Deletion of the SOCS3 gene in liver parenchymal cells promotes hepatitis-induced hepatocarcinogenesis

The role of inflammation and liver cancer

Persistent inflammation is known to promote and exacerbate malignancy. Primary liver cancer, mostly hepatocellular carcinoma (HCC), is a clear example of inflammation-related cancer as more than 90 % of HCCs arise in the context of hepatic injury and inflammation. HCC represents the fifth most common malignancy and the third leading cause of cancer-related death worldwide with about one million new cases diagnosed every year with almost an equal number of deaths. Chronic unresolved inflammation is associated with persistent hepatic injury and concurrent regeneration, leading to sequential development of fibrosis, cirrhosis, and eventually HCC. Irrespective of the intrinsic differences among various etiological factors, a common denominator at the origin of HCC is the perpetuation of a wound-healing response activated by parenchymal cell death and the resulting inflammatory cascade. Hence, the identification of fundamental inflammatory signaling pathways causing transition from chronic liver injury to dysplasia and HCC could depict new predictive biomarkers and targets to identify and treat patients with chronic liver inflammation. This chapter critically discusses the roles of several major cytokines, chemokines, growth factors, transcription factors, and enzymes as well as a distinct network of inflammatory signaling pathways in the development and progression of HCC. It also highlights and analyzes preclinical animal studies showing innovative approaches of targeting inflammatory mediators and signaling by a variety of natural compounds and synthetic agents to achieve effective therapy as well as prevention of hepatic malignancy. Additionally, current limitations and potential challenges associated with the inhibition of inflammatory signaling as well as future directions of research to accelerate clinical development of anti-inflammatory agents to prevent and treat liver cancer are presented.

Correlation between biological marker expression and fluorine-18 fluorodeoxyglucose uptake in hepatocellular carcinoma

OBJECTIVES

This study investigated the association between several biological markers and fluorine-18 fluorodeoxyglucose (FDG) uptake in patients with hepatocellular carcinoma.

METHODS

Forty-two patients with hepatocellular carcinoma who underwent FDG positron emission tomography were included in the study. Tumor sections were immunohistochemically stained for phosphorylated signal transducer and activator of transcription 3 (pSTAT3), hypoxia-inducible factor 1α (HIF1α), glucose transporter 1 (GLUT1), GLUT2, GLUT3, and GLUT4.

RESULTS

The high standardized uptake value (SUV) group showed larger tumor size, more frequent vascular invasion, and poorer differentiation compared with the low SUV group. The high SUV group also showed significantly higher immunohistochemical expression of pSTAT3, HIF1α, and GLUT1. The GLUT1 high-expression group showed higher α-fetoprotein (a tumor marker) and poorer differentiation than did the GLUT1 low-expression group.

CONCLUSIONS

Our study indicates that FDG uptake is associated with the expression of pSTAT3, HIF1α, and GLUT1 in hepatocellular carcinoma. The expression of these proteins shows a correlation with poor differentiation and vascular invasion.

Interleukins in chronic liver disease: lessons learned from experimental mouse models

Interleukins represent a class of immunomodulatory cytokines, small intercellular signaling proteins, that are critically involved in the regulation of immune responses. They are produced in large amounts by various cell types during inflammatory reactions, and the balance of cytokines determines the outcome of an immune response. Therefore, cytokines are regarded as interesting therapeutic targets for the treatment of patients with liver diseases. Mouse models provide a good tool for in vivo studies on cytokine function, as human and mouse cytokines share many homologies. Sophisticated mouse models either mimicking distinct pathological conditions or targeting cytokines and cytokine-signaling pathways in the liver or even in distinct cellular compartments have provided enormous insight into the different functions of interleukins during hepatic inflammation. Interleukins may have pro- as well as anti-inflammatory functions in chronic liver diseases, some interleukins even both, dependent on the inflammatory stimulus, the producing and the responding cell type. IL-17, for example, promotes hepatic fibrogenesis through activation of hepatic stellate cells and facilitates development of liver cancer through recruitment of myeloid-derived suppressor cells. IL-22, on the other hand, protects from development of fibrosis or steatohepatitis. IL-12 balances T-helper (Th)-1 and Th2 cell responses in infectious disease models. IL-13 and IL-33, two cytokines related to Th2 cells and innate lymphoid cells, promote fibrotic responses in the liver. IL-10 is the prototypic anti-inflammatory interleukin with tissue-protective functions during chronic liver injury and fibrogenesis. Despite its critical role for inducing the acute-phase response in the liver, IL-6 signaling is protective during fibrosis progression, but promotes hepatocellular carcinoma. Experimental studies in mice help to define the exact influence of a specific cytokine on the outcome of chronic liver diseases and to identify useful therapeutic targets.

