Regulation of Natural Killer Cell Function by STAT3

IL-10+ NK and TGF-β+ NK cells play negative regulatory roles in HIV infection

Background

Natural killer (NK) cells play cytotoxic roles by targeting tumor cells or virus infected cells, they also play regulatory roles by secreting cytokines and chemokines. Transforming growth factor (TGF)-β and interleukin (IL)-10 are important immunosuppressive cytokines potentially related to the immune dysregulation that occurs in the infection of human immunodeficiency virus (HIV). NK cells are an important source of TGF-β and a main early producer of IL-10 in response to viral infection. Here, we evaluated the percentages of IL-10⁺ and TGF-β⁺ NK cells in HIV-infected patients relative to healthy controls (HCs).

Methods

Study participants (n = 63) included 31 antiretroviral treatment (ART)-naïve HIV-infected patients, 17 ART-treated HIV-infected patients, and 15 HIV-negative HCs. Expression of IL-10 or TGF-β in NK cells was examined by flow cytometry, and the influences of recombinant IL-10 (rIL-10) or recombinant TGF-β (rTGF-β) on NK cell function were investigated in vitro.

Results

Compared with HCs, ART-naïve HIV-infected patients had increased percentages of IL-10⁺ (2.0% vs. 0.4%, p = 0.015) and TGF-β⁺ (4.5% vs. 2.1%, p = 0.022) NK cells, and ART-treated patients also had a higher percentage of IL-10⁺ NK cells (2.5% vs. 0.4%, p = 0.002). The percentages of IL-10⁺ and TGF-β⁺ NK cells were positively correlated (r = 0.388; p = 0.010). The results of in vitro experiments demonstrated that rIL-10 and rTGF-β inhibited NK cell CD107a expression (p = 0.037 and p = 0.024, respectively), IFN-γ secretion (p = 0.006, p = 0.016, respectively), and granzyme B release after stimulation (p = 0.014, p = 0.040, respectively).

Conclusions

Our data suggest that the percentages of IL-10⁺ or TGF-β⁺ NK cells are increased in HIV-infected patients, and that rIL-10 and/or rTGF-β can inhibit NK cell functions in vitro, providing a potential therapeutic target for strategies aimed at combating HIV infection.

CCL3 augments tumor rejection and enhances CD8+ T cell infiltration through NK and CD103+ dendritic cell recruitment via IFNγ

Inflammatory chemokines are critical contributors in attracting relevant immune cells to the tumor microenvironment and driving cellular interactions and molecular signaling cascades that dictate the ultimate outcome of host anti-tumor immune response. Therefore, rational application of chemokines in a spatial-temporal dependent manner may constitute an attractive adjuvant in immunotherapeutic approaches against cancer. Existing data suggest that the macrophage inflammatory protein (MIP)-1 family and related proteins, consisting of CCL3 (MIP-1α), CCL4 (MIP-1β), and CCL5 (RANTES), can be major determinant of immune cellular infiltration in certain tumors through their direct recruitment of antigen presenting cells, including dendritic cells (DCs) to the tumor site. In this study, we examined how CCL3 in a murine colon tumor microenvironment, CT26, enhances antitumor immunity. We identified natural killer (NK) cells as a major lymphocyte subtype that is preferentially recruited to the CCL3-rich tumor site. NK cells contribute to the overall IFNγ content, CD103+ DC accumulation, and augment the production of chemokines CXCL9 and CXCL10 for enhanced T cell recruitment. We further demonstrate that both soluble CCL3 and CCL3-secreting irradiated tumor vaccine can effectively halt the progression of established tumors in a spatial-dependent manner. Our finding implies an important contribution of NK in the CCL3 - CD103+ DC - CXCL9/10 signaling axis in determining tumor immune landscape within the tumor microenvironment.

Activation of TLR4/STAT3 signaling in VTA contributes to the acquisition and maintenance of morphine-induced conditioned place preference

Morphine, commonly used to relieve the acute or chronic pain, has a high potential for addiction and exerts rewarding effects via a critical role for mesolimbic dopamine system. Studies suggest that addiction-related behavior is highly associated with inflammatory immune response, but the mechanisms are poorly understood. The present study showed that intra-VTA microinjection of TLR4 antagonist LPS-RS prevented the acquisition and maintenance, but not the expression, of morphine-induced CPP in rats. In addition, chronic morphine treatment significantly activated STAT3 on day 6 and 11 in VTA, and bilateral microinjection of STAT3 inhibitor S3I-201 into the VTA suppressed the acquisition and maintenance of morphine-induced CPP in rats. Furthermore, local knockout of STAT3 by injection of the AAV-Cre-GFP into the VTA area of STAT3^flox/flox mice also significantly impaired the acquisition of morphine CPP. Importantly, the TLR4 expression is colocalized with p-STAT3-positive cell in VTA, and repeated injection of LPS-RS significantly attenuated the STAT3 activation in VTA induced by chronic morphine treatment. Collectively, these data suggest that TLR4/STAT3 signaling pathway in VTA might play a critical role in the acquisition and maintenance of morphine CPP, and provides new evidence that TLR4/STAT3 signaling pathway might be a potential target for treatment of morphine addiction.

