Natural Killer (NK)/melanoma cell interaction induces NK-mediated release of chemotactic High Mobility Group Box-1 (HMGB1) capable of amplifying NK cell recruitment

NK Cell-Monocyte Cross-talk Underlies NK Cell Activation in Severe COVID-19

NK cells in the peripheral blood of severe COVID-19 patients exhibit a unique profile characterized by activation and dysfunction. Previous studies have identified soluble factors, including type I IFN and TGF-β, that underlie this dysregulation. However, the role of cell-cell interactions in modulating NK cell function during COVID-19 remains unclear. To address this question, we combined cell-cell communication analysis on existing single-cell RNA sequencing data with in vitro primary cell coculture experiments to dissect the mechanisms underlying NK cell dysfunction in COVID-19. We found that NK cells are predicted to interact most strongly with monocytes and that this occurs via both soluble factors and direct interactions. To validate these findings, we performed in vitro cocultures in which NK cells from healthy human donors were incubated with monocytes from COVID-19+ or healthy donors. Coculture of healthy NK cells with monocytes from COVID-19 patients recapitulated aspects of the NK cell phenotype observed in severe COVID-19, including decreased expression of NKG2D, increased expression of activation markers, and increased proliferation. When these experiments were performed in a Transwell setting, we found that only CD56bright CD16- NK cells were activated in the presence of severe COVID-19 patient monocytes. O-link analysis of supernatants from Transwell cocultures revealed that cultures containing severe COVID-19 patient monocytes had significantly elevated levels of proinflammatory cytokines and chemokines, as well as TGF-β. Collectively, these results demonstrate that interactions between NK cells and monocytes in the peripheral blood of COVID-19 patients contribute to NK cell activation and dysfunction in severe COVID-19.

Murine models to study human NK cells in human solid tumors

Since the first studies, the mouse models have provided crucial support for the most important discoveries on NK cells, on their development, function, and circulation within normal and tumor tissues. Murine tumor models were initially set to study murine NK cells, then, ever more sophisticated human-in-mice models have been developed to investigate the behavior of human NK cells and minimize the interferences from the murine environment. This review presents an overview of the models that have been used along time to study NK cells, focusing on the most popular NOG and NSG models, which work as recipients for the preparation of human-in-mice tumor models, the study of transferred human NK cells, and the evaluation of various enhancers of human NK cell function, including cytokines and chimeric molecules. Finally, an overview of the next generation humanized mice is also provided along with a discussion on how traditional and innovative in-vivo and in-vitro approaches could be integrated to optimize effective pre-clinical studies.

CXCL12/CXCR4 Axis is Involved in the Recruitment of NK Cells by HMGB1 Contributing to Persistent Airway Inflammation and AHR During the Late Stage of RSV Infection

We previously showed that both high-mobility group box-1 (HMGB1) and natural killer (NK) cells contribute to respiratory syncytial virus (RSV)-induced persistent airway inflammation and airway hyperresponsiveness (AHR). Meanwhile, Chemokine (C-X-C motif) ligand 12 (CXCL12) and its specific receptor (chemokine receptor 4, CXCR4) play important roles in recruitment of immune cells. CXCL12 has been reported to form a complex with HMGB1 that binds to CXCR4 and increases inflammatory cell migration. The relationship between HMGB1, NK cells and chemokines in RSV-infected model remains unclear. An anti-HMGB1 neutralizing antibody and inhibitor of CXCR4 (AMD3100) was administered to observe changes of NK cells and airway disorders in nude mice and BALB/c mice. Results showed that the mRNA expression and protein levels of HMGB1 were elevated in late stage of RSV infection and persistent airway inflammation and AHR were diminished after administration of anti-HMGB1 antibodies, with an associated significant decrease in CXCR4⁺ NK cells. In addition, CXCL12 and CXCR4 were reduced after HMGB1 blockade. Treatment with AMD3100 significantly suppressed the recruitment of NK cells and alleviated the airway disorders. Thus, CXCL12/CXCR4 axis is involved in the recruitment of NK cells by HMGB1, contributing to persistent airway inflammation and AHR during the late stage of RSV infection.

Anticancer traits of chimeric antigen receptors (CARs)-Natural Killer (NK) cells as novel approaches for melanoma treatment

Owing to non-responsiveness of a high number of patients to the common melanoma therapies, seeking novel approaches seem as an unmet requirement. Chimeric antigen receptor (CAR) T cells were initially employed against recurrent or refractory B cell malignancies. However, advanced stages or pretreated patients have insufficient T cells (lymphopenia) amount for collection and clinical application. Additionally, this process is time-consuming and logistically cumbersome. Another limitation of this approach is toxicity and cytokine release syndrome (CRS) progress and neurotoxicity syndrome (NS). Natural killer (NK) cells are a versatile component of the innate immunity and have several advantages over T cells in the application for therapies such as availability, unique biological features, safety profile, cost effectiveness and higher tissue residence. Additionally, CAR NK cells do not develop Graft-versus-host disease (GvHD) and are independent of host HLA genotype. Notably, the NK cells number and activity is affected in the tumor microenvironment (TME), paving the way for developing novel approaches by enhancing their maturation and functionality. The CAR NK cells short lifespan is a double edge sword declining toxicity and reducing their persistence. Bispecific and Trispecific Killer Cell Engagers (BiKE and Trike, respectively) are emerging and promising immunotherapies for efficient antibody dependent cell cytotoxicity (ADCC). CAR NK cells have some limitations in terms of expanding and transducing NK cells from donors to achieve clinical response. Clinical trials are in scarcity regarding the CAR NK cell-based cancer therapies. The CAR NK cells short life span following irradiation before infusion limits their efficiency inhibiting their in vivo expansion. The CAR NK cells efficacy enhancement in terms of lifespan TME preparation and stability is a goal for melanoma treatment. Combination therapies using CAR NK cells and chemotherapy can also overcome therapy limitations.

