IFN-alpha-induced signal transduction, gene expression, and antitumor activity of immune effector cells are negatively regulated by suppressor of cytokine signaling proteins

One gene to rule them all - clinical perspectives of a potent suppressor of cytokine signaling - SOCS1

The discovery of Suppressor of Cytokine Signaling 1 (SOCS1) in 1997 marked a significant milestone in understanding the regulation of Janus kinase/Signal transducer and activator of transcription (JAK/STAT) signaling pathways. Subsequent research deciphered its cellular functions, and recent insights into SOCS1 deficiencies in humans underscored its critical role in immune regulation. In humans, SOCS-haploinsufficiency (SOCS1-HI) presents a diverse clinical spectrum, encompassing autoimmune diseases, infection susceptibility, and cancer. Variability in disease manifestation, even within families sharing the same genetic variant, raises questions about clinical penetrance and the need for individualized treatments. Current therapeutic strategies include JAK inhibition, with promising results in controlling inflammation in SOCS1-HI patients. Hematopoietic stem cell transplantation and gene therapy emerge as promising avenues for curative treatments. The evolving landscape of SOCS1 research, emphasizes the need for a nuanced understanding of genetic variants and their functional consequences.

Genetic retargeting of E3 ligases to enhance CAR T cell therapy

Chimeric antigen receptor (CAR) T cell therapies are medical breakthroughs in cancer treatment. However, treatment failure is often caused by CAR T cell dysfunction. Additional approaches are needed to overcome inhibitory signals that limit anti-tumor potency. Here, we developed bifunctional fusion "degrader" proteins that bridge one or more target proteins and an E3 ligase complex to enforce target ubiquitination and degradation. Conditional degradation strategies were developed using inducible degrader transgene expression or small molecule-dependent E3 recruitment. We further engineered degraders to block SMAD-dependent TGFβ signaling using a domain from the SARA protein to target both SMAD2 and SMAD3. SMAD degrader CAR T cells were less susceptible to suppression by TGFβ and demonstrated enhanced anti-tumor potency in vivo. These results demonstrate a clinically suitable synthetic biology platform to reprogram E3 ligase target specificity for conditional, multi-specific endogenous protein degradation, with promising applications including enhancing the potency of CAR T cell therapy.

Mechanisms regulating transitory suppressive activity of neutrophils in newborns: PMNs-MDSCs in newborns

Transitory appearance of immune suppressive polymorphonuclear neutrophils (PMNs) defined as myeloid-derived suppressor cells (PMNs-MDSCs) in newborns is important for their protection from inflammation associated with newly established gut microbiota. Here, we report that inhibition of the type I IFN (IFN1) pathway played a major role in regulation of PMNs-MDSCs-suppressive activity during first weeks of life. Expression of the IFN1 receptor IFNAR1 was markedly lower in PMNs-MDSCs. However, in newborn mice, down-regulation of IFNAR1 was not sufficient to render PMNs immune suppressive. That also required the presence of a positive signal from lactoferrin via its receptor low-density lipoprotein receptor-related protein 2. The latter effect was mediated via NF-κB activation, which was tempered by IFN1 in a manner that involved suppressor of cytokine signaling 3. Thus, we discovered a mechanism of tight regulation of immune suppressive PMNs-MDSCs in newborns, which may be used in the development of therapies of neonatal pathologies.

Antiviral activity of a polysaccharide from Radix Isatidis (Isatis indigotica Fortune) against hepatitis B virus (HBV) in vitro via activation of JAK/STAT signal pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Hepatitis B virus (HBV) infection frequently results in both acute and chronic hepatitis and poses serious threats to human health worldwide. Despite the availability of effective HBV vaccine and anti-HBV drugs, apparently inevitable side effects and resistance have limited its efficiency, thus prompt the search for new anti-HBV agents. The traditional Chinese medicine Radix Isatidis has been used for thousands of years, mainly for the treatment of viral and bacterial infection diseases including hepatitis.

AIM OF THE STUDY

In this study, antiviral activities of a Radix Isatidis (Isatis indigotica Fortune) polysaccharide (RIP) were evaluated in vitro model using the HepG2.2.15 cell line and the underlying mechanism was elucidated with the aim of developing a novel anti-HBV therapeutic agent.

MATERIALS AND METHODS

Structure features of the purified polysaccharide RIP were investigated by a combination of chemical and instrumental analysis. Drug cytotoxicity was assessed using the MTT assay. The contents of HBsAg, HBeAg, intracellular and extracellular IFN-α level were measured using respective commercially available ELISA kit. The HBV DNA expression was evaluated by real-time quantitative polymerase chain reaction (PCR) and the relevant proteins involved in TFN/JAK/STAT signaling pathways were examined by western blot assay.

RESULTS

MTT assay showed that RIP had no toxicity on HepG2.2.15 cell line below the concentration 400 μg/ml at Day 3, 6 and 9. Furthermore, RIP at the concentration of 50, 100 and 200 μg/ml significantly reduced extracellular and intracellular level of HBsAg, HBeAg and HBV DNA in HepG2.2.15 cells in a time and dose-dependent manner. Moreover, RIP also enhanced the production of IFN-α in HepG2.2.15 cell via activation of JAK/STAT signal pathway and induction of antiviral proteins, as evidenced by the increased protein expression of p-STAT-1, p-STAT-2, p-JAK1, p-TYK2, OAS1, and Mx in HepG2.2.15 cells. In addition, the over expression of SOCS-1 and SOCS-3 was significantly abolished under same conditions.

CONCLUSIONS

These results suggested that the HBV inhibitory effect of RIP was possibly due to the activation of IFN-α-dependent JAK/STAT signal pathway and induction of the anti-HBV protein expression.

JAK/STAT Cytokine Signaling at the Crossroad of NK Cell Development and Maturation

Natural Killer (NK) cells are cytotoxic lymphocytes of the innate immune system and play a critical role in anti-viral and anti-tumor responses. NK cells develop in the bone marrow from hematopoietic stem cells (HSCs) that differentiate through common lymphoid progenitors (CLPs) to NK lineage-restricted progenitors (NKPs). The orchestrated action of multiple cytokines is crucial for NK cell development and maturation. Many of these cytokines such as IL-2, IL-7, IL-12, IL-15, IL-21, IL-27, and interferons (IFNs) signal via the Janus Kinase / Signal Transducer and Activator of Transcription (JAK/STAT) pathway. We here review the current knowledge about these cytokines and the downstream signaling involved in the development and maturation of conventional NK cells and their close relatives, innate lymphoid cells type 1 (ILC1). We further discuss the role of suppressor of cytokine signaling (SOCS) proteins in NK cells and highlight their potential for therapeutic application.

IL-21 regulates SOCS1 expression in autoreactive CD8+ T cells but is not required for acquisition of CTL activity in the islets of non-obese diabetic mice

In type 1 diabetes, maturation of activated autoreactive CD8⁺ T cells to fully armed effector cytotoxic T lymphocytes (CTL) occurs within the islet. At present the signals required for the maturation process are poorly defined. Cytokines could potentially provide the necessary "third signal" required to generate fully mature CTL capable of killing insulin-producing β-cells. To determine whether autoreactive CTL within islets respond to cytokines we generated non-obese diabetic (NOD) mice with a reporter for cytokine signalling. These mice express a reporter gene, hCD4, under the control of the endogenous regulatory elements for suppressor of cytokine signalling (SOCS)1, which is itself regulated by pro-inflammatory cytokines. In NOD mice, the hCD4 reporter was expressed in infiltrated islets and the expression level was positively correlated with the frequency of infiltrating CD45⁺ cells. SOCS1 reporter expression was induced in transferred β-cell-specific CD8⁺ 8.3T cells upon migration from pancreatic draining lymph nodes into islets. To determine which cytokines induced SOCS1 promoter activity in islets, we examined hCD4 reporter expression and CTL maturation in the absence of the cytokine receptors IFNAR1 or IL-21R. We show that IFNAR1 deficiency does not confer protection from diabetes in 8.3 TCR transgenic mice, nor is IFNAR1 signalling required for SOCS1 reporter upregulation or CTL maturation in islets. In contrast, IL-21R-deficient 8.3 mice have reduced diabetes incidence and reduced SOCS1 reporter activity in islet CTLs. However IL-21R deficiency did not affect islet CD8⁺ T cell proliferation or expression of granzyme B or IFNγ. Together these data indicate that autoreactive CD8⁺ T cells respond to IL-21 and not type I IFNs in the islets of NOD mice, but neither IFNAR1 nor IL-21R are required for islet intrinsic CTL maturation.