Non-coding RNA 886 promotes renal cell carcinoma growth and metastasis through the Janus kinase 2/signal transducer and activator of transcription 3 signaling pathway

Non-coding RNA 886 (nc886) has been suggested to serve tumor-suppressing roles in several cancer cells. However, the expression pattern of nc886 and its function in renal cell carcinoma (RCC) has not been reported until now. The present study aimed to examine the expression of nc886 in human RCC tissues and to investigate the role of nc886 in RCC cell proliferation, apoptosis and invasion in vitro. Furthermore, whether nc886 exerts its function on RCC via Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling was investigated. It was demonstrated that nc886 is overexpressed in human RCC tissues compared with normal tissues, as determined by reverse transcription-quantitative polymerase chain reaction analysis. The nc886 mimic and inhibitor were transfected into the A‑498 cells to overexpress or knock down nc886 expression. Cell proliferation, cell apoptosis rate and cell invasion ability were determined by MTT, flow cytometry and Transwell‑Matrigel invasion assays. The results demonstrated that nc886 overexpression promotes A‑498 cell proliferation and invasion, and inhibits cell apoptosis, while nc886 knockdown resulted in the opposite effects. Furthermore, nc886 could activate the JAK2/STAT3 signaling pathway in A‑498 cells. AG490, an inhibitor of JAK2, could attenuate the effects of nc886 on cell proliferation, apoptosis and invasion. In conclusion, to the best of our knowledge, the present study for the first time revealed the expression profile and the tumor‑promoting role of nc886 in RCC. nc886 affects RCC cell proliferation, apoptosis and invasion at least partially via the activation of JAK2/STAT3 signaling. This study may provide a useful therapeutic target for RCC.

Alterations of oncogenes expression in NK cells in patients with cancer

INTRODUCTION

C-kit/SCF signaling plays a key role in regulating NK cell homeostasis, maturation, proliferation, and cytotoxicity. C-kit-deficiency in NK cells results in significant reduction of their number, suggesting an imperative role for c-kit signaling in NK cell biology. We have recently showed that human NK cells express not only c-kit-receptor, but also both membrane-bound and soluble forms of c-kit ligand-Stem cell factor. The goal of this study was to characterize the c-kit/SCF autocrine loop in peripheral blood NK cells obtained from patients with cancer.

METHODS

Using Smart Flare and qRT-PCR, we have characterized expression of c-kit and two forms of SCF in patients' NK cells and correlated these results with the expression of c-myc and STAT3.

RESULTS

Our results demonstrated that the expression of proto-oncogenes c-myc and c-kit was significantly decreased in NK cells from all cancer patients. Expression of membrane-bound SCF in NK cells correlated with the presence of remote metastases.

CONCLUSIONS

We suggest that the abnormal signaling and expression of c-kit/SCF, c-myc, and STAT3 in NK cells is responsible for the defect in their cytolytic activity in cancer and these defects at the gene expression level may be the cause rather than the result of tumor progression.

Bitter Melon Enhances Natural Killer-Mediated Toxicity against Head and Neck Cancer Cells

Natural killer (NK) cells are one of the major components of innate immunity, with the ability to mediate antitumor activity. Understanding the role of NK-cell-mediated tumor killing in controlling of solid tumor growth is still in the developmental stage. We have shown recently that bitter melon extract (BME) modulates the regulatory T cell (Treg) population in head and neck squamous cell carcinoma (HNSCC). However, the role of BME in NK-cell modulation against HNSCC remains unknown. In this study, we investigated whether BME can enhance the NK-cell killing activity against HNSCC cells. Our results indicated that treatment of human NK-cell line (NK3.3) with BME enhances ability to kill HNSCC cells. BME increases granzyme B accumulation and translocation/accumulation of CD107a/LAMP1 in NK3.3 cells exposed to BME. Furthermore, an increase in cell surface expression of CD16 and NKp30 in BME-treated NK3.3 cells was observed when cocultured with HNSCC cells. Collectively, our results demonstrated for the first time that BME augments NK-cell-mediated HNSCC killing activity, implicating an immunomodulatory role of BME. Cancer Prev Res; 10(6); 337-44. ©2017 AACR.

Nifuroxazide prompts antitumor immune response of TCL-loaded DC in mice with orthotopically-implanted hepatocarcinoma

Hepatocellular carcinoma (HCC) is a highly aggressive malignancy with a poor prognosis and high mortality. At present, vaccination with tumor cell lysate (TCL) loaded dendritic cells (DC) has been shown to be an effective therapy against HCC. However, the ability of promoting the specific T cell immune response is rather weak, influencing the antitumor response. Thus, it is necessary to find a strategy to improve the antitumor effect of TCL-loaded DC. Activation of signal transducer and activator of transcription 3 (STAT3) significantly inhibits antitumor immune response and DC maturity. Nifuroxazide, an antidiarrheal agent, has been proved to directly inhibit STAT3 activation. Thus, we investigated whether nifuroxazide could improve the antitumor immune response in mice vaccinated with TCL-loaded DC. The study provides the theoretical and experimental basis for developing an effective adjuvant for DC vaccine to treat HCC. Our results showed that the administration of nifuroxazide and DC-loaded TCL could significantly improve the survival rate, inhibit the tumor growth, and prompt the antitumor immune responses in mice with orthotopically implanted hepatocarcinomas, thus, possibly providing a new combination strategy to treat HCC.

STATs in NK-Cells: The Good, the Bad, and the Ugly

Natural killer (NK)-cells are major players in the fight against viral infections and transformed cells, but there is increasing evidence attributing a disease-promoting role to NK-cells. Cytokines present in the tumor microenvironment shape NK-cell maturation, function, and effector responses. Many cytokines signal via the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway that is also frequently altered and constitutively active in a broad range of tumor cells. As a consequence, there are currently major efforts to develop therapeutic strategies to target this pathway. Therefore, it is of utmost importance to understand the role and contributions of JAK-STAT molecules in NK-cell biology-only this knowledge will allow us to predict effects of JAK-STAT inhibition for NK-cell functions and to successfully apply precision medicine. We will review the current knowledge on the role of JAK-STAT signaling for NK-cell functions and discuss conditions involved in the switch from NK-cell tumor surveillance to disease promotion.

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.