Pro- and antiinflammatory cytokine signaling: reciprocal antagonism regulates interferon-gamma production by human natural killer cells

SMAD4 promotes TGF-β-independent NK cell homeostasis and maturation and antitumor immunity

SMAD4 is the only common SMAD in TGF-β signaling that usually impedes immune cell activation in the tumor microenvironment. However, we demonstrated here that selective deletion of Smad4 in NK cells actually led to dramatically reduced tumor cell rejection and augmented tumor cell metastases, reduced murine CMV clearance, as well as impeded NK cell homeostasis and maturation. This was associated with a downregulation of granzyme B (Gzmb), Kit, and Prdm1 in Smad4-deficient NK cells. We further unveiled the mechanism by which SMAD4 promotes Gzmb expression. Gzmb was identified as a direct target of a transcriptional complex formed by SMAD4 and JUNB. A JUNB binding site distinct from that for SMAD4 in the proximal Gzmb promoter was required for transcriptional activation by the SMAD4-JUNB complex. In a Tgfbr2 and Smad4 NK cell-specific double-conditional KO model, SMAD4-mediated events were found to be independent of canonical TGF-β signaling. Our study identifies and mechanistically characterizes unusual functions and pathways for SMAD4 in governing innate immune responses to cancer and viral infection, as well as NK cell development.

Molecular Mechanisms Directing Migration and Retention of Natural Killer Cells in Human Tissues

A large body of data shows that Natural Killer (NK) cells are immune effectors exerting a potent cytolytic activity against tumors and virus infected cells. The discovery and characterization of several inhibitory and activating receptors unveiled most of the mechanisms allowing NK cells to spare healthy cells while selectively attacking abnormal tissues. Nevertheless, the mechanisms ruling NK cell subset recirculation among the different compartments of human body have only lately started to be investigated. This is particularly true for pathological settings such as tumors or infected tissues but also for para-physiological condition like pregnant human uterine mucosa. It is becoming evident that the microenvironment associated to a particular clinical condition can deeply influence the migratory capabilities of NK cells. In this review we describe the main mechanisms and stimuli known to regulate the expression of chemokine receptors and other molecules involved in NK cell homing to either normal or pathological/inflamed tissues, including tumors or organs such as lung and liver. We will also discuss the role played by the chemokine/chemokine receptor axes in the orchestration of physiological events such as NK cell differentiation, lymphoid organ retention/egress and recruitment to decidua during pregnancy.

Role of c-Myb in the regulation of natural killer cell activity

The regulation of natural killer (NK) cell activity is an important research goal for the development of immunotherapies. In this study, we identified transcription factors affecting NK cell activity. In particular, we screened transcription factors affected by interleukin-2 (IL-2) and transforming growth factor-beta (TGF-β) by protein/DNA arrays using primary NK cells. We found that celastrol, a c-Myb inhibitor, inhibited NK-92 cells more strongly than any other inhibitors of transcription factor candidates. In addition, c-Myb and c-Myb-related signaling molecules, e.g., Nemo-like kinase (NLK) and c-Myc, were regulated by the activation status of NK cells, suggesting that c-Myb is a key regulator of NK cell activity. We also found that celastrol inhibits NK-92-cell-mediated cytotoxicity via the downregulation of NKG2D and granzyme B. Knockdown studies also showed that c-Myb is important for NK cell activation. In particular, the knockdown of c-Myb did not significantly affect NK cell proliferation and survival but decreased the secretion of IFN-γ and the cytotoxicity of NK cells. Our data demonstrate that c-Myb plays a critical role in the activation of NK cells and therefore is a therapeutic target for cancer and viral diseases.

A Synthetic Disaccharide Derivative of Diphyllin, TAARD, Activates Human Natural Killer Cells to Secrete Interferon-Gamma via Toll-Like Receptor-Mediated NF-κB and STAT3 Signaling Pathways

Natural products and their derivatives have long been used as pharmacological agents in the fight against cancer. Human natural killer (NK) cells are critical in our immune system in that they are capable of destroying tumor cells directly. However, there are few reports that elucidate the role of natural products in activating NK cells. In this study, we discovered that a synthetic disaccharide derivative of diphyllin, 4-O-{[2′′,3′′,4′′-tri-O-acetyl-α-D-arabinopyranosyl-(1′′→4′)]-2′,3′-di-O-acetyl-α-L-rhamnopyranosyl}diphyllin (TAARD), can alone stimulate interferon (IFN)-γ secretion in primary human NK cells and the NKL cell line. Additionally, it had an additive effect with IL-12 or IL-15 on IFN-γ production, but little adverse effects on NK cells. Mechanistically, TAARD induced the phosphorylation of NF-κB and STAT3, resulting in their binding on the IFNG promoter, which was dependent on TLR1 and TLR3 signaling, respectively. STAT3 and NF-κB knockdown with lentivirus shRNA as well as the NF-κB-specific inhibitor, N-tosyl-l-phenylalaninechloromethyl ketone, significantly suppressed TAARD-induced IFN-γ generation in primary NK cells. Blockade of TLR1 and TLR3 with neutralizing antibodies considerably decreased TAARD-induced activation of NF-κB and STAT3, respectively, as well as IFN-γ generation in NK cells. Collectively, our data suggest that TAARD can induce NK cell IFN-γ production through TLR1-NF-κB and TLR3-STAT3 signaling pathways, rendering its potential use as an agent for cancer prevention or treatment.

Combination of Asiatic Acid and Naringenin Modulates NK Cell Anti-cancer Immunity by Rebalancing Smad3/Smad7 Signaling

Transforming growth factor β1 (TGF-β1) plays a promoting role in tumor growth via a mechanism associated with hyperactive Smad3 and suppressed Smad7 signaling in the tumor microenvironment. We report that retrieving the balance between Smad3 and Smad7 signaling with asiatic acid (AA, a Smad7 inducer) and naringenin (NG, a Smad3 inhibitor) effectively inhibited tumor progression in mouse models of invasive melanoma (B16F10) and lung carcinoma (LLC) by promoting natural killer (NK) cell development and cytotoxicity against cancer. Mechanistically, we found that Smad3 physically bound Id2 and IRF2 to suppress NK cell production and NK cell-mediated cytotoxicity against cancer. Treatment with AA and NG greatly inhibited Smad3 translation and phosphorylation while it restored Smad7 expression, and, therefore, it largely promoted NK cell differentiation, maturation, and cytotoxicity against cancer via Id2/IRF2-associated mechanisms. In contrast, silencing Id2 or IRF2 blunted the protective effects of AA and NG on NK cell-dependent anti-cancer activities. Thus, treatment with AA and NG produced an additive effect on inactivating TGF-β1/Smad3 signaling, and, therefore, it suppressed melanoma and lung carcinoma growth by promoting NK cell immunity against cancer via a mechanism associated with Id2 and IRF2.

Enhanced Cancer Immunotherapy with Smad3-Silenced NK-92 Cells

Natural killer (NK) cells, early effectors in anticancer immunity, are paralyzed by TGFβ1, an immunosuppressive cytokine produced by cancer cells. Development and activity of NK cells are largely inhibited in the Smad3-dependent tumor microenvironment. Here, we used genetic engineering to generate a stable SMAD3-silencing human NK cell line, NK-92-S3KD, whose cancer-killing activity and cytokine production were significantly enhanced under TGFβ1-rich condition compared with the parental cell line. Interestingly, we identified that the IFNG gene is a direct E4BP4 target gene. Thus, silencing of SMAD3 allows upregulation of E4BP4 that subsequently promoting interferon-γ (IFNγ) production in the NK-92-S3KD cells. More importantly, NK-92-S3KD immunotherapy increases the production of not only IFNγ, but also granzyme B and perforin in tumors; therefore, inhibiting cancer progression in two xenograft mouse models with human hepatoma (HepG2) and melanoma (A375). Thus, the NK-92-S3KD cell line may be useful for the clinical immunotherapy of cancer. Cancer Immunol Res; 6(8); 965-77. ©2018 AACR.