The molecular details of cytokine signaling via the JAK/STAT pathway

More than 50 cytokines signal via the JAK/STAT pathway to orchestrate hematopoiesis, induce inflammation and control the immune response. Cytokines are secreted glycoproteins that act as intercellular messengers, inducing proliferation, differentiation, growth, or apoptosis of their target cells. They act by binding to specific receptors on the surface of target cells and switching on a phosphotyrosine-based intracellular signaling cascade initiated by kinases then propagated and effected by SH2 domain-containing transcription factors. As cytokine signaling is proliferative and often inflammatory, it is tightly regulated in terms of both amplitude and duration. Here we review molecular details of the cytokine-induced signaling cascade and describe the architectures of the proteins involved, including the receptors, kinases, and transcription factors that initiate and propagate signaling and the regulatory proteins that control it.

Ribonuclease 7 Shields the Kidney and Bladder from Invasive Uropathogenic Escherichia coli Infection

BACKGROUND

Evidence suggests that antimicrobial peptides, components of the innate immune response, protect the kidneys and bladder from bacterial challenge. We previously identified ribonuclease 7 (RNase 7) as a human antimicrobial peptide that has bactericidal activity against uropathogenic Escherichia coli (UPEC). Functional studies assessing RNase 7's contributions to urinary tract defense are limited.

METHODS

To investigate RNase 7's role in preventing urinary tract infection (UTI), we quantified urinary RNase 7 concentrations in 29 girls and adolescents with a UTI history and 29 healthy female human controls. To assess RNase 7's antimicrobial activity in vitro in human urothelial cells, we used siRNA to silence urothelial RNase 7 production and retroviral constructs to stably overexpress RNase 7; we then evaluated UPEC's ability to bind and invade these cells. For RNase 7 in vivo studies, we developed humanized RNase 7 transgenic mice, subjected them to experimental UTI, and enumerated UPEC burden in the urine, bladder, and kidneys.

RESULTS

Compared with controls, study participants with a UTI history had 1.5-fold lower urinary RNase 7 concentrations. When RNase 7 was silenced in vitro, the percentage of UPEC binding or invading human urothelial cells increased; when cells overexpressed RNase 7, UPEC attachment and invasion decreased. In the transgenic mice, we detected RNase 7 expression in the kidney's intercalated cells and bladder urothelium. RNase 7 humanized mice exhibited marked protection from UPEC.

CONCLUSIONS

These findings provide evidence that RNase 7 has a role in kidney and bladder host defense against UPEC and establish a foundation for investigating RNase 7 as a UTI prognostic marker or nonantibiotic-based therapy.

IL-27 mediates HLA class I up-regulation, which can be inhibited by the IL-6 pathway, in HLA-deficient Small Cell Lung Cancer cells

Background

Recently, immunotherapy with anti-PD-1 antibodies has shown clinical benefit in recurrent Small Cell Lung Cancer (SCLC). Since anti-PD-1 re-activates anti-tumor Cytotoxic T Lymphocyte (CTL) responses, it is crucial to understand the mechanisms regulating HLA class I, and PD-L1 expression in HLA-negative SCLC. Here we addressed the role of IL-27, a cytokine related to both IL-6 and IL-12 families.

Methods

The human SCLC cell lines NCI-N592, -H69, -H146, -H446 and -H82 were treated in vitro with different cytokines (IL-27, IFN-γ, IL-6 or a soluble IL-6R/IL-6 chimera [sIL-6R/IL-6]) at different time points and analyzed for tyrosine-phosphorylated STAT proteins by Western blot, for surface molecule expression by immunofluorescence and FACS analyses or for specific mRNA expression by QRT-PCR. Relative quantification of mRNAs was calculated by the ΔΔCT method. The Student’s T test was used for the statistical analysis of experimental replicates.

Results

IL-27 triggered STAT1/3 phosphorylation and up-regulated the expression of surface HLA class I antigen and of TAP1 and TAP2 mRNA in four out of five SCLC cell lines tested. The IL-27-resistant NCI-H146 cells showed up-regulation of HLA class I by IFN-γ. IFN-γ also induced expression of PD-L1 in SCLC cells, while IL-27 was less potent in this respect. IL-27 failed to activate STAT1/3 phosphorylation in NCI-H146 cells, which display a low expression of the IL-27RA and GP130 receptor chains. As GP130 is shared in IL-27R and IL-6R complexes, we assessed its functionality in response to sIL-6R/IL-6. sIL-6R/IL-6 failed to trigger STAT1/3 signaling in NCI-H146 cells, suggesting low GP130 expression or uncoupling from signal transduction. Although both sIL-6R/IL-6 and IL-27 triggered STAT1/3 phosphorylation, sIL-6R/IL-6 failed to up-regulate HLA class I expression, in relationship to the weak activation of STAT1. Finally sIL-6R/IL-6 limited IL-27-effects, particularly in NCI-H69 cells, in a SOCS3-independent manner, but did not modify IFN-γ induced HLA class I up-regulation.

Conclusions

In conclusion, IL-27 is a potentially interesting cytokine for restoring HLA class I expression for SCLC combined immunotherapy purposes. However, the concomitant activation of the IL-6 pathway may limit the IL-27 effect on HLA class I induction but did not significantly alter the responsiveness to IFN-γ.

Electronic supplementary material

The online version of this article (10.1186/s13046-017-0608-z) contains supplementary material, which is available to authorized users.

Involvement of herpes simplex virus type 1 UL13 protein kinase in induction of SOCS genes, the negative regulators of cytokine signaling

The suppressor of cytokine signaling (SOCS) family has eight members and suppresses various cytokine signaling pathways, including IFN signaling. Therefore, some viruses have evolved molecular mechanisms for inducing SOCS proteins and thus escaping host immunity. Herpes simplex virus type 1 (HSV-1) has a mechanism for escaping from type I IFN by induction of both SOCS1 and SOCS3. In this study, expression of the eight members of the SOCS family stimulated by HSV-1 infection was comparatively analyzed by qRT-PCR. It was found that SOCS1 and SOCS3 are induced by HSV-1-infection at 4 hr post infection. However, such induction was not observed in UL13 deficient virus-infected cells, suggesting that UL13 protein kinase participates in induction of both genes. The transcription factor Sp1-binding sites of SOCS3 promoter/enhancer region were identified as the regulatory elements for induction of SOCS3 in HSV-1 infected cells. Accumulation of activated Sp1 was detectable in the nuclei of HSV-1-infected cells before induction of SOCS3. Taken together, these results suggest that HSV-1 has a potent mechanism for escaping from the IFN system.