Paralysis of the cytotoxic granule machinery is a new cancer immune evasion mechanism mediated by chitinase 3-like-1

Background

Natural killer (NK) cells require a functional lytic granule machinery to mediate effective antitumor responses. Evading the lytic cargo deployed at the immune synapse (IS) could be a critical step for cancer progression through yet unidentified mechanisms.

Methods

NK cell antibody-dependent cellular cytotoxicity (ADCC) is a major determinant of the clinical efficacy of some therapeutic antibodies including the anti-HER2 Trastuzumab. Thus, we screened sera of Trastuzumab-resistant HER2 +patients with breast cancer for molecules that could inhibit NK cell ADCC. We validated our findings in vitro using cytotoxicity assays and confocal imaging of the lytic granule machinery and in vivo using syngeneic and xenograft murine models.

Results

We found that sera from Trastuzumab-refractory patients could inhibit healthy NK cell ADCC in vitro. These sera contained high levels of the inflammatory protein chitinase 3-like 1 (CHI3L1) compared with sera from responders and healthy controls. We demonstrate that recombinant CHI3L1 inhibits both ADCC and innate NK cell cytotoxicity. Mechanistically, CHI3L1 prevents the correct polarization of the microtubule-organizing center along with the lytic granules to the IS by hindering the receptor of advanced glycation end-products and its downstream JNK signaling. In vivo, CHI3L1 administration drastically impairs the control of NK cell-sensitive tumors, while CHI3L1 blockade synergizes with ADCC to cure mice with HER2 +xenografts.

Conclusion

Our work highlights a new paradigm of tumor immune escape mediated by CHI3L1 which acts on the cytotoxic machinery and prevents granule polarization. Targeting CHI3L1 could mitigate immune escape and potentiate antibody and cell-based immunotherapies.

Functional Amino Acids and Autophagy: Diverse Signal Transduction and Application

Functional amino acids provide great potential for treating autophagy-related diseases by regulating autophagy. The purpose of the autophagy process is to remove unwanted cellular contents and to recycle nutrients, which is controlled by many factors. Disordered autophagy has been reported to be associated with various diseases, such as cancer, neurodegeneration, aging, and obesity. Autophagy cannot be directly controlled and dynamic amino acid levels are sufficient to regulate autophagy. To date, arginine, leucine, glutamine, and methionine are widely reported functional amino acids that regulate autophagy. As a signal relay station, mammalian target of rapamycin complex 1 (mTORC1) turns various amino acid signals into autophagy signaling pathways for functional amino acids. Deficiency or supplementation of functional amino acids can immediately regulate autophagy and is associated with autophagy-related disease. This review summarizes the mechanisms currently involved in autophagy and amino acid sensing, diverse signal transduction among functional amino acids and autophagy, and the therapeutic appeal of amino acids to autophagy-related diseases. We aim to provide a comprehensive overview of the mechanisms of amino acid regulation of autophagy and the role of functional amino acids in clinical autophagy-related diseases and to further convert these mechanisms into feasible therapeutic applications.

EZH1/2 Inhibitors Favor ILC3 Development from Human HSPC-CD34+ Cells

Simple Summary

It has been well-demonstrated that EZH1/2 enzymes are involved not only in tumor development and progression, but also in the regulation of normal hematopoiesis from CD34⁺-HSPC. Given the crucial role of NK cells in tumor immune surveillance, in this study, we investigated whether EZH1/2 inhibitors can interfere with NK cell differentiation and functional maturation. Our results suggest that EZH1/2 inhibitors push CD56⁺ precursor proliferation, skewing precursor cell lineage commitment towards ILC3. In recent years, several clinical trials on the use of EZH1/2 inhibitors against solid tumors have been carried out. Since these in vitro observations revealed possible epigenetic mechanisms involved in NK/ILC development, it is important to evaluate patient monitoring of competent NK cells repertoire in order to design appropriate therapeutic protocols.