TGF-β in T Cell Biology: Implications for Cancer Immunotherapy

Transforming Growth Factor beta (TGF-β) is a pleiotropic cytokine produced in large amounts within cancer microenvironments that will ultimately promote neoplastic progression, notably by suppressing the host’s T-cell immunosurveillance. This effect is mostly due to the well-known inhibitory effect of TGF-β on T cell proliferation, activation, and effector functions. Moreover, TGF-β subverts T cell immunity by favoring regulatory T-cell differentiation, further reinforcing immunosuppression within tumor microenvironments. These findings stimulated the development of many strategies to block TGF-β or its signaling pathways, either as monotherapy or in combination with other therapies, to restore anti-cancer immunity. Paradoxically, recent studies provided evidence that TGF-β can also promote differentiation of certain inflammatory populations of T cells, such as Th17, Th9, and resident-memory T cells (Trm), which have been associated with improved tumor control in several models. Here, we review current advances in our understanding of the many roles of TGF-β in T cell biology in the context of tumor immunity and discuss the possibility to manipulate TGF-β signaling to improve cancer immunotherapy.

TGF-β in T Cell Biology: Implications for Cancer Immunotherapy

Transforming Growth Factor beta (TGF-β) is a pleiotropic cytokine produced in large amounts within cancer microenvironments that will ultimately promote neoplastic progression, notably by suppressing the host’s T-cell immunosurveillance. This effect is mostly due to the well-known inhibitory effect of TGF-β on T cell proliferation, activation, and effector functions. Moreover, TGF-β subverts T cell immunity by favoring regulatory T-cell differentiation, further reinforcing immunosuppression within tumor microenvironments. These findings stimulated the development of many strategies to block TGF-β or its signaling pathways, either as monotherapy or in combination with other therapies, to restore anti-cancer immunity. Paradoxically, recent studies provided evidence that TGF-β can also promote differentiation of certain inflammatory populations of T cells, such as Th17, Th9, and resident-memory T cells (Trm), which have been associated with improved tumor control in several models. Here, we review current advances in our understanding of the many roles of TGF-β in T cell biology in the context of tumor immunity and discuss the possibility to manipulate TGF-β signaling to improve cancer immunotherapy.

Interferon-Gamma at the Crossroads of Tumor Immune Surveillance or Evasion

Interferon-gamma (IFN-γ) is a pleiotropic molecule with associated antiproliferative, pro-apoptotic and antitumor mechanisms. This effector cytokine, often considered as a major effector of immunity, has been used in the treatment of several diseases, despite its adverse effects. Although broad evidence implicating IFN-γ in tumor immune surveillance, IFN-γ-based therapies undergoing clinical trials have been of limited success. In fact, recent reports suggested that it may also play a protumorigenic role, namely, through IFN-γ signaling insensitivity, downregulation of major histocompatibility complexes, and upregulation of indoleamine 2,3-dioxygenase and of checkpoint inhibitors, as programmed cell-death ligand 1. However, the IFN-γ-mediated responses are still positively associated with patient's survival in several cancers. Consequently, major research efforts are required to understand the immune contexture in which IFN-γ induces its intricate and highly regulated effects in the tumor microenvironment. This review discusses the current knowledge on the pro- and antitumorigenic effects of IFN-γ as part of the complex immune response to cancer, highlighting the relevance to identify IFN-γ responsive patients for the improvement of therapies that exploit associated signaling pathways.

Implication of Interleukin-12/15/18 and Ruxolitinib in the Phenotype, Proliferation, and Polyfunctionality of Human Cytokine-Preactivated Natural Killer Cells

A brief in vitro stimulation of natural killer (NK) cells with interleukin (IL)-12, IL-15, and IL-18 endow them a memory-like behavior, characterized by higher effector responses when they are restimulated after a resting period of time. These preactivated NK cells, also known as cytokine-induced memory-like (CIML) NK cells, have several properties that make them a promising tool in cancer immunotherapy. In the present study, we have described the effect that different combinations of IL-12, IL-15, and IL-18 have on the generation of human CIML NK cells. Our data points to a major contribution of IL-15 to CIML NK cell-mediated cytotoxicity against target cells. However, the synergistic effect of the three cytokines grant them the best polyfunctional profile, that is, cells that simultaneously degranulate (CD107a) and produce multiple cytokines and chemokines such as interferon γ, tumor necrosis factor α, and C-C motif chemokine ligand 3. We have also analyzed the involvement of each cytokine and their combinations in the expression of homing receptors CXCR4 and CD62L, as well as the expression of CD25 and IL-2-induced proliferation. Furthermore, we have tested the effects of the Jak1/2 inhibitor ruxolitinib in the generation of CIML NK cells. We found that ruxolitinib-treated CIML NK cells expressed lower levels of CD25 than non-treated CIML NK cells, but exhibited similar proliferation in response to IL-2. In addition, we have also found that ruxolitinib-treated NK cells displayed reduced effector functions after the preactivation, which can be recovered after a 4 days expansion phase in the presence of low doses of IL-2. Altogether, our results describe the impact that each cytokine and the Jak1/2 pathway have in the phenotype, IL-2-induced proliferation, and effector functions of human CIML NK cells.

Crystal Structures and Human Leukemia Cell Apoptosis Inducible Activities of Parthenolide Analogues Isolated from Piptocoma rufescens

The molecular structures of three parthenolide analogues, (-)-goyazensolide (1), (-)-15-deoxygoyazensolide (2), and (-)-ereglomerulide (3), isolated from the leaves of Piptocoma rufescens in a previous study were determined by X-ray analysis, and the absolute configuration of (-)-goyazensolide (1) was confirmed crystallographically using Cu Kα radiation at low temperature. Compounds 1-3, (+)-rufesolide A (4), and commercial parthenolide were found to be growth inhibitory toward MOLM-13 and EOL-1 human acute myeloid leukemia cells using PKC412 (midostaurin) as the positive control, with 1-3 being more active than parthenolide. Also, compounds 1-4 exhibited synergistic effects when tested with PKC412, but parthenolide did not show this type of activity. At a concentration lower than 2.0 μM, both 1 and 2 induced approximately 50% of the cells to become apoptotic at a late stage of the cell cycle, but no similar apoptotic effects were observed for 3, 4, or parthenolide. Leukemia cell apoptosis was induced by these compounds through the activation of caspase-3 and the inhibition of NF-κB, as indicated by immunoblotting analysis, and compounds 1 and 2 seem to be promising leads for development as potential antileukemic agents.

The natural product chitosan enhances the anti-tumor activity of natural killer cells by activating dendritic cells

Natural products comprise an important class of biologically active molecules. Many of these compounds derived from natural sources exhibit specific physiologic or biochemical effects. An example of a natural product is chitosan, which is enriched in the shells of certain seafood that are frequently consumed worldwide. Like other natural products, chitosan has the potential for applications in clinical medicine and perhaps in cancer therapy. Toward this end, the immunomodulatory or anti-cancer properties of chitosan have yet to be reported. In this study, we discovered that chitosan enhanced the anti-tumor activity of natural killer (NK) cells by activating dendritic cells (DCs). In the presence of DCs, chitosan augmented IFN-γ production by human NK cells. Mechanistically, chitosan activated DCs to express pro-inflammatory cytokines such as interleukin (IL)-12 and IL-15, which in turn activated the STAT4 and NF-κB signaling pathways, respectively, in NK cells. Moreover, chitosan promoted NK cell survival, and also enhanced NK cell cytotoxicity against leukemia cells. Finally, a related in vivo study demonstrated that chitosan activated NK cells against B16F10 tumor cells in an immunocompetent syngeneic murine melanoma model. This effect was accompanied by in vivo upregulation of IL-12 and IL-15 in DCs, as well as increased IFN-γ production and cytolytic degranulation in NK cells. Collectively, our results demonstrate that chitosan activates DCs leading to enhanced capacity for immune surveillance by NK cells. We believe that our study has future clinical applications for chitosan in the prevention or treatment of cancer and infectious diseases.