SOCS3 expression is inversely correlated with Pyk2 in non-small cell lung cancer and exogenous SOCS3 inhibits proliferation and invasion of A549 cells

AIMS

We have confirmed that suppressor of cytokine signalling 3 (SOCS3) is silenced and proline-rich tyrosine kinase 2 (Pyk2) is over-expressed in non-small cell lung cancer (NSCLC). The aim of this study was to investigate the correlation of SOCS3 and Pyk2 expression in NSCLC, and the effects of SOCS3 up-regulation on A549 cells.

METHODS

One hundred cases of NSCLC were detected for the expression of SOCS3 and Pyk2 by immunohistochemistry. The expression of SOCS3 and Pyk2 were also examined in human bronchial epithelial cells (HBE) and six lung cancer cell lines using Western blot and immunofluorescence staining. Then plasmid containing full-length SOCS3 was transfected into A549 cells to further investigate the effects of SOCS3 over-expression on proliferation, apoptosis and invasion of transfected cells, which were examined using MTT, flow cytometry and Transwell assays.

RESULTS

Our results showed a significant negative correlation between SOCS3 and Pyk2 in both NSCLC tissues and cell lines. Up-regulation of SOCS3 increased the apoptotic rates of transfected cells, while the numbers of proliferative and invasive cells were decreased.

CONCLUSIONS

Our data indicate that SOCS3 definitely plays roles in regulating Pyk2 expression, and up-regulation of SOCS3 could be an effective way to prevent the progression of NSCLC.

Hepatitis C virus-induced hepatocyte cell death and protection by inhibition of apoptosis

Chronic hepatitis C virus (HCV) infection results in progressive liver fibrosis leading to cirrhosis and liver cancer. The mechanism for this remains unclear but hepatocyte apoptosis is thought to play a major role. Hepatocyte apoptosis in human liver tissue was determined by immunohistochemistry for cytokeratin 18 (M30 CytoDEATH) and cleaved poly(ADP-ribose) polymerase (PARP). In vitro studies were performed with replication-defective recombinant adenoviruses expressing HCV proteins (rAdHCV) to study the effects of HCV on cell death in Huh7 cells, primary mouse hepatocytes (PMoHs) and primary human hepatocytes (PHHs). Cell viability and apoptosis were studied using crystal violet assays and Western blots probed for cleaved caspase-3 and cleaved PARP, with and without treatment with the pan-caspase inhibitor Q-VD-OPh and necrostatin-1. Liver tissue of HCV-infected patients expressed elevated levels of apoptotic markers compared with HCV-negative patients. rAdHCV infection reduced cell viability compared with uninfected controls and cells infected with control virus (rAdGFP). Huh7, PMoHs and PHHs infected with rAdHCV showed significantly increased levels of apoptotic markers compared with uninfected controls and rAdGFP-infected cells. In rAdHCV-infected Huh7, treatment with Q-VD-OPh and necrostatin-1 both improved cell viability. Q-VD-Oph also reduced cleaved PARP in rAdHCV-infected Huh7 and PMoHs. Hepatocyte apoptosis is known to be increased in the livers of HCV-infected patients. HCV promoted cell death in primary and immortalized hepatocytes, and this was inhibited by Q-VD-OPh and necrostatin-1. These findings indicate that HCV-induced cell death occurs by both apoptosis and necroptosis, and provide new insights into the mechanisms of HCV-induced liver injury.