Abstract

The dysregulation of epigenetic modifications has a well-established role in the development and progression of hematological malignancies and of solid tumors. In this context, EZH1/2 inhibitors have been designed to interfere with EZH1/2 enzymes involved in histone methylation (e.g., H3K27me3), leading to tumor growth arrest or the restoration of tumor suppressor gene transcription. However, these compounds also affect normal hematopoiesis, interfering with self-renewal and differentiation of CD34⁺-Hematopoietic Stem/Progenitor Cells (HSPC), and, in turn, could modulate the generation of potential anti-tumor effector lymphocytes. Given the important role of NK cells in the immune surveillance of tumors, it would be useful to understand whether epigenetic drugs can modulate NK cell differentiation and functional maturation. CD34⁺-HSPC were cultured in the absence or in the presence of the EZH1/2 inhibitor UNC1999 and EZH2 inhibitor GSK126. Our results show that UNC1999 and GSK126 increased CD56⁺ cell proliferation compared to the control condition. However, UNC1999 and GSK 126 favored the proliferation of no-cytotoxic CD56⁺ILC3, according to the early expression of the AHR and ROR-γt transcription factors. Our results describe novel epigenetic mechanisms involved in the modulation of NK cell maturation that may provide new tools for designing NK cell-based immunotherapy.

miR-142-3p reduces the viability of human cervical cancer cells by negatively regulating the cytoplasmic localization of HMGB1

High mobility group protein B1 (HMGB1) is a nuclear protein that has been reported to contribute to tumor growth in humans. The present study identified a microRNA (miR/miRNA) that targets the 3' untranslated region (3'UTR) of the HMGB1 gene and assessed its effects on the proliferation of human cervical cancer cells and associated molecular mechanism. Western blotting was performed to determine HMGB1 levels in HeLa cells. TargetScan software was used to identify miRNA binding sites adjacent to the HMGB1. The viability of HeLa cells transfected with miR-142-3p mimics or inhibitors was determined using an MTT assay. The subcellular distribution (cytoplasmic or nuclear) of HMGB1 in HeLa cells was observed by western blotting. HMGB1 expression in HeLa and CaSKi cells was significantly higher compared with normal control cervical cells. TargetScan analysis indicated that miR-142-3p binds to the 3'UTR of HMGB1. Transfection with a miR-142-3p inhibitor increased cytoplasmic HMGB1 expression in HeLa cells, as shown by western blot analysis, while transfection with miR-142-3p mimics decreased the cytoplasmic expression of HMGB1 in HeLa cells. Therefore, miR-142-3p negatively regulated HMGB1 levels in cervical cancer cells. These findings indicated that miR-142-3p inhibited the proliferation of human cervical cancer cells, at least in part, by negatively regulating the cytoplasmic localization of HMGB1.

Role of HMGB1 in Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN), one of major dose-limiting side effects of first-line chemotherapeutic agents such as paclitaxel, oxaliplatin, vincristine, and bortezomib is resistant to most of existing medicines. The molecular mechanisms of CIPN have not been fully understood. High mobility group box 1 (HMGB1), a nuclear protein, is a damage-associated molecular pattern protein now considered to function as a pro-nociceptive mediator once released to the extracellular space. Most interestingly, HMGB1 plays a key role in the development of CIPN. Soluble thrombomodulin (TMα), known to degrade HMGB1 in a thrombin-dependent manner, prevents CIPN in rodents treated with paclitaxel, oxaliplatin, or vincristine and in patients with colorectal cancer undergoing oxaliplatin-based chemotherapy. In this review, we describe the role of HMGB1 and its upstream/downstream mechanisms in the development of CIPN and show drug candidates that inhibit the HMGB1 pathway, possibly useful for prevention of CIPN.

Role of the Main Non HLA-Specific Activating NK Receptors in Pancreatic, Colorectal and Gastric Tumors Surveillance

Human NK cells can control tumor growth and metastatic spread thanks to their powerful cytolytic activity which relies on the expression of an array of activating receptors. Natural cytotoxicity receptors (NCRs) NKG2D and DNAM-1 are those non-HLA-specific activating NK receptors that are mainly involved in sensing tumor transformation by the recognition of different ligands, often stress-induced molecules, on the surface of cancer cells. Tumors display several mechanisms aimed at dampening/evading NK-mediated responses, a relevant fraction of which is based on the downregulation of the expression of activating receptors and/or their ligands. In this review, we summarize the role of the main non-HLA-specific activating NK receptors, NCRs, NKG2D and DNAM-1, in controlling tumor growth and metastatic spread in solid malignancies affecting the gastrointestinal tract with high incidence in the world population, i.e., pancreatic ductal adenocarcinoma (PDAC), colorectal cancer (CRC), and gastric cancer (GC), also describing the phenotypic and functional alterations induced on NK cells by their tumor microenvironment.

