Villarino et al. demonstrate that STAT5 is required for accumulation and function of all ILC subsets in mice. They also define a STAT5-driven transcriptional signature in NK cells and reveal a cooperative relationship with T-bet, another key ILC transcription factor.

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Innate immune responses rely on rapid and precise gene regulation mediated by accessibility of regulatory regions to transcription factors (TFs). In natural killer (NK) cells and other innate lymphoid cells, competent enhancers are primed during lineage acquisition, and formation of de novo enhancers characterizes the acquisition of innate memory in activated NK cells and macrophages. Here, we investigated how primed and de novo enhancers coordinate to facilitate high-magnitude gene induction during acute activation. Epigenomic and transcriptomic analyses of regions near highly induced genes (HIGs) in NK cells both in vitro and in a model of Toxoplasma gondii infection revealed de novo chromatin accessibility and enhancer remodeling controlled by signal-regulated TFs STATs. Acute NK cell activation redeployed the lineage-determining TF T-bet to de novo enhancers, independent of DNA-sequence-specific motif recognition. Thus, acute stimulation reshapes enhancer function through the combinatorial usage and repurposing of both lineage-determining and signal-regulated TFs to ensure an effective response.

BackgroundAnti-cancer immune responses may contribute to the control of tumors after conventional chemotherapy, and different observations have indicated that chemotherapeutic agents can induce immune responses resulting in cancer cell death and immune-stimulatory side effects. Increasing experimental and clinical evidence highlight the importance of natural killer (NK) cells in immune responses toward multiple myeloma (MM), and combination therapies able to enhance the activity of NK cells against MM are showing promise in treating this hematologic cancer. The epigenetic readers of acetylated histones bromodomain and extra-terminal (BET) proteins are critical regulators of gene expression. In cancer, they can upregulate transcription of key oncogenes such as cMYC, IRF4, and BCL-2. In addition, the activity of these proteins can regulate the expression of osteoclastogenic cytokines during cancer progression. Here, we investigated the effect of BET bromodomain protein inhibition, on the expression of NK cell-activating ligands in MM cells.MethodsFive MM cell lines [SKO-007(J3), U266, RPMI-8226, ARP-1, JJN3] and CD138+ MM cells isolated from MM patients were used to investigate the activity of BET bromodomain inhibitors (BETi) (JQ1 and I-BET151) and of the selective BRD4-degrader proteolysis targeting chimera (PROTAC) (ARV-825), on the expression and function of several NK cell-activating ligands (NKG2DLs and DNAM-1Ls), using flow cytometry, real-time PCR, transient transfections, and degranulation assays.ResultsOur results indicate that inhibition of BET proteins via small molecule inhibitors or their degradation via a hetero-bifunctional PROTAC probe can enhance the expression of MICA, a ligand of the NKG2D receptor, in human MM cell lines and primary malignant plasma cells, rendering myeloma cells more efficient to activate NK cell degranulation. Noteworthy, similar results were obtained using selective CBP/EP300 bromodomain inhibition. Mechanistically, we found that BETi-mediated inhibition of cMYC correlates with the upregulation of miR-125b-5p and the downregulation of the cMYC/miR-125b-5p target gene IRF4, a transcriptional repressor of MICA.ConclusionsThese findings provide new insights on the immuno-mediated antitumor activities of BETi and further elucidate the molecular mechanisms that regulate NK cell-activating ligand expression in MM.Electronic supplementary materialThe online version of this article (doi:10.1186/s13045-016-0362-2) contains supplementary material, which is available to authorized users.

Tumor microenvironments (TMEs) influence cancer progression but are complex and often differ between patients. Considering that microenvironment variations may reveal rules governing intratumoral cellular programs and disease outcome, we focused on tumor-to-tumor variation to examine 52 head and neck squamous cell carcinomas. We found that macrophage polarity—defined by CXCL9 and SPP1 (CS) expression but not by conventional M1 and M2 markers—had a noticeably strong prognostic association. CS macrophage polarity also identified a highly coordinated network of either pro- or antitumor variables, which involved each tumor-associated cell type and was spatially organized. We extended these findings to other cancer indications. Overall, these results suggest that, despite their complexity, TMEs coordinate coherent responses that control human cancers and for which CS macrophage polarity is a relevant yet simple variable.