Dysregulation of SOCS-Mediated Negative Feedback of Cytokine Signaling in Carcinogenesis and Its Significance in Cancer Treatment

Suppressor of cytokine signaling (SOCS) proteins are major negative feedback regulators of cytokine signaling mediated by the Janus kinase (JAK)-signal transducer and activator of transcription signaling pathway. In particular, SOCS1 and SOCS3 are strong inhibitors of JAKs and can play pivotal roles in the development and progression of cancers. The abnormal expression of SOCS1 and SOCS3 in cancer cells is associated with the dysregulation of cell growth, migration, and death induced by multiple cytokines and hormones in human carcinomas. In addition, the mechanisms involved in SOCS1- and SOCS3-regulated abnormal development and activation of immune cells in carcinogenesis, including T cells, macrophages, dendritic cells, and myeloid-derived suppressor cells, are still unclear. Therefore, this study aims to further discuss the molecules and signal pathways regulating the expression and function of SOCS1 and SOCS3 in various types of cancers and elucidate the feasibility and efficiency of SOCS-based target therapeutic strategy in anticancer treatment.

Age-Associated Failure To Adjust Type I IFN Receptor Signaling Thresholds after T Cell Activation

With increasing age, naive CD4 T cells acquire intrinsic defects that compromise their ability to respond and differentiate. Type I IFNs, pervasive constituents of the environment in which adaptive immune responses occur, are known to regulate T cell differentiation and survival. Activated naive CD4 T cells from older individuals have reduced responses to type I IFN, a defect that develops during activation and that is not observed in quiescent naive CD4 T cells. Naive CD4 T cells from young adults upregulate the expression of STAT1 and STAT5 after activation, lowering their threshold to respond to type I IFN stimulation. The heightened STAT signaling is critical to maintain the expression of CD69 that regulates lymphocyte egress and the ability to produce IL-2 and to survive. Although activation of T cells from older adults also induces transcription of STAT1 and STAT5, failure to exclude SHP-1 from the signaling complex blunts their type I IFN response. In summary, our data show that type I IFN signaling thresholds in naive CD4 T cells after activation are dynamically regulated to respond to environmental cues for clonal expansion and memory cell differentiation. Naive CD4 T cells from older adults have a defect in this threshold calibration. Restoring their ability to respond to type I IFN emerges as a promising target to restore T cell responses and to improve the induction of T cell memory.

Study of interferon-β antiviral activity against Herpes simplex virus type 1 in neuron-enriched trigeminal ganglia cultures

Herpes simplex virus type 1 (HSV-1) causes a lytic infection in epithelial cells before being captured and moved via retrograde axonal transport to the nuclei of the sensory neurons of the trigeminal ganglion or dorsal root, where it establishes a latent infection. HSV-1 infection induces an antiviral response through the production of Beta Interferon (IFN-β) in infected trigeminal ganglia. The aim of this work was to characterize the response induced by IFN-β in neuron-enriched trigeminal ganglia primary cultures infected with HSV-1. An antiviral effect of IFN-β in these cultures was observed, including reduced viral production and increased cell survival. In contrast, viral infection significantly decreased both double stranded RNA dependent protein kinase (Pkr) transcription and Jak-1 and Stat-1 phosphorylation, suggesting a possible HSV-1 immune evasion mechanism in trigeminal cells. Additionally, HSV-1 infection upregulated Suppressor of Cytokine Signaling-3 (Socs3) mRNA; upregulation of socs3 was inhibited in IFN-β treated cultures. HSV-1 infection increased the number of Socs3 positive cells and modified the intracellular distribution of Socs3 protein, in infected cells. This neuron-enriched trigeminal ganglia culture model could be used to elucidate the HSV-1 viral cycle in sensory neurons and to study cellular antiviral responses and possible viral evasion mechanisms that underlie the choice between viral replication and latency.

Analysis of surrogate gene expression markers in peripheral blood of melanoma patients to predict treatment outcome of adjuvant pegylated interferon alpha 2b (EORTC 18991 side study)

We analysed mRNA levels of interferon response genes (ISG15, STAT1, CXCL10) of inhibitors of the JAK/STAT pathway (STAT3, SOCS1, SOCS3) and of cytokines (TNFα, IL10, TGFß1) in peripheral blood of 91 stage III melanoma patients enrolled in EORTC 18991 trial to find biomarkers indicative for disease stage and predictive for efficacy of pegylated interferon alpha-2b (PEG-IFNα-2b) therapy. mRNA levels were analysed at baseline and after 6 months. Univariate and multivariate analyses were performed to estimate the prognostic and predictive role of mRNA levels for distant metastasis-free survival (DMFS) and relapse-free survival (RFS). Compared to healthy controls, melanoma patients showed significantly higher TGFβ1 mRNA levels. In a multivariate model, increasing SOCS1 and SOCS3 mRNA levels were associated with worse RFS (P = 0.02 and P = 0.04, respectively) and DMFS (P = 0.05 and P = 0.05, respectively) due to negative correlation between, respectively, SOCS1/SOCS3 mRNA levels and ulceration or Breslow thickness. No impact of PEG-IFNα-2b on mRNA levels was observed except for ISG15 mRNA levels, which decreased in the treatment arm (P = 0.001). It seems that patients with a decrease >60 % of ISG15 mRNA levels during 6 months PEG-IFNα-2b had inferior outcome.

Enhanced activation of human dendritic cells by silencing SOCS1 and activating TLRs simultaneously

There was established evidence that silencing the attenuator and activating the TLRs could activate the dendritic cells in synergic effects. In this study, we constructed a plasmid, namely pshS1NH, which encodes SOCS1-shRNA, NY-ESO-1-MAGE3 (HLA-A2*0201) fusion antigen and secretory HMGB1, an agent used to modify dendritic cells (DCs), aiming to generate potent DC vaccine against tumors. The SOCS1-shRNA could efficiently downregulate the expression of SOCS1, as indicated by real-time RT-PCR and Western blot. The fusion antigen was detected in the pshS1NH-DCs by PCR and Western blot. Simultaneously, HMGB1 level in the pshS1NH-DCs culture media was significantly higher than that in the control DCs culture media. Levels of Th1 cytokines in pshS1NH-DCs culture media, such as IL-1β, IL-6, TNF-α and IL-12p70, were dramatically higher than those in control DCs culture media. In addition, lymphocytes co-cultured with pshS1NH-DCs secreted dramatically higher level of IFN-γ, whereas no difference was detected in IL-4 levels. Taken together, these data suggest that pshS1NH-DCs may be a potential adjuvant immunotherapy for cancers in clinical applications.

Contrasting effects of IFNα on MHC class II expression in professional vs. nonprofessional APCs: Role of CIITA type IV promoter

We previously demonstrated that, in ex vivo cultures, IFNα downregulates the expression of MHC class II (MHCII) genes in human non-professional APCs associated with pancreatic islets. IFNα has an opposing effect on MHCII expression in professional APCs. In this study, we found that the mechanism responsible for the IFNα-mediated MHCII's downregulation in human MHCII-positive non-professional antigen presenting human non-hematopoietic cell lines is the result of the negative feedback system that regulates cytokine signal transduction, which eventually inhibits promoters III and IV of CIITA gene. Because the CIITA-PIV isoform is mostly responsible for the constitutive expression of MHCII genes in non-professional APCs, we pursued and achieved the specific knockdown of CIITA-PIV mRNA in our in vitro system, obtaining a partial silencing of MHCII molecules similar to that obtained by IFNα. We believe that our results offer a new understanding of the potential significance of CIITA-PIV as a therapeutic target for interventional strategies that can manage autoimmune disease and allograft rejection with little interference on the function of professional APCs of the immune system.