Regulation of Human Natural Killer Cell IFN-γ Production by MicroRNA-146a via Targeting the NF-κB Signaling Pathway

Natural killer (NK) cells are one group of innate lymphocytes that are important for host defense against malignancy and viruses. MicroRNAs (miRNAs) play a critical role in regulating responses of immune cells including NK cells. Accumulating evidence suggests that miR-146a is involved in the regulation of immune responses. However, the mechanism by which miR-146a regulates NK cell function is largely unknown. In the current study, we found that miR-146a intrinsically regulated NK cell function. Forced overexpression of miR-146a decreased IFN-γ production, whereas downregulation of miR-146a by anti-miR-146a significantly enhanced IFN-γ production in the human NK-92 cell line and primary human NK cells upon stimulation with IL-12 or co-stimulation with IL-12 and IL-18. Mechanistically, miR-146a regulated IFN-γ production via NF-κB, as evidenced in NK-92 cells, by downregulation of NF-κB p65 phosphorylation when miR-146a was overexpressed but upregulation of NF-κB p65 phosphorylation when anti-miR-146a was overexpressed. miR-146a directly targeted IRAK1 and TRAF6, the upstream signaling components of the NF-κB signaling pathway. This direct targeting mechanism confirmed the above gain- and loss-of-function approaches. However, the potent IFN-γ-producing subset, CD56^bright NK cells, expressed higher levels of miR-146a than the lesser IFN-γ-producing subset, CD56^dim NK cells. We also observed that co-stimulation of IL-12 and IL-18 significantly increased miR-146a expression in bulk NK cells and in the CD56^bright subset in a time-dependent manner, correlating with augmented IFN-γ production. These data suggest that miR-146a plays a negative role in IFN-γ production by human NK cells and this miRNA may be critical in preventing NK cells from being super activated and overproducing IFN-γ.

TGF-β1 promotes colorectal cancer immune escape by elevating B7-H3 and B7-H4 via the miR-155/miR-143 axis

Transforming growth factor-beta 1 (TGF-β1) suppresses T cell function, promoting tumor immune escape. Yet, whether the depression of TGF-β1 on T cell function is mediated by co-inhibitory molecules B7-H3 and B7-H4 remains largely unclear. Here, we demonstrated that TGF-β1 elevated the expression of miR-155 in colorectal cancer cells through SMAD3 and SMAD4. The upregulated miR-155 attenuated miR-143 by inhibiting its direct target, the transcription factor CEBPB. Consequently, the direct target genes of miR-143, B7-H3 and B7-H4, were augmented in the cytoplasm and membrane of tumor cells. Over-expression of B7-H3 and B7-H4 in HCT-116 cells induced T cells to secrete TGF-β1 and the immunosuppressive cytokines IL-2, IL-6, and IL-17. Restoration of miR-143 inhibited the growth of HCT-116 xenograft tumors in mice, and also repressed the expression of B7-H3 and B7-H4 in the tumors. Thus, this study reveals the mechanism by which TGF-β1 leads to T cell-mediated tumor evasion through an increase in B7-H3 and B7-H4 expression.

An IL-15 superagonist/IL-15Rα fusion complex protects and rescues NK cell-cytotoxic function from TGF-β1-mediated immunosuppression

Natural killer (NK) cells are innate cytotoxic lymphocytes that play a fundamental role in the immunosurveillance of cancers. NK cells of cancer patients exhibit impaired function mediated by immunosuppressive factors released from the tumor microenvironment (TME), such as transforming growth factor (TGF)-β1. An interleukin (IL)-15 superagonist/IL-15 receptor α fusion complex (IL-15SA/IL-15RA; ALT-803) activates the IL-15 receptor on CD8 T cells and NK cells, and has shown significant anti-tumor activity in several in vivo studies. This in vitro study investigated the efficacy of IL-15SA/IL-15RA on TGF-β1-induced suppression of NK cell-cytotoxic function. IL-15SA/IL-15RA inhibited TGF-β1 from decreasing NK cell lysis of four of four tumor cell lines (H460, LNCap, MCF7, MDA-MB-231). IL-15SA/IL-15RA rescued healthy donor and cancer patient NK cell-cytotoxicity, which had previously been suppressed by culture with TGF-β1. TGF-β1 downregulated expression of NK cell-activating markers and cytotoxic granules, such as CD226, NKG2D, NKp30, granzyme B, and perforin. Smad2/3 signaling was responsible for this TGF-β1-induced downregulation of NK cell-activating markers and cytotoxic granules. IL-15SA/IL-15RA blocked Smad2/3-induced transcription, resulting in the rescue of NK cell-cytotoxic function from TGF-β1-induced suppression. These findings suggest that in addition to increasing NK cell function via promoting the IL-15 signaling pathway, IL-15SA/IL-15RA can function as an inhibitor of TGF-β1 signaling, providing a potential remedy for NK cell dysfunction in the immunosuppressive tumor microenvironment.

IL-12/IL-18-preactivated donor NK cells enhance GVL effects and mitigate GvHD after allogeneic hematopoietic stem cell transplantation

Adoptive transfer of donor NK cells has the potential of mediating graft-versus-leukemia (GVL) effect while suppressing acute graft-versus-host-disease (aGVHD) during allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, these beneficial effects are limited by the transient function of adoptively transferred NK cells. Previous studies demonstrate that cytokine-induced memory-like NK cells that are preactivated by IL-12, IL-15, and IL-18 have enhanced effector functions and long life span in vivo. Here, we investigated the effects of IL-12/18-preactivated and IL-12/15/18-preactivated donor NK cells on GVL and aGVHD in a murine model of allo-HSCT. We found that both IL-12/18- and IL-12/15/18-preactivated NK cells mediated stronger GVL effect than control NK cells mainly due to their elevated activation/cytotoxicity and sustained proliferative potential. Interestingly, we observed that although both IL-12/18- and IL-12/15/18-preactivated NK cells significantly inhibited severe aGVHD, only the IL-12/18-preactivated NK cells maintained the beneficial effect of donor NK cells on mild aGVHD. The IL-12/15/18-preactivated NK cell infusion accelerated aGVHD in the fully-mismatched mild aGVHD model. Our results demonstrated that IL-12/18-preactivated NK cells displayed sustained and enhanced GVL functions, and could mitigate aGVHD despite the severity of the disease. IL-12/18-preactivated donor NK cell infusion may be an effective and safe adoptive therapy after allo-HSCT.

Environmental stimuli shape microglial plasticity in glioma

In glioma, microglia and infiltrating macrophages are exposed to factors that force them to produce cytokines and chemokines, which contribute to tumor growth and to maintaining a pro-tumorigenic, immunosuppressed microenvironment. We demonstrate that housing glioma-bearing mice in enriched environment (EE) reverts the immunosuppressive phenotype of infiltrating myeloid cells, by modulating inflammatory gene expression. Under these conditions, the branching and patrolling activity of myeloid cells is increased, and their phagocytic activity is promoted. Modulation of gene expression depends on interferon-(IFN)-γ produced by natural killer (NK) cells. This modulation disappears in mice depleted of NK cells or lacking IFN-γ, and was mimicked by exogenous interleukin-15 (IL-15). Further, we describe a key role for brain-derived neurotrophic factor (BDNF) that is produced in the brain of mice housed in EE, in mediating the expression of IL-15 in CD11b⁺ cells. These data define novel mechanisms linking environmental cues to the acquisition of a pro-inflammatory, anti-tumor microenvironment in mouse brain.

IL-18 Drives ILC3 Proliferation and Promotes IL-22 Production via NF-κB

Group 3 innate lymphoid cells (ILC3s) are important regulators of the immune system, maintaining homeostasis in the presence of commensal bacteria, but activating immune defenses in response to microbial pathogens. ILC3s are a robust source of IL-22, a cytokine critical for stimulating the antimicrobial response. We sought to identify cytokines that can promote proliferation and induce or maintain IL-22 production by ILC3s and determine a molecular mechanism for this process. We identified IL-18 as a cytokine that cooperates with an ILC3 survival factor, IL-15, to induce proliferation of human ILC3s, as well as induce and maintain IL-22 production. To determine a mechanism of action, we examined the NF-κB pathway, which is activated by IL-18 signaling. We found that the NF-κB complex signaling component, p65, binds to the proximal region of the IL22 promoter and promotes transcriptional activity. Finally, we observed that CD11c+ dendritic cells expressing IL-18 are found in close proximity to ILC3s in human tonsils in situ. Therefore, we identify a new mechanism by which human ILC3s proliferate and produce IL-22, and identify NF-κB as a potential therapeutic target to be considered in pathologic states characterized by overproduction of IL-18 and/or IL-22.