NK cells and ILCs in tumor immunotherapy

Cells of the innate immunity play an important role in tumor immunotherapy. Thus, NK cells can control tumor growth and metastatic spread. Thanks to their strong cytolytic activity against tumors, different approaches have been developed for exploiting/harnessing their function in patients with leukemia or solid tumors. Pioneering trials were based on the adoptive transfer of autologous NK cell-enriched cell populations that were expanded in vitro and co-infused with IL-2. Although relevant results were obtained in patients with advanced melanoma, the effect was mostly limited to certain metastatic localizations, particularly to the lung. In addition, the severe IL-2-related toxicity and the preferential IL-2-induced expansion of Treg limited this type of approach. This limitation may be overcome by the use of IL-15, particularly of modified IL-15 molecules to improve its half-life and optimize the biological effects. Other approaches to harness NK cell function include stimulation via TLR, the use of bi- and tri-specific NK cell engagers (BiKE and TriKE) linking activating NK receptors (e.g. CD16) to tumor-associated antigens and even incorporating an IL-15 moiety (TriKE). As recently shown, in tumor patients, NK cells may also express inhibitory checkpoints, primarily PD-1. Accordingly, the therapeutic use of checkpoint inhibitors may unleash NK cells against PD-L1⁺ tumors. This effect may be predominant and crucial in tumors that have lost HLA cl-I expression, thus resulting "invisible" to T lymphocytes. Additional approaches in which NK cells may represent an important tool for cancer therapy, are to exploit the unique properties of the "adaptive" NK cells. These CD57⁺ NKG2C⁺ cells, despite their mature stage and a potent cytolytic activity, maintain a strong proliferating capacity. This property revealed to be crucial in hematopoietic stem cell transplantation (HSCT), particularly in the haplo-HSCT setting, to cure high-risk leukemias. T depleted haplo-HSCT (e.g. from one of the parents) allowed to save the life of thousands of patients lacking a HLA-compatible donor. In this setting, NK cells have been shown to play an essential role against leukemia cells and infections. Another major advance is represented by chimeric antigen receptor (CAR)-engineered NK cells. CAR-NK, different from CAR-T cells, may be obtained from allogeneic donors since they do not cause GvHD. Accordingly, they may represent "off-the-shelf" products to promptly treat tumor patients, with affordable costs. Different from NK cells, helper ILC (ILC1, ILC2 and ILC3), the innate counterpart of T helper cell subsets, remain rather ambiguous with respect to their anti-tumor activity. A possible exception is represented by a subset of ILC3: their frequency in peri-tumoral tissues in patients with NSCLC directly correlates with a better prognosis, possibly reflecting their ability to contribute to the organization of tertiary lymphoid structures, an important site of T cell-mediated anti-tumor responses. It is conceivable that innate immunity may significantly contribute to the major advances that immunotherapy has ensured and will continue to ensure to the cure of cancer.

U3-1402 sensitizes HER3-expressing tumors to PD-1 blockade by immune activation

Immunotherapy targeting programmed cell death-1 (PD-1) induces durable antitumor efficacy in many types of cancer. However, such clinical benefit is limited because of the insufficient reinvigoration of antitumor immunity with the drug alone; therefore, rational therapeutic combinations are required to improve its efficacy. In our preclinical study, we evaluated the antitumor effect of U3-1402, a human epidermal growth factor receptor 3-targeting (HER3-targeting) antibody-drug conjugate, and its potential synergism with PD-1 inhibition. Using a syngeneic mouse tumor model that is refractory to anti-PD-1 therapy, we found that treatment with U3-1402 exhibited an obvious antitumor effect via direct lysis of tumor cells. Disruption of tumor cells by U3-1402 enhanced the infiltration of innate and adaptive immune cells. Chemotherapy with exatecan derivative (Dxd, the drug payload of U3-1402) revealed that the enhanced antitumor immunity produced by U3-1402 was associated with the induction of alarmins, including high-mobility group box-1 (HMGB-1), via tumor-specific cytotoxicity. Notably, U3-1402 significantly sensitized the tumor to PD-1 blockade, as a combination of U3-1402 and the PD-1 inhibitor significantly enhanced antitumor immunity. Further, clinical analyses indicated that tumor-specific HER3 expression was frequently observed in patients with PD-1 inhibitor-resistant solid tumors. Overall, U3-1402 is a promising candidate as a partner of immunotherapy for such patients.

miRNAs in NK Cell-Based Immune Responses and Cancer Immunotherapy

The incidence of certain forms of tumors has increased progressively in recent years and is expected to continue growing as life expectancy continues to increase. Tumor-infiltrating NK cells may contribute to develop an anti-tumor response. Optimized combinations of different cancer therapies, including NK cell-based approaches for targeting tumor cells, have the potential to open new avenues in cancer immunotherapy. Functional inhibitory receptors on NK cells are needed to prevent their attack on healthy cells. Nevertheless, disruption of inhibitory receptors function on NK cells increases the cytotoxic capacity of NK cells against cancer cells. MicroRNAs (miRNAs) are small non-coding RNA molecules that target mRNA and thus regulate the expression of genes involved in the development, maturation, and effector functions of NK cells. Therapeutic strategies that target the regulatory effects of miRNAs have the potential to improve the efficiency of cancer immunotherapy. Interestingly, emerging evidence points out that some miRNAs can, directly and indirectly, control the surface expression of immune checkpoints on NK cells or that of their ligands on tumor cells. This suggests a possible use of miRNAs in the context of anti-tumor therapy. This review provides the current overview of the connections between miRNAs and regulation of NK cell functions and discusses the potential of these miRNAs as innovative biomarkers/targets for cancer immunotherapy.