Structurally modified curcumin analogs inhibit STAT3 phosphorylation and promote apoptosis of human renal cell carcinoma and melanoma cell lines

The Janus kinase-2 (Jak2)-signal transducer and activator of transcription-3 (STAT3) pathway is critical for promoting an oncogenic and metastatic phenotype in several types of cancer including renal cell carcinoma (RCC) and melanoma. This study describes two small molecule inhibitors of the Jak2-STAT3 pathway, FLLL32 and its more soluble analog, FLLL62. These compounds are structurally distinct curcumin analogs that bind selectively to the SH2 domain of STAT3 to inhibit its phosphorylation and dimerization. We hypothesized that FLLL32 and FLLL62 would induce apoptosis in RCC and melanoma cells and display specificity for the Jak2-STAT3 pathway. FLLL32 and FLLL62 could inhibit STAT3 dimerization in vitro. These compounds reduced basal STAT3 phosphorylation (pSTAT3), and induced apoptosis in four separate human RCC cell lines and in human melanoma cell lines as determined by Annexin V/PI staining. Apoptosis was also confirmed by immunoblot analysis of caspase-3 processing and PARP cleavage. Pre-treatment of RCC and melanoma cell lines with FLLL32/62 did not inhibit IFN-γ-induced pSTAT1. In contrast to FLLL32, curcumin and FLLL62 reduced downstream STAT1-mediated gene expression of IRF1 as determined by Real Time PCR. FLLL32 and FLLL62 significantly reduced secretion of VEGF from RCC cell lines in a dose-dependent manner as determined by ELISA. Finally, each of these compounds inhibited in vitro generation of myeloid-derived suppressor cells. These data support further investigation of FLLL32 and FLLL62 as lead compounds for STAT3 inhibition in RCC and melanoma.

Myeloid-derived suppressor cell inhibition of the IFN response in tumor-bearing mice

Our group and others have determined that immune effector cells from patients with advanced cancers exhibit reduced activation of IFN signaling pathways. We hypothesized that increases in immune regulatory cells termed myeloid-derived suppressor cells (MDSC) could interfere with the host immune response to tumors by inhibiting immune cell responsiveness to IFNs. The C26 murine adenocarcinoma model was employed to study immune function in advanced malignancy. C26-bearing mice had significantly elevated levels of GR1(+)CD11b(+) MDSC as compared with control mice, and splenocytes from tumor-bearing mice exhibited reduced phosphorylation of STAT1 (P-STAT1) on Tyr(701) in response to IFN-α or IFN-γ. This inhibition was seen in splenic CD4(+) and CD8(+) T cells as well as natural killer cells. In vitro coculture experiments revealed that MDSC inhibited the IFN responsiveness of splenocytes from normal mice. Treatment of C26-bearing mice with gemcitabine or an anti-GR1 antibody led to depletion of MDSC and restored splenocyte IFN responsiveness. Spleens from C26-bearing animals displayed elevated levels of iNOS protein and nitric oxide. In vitro treatment of splenocytes with a nitric oxide donor led to a decreased STAT1 IFN response. The elevation in nitric oxide in C26-bearing mice was associated with increased levels of nitration on STAT1. Finally, splenocytes from iNOS knockout mice bearing C26 tumors exhibited a significantly elevated IFN response as compared with control C26 tumor-bearing mice. These data suggest that nitric oxide produced by MDSC can lead to reduced IFN responsiveness in immune cells.

STAT3: a target to enhance antitumor immune response

Signal transducer and activator of transcription 3 (Stat3) has emerged as a critical regulator for tumor-associated inflammation. Activation of Stat3 negatively regulates the Th1-type immune response and promotes expansion of myeloid-derived suppressor cells (MDSCs) and regulatory T-cell functions in the tumor microenvironment. Mounting evidence suggests that Stat3 and related pathways may serve as a target for changing the tumor immunologic microenvironment to benefit cancer immunotherapies. Many recent studies support the use of certain tyrosine kinase inhibitors, through inhibition of Stat3, in decreasing immunosuppression in the tumor microenvironment. Other potential therapeutic avenues include the use of targeted delivery of Stat3 siRNA into immune cells. Here, we describe the role of Stat3 in regulating the immunologic properties of tumors as a background for Stat3-based therapeutic interventions.

Enhanced anti-tumor activity of interferon-alpha in SOCS1-deficient mice is mediated by CD4⁺ and CD8⁺ T cells

Interferon-alpha (IFN-α) is an immunomodulatory cytokine that is used clinically for the treatment of melanoma in the adjuvant setting. The cellular actions of IFN-α are regulated by the suppressors of cytokine signaling (SOCS) family of proteins. We hypothesized that the anti-tumor activity of exogenous IFN-α would be enhanced in SOCS1-deficient mice. SOCS1-deficient (SOCS1(-/-)) or control (SOCS1(+/+)) mice on an IFN-γ(-/-) C57BL/6 background bearing intraperitoneal (i.p.) JB/MS murine melanoma cells were treated for 30 days with i.p. injections of IFN-A/D or PBS (vehicle). Log-rank Kaplan-Meier survival curves were used to evaluate survival. Tumor-bearing control SOCS1(+/+) mice receiving IFN-A/D had significantly enhanced survival versus PBS-treated mice (P = 0.0048). The anti-tumor effects of IFN-A/D therapy were significantly enhanced in tumor-bearing SOCS1(-/-) mice; 75% of these mice survived tumor challenge, whereas PBS-treated SOCS1(-/-) mice all died at 13-16 days (P = 0.00038). Antibody (Ab) depletion of CD8(+) T cells abrogated the anti-tumor effects of IFN-A/D in SOCS1(-/-) mice as compared with mice receiving a control antibody (P = 0.0021). CD4(+) T-cell depletion from SOCS1(-/-) mice also inhibited the effects of IFN-A/D (P = 0.0003). IFN-A/D did not alter expression of CD80 or CD86 on splenocytes of SOCS1(+/+) or SOCS1(-/-) mice, or the proportion of T regulatory cells or myeloid-derived suppressor cells in SOCS1(+/+) or SOCS1(-/-) mice. An analysis of T-cell function did reveal increased proliferation of SOCS1-deficient splenocytes at baseline and in response to mitogenic stimuli. These data suggest that modulation of SOCS1 function in T-cell subsets could enhance the anti-tumor effects of IFN-α in the setting of melanoma.

Interferon signaling patterns in peripheral blood lymphocytes may predict clinical outcome after high-dose interferon therapy in melanoma patients

Background

High-dose Interferon (HDI) therapy produces a clinical response and achieves relapse-free survival in 20-33% of patients with operable high risk or metastatic melanoma. However, patients may develop significant side effects frequently necessitating dose reduction or discontinuation of therapy. We recently showed that peripheral blood lymphocytes (PBL) from some melanoma patients have impaired interferon (IFN) signaling which could be restored with high concentrations of IFN. This exploratory study evaluated IFN signaling in PBL of melanoma patients to assess whether the restoration of PBL IFN signaling may predict a beneficial effect for HDI in melanoma patients.

Methods

PBL from 14 melanoma patients harvested on Day 0 and Day 29 of neoadjuvant HDI induction therapy were analyzed using phosflow to assess their interferon signaling patterns through IFN-α induced phosphorylation of STAT1-Y701.

Results

Patients who had a clinical response to HDI showed a lower PBL interferon signaling capacity than non-responders at baseline (Day 0). Additionally, clinical responders and patients with good long-term outcome showed a significant increase in their PBL interferon signaling from Day 0 to Day 29 compared to clinical non-responders and patients that developed metastatic disease. The differences in STAT1 activation from pre- to post- HDI treatment could distinguish between patients who were inclined to have a favorable or unfavorable outcome.

Conclusion

While the sample size is small, these results suggest that interferon signaling patterns in PBL correlate with clinical responses and may predict clinical outcome after HDI in patients with melanoma. A larger confirmatory study is warranted, which may yield a novel approach to select patients for HDI therapy.