Regulation of mTOR, Metabolic Fitness, and Effector Functions by Cytokines in Natural Killer Cells

The control of cellular metabolism is now recognized as key to regulate functional properties of immune effectors such as T or Natural Killer (NK) cells. During persistent infections or in the tumor microenvironment, multiple metabolic changes have been highlighted in T cells that contribute to their dysfunctional state or exhaustion. NK cells may also undergo major phenotypic and functional modifications when infiltrating tumors that could be linked to metabolic alterations. The mammalian target of rapamycin (mTOR) kinase is a central regulator of cellular metabolism. mTOR integrates various extrinsic growth or immune signals and modulates metabolic pathways to fulfill cellular bioenergetics needs. mTOR also regulates transcription and translation thereby adapting cellular pathways to the growth or activation signals that are received. Here, we review the role and regulation of mTOR in NK cells, with a special focus on cytokines that target mTOR such as IL-15 and TGF-β. We also discuss how NK cell metabolic activity could be enhanced or modulated to improve their effector anti-tumor functions in clinical settings.

Developmental and Functional Control of Natural Killer Cells by Cytokines

Natural killer (NK) cells are effective in combating infections and tumors and as such are tempting for adoptive transfer therapy. However, they are not homogeneous but can be divided into three main subsets, including cytotoxic, tolerant, and regulatory NK cells, with disparate phenotypes and functions in diverse tissues. The development and functions of such NK cells are controlled by various cytokines, such as fms-like tyrosine kinase 3 ligand (FL), kit ligand (KL), interleukin (IL)-3, IL-10, IL-12, IL-18, transforming growth factor-β, and common-γ chain family cytokines, which operate at different stages by regulating distinct signaling pathways. Nevertheless, the specific roles of each cytokine that regulates NK cell development or that shapes different NK cell functions remain unclear. In this review, we attempt to describe the characteristics of each cytokine and the existing protocols to expand NK cells using different combinations of cytokines and feeder cells. A comprehensive understanding of the role of cytokines in NK cell development and function will aid the generation of better efficacy for adoptive NK cell treatment.

Ash1l and lnc-Smad3 coordinate Smad3 locus accessibility to modulate iTreg polarization and T cell autoimmunity

Regulatory T (Treg) cells are important for the maintenance of immune homoeostasis and prevention of autoimmune diseases. Epigenetic modifications have been reported to modulate autoimmunity by altering Treg cell fate. Here we show that the H3K4 methyltransferase Ash1l facilitates TGF-β-induced Treg cell polarization in vitro and protects mice from T cell-mediated colitis in vivo. Ash1l upregulates Smad3 expression by directly targeting Smad3 promoter to increase local H3K4 trimethylation. Furthermore, we identify an lncRNA, namely lnc-Smad3, which interacts with the histone deacetylase HDAC1 and silences Smad3 transcription. After TGF-β stimulation, activated Smad3 suppresses lnc-Smad3 transcription, thereby recovering the Smad3 promoter accessibility to Ash1l. By revealing the opposite regulatory functions of Ash1l and lnc-Smad3 in Smad3 expression, our data provide insights for the epigenetic control of Treg cell fate to potentially aid in the development of therapeutic intervention for autoimmune diseases.

The transcriptional program activated by Smad2/Smad3 is critical for the induction and function of regulatory T cells. Here the authors show that the expression of Smad3 is modulated by the complementary functions of a methyltransferase Ash1l and an lncRNA lnc-Smad3 on the promoter accessibility of the mouse Smad3 locus.

Regulation of the Immune Response by TGF-β: From Conception to Autoimmunity and Infection

Transforming growth factor β (TGF-β) is a pleiotropic cytokine involved in both suppressive and inflammatory immune responses. After 30 years of intense study, we have only begun to elucidate how TGF-β alters immunity under various conditions. Under steady-state conditions, TGF-β regulates thymic T-cell selection and maintains homeostasis of the naïve T-cell pool. TGF-β inhibits cytotoxic T lymphocyte (CTL), Th1-, and Th2-cell differentiation while promoting peripheral (p)Treg-, Th17-, Th9-, and Tfh-cell generation, and T-cell tissue residence in response to immune challenges. Similarly, TGF-β controls the proliferation, survival, activation, and differentiation of B cells, as well as the development and functions of innate cells, including natural killer (NK) cells, macrophages, dendritic cells, and granulocytes. Collectively, TGF-β plays a pivotal role in maintaining peripheral tolerance against self- and innocuous antigens, such as food, commensal bacteria, and fetal alloantigens, and in controlling immune responses to pathogens.

TGFβR1 Blockade with Galunisertib (LY2157299) Enhances Anti-Neuroblastoma Activity of the Anti-GD2 Antibody Dinutuximab (ch14.18) with Natural Killer Cells

PURPOSE

Immunotherapy of high-risk neuroblastoma using the anti-GD2 antibody dinutuximab induces antibody-dependent cell-mediated cytotoxicity (ADCC). Galunisertib, an inhibitor of TGFβR1, was examined for its ability to enhance the efficacy of dinutuximab in combination with human ex vivo activated NK (aNK) cells against neuroblastoma.

EXPERIMENTAL DESIGN

TGFB1 and TGFBR1 mRNA expression was determined for 249 primary neuroblastoma tumors by microarray analysis. The ability of galunisertib to inhibit SMAD activity induced by neuroblastoma patient blood and bone marrow plasmas in neuroblastoma cells was tested. The impact of galunisertib on TGFβ1-induced inhibition of aNK cytotoxicity and ADCC in vitro and on anti-neuroblastoma activity in NOD-scid gamma (NSG) mice was determined.

RESULTS

Neuroblastomas express TGFB1 and TGFBR1 mRNA. Galunisertib suppressed SMAD activation in neuroblastoma cells induced by exogenous TGFβ1 or by patient blood and bone marrow plasma, and suppressed SMAD2 phosphorylation in human neuroblastoma cells growing in NSG mice. In NK cells treated in vitro with exogenous TGFβ1, galunisertib suppressed SMAD2 phosphorylation and restored the expression of DNAM-1, NKp30, and NKG2D cytotoxicity receptors and the TRAIL death ligand, the release of perforin and granzyme A, and the direct cytotoxicity and ADCC of aNK cells against neuroblastoma cells. Addition of galunisertib to adoptive cell therapy with aNK cells plus dinutuximab reduced tumor growth and increased survival of mice injected with two neuroblastoma cell lines or a patient-derived xenograft.

CONCLUSIONS

Galunisertib suppresses activation of SMAD2 in neuroblastomas and aNK cells, restores NK cytotoxic mechanisms, and increases the efficacy of dinutuximab with aNK cells against neuroblastoma tumors. Clin Cancer Res; 23(3); 804-13. ©2016 AACRSee related commentary by Zenarruzabeitia et al., p. 615.

The Interaction Between Human Papillomaviruses and the Stromal Microenvironment

Human papillomaviruses (HPVs) are small, double-stranded DNA viruses that replicate in stratified squamous epithelia and cause a variety of malignancies. Current efforts in HPV biology are focused on understanding the virus-host interactions that enable HPV to persist for years or decades in the tissue. The importance of interactions between tumor cells and the stromal microenvironment has become increasingly apparent in recent years, but how stromal interactions impact the normal, benign life cycle of HPVs, or progression of lesions to cancer is less understood. Furthermore, how productively replicating HPV impacts cells in the stromal environment is also unclear. Here we bring together some of the relevant literature on keratinocyte-stromal interactions and their impacts on HPV biology, focusing on stromal fibroblasts, immune cells, and endothelial cells. We discuss how HPV oncogenes in infected cells manipulate other cells in their environment, and, conversely, how neighboring cells may impact the efficiency or course of HPV infection.