SOCS3 expression correlates with severity of inflammation in mouse hepatitis virus strain 3-induced acute liver failure and HBV-ACLF

Recently, suppressor of cytokine signaling-3 (SOCS3) has been shown to be an inducible endogenous negative regulator of Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway which is relevant in inflammatory response, while its functions in acute liver failure and HBV-induced acute-on-chronic liver failure (HBV-ACLF) have not been fully elucidated. In this study, we explored the role of SOCS3 in the development of mouse hepatitis virus strain 3 (MHV-3)-induced acute liver failure and its expression in liver and peripheral blood mononuclear cells (PBMCs) of patients with HBV-ACLF. Inflammation-related gene expression was detected by real-time PCR, immunohistochemistry and Western blotting. The correlation between SOCS3 level and liver injury was studied. Our results showed that the SOCS3 expression was significantly elevated in both the liver tissue and PBMCs from patients with HBV-ACLF compared to mild chronic hepatitis B (CHB). Moreover, a time course study showed that SOCS3 level was increased remarkably in the liver of BALB/cJ mice at 72 h post-infection. Pro-inflammatory cytokines, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, were also increased significantly at 72 h post-infection. There was a close correlation between hepatic SOCS3 level and IL-6, and the severity of liver injury defined by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, respectively. These data suggested that SOCS3 may play a pivotal role in the pathogenesis of MHV-3-induced acute liver failure and HBV-ACLF.

STAT3 and epithelial-mesenchymal transitions in carcinomas

Cellular programs coupled to cycles of epithelial–mesenchymal transitions (EMTs) play critical roles during embryogenesis, as well as during tissue development, remodeling, and repair. Research over the last decade has established the importance of an ever-expanding list of master EMT transcription factors, whose activity is regulated by STAT3 and function to stimulate the rapid transition of cells between epithelial and mesenchymal phenotypes. Importantly, inappropriate reactivation of embryonic EMT programs in carcinoma cells underlies their metastasis to distant organ sites, as well as their acquisition of stem cell-like and chemoresistant phenotypes operant in eliciting disease recurrence. Thus, targeted inactivation of master EMT transcription factors may offer new inroads to alleviate metastatic disease. Here we review the molecular, cellular, and microenvironmental factors that contribute to the pathophysiological activities of STAT3 during its regulation of EMT programs in human carcinomas.

Role of estrogen in hepatocellular carcinoma: is inflammation the key?

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and accounts for the third-leading cause of cancer-related deaths. Over the past decades, advances have been made in the field of surgery, but effective treatment of HCC is lacking. Due to a marked male predominance in morbidity and mortality in HCC patients, it has long been considered that sex hormones play a role in HCC development. Recently estrogen has been proven to exert protective effects against HCC through IL-6 restrictions, STAT3 inactivation and tumour-associated macrophage inhibition. While IL-6-dependent STAT3 activation is considered a key event in inflammation-induced liver cancer, the anti-inflammation effect of estrogen is well documented. The roles of the estrogen receptor and aromatase and interactions between microRNAs and estrogen in HCC have been investigated. In this review, we present a novel model to elucidate the mechanism of estrogen-mediated inhibition of HCC development through an anti-inflammation effect and provide new insights into the roles of estrogen in liver disease.

The role of suppressors of cytokine signalling in human neoplasms

Suppressors of cytokine signalling 1-7 (SOCS1-7) and cytokine-inducible SH2-containing protein (CIS) are a group of intracellular proteins that are well known as JAK-STAT and several other signalling pathways negative feedback regulators. More recently several members have been identified as tumour suppressors and dysregulation of their biological roles in controlling cytokine and growth factor signalling may contribute to the development of many solid organ and haematological malignancies. This review explores their biological functions and their possible tumour suppressing role in human neoplasms.