Interferon-alpha triggers B cell effector 1 (Be1) commitment

B-cells can contribute to the pathogenesis of autoimmune diseases not only through auto-antibody secretion but also via cytokine production. Therapeutic depletion of B-cells influences the functions and maintenance of various T-cell subsets. The mechanisms governing the functional heterogeneity of B-cell subsets as cytokine-producing cells are poorly understood. B-cells can differentiate into two functionally polarized effectors, one (B-effector-1-cells) producing a Th-1-like cytokine pattern and the other (Be2) producing a Th-2-like pattern. IL-12 and IFN-γ play a key role in Be1 polarization, but the initial trigger of Be1 commitment is unclear. Type-I-interferons are produced early in the immune response and prime several processes involved in innate and adaptive responses. Here, we report that IFN-α triggers a signaling cascade in resting human naive B-cells, involving STAT4 and T-bet, two key IFN-γ gene imprinting factors. IFN-α primed naive B-cells for IFN-γ production and increased IFN-γ gene responsiveness to IL-12. IFN-γ continues this polarization by re-inducing T-bet and up-regulating IL-12Rβ2 expression. IFN-α and IFN-γ therefore pave the way for the action of IL-12. These results point to a coordinated action of IFN-α, IFN-γ and IL-12 in Be1 polarization of naive B-cells, and may provide new insights into the mechanisms by which type-I-interferons favor autoimmunity.

Suppression of SOCS3 increases susceptibility of renal cell carcinoma to interferon-α

Interferon (IFN)-α is one of the most commonly used agents in immunotherapy for patients with advanced stage renal cell carcinoma. However, because of the drug resistance to IFN-α, its benefits are limited. In this study, we examined whether repression of suppressor of cytokine signaling (SOCS) proteins, which are involved in the IFN-induced signaling pathway, can overcome the IFN resistance of renal cell carcinoma. The effect of IFN-α on SOCS3 expression and cell proliferation was examined using IFN-resistant 786-O and IFN-sensitive ACHN cell lines. The effects of SOCS3-targeted siRNA on 786-O xenografts were determined by SOCS3 expression, morphological observation, and tumor volume. The SOCS3 mRNA expression level was significantly increased by IFN-α stimulation in 786-O, but not in ACHN cells. The overexpression of SOCS3 by gene transfection in ACHN cells significantly inhibited the growth-inhibitory effect of IFN-α. Suppression of SOCS3 expression in 786-O cells by siRNA activated the IFN signaling pathway through signal transducer and activator of transcription 1 phosphorylation and recovered sensitivity to IFN-α. An in vivo study indicated that co-administration of SOCS3-targeted siRNA promoted IFN-α-induced cell death and growth suppression in 786-O cell xenograft in nude mice. Morphological observation of the tumors revealed the inhibition of SOCS3-induced apoptosis, invasion of inflammatory cells and fibrosis. SOCS3 could be a key component in the resistance to IFN treatment of renal cell carcinoma. Silencing SOCS3 gene expression could be an effective strategy to enhance the antitumor effect of IFN in human renal cell carcinoma cells.

Braking bad: blockade of inhibitory pathways improves interleukin-15 therapy

Blockade of the CTLA-4 and PD-1 inhibitory pathways in T cells via the administration of neutralizing antibodies at the time of interleukin (IL)-15 therapy markedly enhanced the survival of tumor-bearing mice as compared with those receiving IL-15 alone or IL-15 in combination with just one of the antibodies.

Altered interferon-alpha-signaling in natural killer cells from patients with chronic hepatitis C virus infection

BACKGROUND & AIMS

Natural killer (NK) cells play an important role in the immune response against virus infection. Interferon (IFN)-alpha, an essential component in therapy against hepatitis C virus (HCV) infection, regulates NK cell function. However, it remains obscure how chronic HCV infection (CHC) modifies intracellular IFN-alpha signaling in NK cells. We investigated IFN-alpha signaling in NK cells in patients with CHC.

METHODS

Peripheral blood mononuclear cells were obtained from patients with CHC and healthy subjects (HS) as controls.

RESULTS

The expression level of signal transducer and activator of transcription (STAT) 1, a key molecule of IFN-alpha signaling, was clearly higher in NK cells from the CHC patients than in those from HS. The phosphorylation level of STAT1 with IFN-alpha stimulation was significantly greater in NK cells from the CHC patients than in those from the HS, while that of STAT4 was significantly less. These phosphorylation levels of STAT1 and STAT4 positively and negatively correlated with the STAT1 level in NK cells, respectively. The IFN-alpha induced messenger RNA level of the suppressor of cytokine signaling 1, which is a downstream gene of phosphorylated-STAT1, was clearly greater in NK cells from the CHC patients than in those from the HS, while that of IFN-gamma, which is a downstream gene of phosphorylated-STAT4, was clearly lower.

CONCLUSIONS

These results indicate altered IFN-alpha signaling in NK cells in CHC patients, suggesting that this alteration is associated with the persistence of HCV infection and resistance to IFN-alpha therapy.

The small molecule curcumin analog FLLL32 induces apoptosis in melanoma cells via STAT3 inhibition and retains the cellular response to cytokines with anti-tumor activity

Background

We characterized the biologic effects of a novel small molecule STAT3 pathway inhibitor that is derived from the natural product curcumin. We hypothesized this lead compound would specifically inhibit the STAT3 signaling pathway to induce apoptosis in melanoma cells.

Results

FLLL32 specifically reduced STAT3 phosphorylation at Tyr705 (pSTAT3) and induced apoptosis at micromolar amounts in human melanoma cell lines and primary melanoma cultures as determined by annexin V/propidium iodide staining and immunoblot analysis. FLLL32 treatment reduced expression of STAT3-target genes, induced caspase-dependent apoptosis, and reduced mitochondrial membrane potential. FLLL32 displayed specificity for STAT3 over other homologous STAT proteins. In contrast to other STAT3 pathway inhibitors (WP1066, JSI-124, Stattic), FLLL32 did not abrogate IFN-γ-induced pSTAT1 or downstream STAT1-mediated gene expression as determined by Real Time PCR. In addition, FLLL32 did not adversely affect the function or viability of immune cells from normal donors. In peripheral blood mononuclear cells (PBMCs), FLLL32 inhibited IL-6-induced pSTAT3 but did not reduce signaling in response to immunostimulatory cytokines (IFN-γ, IL 2). Treatment of PBMCs or natural killer (NK) cells with FLLL32 also did not decrease viability or granzyme b and IFN-γ production when cultured with K562 targets as compared to vehicle (DMSO).

Conclusions

These data suggest that FLLL32 represents a lead compound that could serve as a platform for further optimization to develop improved STAT3 specific inhibitors for melanoma therapy.

Enhancement of antiviral immunity by small molecule antagonist of suppressor of cytokine signaling

Suppressors of cytokine signaling (SOCSs) are negative regulators of both innate and adaptive immunity via inhibition of signaling by cytokines such as type I and type II IFNs. We have developed a small peptide antagonist of SOCS-1 that corresponds to the activation loop of JAK2. SOCS-1 inhibits both type I and type II IFN activities by binding to the kinase activation loop via the kinase inhibitory region of the SOCS. The antagonist, pJAK2(1001-1013), inhibited the replication of vaccinia virus and encephalomyocarditis virus in cell culture, suggesting that it possesses broad antiviral activity. In addition, pJAK2(1001-1013) protected mice against lethal vaccinia and encephalomyocarditis virus infection. pJAK2(1001-1013) increased the intracellular level of the constitutive IFN-beta, which may play a role in the antagonist antiviral effect at the cellular level. Ab neutralization suggests that constitutive IFN-beta may act intracellularly, consistent with recent findings on IFN-gamma intracellular signaling. pJAK2(1001-1013) also synergizes with IFNs as per IFN-gamma mimetic to exert a multiplicative antiviral effect at the level of transcription, the cell, and protection of mice against lethal viral infection. pJAK2(1001-1013) binds to the kinase inhibitory region of both SOCS-1 and SOCS-3 and blocks their inhibitory effects on the IFN-gamma activation site promoter. In addition to a direct antiviral effect and synergism with IFN, the SOCS antagonist also exhibits adjuvant effects on humoral and cellular immunity as well as an enhancement of polyinosinic-polycytidylic acid activation of TLR3. The SOCS antagonist thus presents a novel and effective approach to enhancement of host defense against viruses.