Adoptively transferred natural killer cells maintain long-term antitumor activity by epigenetic imprinting and CD4+ T cell help

Natural killer (NK) cell infusions can induce remissions in subsets of patients with different types of cancer. The optimal strategies for NK cell activation prior to infusion are still under debate. There is recent evidence that NK cells can acquire long-term functional competence by preactivation with the cytokines IL-12/15/18. The mechanisms supporting the maintenance of long-term NK cell antitumor activity are incompletely under-stood. Here, we show that NK cells preactivated in vitro with IL-12/15/18, but not with IL-15 alone, maintained high antitumor activity even 1 mo after transfer into lymphopenic RAG-2^-/-γc^-/- mice. The NK cell intrinsic ability for IFNγ production coincided with demethylation of the conserved non-coding sequence (CNS) 1 in the Ifng locus, previously shown to enhance transcription of Ifng. In a xenograft melanoma mouse model, human IL-12/15/18-preactivated NK cells rejected tumors more efficiently. In RAG-2^-/-γc^-/- mice, co-transfer of CD4⁺ T cells further improved the long-term competence of NK cells for IFNγ production that was dependent on IL-2. CD4⁺ T cell activation during homeostatic proliferation required macrophages and further promoted the long-term NK cell antitumor activity. Thus, NK cells can "remember" a previous exposure to cytokines by epigenetic imprinting resulting in a remarkable stability of the IFNγ-producing phenotype after adoptive transfer. In addition, our results support combination of cytokine-preactivated NK cells with CD4⁺ T cell activation upon lymphopenic conditioning to achieve long-term NK cell effector function for cancer immunotherapy.

Human mesenchymal stromal/stem cells acquire immunostimulatory capacity upon cross-talk with natural killer cells and might improve the NK cell function of immunocompromised patients

BACKGROUND

The suppressive effect of mesenchymal stromal/stem cells (MSCs) on diverse immune cells is well known, but it is unclear whether MSCs additionally possess immunostimulatory properties. We investigated the impact of human MSCs on the responsiveness of primary natural killer (NK) cells in terms of cytokine secretion.

METHODS

Human MSCs were generated from bone marrow and nasal mucosa. NK cells were isolated from peripheral blood of healthy volunteers or of immunocompromised patients after severe injury. NK cells were cultured with MSCs or with MSC-derived conditioned media in the absence or presence of IL-12 and IL-18. C-C chemokine receptor (CCR) 2, C-C chemokine ligand (CCL) 2, and the interferon (IFN)-γ receptor was blocked by specific inhibitors or antibodies. The synthesis of IFN-γ and CCL2 was determined.

RESULTS

In the absence of exogenous cytokines, trace amounts of NK cell-derived IFN-γ licensed MSCs for enhanced synthesis of CCL2. In turn, MSCs primed NK cells for increased release of IFN-γ in response to IL-12 and IL-18. Priming of NK cells by MSCs occurred in a cell-cell contact-independent manner and was impaired by inhibition of the CCR2, the receptor of CCL2, on NK cells. CD56(bright) NK cells expressed higher levels of CCR2 and were more sensitive to CCL2-mediated priming by MSCs and by recombinant CCR2 ligands than cytotoxic CD56(dim) NK cells. NK cells from severely injured patients were impaired in cytokine-induced IFN-γ synthesis. Co-culture with MSCs or with conditioned media from MSCs and MSC/NK cell co-cultures from healthy donors improved the IFN-γ production of the patients' NK cells in a CCR2-dependent manner.

CONCLUSIONS

A positive feedback loop driven by NK cell-derived IFN-γ and MSC-derived CCL2 increases the inflammatory response of cytokine-stimulated NK cells not only from healthy donors but also from immunocompromised patients. Therapeutic application of MSCs or their soluble factors might thus improve the NK function after severe injury.

T-bet and Eomesodermin in NK Cell Development, Maturation, and Function

Recent reports give insights into the role of the T-box transcription factors, T-bet and Eomesodermin (Eomes), in NK cell biology. In this mini-review, we recapitulate the initial reports that delineate T-bet and Eomes as master regulators of NK cell development, maturation, and function. We discuss how T-bet and Eomes expression is regulated during NK cell development and peripheral maturation. Furthermore, we summarize the current literature on the role of T-bet and Eomes in the transcriptional regulation of NK cell function and review possible effects of T-box transcription factor anomalies during aging, infection, cancer, and after hematopoietic stem cell transplantation. We discuss how the current data argue in favor of a model of T-bet and Eomes synergy in transcriptional regulation of NK cell function and identify T-box transcription factors as potential targets for therapeutic interventions.

TGF-β inhibits the activation and functions of NK cells by repressing the mTOR pathway

Transforming growth factor-β (TGF-β) is a major immunosuppressive cytokine that maintains immune homeostasis and prevents autoimmunity through its antiproliferative and anti-inflammatory properties in various immune cell types. We provide genetic, pharmacologic, and biochemical evidence that a critical target of TGF-β signaling in mouse and human natural killer (NK) cells is the serine and threonine kinase mTOR (mammalian target of rapamycin). Treatment of mouse or human NK cells with TGF-β in vitro blocked interleukin-15 (IL-15)-induced activation of mTOR. TGF-β and the mTOR inhibitor rapamycin both reduced the metabolic activity and proliferation of NK cells and reduced the abundances of various NK cell receptors and the cytotoxic activity of NK cells. In vivo, constitutive TGF-β signaling or depletion of mTOR arrested NK cell development, whereas deletion of the TGF-β receptor subunit TGF-βRII enhanced mTOR activity and the cytotoxic activity of the NK cells in response to IL-15. Suppression of TGF-β signaling in NK cells did not affect either NK cell development or homeostasis; however, it enhanced the ability of NK cells to limit metastases in two different tumor models in mice. Together, these results suggest that the kinase mTOR is a crucial signaling integrator of pro- and anti-inflammatory cytokines in NK cells. Moreover, we propose that boosting the metabolic activity of antitumor lymphocytes could be an effective strategy to promote immune-mediated tumor suppression.

Epithelial and stromal-specific immune pathway activation in the murine endometrium post-coitum

The endometrium is a dynamic tissue, demonstrating cyclical growth/remodelling in preparation for implantation. In mice, seminal constituents trigger mechanisms to prepare the endometrium, a process dubbed 'seminal priming' that modifies immune system components and mediates endometrial remodelling in preparation for pregnancy. An array of cytokines has been reported to mediate this interaction, although much of the literature relates to in vitro studies on isolated endometrial epithelial cells. This study measured changes in immune-related gene expression in endometrial epithelial and stromal cells in vivo following natural mating. CD1 mice were naturally mated and sacrificed over the first 4 days post-coitum (n=3 each day). Endometrial epithelial and stromal compartments were isolated by laser capture microdissection. Labelled cRNA was generated and hybridised to genome-wide expression microarrays. Pathway analysis identified several immune-related pathways active within epithelial and stromal compartments, in particular relating to cytokine networks, matrix metalloproteinases and prostaglandin synthesis. Cluster analysis demonstrated that the expression of factors involved in immunomodulation/endometrial remodelling differed between the epithelial and stromal compartments in a temporal fashion. This study is the first to examine the disparate responses of the endometrial epithelial and stromal compartments to seminal plasma in vivo in mice, and demonstrates the complexity of the interactions between these two compartments needed to create a permissive environment for implantation.

Transcription factor Foxo1 is a negative regulator of natural killer cell maturation and function

Little is known about the role of negative regulators in controlling natural killer (NK) cell development and effector functions. Foxo1 is a multifunctional transcription factor of the forkhead family. Using a mouse model of conditional deletion in NK cells, we found that Foxo1 negatively controlled NK cell differentiation and function. Immature NK cells expressed abundant Foxo1 and little Tbx21 relative to mature NK cells, but these two transcription factors reversed their expression as NK cells proceeded through development. Foxo1 promoted NK cell homing to lymph nodes by upregulating CD62L expression and inhibited late-stage maturation and effector functions by repressing Tbx21 expression. Loss of Foxo1 rescued the defect in late-stage NK cell maturation in heterozygous Tbx21(+/-) mice. Collectively, our data reveal a regulatory pathway by which the negative regulator Foxo1 and the positive regulator Tbx21 play opposing roles in controlling NK cell development and effector functions.

