8 + T cells in clusters and are associated with patient survival. Our findings reveal an intratumoral phase of the anti-cancer T cell response orchestrated by tumor-residing cDC1 that determines protective versus ineffective immunity and could be exploited for cancer therapy., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Type 1 conventional dendritic cells (cDC1s) are critical for anti-cancer immunity. Protective anti-cancer immunity is thought to require cDC1s to sustain T cell responses within tumors, but it is poorly understood how this function is regulated and whether its subversion contributes to immune evasion. Here, we show that tumor-derived prostaglandin E2 (PGE 2 ) programmed a dysfunctional state in intratumoral cDC1s, disabling their ability to locally orchestrate anti-cancer CD8 + T cell responses. Mechanistically, cAMP signaling downstream of the PGE 2 -receptors EP2 and EP4 was responsible for the programming of cDC1 dysfunction, which depended on the loss of the transcription factor IRF8. Blockade of the PGE 2 -EP2/EP4-cDC1 axis prevented cDC1 dysfunction in tumors, locally reinvigorated anti-cancer CD8 + T cell responses, and achieved cancer immune control. In human cDC1s, PGE 2 -induced dysfunction is conserved and associated with poor cancer patient prognosis. Our findings reveal a cDC1-dependent intratumoral checkpoint for anti-cancer immunity that is targeted by PGE 2 for immune evasion., Competing Interests: Declaration of interests The authors declare that they have no competing interests., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Natural killer (NK) cells are innate immune cells critically involved in the control of cancer. Their important role in cancer immunity reflects the ability of NK cells to recognize malignant cells through an array of germline-encoded receptors expressed on their surface, enabling NK cells to detect and rapidly kill tumor cells through targeted cytotoxicity. In addition to their cytotoxic activity, NK cells fulfill a fundamental and often underappreciated role in the local orchestration of cancer immunity through their ability to communicate with innate and adaptive immune cells within the tumor microenvironment (TME), which is achieved through the secretion of multiple chemokines, cytokines, and growth factors. Within tumor tissue, NK cells regulate the recruitment, survival and functional activity of various immune cells including monocytes, granulocytes, dendritic cells and T cells, thereby shaping intratumoral immune cell composition and functionality. Emerging evidence further suggest a role of NK cells in the regulation of stromal cells within the TME. Here, we discuss key aspects of NK cell communication with other intratumoral cell types and its role for cancer immunity. Strategies aimed at boosting anti-cancer immunity by enhancing NK cell communication and functionality within tumor tissue provide attractive new ways for treatment of cancer patients., Competing Interests: Conflict of interest T. Bald has research agreements with ENA Therapeutics and Bristol Myers Squibb and is on the scientific advisory board of Oncomyx. J.P. Böttcher, A. Pedde and D. Corvino declare no conflict of interest., (© 2020 Elsevier Inc. All rights reserved.)