Distribution of positively charged amino acid residues in antimicrobial peptide epinecidin-1 is crucial for in vitro glioblastoma cytotoxicity and its underlying mechanisms

Epinecidin-1 (epi) was identified from orange-spotted grouper (Epinephelus coioides) and exhibits diverse biological activities. The aims of this study were to investigate how the distribution of positively charged amino acid residues affects epi-mediated cytotoxicity and to examine the molecular mechanism underlying epi-induced cytotoxicity in U87MG human glioblastoma cells. MTS/PMS and trypan blue exclusion assay were used to measure cell viability. Necrotic cell death was confirmed by detecting cyclophilin A release and propidium iodide incorporation. DNA damage was evaluated by measuring phosphorylated H2AX. Intracellular reactive oxygen species (ROS) were analyzed by flow cytometry using dihydroergotamine. Mitochondrial membrane potential was detected by flow cytometry using tetramethylrhodamine, ethyl ester. Overall, we found that epi caused cytotoxicity in U87MG cells by inducing DNA damage and necrosis through mitochondrial hyperpolarization and subsequent ROS production. The proper folding of epi into an α-helical structure was essential for epi-mediated anti-glioblastoma effects. In addition, NFκB signaling was activated in U87MG cells after exposure to epi. Suppression of NFκB further enhanced epi-induced cytotoxicity, ROS generation and DNA damage, indicating that NFκB may play a protective role in epi-induced cytotoxicity. Our findings may be useful for the design and improvement of antimicrobial peptides with anti-cancer activity.

NK Cell-Based Immunotherapy for Hematological Malignancies

Natural killer (NK) lymphocytes are an integral component of the innate immune system and represent important effector cells in cancer immunotherapy, particularly in the control of hematological malignancies. Refined knowledge of NK cellular and molecular biology has fueled the interest in NK cell-based antitumor therapies, and recent efforts have been made to exploit the high potential of these cells in clinical practice. Infusion of high numbers of mature NK cells through the novel graft manipulation based on the selective depletion of T cells and CD19+ B cells has resulted into an improved outcome in children with acute leukemia given human leucocyte antigen (HLA)-haploidentical hematopoietic transplantation. Likewise, adoptive transfer of purified third-party NK cells showed promising results in patients with myeloid malignancies. Strategies based on the use of cytokines or monoclonal antibodies able to induce and optimize NK cell activation, persistence, and expansion also represent a novel field of investigation with remarkable perspectives of favorably impacting on outcome of patients with hematological neoplasia. In addition, preliminary results suggest that engineering of mature NK cells through chimeric antigen receptor (CAR) constructs deserve further investigation, with the goal of obtaining an "off-the-shelf" NK cell bank that may serve many different recipients for granting an efficient antileukemia activity.

Mechanism and medical implications of mammalian autophagy

Autophagy is a highly conserved catabolic process induced under various conditions of cellular stress, which prevents cell damage and promotes survival in the event of energy or nutrient shortage and responds to various cytotoxic insults. Thus, autophagy has primarily cytoprotective functions and needs to be tightly regulated to respond correctly to the different stimuli that cells experience, thereby conferring adaptation to the ever-changing environment. It is now apparent that autophagy is deregulated in the context of various human pathologies, including cancer and neurodegeneration, and its modulation has considerable potential as a therapeutic approach.

Cancer Immunoediting by Innate Lymphoid Cells

The immune system plays a dual role in cancer. It conveys protective immunity but also facilitates malignant progression, either by sculpting tumor immunogenicity or by creating a microenvironment that can stimulate tumor outgrowth or aid in a subsequent metastatic cascade. Innate lymphoid cells (ILCs) embody this functional heterogeneity, although the nature of their responses in cancer has only recently begun to be unveiled. We provide an overview of recent insights into the role of ILCs in cancer. We also discuss how ILCs fit into the conceptual framework of cancer immunoediting, which integrates the dual role of the immune system in carcinogenesis. A broader understanding of their relevance in cancer is essential towards the design of successful therapeutic strategies.

The Uncovered Role of Immune Cells and NK Cells in the Regulation of Bone Metastasis

Bone is one of the main metastatic sites of solid tumors like breast, lung, and prostate cancer. Disseminated tumor cells (DTCs) and cancer stem cells (CSCs) represent the main target to counteract bone metastatization. These cells often localize in bone marrow (BM) at level of pre-metastatic niche: they can remain dormant for years or directly grow and create bone lesion, according to the different stimulations received in BM. The immune system in bone marrow is dampened and represents an appealing site for DTCs/CSCs. NK cells have an important role in controlling tumor progression, but their involvement in bone metastasis formation is an interesting and not fully investigated issue. Indeed, whether NK cells can interfere with CSC formation, kill them at the site of primary tumor, during circulation or in the pre-metastic niche needs to be elucidated. This review focuses on different aspects that regulate DTC/CSC life in bone and how NK cells potentially control bone metastasis formation.

Isolation, Expansion, and Characterization of Natural Killer Cells and Their Precursors as a Tool to Study Cancer Immunosurveillance

This chapter will describe the current methodologies to isolate and expand NK cells from Peripheral Blood (PB) or tissues for "in vitro" studies, including NK cell antitumor immune function. In addition, methods to induce NK cell maturation, differentiation, and expansion from CD34⁺ precursors will also be described. Finally, it will also be treated the topical issue of the characterization of new functionally and phenotypically defined NK cell subsets.