Modulation of SOCS protein expression influences the interferon responsiveness of human melanoma cells

Background

Endogenously produced interferons can regulate the growth of melanoma cells and are administered exogenously as therapeutic agents to patients with advanced cancer. We investigated the role of negative regulators of interferon signaling known as suppressors of cytokine signaling (SOCS) in mediating interferon-resistance in human melanoma cells.

Methods

Basal and interferon-alpha (IFN-α) or interferon-gamma (IFN-γ)-induced expression of SOCS1 and SOCS3 proteins was evaluated by immunoblot analysis in a panel of n = 10 metastatic human melanoma cell lines, in human embryonic melanocytes (HEM), and radial or vertical growth phase melanoma cells. Over-expression of SOCS1 and SOCS3 proteins in melanoma cells was achieved using the PINCO retroviral vector, while siRNA were used to inhibit SOCS1 and SOCS3 expression. Tyr⁷⁰¹-phosphorylated STAT1 (P-STAT1) was measured by intracellular flow cytometry and IFN-stimulated gene expression was measured by Real Time PCR.

Results

SOCS1 and SOCS3 proteins were expressed at basal levels in melanocytes and in all melanoma cell lines examined. Expression of the SOCS1 and SOCS3 proteins was also enhanced following stimulation of a subset of cell lines with IFN-α or IFN-γ. Over-expression of SOCS proteins in melanoma cell lines led to significant inhibition of Tyr⁷⁰¹-phosphorylated STAT1 (P-STAT1) and gene expression following stimulation with IFN-α (IFIT2, OAS-1, ISG-15) or IFN-γ (IRF1). Conversely, siRNA inhibition of SOCS1 and SOCS3 expression in melanoma cells enhanced their responsiveness to interferon stimulation.

Conclusions

These data demonstrate that SOCS proteins are expressed in human melanoma cell lines and their modulation can influence the responsiveness of melanoma cells to IFN-α and IFN-γ.

Suppressor of cytokine signaling 3 suppresses hepatitis C virus replication in an mTOR-dependent manner

We and others have observed that hepatic levels of suppressor of cytokine signaling 3 (SOCS3) are significantly higher in persons with chronic hepatitis C, particularly those who are nonresponders to interferon (IFN) treatment, than in healthy individuals. However, the relationship between SOCS3 and hepatitis C virus (HCV) replication remains unclear. Given its putative role, we hypothesized that SOCS3 is permissive for viral replication. We therefore used the OR6 cell line, which harbors a genotype 1b full-length HCV replicon, and the genotype 2a full-length HCV strain JFH1 infection system to analyze the effects of SOCS3 overexpression and short hairpin RNA (shRNA)-mediated knockdown on HCV replication. We further analyzed the role of mTOR in the effects of SOCS3 by treating selected cells with rapamycin. OR6 cells and JFH1-infected Huh7.5.1 cells expressed significantly less SOCS3 than control cells. Furthermore, inhibition of HCV replication with the HCV protease inhibitor BILN 2061 restored SOCS3 protein levels. SOCS3 overexpression in OR6 cells and JFH1-infected Huh7.5.1 cells resulted in significantly lower HCV replication than that in the control cells, despite SOCS3-related inhibition of STAT1 phosphorylation and type I IFN signaling. In contrast, JFH1-infected cells with stable SOCS3 knockdown expressed higher levels of HCV proteins and RNA than did control cells. SOCS3-targeting shRNA also knocked down mTOR and phospho-mTOR. The mTOR inhibitor rapamycin reversed the inhibitory effects of SOCS3. In independent investigations, SOCS3 unexpectedly suppressed HCV replication in an mTOR-dependent manner. These findings suggest that increased SOCS3 levels consistently observed in chronic IFN nonresponders may reflect a compensatory host antiviral response to persistent infection and that manipulation of SOCS3/mTOR may offer benefit against HCV infection.

Deficient SOCS3 and SHP-1 expression in psoriatic T cells

IFN-alpha and skin-infiltrating activated T lymphocytes have important roles in the pathogenesis of psoriasis. T cells from psoriatic patients display an increased sensitivity to IFN-alpha, but the pathological mechanisms behind the hyperresponsiveness to IFN-alpha remained unknown. In this study, we show that psoriatic T cells display deficient expression of the suppressor of cytokine signaling (SOCS)3 in response to IFN-alpha and a low baseline expression of the SH2-domain-containing protein-tyrosine phosphatase (SHP)-1 when compared with skin T cells from nonpsoriatic donors. Moreover, IFN-alpha-stimulated psoriatic T cells show enhanced activation of JAKs (JAK1 and TYK2) and signal transducers and activators of transcription. Increased expression of SOCS3 proteins resulting from proteasomal blockade partially inhibits IFN-alpha response. Similarly, forced expression of SOCS3 and SHP-1 inhibits IFN-alpha signaling in psoriatic T cells. In conclusion, our data suggest that loss of regulatory control is involved in the aberrant hypersensitivity of psoriatic T cells to IFN-alpha.

Local expression of interferon-alpha and interferon receptors in cervical intraepithelial neoplasia

PURPOSE

The present study evaluated mRNA expression of interferon-alpha (IFN-alpha), IFN-alpha receptor subunits (IFNAR-1 and IFNAR-2) and an IFN-stimulated gene encoding the enzyme 2',5'-oligoadenylate synthetase (2'5'OAS) in biopsies on patients with varying grades of cervical intraepithelial neoplasia (CIN I, II and III).

METHODS

Uterine cervix biopsies were collected from women with CIN I, II and III (n = 28) and controls without CIN lesions or human papilloma virus (HPV) infection (n = 17). The presence of high and low-risk HPV DNA was determined using hybrid capture. The mRNA levels of IFNAR-1, IFNAR-2, IFN-alpha and 2'5'OAS were determined by RT-PCR with specific primers.

RESULTS

The control group exhibited a greater frequency of IFNAR-1 expression (10/17; 58.3%) than the CIN samples (4/28; 14.2%) (P = 0.0018), while, the expression of IFNAR-2 was also greater in the control samples (11/17; 64.7%) than in the patients with lesions (2/28; 7.1%) (P = 0.0018). Importantly, simultaneous expression of both receptors was observed only in the control group (8/17; 47.0%) (P = 0.0001). Among the CIN samples, there was one case of low expression of mRNA of IFNAR-1 and IFNAR-2. IFN-alpha was present in 14.2% (4/28) of the CIN samples but was not expressed in the control group. mRNA 2'5'OAS were expressed in 28.5% (8/28) of the CIN samples and 11.7% (2/17) of the control samples (not statistically significant). Fifty percent (14/28) of the CIN samples were positive for HPV DNA.

CONCLUSIONS

Cervical biopsy samples from control women or those without neoplasia or HPV infection displayed higher IFN-alpha receptor expression than those with CIN, while simultaneous expression of both IFN-alpha receptor subunits was found only in the control group. There was no significant difference in mRNA expression of IFN-alpha and 2'5'OAS between the control and CIN groups. Then we concluded that the samples obtained from patients with CIN present low levels of the IFN-alpha receptor mRNA.