CD155 is an adhesion molecule belonging to the Nectin/Nectin-like family often overexpressed on tumor cells and involved in many different processes such as cell adhesion, migration and proliferation. In contrast to these pro-tumorigenic functions, CD155 is also a ligand for the activating receptor DNAM-1 expressed on cytotoxic lymphocytes including Natural Killer (NK) cells and involved in anti-tumor immune response. However, during tumor progression inhibitory receptors for CD155 are up-regulated on the surface of effector cells, contributing to an impairment of their cytotoxic capacity. In this review we will focus on the roles of CD155 as a ligand for the activating receptor DNAM-1 regulating immune surveillance against cancer and as pro-oncogenic molecule favoring tumor proliferation, invasion and immune evasion. A deeper understanding of the multiple roles played by CD155 in cancer development contributes to improving anti-tumor strategies aimed to potentiate immune response against cancer.

Cytotoxic lymphocytes share the presence of the activating receptor NK receptor group 2, member D (NKG2D) and the signaling-competent adaptor DNAX-activating protein 10 (DAP10), which together play an important role in antitumor immune surveillance. Ligand stimulation induces the internalization of NKG2D-DAP10 complexes and their delivery to lysosomes for degradation. In experiments with human NK cells and cell lines, we found that the ligand-induced endocytosis of NKG2D-DAP10 depended on the ubiquitylation of DAP10, which was also required for degradation of the internalized complexes. Moreover, through combined biochemical and microscopic analyses, we showed that ubiquitin-dependent receptor endocytosis was required for the activation of extracellular signal-regulated kinase (ERK) and NK cell functions, such as the secretion of cytotoxic granules and the inflammatory cytokine interferon-γ. These results suggest that NKG2D-DAP10 endocytosis represents a means to decrease cell surface receptor abundance, as well as to control signaling outcome in cytotoxic lymphocytes.

The NKG2D activating receptor on human NK cells mediates "altered self" recognition, as its ligands (NKG2DLs) are upregulated on target cells in a variety of stress conditions. Evidence collected in the past years shows that, even though expression of NKG2DLs acts as a danger signal that renders tumor cells susceptible to cytotoxicity, chronic exposure to soluble or membrane-bound NKG2DLs can lead to down-modulation of receptor expression and impairment of NKG2D-mediated cell functions. Here, we evaluated whether different cell-bound NKG2DLs, namely MICA and ULBP2, are equivalently able to induce NKG2D down-modulation on human NK cells. We found that although both ligands reduce NKG2D surface expression, MICA promotes a stronger receptor downmodulation than ULBP2, leading to a severe impairment of NKG2D-dependent NK-cell cytotoxicity. We also provide evidence that the ubiquitin pathway and c-Cbl direct MICAinduced but not ULBP2-induced NKG2D internalization and degradation, thus identifying a molecular mechanism to explain the differential effects of MICA and ULBP2 on NKG2D expression. A better understanding of the molecular mechanisms employed by the different NKG2DLs to control NKG2D surface expression could be useful for the development of anti-tumor strategies to restore a normal level of NKG2D receptors on human NK cells. Keywords:Endocytosis r NK cells r NKG2D ligands r NKG2D receptor Additional supporting information may be found in the online version of this article at the publisher's web-site Introduction NK cells are an important arm of the innate immune system directly involved in the recognition and lysis of virus-infected and tumor cells. NK-cell functional activation mainly depends on the interplay between inhibitory receptors for MHC class I molecules Correspondence: Prof. Rossella Paolini e-mail: rossella.paolini@uniroma1.it and a wide array of activating receptors that act in concert to induce efficient target cell elimination [1][2][3]. One of the best characterized activating receptors is NKG2D (NK receptor group 2, member D), whose expression is not restricted to NK cells, as it is also found on many T-cell subsets [4,5]. NKG2D mediates "altered self" recognition, in that it recognizes ligands absent or poorly expressed on most tissues and upregulated by conditions of stress or infection, in autoimmune diseases and malignant transformation, thus rendering damaged cells susceptible to NKG2D-mediated cellular cytotoxicity [6,7]. Eur. J. Immunol. 2014Immunol. . 44: 2761Immunol. -2770 The early hypothesis claiming a prominent role of NKG2D in tumor immune surveillance [8] has been supported by studies using various animal tumor models and NKG2D-deficient mice [9][10][11][12]. In humans, a remarkable characteristic of NKG2D resides in the interaction of a single invariant receptor with two structurally distinct families of MHC class I-related cell surface glycoproteins that differ in modes of membrane anchor and affinities for their common receptor: the polymorphic MHC class I-related Chain (MIC...