Hypoxia Modifies the Transcriptome of Human NK Cells, Modulates Their Immunoregulatory Profile, and Influences NK Cell Subset Migration

Hypoxia, which characterizes most tumor tissues, can alter the function of different immune cell types, favoring tumor escape mechanisms. In this study, we show that hypoxia profoundly acts on NK cells by influencing their transcriptome, affecting their immunoregulatory functions, and changing the chemotactic responses of different NK cell subsets. Exposure of human peripheral blood NK cells to hypoxia for 16 or 96 h caused significant changes in the expression of 729 or 1,100 genes, respectively. Gene Set Enrichment Analysis demonstrated that these changes followed a consensus hypoxia transcriptional profile. As assessed by Gene Ontology annotation, hypoxia-targeted genes were implicated in several biological processes: metabolism, cell cycle, differentiation, apoptosis, cell stress, and cytoskeleton organization. The hypoxic transcriptome also showed changes in genes with immunological relevance including those coding for proinflammatory cytokines, chemokines, and chemokine-receptors. Quantitative RT-PCR analysis confirmed the modulation of several immune-related genes, prompting further immunophenotypic and functional studies. Multiplex ELISA demonstrated that hypoxia could variably reduce NK cell ability to release IFNγ, TNFα, GM-CSF, CCL3, and CCL5 following PMA+Ionomycin or IL15+IL18 stimulation, while it poorly affected the response to IL12+IL18. Cytofluorimetric analysis showed that hypoxia could influence NK chemokine receptor pattern by sustaining the expression of CCR7 and CXCR4. Remarkably, this effect occurred selectively (CCR7) or preferentially (CXCR4) on CD56^bright NK cells, which indeed showed higher chemotaxis to CCL19, CCL21, or CXCL12. Collectively, our data suggest that the hypoxic environment may profoundly influence the nature of the NK cell infiltrate and its effects on immune-mediated responses within tumor tissues.

NK-cell Editing Mediates Epithelial-to-Mesenchymal Transition via Phenotypic and Proteomic Changes in Melanoma Cell Lines

Tumor cell plasticity is a major obstacle for the cure of malignancies as it makes tumor cells highly adaptable to microenvironmental changes, enables their phenotype switching among different forms, and favors the generation of prometastatic tumor cell subsets. Phenotype switching toward more aggressive forms involves different functional, phenotypic, and morphologic changes, which are often related to the process known as epithelial-mesenchymal transition (EMT). In this study, we report natural killer (NK) cells may increase the malignancy of melanoma cells by inducing changes relevant to EMT and, more broadly, to phenotype switching from proliferative to invasive forms. In coculture, NK cells induced effects on tumor cells similar to those induced by EMT-promoting cytokines, including upregulation of stemness and EMT markers, morphologic transition, inhibition of proliferation, and increased capacity for Matrigel invasion. Most changes were dependent on the engagement of NKp30 or NKG2D and the release of cytokines including IFNγ and TNFα. Moreover, EMT induction also favored escape from NK-cell attack. Melanoma cells undergoing EMT either increased NK-protective HLA-I expression on their surface or downregulated several tumor-recognizing activating receptors on NK cells. Mass spectrometry-based proteomic analysis revealed in two different melanoma cell lines a partial overlap between proteomic profiles induced by NK cells or by EMT cytokines, indicating that various processes or pathways related to tumor progression are induced by exposure to NK cells.Significance: NK cells can induce prometastatic properties on melanoma cells that escape from killing, providing important clues to improve the efficacy of NK cells in innovative antitumor therapies. Cancer Res; 78(14); 3913-25. ©2018 AACR.

Redox control of cancer cell destruction

Redox regulation has been proposed to control various aspects of carcinogenesis, cancer cell growth, metabolism, migration, invasion, metastasis and cancer vascularization. As cancer has many faces, the role of redox control in different cancers and in the numerous cancer-related processes often point in different directions. In this review, we focus on the redox control mechanisms of tumor cell destruction. The review covers the tumor-intrinsic role of oxidants derived from the reduction of oxygen and nitrogen in the control of tumor cell proliferation as well as the roles of oxidants and antioxidant systems in cancer cell death caused by traditional anticancer weapons (chemotherapeutic agents, radiotherapy, photodynamic therapy). Emphasis is also put on the role of oxidants and redox status in the outcome following interactions between cancer cells, cytotoxic lymphocytes and tumor infiltrating macrophages.

Interplay between Natural Killer Cells and Anti-HER2 Antibodies: Perspectives for Breast Cancer Immunotherapy