SOCS3-mediated regulation of inflammatory cytokines in PTEN and p53 inactivated triple negative breast cancer model

Somatic mutations or deletions of TP53 and PTEN in ductal carcinoma in situ (DCIS) lesions have been implicated in progression to invasive ductal carcinomas. A recent molecular and mutational analysis of breast cancers revealed that inactivation of tumor suppressors, p53 and PTEN are strongly associated with triple negative breast cancer. In addition, these tumor suppressors play important roles in regulating self-renewal in normal and malignant stem cells. To investigate their role in breast carcinogenesis, we knocked down these genes in human mammary cells and in non-transformed MCF10A cells. p53 and PTEN knockdown synergized to activate pro-inflammatory IL6/Stat3/NF-κB signaling. This resulted in generation of highly metastatic EMT-like cancer stem cells (CSCs) resulting in tumors whose gene expression profile mimicked that found in basal/claudin-low molecular subtype within the triple negative breast tumors. Constitutive activation of this loop in transformed cells was dependent on proteolytic degradation of SOCS3 resulting in low levels of this protein in basal/claudin low cell lines and primary tumors. In non-transformed cells, transient activation of the IL6 inflammatory loop induced SOCS3 expression leading to pathway inactivation. In transformed cells, enforced expression of SOCS3 or interfering with IL6 pathway via IL6R blockade inhibited tumor growth and metastasis in mouse xenograft models. Furthermore, circulating tumor cells were significantly reduced in tumor bearing animals when treated with anti-IL6R antibodies. These studies uncover important connections between inflammation and carcinogenesis and suggest that blocking pro-inflammatory cytokines may be utilized as an attractive strategy to target triple negative breast tumors which currently lacks molecularly targeted therapies.

IL-6 and related cytokines as the critical lynchpins between inflammation and cancer

Inflammatory responses play pivotal roles in cancer development, including tumor initiation, promotion, progression, and metastasis. Cytokines are now recognized as important mediators linking inflammation and cancer, and are therefore potential therapeutic and preventive targets as well as prognostic factors. The interleukin (IL)-6 family of cytokines, especially IL-6 and IL-11, is highly up-regulated in many cancers and considered as one of the most important cytokine families during tumorigenesis and metastasis. This review discusses molecular mechanisms linking the IL-6 cytokine family to solid malignancies and their treatment.

Interleukin-6 signaling drives fibrosis in unresolved inflammation

Fibrosis in response to tissue damage or persistent inflammation is a pathological hallmark of many chronic degenerative diseases. By using a model of acute peritoneal inflammation, we have examined how repeated inflammatory activation promotes fibrotic tissue injury. In this context, fibrosis was strictly dependent on interleukin-6 (IL-6). Repeat inflammation induced IL-6-mediated T helper 1 (Th1) cell effector commitment and the emergence of STAT1 (signal transducer and activator of transcription-1) activity within the peritoneal membrane. Fibrosis was not observed in mice lacking interferon-γ (IFN-γ), STAT1, or RAG-1. Here, IFN-γ and STAT1 signaling disrupted the turnover of extracellular matrix by metalloproteases. Whereas IL-6-deficient mice resisted fibrosis, transfer of polarized Th1 cells or inhibition of MMP activity reversed this outcome. Thus, IL-6 causes compromised tissue repair by shifting acute inflammation into a more chronic profibrotic state through induction of Th1 cell responses as a consequence of recurrent inflammation.

Mechanisms of STAT3 activation in the liver of FXR knockout mice

Farnesoid X receptor (FXR, Nr1h4) is a ligand-activated transcription factor belonging to the nuclear receptor superfamily. FXR is essential in maintaining bile acid (BA) homeostasis, and FXR(-/-) mice develop cholestasis, inflammation, and spontaneous liver tumors. The signal transducer and activator of transcription 3 (STAT3) is well known to regulate liver growth, and STAT3 is feedback inhibited by its target gene, the suppressor of cytokine signaling 3 (SOCS3). Strong activation of STAT3 was detected in FXR(-/-) mouse livers. However, the mechanism of STAT3 activation with FXR deficiency remains elusive. Wild-type (WT) and FXR(-/-) mice were used to detect STAT3 pathway activation in the liver. In vivo BA feeding or deprivation was used to determine the role of BAs in STAT3 activation, and in vitro molecular approaches were used to determine the direct transcriptional regulation of SOCS3 by FXR. STAT3 was activated in FXR(-/-) but not WT mice. BA feeding increased, but deprivation by cholestyramine reduced, serum inflammatory markers and STAT3 activation. Furthermore, the Socs3 gene was determined as a direct FXR target gene. The elevated BAs and inflammation, along with reduced SOCS3, collectively contribute to the activation of the STAT3 signaling pathway in the liver of FXR(-/-) mice. This study suggests that the constitutive activation of STAT3 may be a mechanism of liver carcinogenesis in FXR(-/-) mice.