Cross-regulation of signaling pathways by interferon-gamma: implications for immune responses and autoimmune diseases

Interferon-gamma (IFN-gamma) is an important mediator of immunity and inflammation that utilizes the JAK-STAT signaling pathway to activate the STAT1 transcription factor. Many functions of IFN-gamma have been ascribed to direct STAT1-mediated induction of immune effector genes, but recently it has become clear that key IFN-gamma functions are mediated by cross-regulation of cellular responses to other cytokines and inflammatory factors. Here, we review mechanisms by which IFN-gamma and STAT1 regulate signaling by Toll-like receptors, inflammatory factors, tissue-destructive cytokines, anti-inflammatory cytokines, and cytokines that activate opposing STATs. These signaling mechanisms reveal insights about how IFN-gamma regulates macrophage activation, inflammation, tissue remodeling, and helper and regulatory T cell differentiation and how Th1 and Th17 cell responses are integrated in autoimmune diseases.

SOCS1 and SOCS3 in the control of CNS immunity

In the decade following their initial discovery, the suppressor of cytokine signaling (SOCS) proteins have been studied for their potential use as immunomodulators in disease. SOCS proteins, especially SOCS1 and SOCS3, are expressed by immune cells and cells of the central nervous system (CNS) and have the potential to impact immune processes within the CNS, including inflammatory cytokine and chemokine production, activation of microglia, macrophages and astrocytes, immune cell infiltration and autoimmunity. We describe CNS-relevant in vitro and in vivo studies that have examined the function of SOCS1 or SOCS3 under various neuroinflammatory or neuropathological conditions, including exposure of CNS cells to inflammatory cytokines or bacterial infection, demyelinating insults, stroke, spinal cord injury, multiple sclerosis and glioblastoma multiforme.

MicroRNA Expression Profiling by Bead Array Technology in Human Tumor Cell Lines Treated with Interferon-Alpha-2a

MicroRNAs are positive and negative regulators of eukaryotic gene expression that modulate transcript abundance by specific binding to sequence motifs located prevalently in the 3' untranslated regions of target messenger RNAs (mRNA). Interferon-alpha-2a (IFNα) induces a large set of protein coding genes mediating antiproliferative and antiviral responses. Here we use a global microarray-based microRNA detection platform to identify genes that are induced by IFNα in hepatoma- or melanoma-derived human tumor cell lines. Despite the enormous differences in expression levels between these models, we were able to identify microRNAs that are upregulated by IFNα in both lines suggesting the possibility that interferon-regulated microRNAs are involved in the transcriptional repression of mRNA relevant to cytokine responses.

Control of T helper cell differentiation through cytokine receptor inclusion in the immunological synapse

The antigen recognition interface formed by T helper precursors (Thps) and antigen-presenting cells (APCs), called the immunological synapse (IS), includes receptors and signaling molecules necessary for Thp activation and differentiation. We have recently shown that recruitment of the interferon-gamma receptor (IFNGR) into the IS correlates with the capacity of Thps to differentiate into Th1 effector cells, an event regulated by signaling through the functionally opposing receptor to interleukin-4 (IL4R). Here, we show that, similar to IFN-gamma ligation, TCR stimuli induce the translocation of signal transducer and activator of transcription 1 (STAT1) to IFNGR1-rich regions of the membrane. Unexpectedly, STAT1 is preferentially expressed, is constitutively serine (727) phosphorylated in Thp, and is recruited to the IS and the nucleus upon TCR signaling. IL4R engagement controls this process by interfering with both STAT1 recruitment and nuclear translocation. We also show that in cells with deficient Th1 or constitutive Th2 differentiation, the IL4R is recruited to the IS. This observation suggest that the IL4R is retained outside the IS, similar to the exclusion of IFNGR from the IS during IL4R signaling. This study provides new mechanistic cues for the regulation of lineage commitment by mutual immobilization of functionally antagonistic membrane receptors.

Hepatic SOCS3 expression is strongly associated with non-response to therapy and race in HCV and HCV/HIV infection

BACKGROUND/AIMS

The response rates of HCV infection to interferon therapy vary depending on viral and host factors. We hypothesized that key regulators of the IFN signaling pathway are predictive of treatment outcome.

METHODS

We measured the expression of signal transducer and activator of transcription 1 (STAT1) and suppressor of cytokine signaling 3 (SOCS3) in pretreatment liver biopsies. Staining quantitation was compared to treatment outcomes.

RESULTS

Forty-nine patients with HCV and 25 patients with HCV/HIV infection treated with peginterferon/ribavirin were analyzed. Pretreatment hepatic SOCS3 expression was higher in non-responders than responders. Genotype 1 responders had similar levels of SOCS3 as genotype 2/3 responders. African Americans (AA) had higher hepatic SOCS3 than non-AA. Pretreatment hepatic SOCS3 was the most powerful independent predictor of sustained virologic response (SVR), even more so than genotype by logistic regression analysis. Failure to achieve SVR and AA race were independently associated with high hepatic SOCS3 levels. The hepatic expression of STAT-1 did not differ between responders and non-responders.

CONCLUSIONS

Our data indicate that hepatic SOCS3 is a stronger baseline predictor of antiviral response than viral genotype. Poor response to antiviral therapy in AA may be associated with higher hepatic SOCS3 expression.

SOCS1 regulates the IFN but not NFkappaB pathway in TLR-stimulated human monocytes and macrophages

SOCS1 can regulate TLR-mediated signal transduction, yet mechanistic studies in murine macrophages have been confusing and contradictory. This study has used an adenoviral transfection system to determine the role of SOCS1 in the regulation of TNF-alpha production by activated human monocytes. Monocytes were infected with AdV-SOCS1 or with an empty vector control, AdV-GFP, for 24 h before activation with the TLR4 ligand, LPS. SOCS1 did not regulate TNF-alpha mRNA or protein production within the first two hours of TLR4 activation. However, SOCS1 suppressed the sustained production of TNF-alpha by primary human monocytes and synovial fluid macrophages ex vivo. In addition, SOCS1 regulated the production of IL-6, but not IL-10, by monocytes. Analysis of the early signaling pathway downstream of TLR4 demonstrated that SOCS1 had no regulatory effect on the activation or on the DNA binding capacity of NFkappaB. The late effects of LPS are mediated in part through the MyD88-independent pathway activating IRF3 and initiating the production of IFN-beta. In response to adenoviral infection and before LPS exposure, monocytes expressed enhanced levels of IFN-beta and Myxovirus A mRNA, an anti-viral molecule characterizing IFN-beta activity. These two genes were reduced in AdV-SOCS1-infected cells. Further, SOCS1 regulated IFN-dependent pathways in LPS-activated cells as evidenced by reduced IFN-beta production and STAT1 phosphorylation. Using AdV-infection to dissect SOCS1 control of IFN-dependent pathways, this study suggests that SOCS1-regulation of the IFN-dependent component of the LPS-induced TLR4 signaling pathway may contribute to the down-regulation of inflammatory cytokine production by AdV-SOCS1-infected human monocytes.