Overexpression of the human epidermal growth factor receptor 2 (HER2) defines a subgroup of breast tumors with aggressive behavior. The addition of HER2-targeted antibodies (i.e., trastuzumab, pertuzumab) to chemotherapy significantly improves relapse-free and overall survival in patients with early-stage and advanced disease. Nonetheless, considerable proportions of patients develop resistance to treatment, highlighting the need for additional and co-adjuvant therapeutic strategies. HER2-specific antibodies can trigger natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity and indirectly enhance the development of tumor-specific T cell immunity; both mechanisms contributing to their antitumor efficacy in preclinical models. Antibody-dependent NK cell activation results in the release of cytotoxic granules as well as the secretion of pro-inflammatory cytokines (i.e., IFNγ and TNFα) and chemokines. Hence, NK cell tumor suppressive functions include direct cytolytic killing of tumor cells as well as the regulation of subsequent antitumor adaptive immunity. Albeit tumors with gene expression signatures associated to the presence of cytotoxic lymphocyte infiltrates benefit from trastuzumab-based treatment, NK cell-related biomarkers of response/resistance to HER2-specific therapeutic antibodies in breast cancer patients remain elusive. Several variables, including (i) the configuration of the patient NK cell repertoire; (ii) tumor molecular features (i.e., estrogen receptor expression); (iii) concomitant therapeutic regimens (i.e., chemotherapeutic agents, tyrosine kinase inhibitors); and (iv) evasion mechanisms developed by progressive breast tumors, have been shown to quantitatively and qualitatively influence antibody-triggered NK cell responses. In this review, we discuss possible interventions for restoring/enhancing the therapeutic activity of HER2 therapeutic antibodies by harnessing NK cell antitumor potential through combinatorial approaches, including immune checkpoint blocking/stimulatory antibodies, cytokines and toll-like receptor agonists.

Profile of differentially expressed Toll-like receptor signaling genes in the natural killer cells of patients with Sézary syndrome

Sézary syndrome (SS), an aggressive and leukemic form of cutaneous T-cell lymphoma, usually results in shortened survival. Improving innate immunity in SS by targeting natural killer (NK) cells with Toll-like receptor (TLR) agonists could be an interesting modulatory strategy. We evaluated the NK cell populations in SS patients assessing activating and inhibitory receptors expression and profiled the differential expression of TLR signaling pathway genes in unstimulated NK cells and after TLR7/8 stimulation. We observed preserved CD56^bright NK cells and a low percentage of CD56^dim NK cells in the peripheral blood of SS patients compared to those in the healthy control group. Both NK cell populations showed down-modulation of NKG2C and NKG2D expression, which was associated with high serum levels of the soluble form of NKG2D ligands. In contrast, an expansion of “memory” CD57+ NKG2C+ NK cells and high cytomegalovirus antibody titers were detected in SS patients. Profiling of the TLR signaling genes in NK cells from SS patients showed an abundance of differentially expressed genes (DEGs) in NK cells in the unstimulated condition, with mostly up-regulation of NFκB/JNK p38 pathway genes, but there was down-regulation of type I (IFN-α/β) and II (IFN-γ) interferon and IL-12A. After activation of NK cells with TLR7/8 agonist, the down-regulated genes correlated with the IFN response, and IL-12 became up-regulated, together with other antitumor factors. NK cell activation with a dual agonist for TLR7 and TLR8 is able to induce the expression of IFN-γ and type I IFN, which can improve immunity in SS patients.

Natural Killer Cell Response to Chemotherapy-Stressed Cancer Cells: Role in Tumor Immunosurveillance

Natural killer (NK) cells are innate cytotoxic lymphoid cells that actively prevent neoplastic development, growth, and metastatic dissemination in a process called cancer immunosurveillance. An equilibrium between immune control and tumor growth is maintained as long as cancer cells evade immunosurveillance. Therapies designed to kill cancer cells and to simultaneously sustain host antitumor immunity are an appealing strategy to control tumor growth. Several chemotherapeutic agents, depending on which drugs and doses are used, give rise to DNA damage and cancer cell death by means of apoptosis, immunogenic cell death, or other forms of non-apoptotic death (i.e., mitotic catastrophe, senescence, and autophagy). However, it is becoming increasingly clear that they can trigger additional stress responses. Indeed, relevant immunostimulating effects of different therapeutic programs include also the activation of pathways able to promote their recognition by immune effector cells. Among stress-inducible immunostimulating proteins, changes in the expression levels of NK cell-activating and inhibitory ligands, as well as of death receptors on tumor cells, play a critical role in their detection and elimination by innate immune effectors, including NK cells. Here, we will review recent advances in chemotherapy-mediated cellular stress pathways able to stimulate NK cell effector functions. In particular, we will address how these cytotoxic lymphocytes sense and respond to different types of drug-induced stresses contributing to anticancer activity.

HMGB1 induces lung fibroblast to myofibroblast differentiation through NF‑κB‑mediated TGF‑β1 release

The proinflammatory factor high-mobility group box protein 1 (HMGB1) has been implicated in the pathogenesis of lung fibrosis; however, the role of HMGB1 in lung fibrosis remains unclear. It has previously been reported that nuclear factor (NF)-κB and transforming growth factor (TGF)-β1 may be involved in lung fibrosis. Therefore, the present study aimed to examine the potential molecular mechanisms that underlie HMGB1-induced lung fibrosis via the regulation of NF-κB and TGF-β1. The results demonstrated that HMGB1 stimulation increased the activation of NF-κB and the release of TGF-β1, as well as the expression of α-smooth muscle actin (α-SMA) and collagen I in human lung fibroblasts in vitro. In addition, inhibition of NF-κB activation blocked HMGB1-induced TGF-β1 release, as well as α-SMA and collagen I expression in lung fibroblasts. Preventing the release of TGF-β1 inhibited HMGB1-induced α-SMA and collagen I expression; however, it had no effect on NF-κB activation. Collectively, these findings indicate that HMGB1 induces fibroblast to myofibroblast differentiation of lung fibroblasts via NF-κB-mediated TGF-β1 release.