Cytotoxic and natural killer cell stimulatory constituents of Phyllanthus songboiensis

A dichapetalin-type triterpenoid and a dibenzylbutyrolactone-type lignan, together with five known lignans, a known aromatic diterpenoid, and a known acylated phytosterol, were isolated from the aerial parts of Phyllanthus songboiensis, collected in Vietnam. Their structures were determined by interpretation of the spectroscopic data, and the inhibitory activity toward HT-29 human colon cancer cells of all isolates was evaluated by a cytotoxicity assay. The known arylnaphthalene lignan, (+)-acutissimalignan A, was highly cytotoxic toward HT-29 cells, with an IC50 value of 19 nM, but this compound was inactive as a DNA topoisomerase IIα (topo IIα) poison. The known phytosterol, (-)-β-sitosterol-3-O-β-D-(6-O-palmitoyl)glucopyranoside, was found to stimulate natural killer (NK) cells at a concentration of 10μM in the presence of interleukin 12 (IL-12).

Clinical implications of interferon-γ genetic and epigenetic variants

Interferon-γ (IFN-γ) is an integral and critical molecule of the immune system, with multiple functions, mostly related to the T helper type 1 (Th1) response to infection. It is critical for defence against mycobacterial infection and is of increasing interest in defence against fungi. In this article, we review the genetic and epigenetic variants affecting IFN-γ expression and investigate its role in disease, with an emphasis on fungal diseases such as invasive and chronic pulmonary aspergillosis. Over 347 IFN-γ gene variants have been described, in multiple ethnic populations. Many appear to confer a susceptibility to disease, especially tuberculosis (TB) and hepatitis, but also some non-infectious conditions such as aplastic anaemia, cervical cancer and psoriasis. Several epigenetic modifications are also described, increasing IFN-γ expression in Th1 lymphocytes and reducing IFN-γ expression in Th2 lymphocytes. Recombinant IFN-γ administration is licensed for the prophylaxis of infection (bacterial and fungal) in patients with the phagocyte functional deficiency syndrome chronic granulomatous disease, although the benefits appear limited. Interferon-γ therapy is given to patients with profound defects in IFN-γ and interleukin-12 production and appears to be beneficial for patients with invasive aspergillosis and cryptococcal meningitis, but the studies are not definitive. A high proportion of patients with chronic pulmonary aspergillosis are poor producers of IFN-γ in response to multiple stimuli and could also benefit from IFN-γ administration. The investigation and management of patients with possible or demonstrated IFN-γ deficiency in adulthood is poorly studied and could be greatly enhanced with the integration of genetic data.

Harnessing the power of alloreactivity without triggering graft-versus-host disease: how non-engrafting alloreactive cellular therapy might change the landscape of acute myeloid leukemia treatment

Human leukocyte antigen-mismatched leukocyte infusions outside of the context of transplantation are a promising strategy for acute myeloid leukemia. Recent studies using such non-engrafting alloreactive cellular therapy (NEACT) revealed that survival of elderly patients increased from 10% to 39% when NEACT was given following chemotherapy, and that durable complete remissions were achieved in about a third of patients with relapsed or chemorefractory disease. We review the clinical reports of different NEACT approaches to date and describe how although T-cell and NK alloreactivity could generate immediate anti-leukemic effects, long-term disease control may be achieved by stimulating recipient-derived T-cell responses against tumor-associated antigens. Other variables likely impacting NEACT such as the release of pro-inflammatory cytokines from donor-host bidirectional alloreactivity and the choice of chemotherapeutics as well as future avenues for improving NEACT, such as optimizing the cell dose and potential synergies with adjuvant pharmacologic immune checkpoint blockade, are discussed.

The natural product phyllanthusmin C enhances IFN-γ production by human NK cells through upregulation of TLR-mediated NF-κB signaling

Natural products are a major source for cancer drug development. NK cells are a critical component of innate immunity with the capacity to destroy cancer cells, cancer-initiating cells, and clear viral infections. However, few reports describe a natural product that stimulates NK cell IFN-γ production and unravel a mechanism of action. In this study, through screening, we found that a natural product, phyllanthusmin C (PL-C), alone enhanced IFN-γ production by human NK cells. PL-C also synergized with IL-12, even at the low cytokine concentration of 0.1 ng/ml, and stimulated IFN-γ production in both human CD56(bright) and CD56(dim) NK cell subsets. Mechanistically, TLR1 and/or TLR6 mediated PL-C's activation of the NF-κB p65 subunit that in turn bound to the proximal promoter of IFNG and subsequently resulted in increased IFN-γ production in NK cells. However, IL-12 and IL-15Rs and their related STAT signaling pathways were not responsible for the enhanced IFN-γ secretion by PL-C. PL-C induced little or no T cell IFN-γ production or NK cell cytotoxicity. Collectively, we identify a natural product with the capacity to selectively enhance human NK cell IFN-γ production. Given the role of IFN-γ in immune surveillance, additional studies to understand the role of this natural product in prevention of cancer or infection in select populations are warranted.

The transcription Factor AHR prevents the differentiation of a stage 3 innate lymphoid cell subset to natural killer cells

Accumulating evidence indicates that human natural killer (NK) cells develop in secondary lymphoid tissue (SLT) through a so-called "stage 3" developmental intermediate minimally characterized by a CD34(-)CD117(+)CD94(-) immunophenotype that lacks mature NK cell function. This stage 3 population is heterogeneous, potentially composed of functionally distinct innate lymphoid cell (ILC) types that include interleukin-1 receptor (IL-1R1)-positive, IL-22-producing ILC3s. Whether human ILC3s are developmentally related to NK cells is a subject of ongoing investigation. Here, we show that antagonism of the aryl hydrocarbon receptor (AHR) or silencing of AHR gene expression promotes the differentiation of tonsillar IL-22-producing IL-1R1(hi) human ILC3s to CD56(bright)CD94(+) interferon (IFN)-γ-producing cytolytic mature NK cells expressing eomesodermin (EOMES) and T-Box Protein 21 (TBX21 or TBET). Hence, we demonstrate the lineage plasticity of human ILCs by identifying AHR as a transcription factor that prevents IL-1R1(hi) ILC3s from differentiating into NK cells.

Potent cytotoxic arylnaphthalene lignan lactones from Phyllanthus poilanei

Two new (1 and 2) and four known arylnaphthalene lignan lactones (3-6) were isolated from different plant parts of Phyllanthus poilanei collected in Vietnam, with two further known analogues (7 and 8) being prepared from phyllanthusmin C (4). The structures of the new compounds were determined by interpretation of their spectroscopic data and by chemical methods, and the structure of phyllanthusmin D (1) was confirmed by single-crystal X-ray diffraction analysis. Several of these arylnaphthalene lignan lactones were cytotoxic toward HT-29 human colon cancer cells, with compounds 1 and 7-O-[(2,3,4-tri-O-acetyl)-α-L-arabinopyranosyl)]diphyllin (7) found to be the most potent, exhibiting IC50 values of 170 and 110 nM, respectively. Compound 1 showed activity when tested in an in vivo hollow fiber assay using HT-29 cells implanted in immunodeficient NCr nu/nu mice. Mechanistic studies showed that this compound mediated its cytotoxic effects by inducing tumor cell apoptosis through activation of caspase-3, but it did not inhibit DNA topoisomerase IIα activity.

Interaction with mesenchymal stem cells provokes natural killer cells for enhanced IL-12/IL-18-induced interferon-gamma secretion

Tissue injury induces an inflammatory response accompanied by the recruitment of immune cells and of mesenchymal stem cells (MSC) that contribute to tissue regeneration. After stimulation with interleukin- (IL-) 12 and IL-18 natural killer (NK) cells secrete the proinflammatory cytokine interferon- (IFN-) γ. IFN-γ plays a crucial role in the defense against infections and modulates tissue regeneration. In consideration of close proximity of NK cells and MSC at the site of injury we investigated if MSC could influence the ability of NK-cells to produce IFN-γ. Coculture experiments were performed with bone marrow-derived human MSC and human NK cells. MSC enhanced the ability of IL-12/IL-18-stimulated NK cells to secrete IFN-γ in a dose-dependent manner. This activation of NK cells was dependent on cell-cell contact as well as on soluble factors. The increased IFN-γ secretion from NK cells after contact with MSC correlated with an increased level of intracellular IFN-γ. Alterations in the IL-12 signaling pathway including an increased expression of the IL-12β1 receptor subunit and an increased phosphorylation of signal transducer and activator of transcription 4 (STAT4) could be observed. In conclusion, MSC enhance the IFN-γ release from NK cells which might improve the defense against infections at the site of injury but additionally might affect tissue regeneration.