Molecular basis of oncostatin M-induced SOCS-3 expression in astrocytes

Under neuropathological conditions, reactive astrocytes release cytokines and chemokines, which act in an autocrine and/or paracrine fashion to modulate production of immunoregulatory factors from cells including microglia, astrocytes, and neurons. In this way, astrocytes play an important role in orchestrating immune responses within the central nervous system (CNS). Suppressor of cytokine signaling (SOCS) proteins are endogenous, negative regulators of the JAK/STAT signaling pathway and function as attenuators of the immune and inflammatory responses. As such, SOCS proteins may have critical roles in the CNS under neuroinflammatory conditions. In the inflamed CNS, expression of IL-6 cytokine family member oncostatin M (OSM) is elevated; however, its functional effects are not well understood. We demonstrate that OSM is a potent inducer of SOCS-3 in astrocytes. Analysis of the SOCS-3 promoter revealed that an AP-1 element, two IFN-gamma activation sequence (GAS) elements, and a GC-rich region are crucial for SOCS-3 gene expression. Using small interfering RNA against STAT-3, as well as a STAT-3 dominant-negative construct, we demonstrate that STAT-3 activation is critical for OSM induction of SOCS-3 expression. The ERK1/2 and JNK pathways also contribute to OSM-induced SOCS-3 gene expression. OSM stimulation led to a time-dependent recruitment of the transcription factors STAT-3, c-Fos, c-Jun, and Sp1 and the coactivators CREB-binding protein (CBP) and p300 to the endogenous SOCS-3 promoter. These data indicate that OSM-induced activation of STAT-3 and the ERK1/2 and JNK pathways are critical for astrocytic expression of SOCS-3, which provides for feedback inhibition of cytokine-induced inflammatory responses in the CNS.

Gene expression profiling reveals similarities between the in vitro and in vivo responses of immune effector cells to IFN-alpha

PURPOSE

The precise molecular targets of IFN-alpha therapy in the context of malignant melanoma are unknown but seem to involve signal transducers and activators of transcription 1 signal transduction within host immune effector cells. We hypothesized that the in vitro transcriptional response of patient peripheral blood mononuclear cells (PBMC) to IFN-alpha would be similar to the in vivo response to treatment with high-dose IFN-alpha.

EXPERIMENTAL DESIGN

The gene expression profiles of PBMCs and immune cell subsets treated in vitro with IFN-alpha were evaluated, as were PBMCs obtained from melanoma patients receiving adjuvant IFN-alpha.

RESULTS

Twenty-seven genes were up-regulated in PBMCs from normal donors after treatment with IFN-alpha in vitro for 18 hours (>2-fold, P < 0.001). A subset of these genes (in addition to others) was significantly expressed in IFN-alpha-treated T cells, natural killer cells, and monocytes. Analysis of gene expression within PBMCs from melanoma patients (n = 13) receiving high-dose IFN-alpha-2b (20 MU/m(2) i.v.) revealed significant up-regulation (>2-fold) of 21 genes (P < 0.001). Also, the gene expression profile of in vitro IFN-alpha-stimulated patient PBMCs was similar to that of PBMCs obtained from the same patient after IFN-alpha therapy.

CONCLUSIONS

This report is the first to describe the transcriptional response of T cells, natural killer cells, and monocytes to IFN-alpha and characterize the transcriptional profiles of PBMCs from melanoma patients undergoing IFN-alpha immunotherapy. In addition, it was determined that microarray analysis of patient PBMCs after in vitro stimulation with IFN-alpha may be a useful predictor of the in vivo response of immune cells to IFN-alpha immunotherapy.

Review article: nonalcoholic fatty liver disease and hepatitis C virus--partners in crime

BACKGROUND

Both nonalcoholic fatty liver disease (NAFLD) and chronic hepatitis C (CHC) are frequent causes of chronic liver disease. In recent years, there have been significant revelations as regards the relationship between NAFLD and CHC.

AIM

To conduct a systematic, evidence-based review of the epidemiology, pathophysiology and potential treatments of coexistent NAFLD and CHC.

METHODS

The terms such as hepatitis C, fatty liver, NAFLD, nonalcoholic steatohepatitis and steatosis were searched on PubMed up to January 2008. References from selected articles and pertinent abstracts were also included.

RESULTS

Hepatic steatosis affects up to 80% of patients with CHC and is dependent on both viral and host factors. While insulin resistance (IR) is associated with hepatic steatosis and hepatitis C virus, genotype-specific pathogenic mechanisms have been identified and are currently the focus of intense investigation in the literature. Clinical implications of concurrent NAFLD, CHC and IR include increased disease progression, elevated risk of hepatocellular carcinoma, and decreased response to antiviral therapy.

CONCLUSIONS

NAFLD and IR are common in patients with CHC virus infection. IR is a driving force in the development of hepatic steatosis. Because of the clinical implications of hepatic steatosis and IR in the setting of CHC, further studies evaluating treatments, which may increase response to antiviral therapy, are needed.

Role of gp130-mediated signalling pathways in the heart and its impact on potential therapeutic aspects

IL-6-type cytokines bind to plasma membrane receptor complexes containing the common signal transducing receptor chain gp130 that is ubiquitously expressed in most tissues including the heart. The two major signalling cascades activated by the gp130 receptor, SHP2/ERK and STAT pathways, have been demonstrated to play important roles in cardiac development, hypertrophy, protection and remodelling in response to physiological and pathophysiological stimuli. Experimental data, both in vivo and in vitro, imply beneficial effects of gp130 signalling on cardiomyocytes in terms of growth and survival. In contrast, it has been reported that elevated serum levels of IL-6 cytokines and gp130 proteins are strong prognostic markers for morbidity and mortality in patients with heart failure or after myocardial infarction. Moreover, it has been shown that the local gp130 receptor system is altered in failing human hearts. In the present review, we summarize the basic principles of gp130 signalling, which requires simultaneous activation of STAT and ERK pathways under the tight control of positive and negative intracellular signalling modulators to provide a balanced biological outcome. Furthermore, we highlight the key role of the gp130 receptor and its major downstream effectors in the heart in terms of development and regeneration and in response to various physiological and pathophysiological stress situations. Finally, we comment on tissue-specific diversity and challenges in targeted pharmacological interference with components of the gp130 receptor system.

SOCS1 downregulation in dendritic cells promotes memory T-cell responses

SOCS1-1 is crucial for control of immune cell cytokine expression, including those cytokines known to enable memory T-cell formation and homeostasis. In this study, we found that immunization with SOCS1-downregulated bone marrow-derived dendritic cells generated increased antigen-specific CD8(+) T memory cells and antigen-specific responses, as measured by ELISPOT, CTL assays, serum ELISAs, and T-cell proliferation assays. Bone marrow-derived dendritic cells in which SOCS1 was downregulated expressed increased levels of surface IL-15Ra and thymic leukemia (TL) antigen, both of which support memory cell development. This work supports a crucial role for SOCS1 in regulation of dendritic cell-directed generation of memory T-cell responses.

STAT1-dependent and STAT1-independent gene expression in murine immune cells following stimulation with interferon-alpha

PURPOSE

The precise molecular targets of interferon-alpha (IFN-alpha) therapy of melanoma are unknown but likely involve signal transducer and activator of transcription 1 (STAT1) signal transduction within host immune effector cells. We hypothesized that microarray analysis could be utilized to identify candidate molecular targets important for mediating the anti-tumor effect of exogenously administered IFN-alpha.

EXPERIMENTAL METHODS

To identify the STAT1-dependent genes regulated by IFN-alpha, the gene expression profile of splenocytes from wild type (WT) and STAT1(-/-) mice was characterized.

RESULTS

This analysis identified 30 genes that required STAT1 signal transduction for optimal expression in response to IFN-alpha (p < 0.001). These genes include granzyme b (Gzmb), interferon regulatory factor 7 (Irf7), Fas death domain-associated protein (Daxx), and lymphocyte antigen 6 complex, locus C (Ly6c). The expression of 20 genes was found to be suppressed in the presence of STAT1 including chemokine ligand 2 (Ccl2), Ccl5, and Ccl7. Nineteen genes were significantly upregulated in murine splenocytes following treatment with IFN-alpha regardless of the presence of STAT1 including CD86, lymphocyte antigen 6 complex, locus A (Ly6a), and Tap binding protein (Tapbp). The expression of representative IFN-responsive genes was confirmed at the transcriptional level by Real Time PCR.

CONCLUSION

This report is the first to demonstrate that STAT1-mediated signal transduction plays a major role in the transcriptional response of murine immune cells to IFNalpha.