Autophagy-dependent danger signaling and adaptive immunity to poorly immunogenic tumors

Recent data suggest that autophagy does not influence spontaneous and therapy-elicited tumor infiltration by immune cells in murine models of melanoma and breast carcinoma. These findings, which have been obtained in the absence of a therapeutically relevant anticancer immune response, indicate that the intrinsically low immunogenicity of some tumors cannot be compensated for by increased danger signaling.

Monocyte/Macrophage: NK Cell Cooperation-Old Tools for New Functions

Monocyte/macrophage and natural killer (NK) cells are partners from a phylogenetic standpoint of innate immune system development and its evolutionary progressive interaction with adaptive immunity. The equally conservative ways of development and differentiation of both invertebrate hemocytes and vertebrate macrophages are reviewed. Evolutionary conserved molecules occurring in macrophage receptors and effectors have been inherited by vertebrates after their common ancestor with invertebrates. Cytolytic functions of mammalian NK cells, which are rooted in immune cells of invertebrates, although certain NK cell receptors (NKRs) are mammalian new events, are characterized. Broad heterogeneity of macrophage and NK cell phenotypes that depends on surrounding microenvironment conditions and expression profiles of specific receptors and activation mechanisms of both cell types are discussed. The particular tissue specificity of macrophages and NK cells, as well as their plasticity and mechanisms of their polarization to different functional subtypes have been underlined. The chapter summarized studies revealing the specific molecular mechanisms and regulation of NK cells and macrophages that enable their highly specific cross-cooperation. Attention is given to the evolving role of human monocyte/macrophage and NK cell interaction in pathogenesis of hypersensitivity reaction-based disorders, including autoimmunity, as well as in cancer surveillance and progression.

Receptor for Advanced Glycation End Products (RAGE) in Type 1 Diabetes Pathogenesis

The receptor for advanced glycation end products (RAGE) is a novel protein increasingly studied in the pathogenesis of type 1 diabetes (T1D). RAGE is expressed by several immune cell types, including T cells, antigen-presenting cells, endothelial cells, and the endocrine cells of the pancreatic islets. RAGE binds various ligands including advanced glycation end products (AGEs), high-mobility group box protein 1 (HMGB1), S100 proteins, β-amyloid, β-sheet fibrils, and lipopolysaccharide. AGEs are a particularly interesting ligand because their exogenous introduction into the body can be accelerated by the consumption of AGE-rich processed foods. This review will detail RAGE isoforms and its ligands and discuss how RAGE binding on the aforementioned cells could be linked to T1D pathogenesis.

NK Cells, Tumor Cell Transition, and Tumor Progression in Solid Malignancies: New Hints for NK-Based Immunotherapy?

Several evidences suggest that NK cells can patrol the body and eliminate tumors in their initial phases but may hardly control established solid tumors. Multiple factors, including the transition of tumor cells towards a proinvasive/prometastatic phenotype, the immunosuppressive effect of the tumor microenvironment, and the tumor structure complexity, may account for limited NK cell efficacy. Several putative mechanisms of NK cell suppression have been defined in these last years; conversely, the cross talk between NK cells and tumor cells undergoing different transitional phases remains poorly explored. Nevertheless, recent in vitro studies and immunohistochemical analyses on tumor biopsies suggest that NK cells could not only kill tumor cells but also influence their evolution. Indeed, NK cells may induce tumor cells to change the expression of HLA-I, PD-L1, or NKG2D-L and modulate their susceptibility to the immune response. Moreover, NK cells may be preferentially located in the borders of tumor masses, where, indeed, tumor cells can undergo Epithelial-to-Mesenchymal Transition (EMT) acquiring prometastatic phenotype. Finally, the recently highlighted role of HMGB1 both in EMT and in amplifying the recruitment of NK cells provides further hints on a possible effect of NK cells on tumor progression and fosters new studies on this issue.

HMGB1 Osteo-Modulatory Action on Osteosarcoma SaOS-2 Cell Line: An Integrated Study From Biochemical and -Omics Approaches

High mobility group box protein-1 (HMGB1) is released from cells under various pathological conditions and it plays a pivotal role as an alarmin signaling tissue damage. Little is known about the impact of HMGB1 in bone repair and remodeling. To this aim, we focused on HMGB1-induced effects on the in vitro osteoblast model SaOS-2. Cell proliferation was stimulated with a maximum at concentration of 2.5 nM, and such a dose also stimulated cell migration and scratch wound healing. We then characterized the modulatory effect of HMGB1 on bone biology, by using osteogenesis/mineralization assays, a PCR array, and the analysis of a series of osteogenic markers. We performed also a proteomic screening using SWATH-MS on SaOS-2 cell exposed to HMGB1 and we provide evidence for proteins modulated in HMGB1 exposed cells. Taken together, our data demonstrate that SaOS-2 cell proliferation, migration, and osteogenic differentiation were increased by HMGB1. We, therefore, propose that HMGB1 could be a potent bone-remodeling signal but the physiological meaning of this property remains to be more ascertained. J. Cell. Biochem. 117: 2559-2569, 2016. © 2016 Wiley Periodicals, Inc.