Genetic modification of T cells redirected toward CS1 enhances eradication of myeloma cells

PURPOSE

Our goal is to test whether CS1 could be targeted by chimeric antigen receptor (CAR) T cells to treat multiple myeloma (MM).

EXPERIMENTAL DESIGN

We generated a retroviral construct of a CS1-specific CAR and engineered primary human T cells expressing the CAR. We then tested the capacity of CS1-CAR T cells to eradicate human MM tumor cells in vitro, ex vivo, and in vivo using orthotopic MM xenograft mouse models.

RESULTS

In vitro, compared with mock-transduced T cells, upon recognizing CS1-positive MM cells, CS1-CAR-transduced T cells secreted more IFN-γ as well as interleukin (IL)-2, expressed higher levels of the activation marker CD69, showed higher capacity for degranulation, and displayed enhanced cytotoxicity. Ectopically forced expression of CS1 in MM cells with low CS1 expression enhanced recognition and killing by CAR T cells. Ex vivo, CS1-CAR T cells also showed similarly enhanced activities when responding to primary MM cells. More importantly, in orthotopic MM xenograft mouse models, adoptive transfer of human primary T cells expressing CS1-CAR efficiently suppressed the growth of human MM.1S and IM9 myeloma cells and significantly prolonged mouse survival.

CONCLUSIONS

CS1 is a promising antigen that can be targeted by CAR-expressing T cells for treatment of MM.

Imitating a stress response: a new hypothesis about the innate immune system's role in pregnancy

Recent research challenges long-held hypotheses about mechanisms through which pregnancy induces maternal immune suppression or tolerance of the embryo/fetus. It is now understood that normal pregnancy engages the immune system and that the immune milieu changes with advancing gestation. We suggest that pregnancy mimics the innate immune system's response to stress, causing a sterile inflammatory response that is necessary for successful reproduction. The relationship between external stressors and immunomodulation in pregnancy has been acknowledged, but the specific mechanisms are still being explicated. Implantation and the first trimester are times of immune activation and intensive inflammation in the uterine environment. A period of immune quiescence during the second trimester allows for the growth and development of the maturing fetus. Labor is also an inflammatory event. The length of gestation and timing of parturition can be influenced by environmental stressors. These stressors affect pregnancy through neuroendocrine interaction with the immune system, specifically through the hypothalamic-pituitary-adrenal (HPA) axis and the hypothalamic-pituitary-ovarian axis. Trophoblastic cells that constitute the maternal-fetal interface appear to harness the maternal immune system to promote and maximize the reproductive success of the mother and fetus. Pregnancy is a time of upregulated innate immune responses and decreased adaptive, cell-mediated responses. The inflammatory processes of pregnancy resemble an immune response to brief naturalistic stressors: there is a shift from T helper (Th) 1 to T helper (Th) 2 dominant adaptive immunity with a concomitant shift in cytokine production, decreased proliferation of T cells, and decreased cytotoxicity of natural killer (NK) cells. Inclusion of both murine and human studies, allows an exploration of insights into how trophoblasts influence the activity of the maternal innate immune system during gestation.

TLR activation of tumor-associated macrophages from ovarian cancer patients triggers cytolytic activity of NK cells

We analyzed the functional outcome of the interaction between tumor-associated macrophages (TAMs) and natural killer (NK) cells. TAMs from ascites of ovarian cancer patients displayed an alternatively activated functional phenotype (M2) characterized by a remarkably high frequency and surface density of membrane-bound IL-18. Upon TLR engagement, TAMs acquired a classically activated functional phenotype (M1), released immunostimulatory cytokines (IL-12, soluble IL-18), and efficiently triggered the cytolytic activity of NK cells. TAMs also induced the release of IFN-γ from NK cells, which however was significantly lower compared with that induced by in vitro-polarized M2 cells. Most tumor-associated NK cells displayed a CD56(bright) , CD16(neg) or CD56(bright) , CD16(dim) phenotype, and very poor cytolytic activities, despite an increased expression of the activation marker CD69. They also showed downregulation of DNAM-1, 2B4, and NTB-A activating receptors, and an altered chemokine receptor repertoire. Importantly however, when appropriately stimulated, NK cells from the patients, including those cells isolated from ascites, efficiently killed autologous TAMs that expressed low, "nonprotective" levels of HLA class I molecules. Overall, our data show the existence of a complex tumor microenvironment in which poorly cytolytic/immature NK cells deal with immunosuppressive tumor-educated macrophages.

TGF-β-inducible microRNA-183 silences tumor-associated natural killer cells

Transforming growth factor β1 (TGF-β), enriched in the tumor microenvironment and broadly immunosuppressive, inhibits natural killer (NK) cell function by yet-unknown mechanisms. Here we show that TGF-β-treated human NK cells exhibit reduced tumor cytolysis and abrogated perforin polarization to the immune synapse. This result was accompanied by loss of surface expression of activating killer Ig-like receptor 2DS4 and NKp44, despite intact cytoplasmic stores of these receptors. Instead, TGF-β depleted DNAX activating protein 12 kDa (DAP12), which is critical for surface NK receptor stabilization and downstream signal transduction. Mechanistic analysis revealed that TGF-β induced microRNA (miR)-183 to repress DAP12 transcription/translation. This pathway was confirmed with luciferase reporter constructs bearing the DAP12 3' untranslated region as well as in human NK cells by use of sense and antisense miR-183. Moreover, we documented reduced DAP12 expression in tumor-associated NK cells in lung cancer patients, illustrating this pathway to be consistently perturbed in the human tumor microenvironment.

TGF-β1 precursor and CD8 are potential prognostic and predictive markers in operated breast cancer

The transforming growth factor β1 (TGF-β1) and CD8-positive T cells are two important immune factors that function at opposite directions. The purpose of this study was to verify the relationship between the two factors and their associations with long-term effects of adjuvant chemotherapy or endocrine therapy in breast cancer. Expression of TGF-β1 precursor and CD8 was immunohistochemically detected on surgically-obtained tumor samples of 130 (stage I-III) invasive breast carcinomas from Chinese subjects, who were followed up for a mean time of 112 months. Interstitial CD8-positive cells and TGF-β1 precursor-positive cells adjacent to tumor nests were counted. Infiltration of CD8-positive lymphocytes into tumor nests and TGF-β1 precursor expression in tumor cells were observed and survival analysis was performed. Our results showed that density of interstitial CD8-positive lymphocytes was an independent adverse prognostic factor for distant disease-free survival (DDFS) (HR=8.416, 95% CI=1.636-43.292, P=0.011) in hormone receptor-positive patients who were on adjuvant endocrine therapy. For breast cancer patients who did not receive adjuvant chemotherapy, those without infiltration of CD8-positive cells into tumor nests had a shorter overall survival (OS) than their counterparts with CD8-positive cell infiltration into tumor nests (Log-Rank, P=0.003). But OS of patients without infiltration of CD8-positive cells into tumor nests was significantly prolonged by adjuvant chemotherapy (Log-Rank, P=0.013) and paralleled that of patients with CD8-positive cell infiltration. Although OS was shorter in the tumor cell TGF-β1 precursor (t-TGF-β1-pre)-positive patients than in the negative patients in patients without receiving chemotherapy (P=0.053), OS of t-TGF-β1-pre-positive patients was significantly prolonged by adjuvant chemotherapy (P=0.035) and was longer than that of t-TGF-β1-pre-negative patients. Analysis showed that t-TGF-β1-pre was an independent positive prognostic factor for DDFS (HR=0.392 95% CI=0.157-0.978, P=0.045) in patients who received adjuvant chemotherapy. This study suggested that density of interstitial CD8-positive lymphocytes was of prognostic value in hormone receptor-positive patients who received adjuvant endocrine therapy. Our study verified that adverse immunologic signatures consisting of absence of CD8-positive cells in tumor nests or expression of TGF-β1 precursor in tumor cells in breast cancer were associated with worse prognosis and significantly improved long-term survival with adjuvant chemotherapy, respectively.

Flow cytometric detection of p38 MAPK phosphorylation and intracellular cytokine expression in peripheral blood subpopulations from patients with autoimmune rheumatic diseases

Flow cytometric analysis of p38 mitogen-activated protein kinase (p38 MAPK) signaling cascade is optimally achieved by methanol permeabilization protocols. Such protocols suffer from the difficulties to accurately detect intracellular cytokines and surface epitopes of infrequent cell subpopulations, which are removed by methanol. To overcome these limitations, we have modified methanol-based phosphoflow protocols using several commercially available antibody clones suitable for surface antigens, intracellular cytokines, and p38 MAPK. These included markers of B cells (CD19, CD20, and CD22), T cells (CD3, CD4, and CD8), NK (CD56 and CD7), and dendritic cells (CD11c). We have also tested surface markers of costimulatory molecules, such as CD27. We have successfully determined simultaneous expression of IFN- γ , as well as IL-10, and phosphorylated p38 in cell subsets. The optimized phosphoflow protocol has also been successfully applied in peripheral blood mononuclear cells or purified cell subpopulations from patients with various autoimmune diseases. In conclusion, our refined phosphoflow cytometric approach allows simultaneous detection of p38 MAPK activity and intracellular cytokine expression and could be used as an important tool to study signaling cascades in autoimmunity.

Soypeptide lunasin in cytokine immunotherapy for lymphoma

Immunostimulatory cytokines can enhance anti-tumor immunity and are part of the therapeutic armamentarium for cancer treatment. We have previously reported that post-transplant lymphoma patients have an acquired deficiency of signal transducer and activator of transcription 4, which results in defective IFNγ production during clinical immunotherapy. With the goal of further improving cytokine-based immunotherapy, we examined the effects of a soybean peptide called lunasin that synergistically works with cytokines on natural killer (NK) cells. Peripheral blood mononuclear cells of healthy donors and post-transplant lymphoma patients were stimulated with or without lunasin in the presence of IL-12 or IL-2. NK activation was evaluated, and its tumoricidal activity was assessed using in vitro and in vivo tumor models. Chromatin immunoprecipitation assay was performed to evaluate the histone modification of gene loci that are regulated by lunasin and cytokine. Adding lunasin to IL-12- or IL-2-stimulated NK cells demonstrated synergistic effects in the induction of IFNG and GZMB involved in cytotoxicity. The combination of lunasin and cytokines (IL-12 plus IL-2) was capable of restoring IFNγ production by NK cells from post-transplant lymphoma patients. In addition, NK cells stimulated with lunasin plus cytokines displayed higher tumoricidal activity than those stimulated with cytokines alone using in vitro and in vivo tumor models. The underlying mechanism responsible for the effects of lunasin on NK cells is likely due to epigenetic modulation on target gene loci. Lunasin represents a different class of immune modulating agent that may augment the therapeutic responses mediated by cytokine-based immunotherapy.

Regulation of mouse NK cell development and function by cytokines

Natural Killer (NK) cells are innate lymphocytes with an important role in the early defense against intracellular pathogens and against tumors. Like other immune cells, almost every aspects of their biology are regulated by cytokines. Interleukin (IL)-15 is pivotal for their development, homeostasis, and activation. Moreover, numerous other activating or inhibitory cytokines such as IL-2, IL-4, IL-7, IL-10, IL-12, IL-18, IL-21, Transforming growth factor-β (TGFβ) and type I interferons regulate their activation and their effector functions at different stages of the immune response. In this review we summarize the current understanding on the effect of these different cytokines on NK cell development, homeostasis, and functions during steady-state or upon infection by different pathogens. We try to delineate the cellular sources of these cytokines, the intracellular pathways they trigger and the transcription factors they regulate. We describe the known synergies or antagonisms between different cytokines and highlight outstanding questions in this field of investigation. Finally, we discuss how a better knowledge of cytokine action on NK cells could help improve strategies to manipulate NK cells in different clinical situations.

Enhancement of adaptive immunity to Neisseria gonorrhoeae by local intravaginal administration of microencapsulated interleukin 12

Gonorrhea remains one of the most frequent infectious diseases, and Neisseria gonorrhoeae is emerging as resistant to most available antibiotics, yet it does not induce a state of specific protective immunity against reinfection. Our recent studies have demonstrated that N. gonorrhoeae proactively suppresses host T-helper (Th) 1/Th2-mediated adaptive immune responses, which can be manipulated to generate protective immunity. Here we show that intravaginally administered interleukin 12 (IL-12) encapsulated in sustained-release polymer microspheres significantly enhanced both Th1 and humoral immune responses in a mouse model of genital gonococcal infection. Treatment of mice with IL-12 microspheres during gonococcal challenge led to faster clearance of infection and induced resistance to reinfection, with the generation of gonococcus-specific circulating immunoglobulin G and vaginal immunoglobulin A and G antibodies. These results suggest that local administration of microencapsulated IL-12 can serve as a novel therapeutic and prophylactic strategy against gonorrhea, with implications for the development of an effective vaccine.

Pre-eclampsia affects cord blood NK cell expression of activation receptors and serum cytokine levels but not CB monocyte characteristics

PROBLEM

Maternal immunopathology in pre-eclampsia is well studied; however, less is known regarding the immunological effects on the newborns. Increased inflammation and activation of immune cells at the fetal-maternal interface in pre-eclampsia could influence the neonatal immune compartment.

METHOD OF STUDY

Monocytes and natural killer (NK) cells from cord blood (CB) of children with pre-eclamptic or healthy mothers were analyzed by flow cytometry for surface markers and intracellular cytokines. In addition, serum cytokine profiles were investigated using ELISA or cytometric bead array.

RESULTS

Neonates born to pre-eclamptic mothers had an inflammatory serum cytokine profile. While CB monocyte characteristics seemed unaffected, CB NK cells from pre-eclamptic pregnancies had higher NKp30, but borderline lower NKG2D expression.

CONCLUSION

In utero inflammatory priming of neonatal innate immunity taking place in pre-eclamptic pregnancies might influence specific NK cell functions in newborns.

Small GTPase Rap1 regulates cell migration through regulation of small GTPase RhoA activity in response to transforming growth factor-β1

Transforming growth factor (TGF)-β1 regulates diverse cellular functions. Particularly, TGF-β1 induces monocyte migration to sites of injury or inflammation in early period, whereas TGF-β1 inhibits cell migration in late phase. In this study, we attempted to understand how TGF-β1 suppresses cell migration in late phase. We found that TGF-β1 of short exposure induces the production of chemokines, such as macrophage inflammatory protein (MIP)-1α, by Raw 264.7 cells. However, knock-down of small GTPase RhoA by sh-RhoA inhibited the production of MIP-1α and macrophage migration, suggesting that RhoA is essential for expression of this chemokine. An activator of Epac (exchange proteins directly activated by cAMP; a guanine nucleotide exchange factor of Rap1), 8CPT-2Me-cAMP which leads to Rap1 activation abrogated MIP-1α expression and macrophage migration. Indeed, GTP-RhoA and GTP-Rap1 levels were reciprocally regulated in a time-dependent manner following TGF-β1 stimulation. 8CPT-2Me-cAMP suppressed GTP-RhoA levels, whereas si-Rap1 augmented GTP-RhoA levels and cell migration. TGF-β1 produced cAMP in late period and si-RNAs of Epac1 and Epac2 reduced GTP-Rap1 levels leading to promotion of GTP-RhoA levels. Furthermore, si-RNA of ARAP3 (Rap-dependent RhoGAP) increased GTP-RhoA level and cell migration. Therefore, we propose the mechanism that prolonged TGF-β1 treatment produce cAMP, which activates sequentially Epac, Rap1 and ARAP3, resulting in suppression of RhoA, chemokine expression, and macrophage migration. Contrary to the general concept that Rap1 stimulates cell migration, we demonstrated in this study that Rap1 inhibits cell migration by suppression of RhoA activity in response to TGF-β1.