SOCS, inflammation, and cancer

Signal transduction pathways elicited by cytokines and hormones have been shown to regulate distinct stages of development. Suppressor of cytokine signaling (SOCS) proteins are negative feedback regulators of cytokine signaling mediated by the JAK-STAT signaling pathway. In particular, SOCS1 and SOCS3 are potent inhibitors of JAKs and can play pivotal roles in inflammation, as well as in the development and progression of cancers. Abnormal expression of SOCS1 and SOCS3 in cancer cells has been reported in human carcinoma associated with dysregulation of signals from cytokine receptors, Toll-like receptors (TLRs), and hormone receptors, resulting in malignancies. In this review, we focus on the role of SOCS1 and SOCS3 in cancer development. In addition, the potential of SOCS as a therapeutic target and diagnostic aid will be discussed.

Lymph node metastasis is mediated by suppressor of cytokine signaling-3 in gastric cancer

Suppressor of cytokine signaling-3 (SOCS-3), a multifunctional cytokine, is able to inhibit cell growth and migration by blocking the Janus kinase signal transducers and activators of transcription signaling (JAK/STAT) activation in oncogenesis. Although the STAT-3 expression was associated with lymph node metastasis from gastric cancer (GC), the implication of SOCS-3 expression in GC is not clearly elucidated. In this study, SOCS-3, STAT-3, and pSTAT-3 were evaluated in GC tissues and adjacent non-tumor tissues of 107 patients who underwent curative surgery by immunohistochemistry. Further, SOCS-3 and STAT-3 mRNA levels were also detected simultaneously. In addition, survival analysis was performed between clinicopathologic variables and prognosis of GC patients. Finally, correlative analysis was adopted for demonstration the best predicator of the survival independent factor. From the results, we demonstrated that only the lymph node metastasis was the independent predictor of the overall survival (OS) of GC patients, although SOCS-3, STAT-3, and other variables were significantly relative to OS. With multivariate logistical regression analysis, SOCS-3, STAT-3, and the status of extragastric nodal metastasis were identified to be the independent factors of the lymph node metastasis from GC. Ultimately, the SOCS-3 was the best predicator of lymph node metastasis from GC identified with the nominal regression analysis. Therefore, SOCS-3 should be considered as a potential indicator for prediction the lymph node metastasis from GC.

A20 promotes liver regeneration by decreasing SOCS3 expression to enhance IL-6/STAT3 proliferative signals

Liver regeneration is of major clinical importance in the setting of liver injury, resection, and transplantation. A20, a potent antiinflammatory and nuclear factor kappa B (NF-κB) inhibitory protein, has established pro-proliferative properties in hepatocytes, in part through decreasing expression of the cyclin dependent kinase inhibitor, p21. Both C-terminal (7-zinc fingers; 7Zn) and N-terminal (Nter) domains of A20 were required to decrease p21 and inhibit NF-κB. However, both independently increased hepatocyte proliferation, suggesting that additional mechanisms contributed to the pro-proliferative function of A20 in hepatocytes. We ascribed one of A20's pro-proliferative mechanisms to increased and sustained interleukin (IL)-6-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation, as a result of decreased hepatocyte expression of the negative regulator of IL-6 signaling, suppressor of cytokine signaling 3 (SOCS3). This novel A20 function segregates with its 7Zn not Nter domain. Conversely, total and partial loss of A20 in hepatocytes increased SOCS3 expression, hampering IL-6-induced STAT3 phosphorylation. Following liver resection in mice pro-proliferative targets downstream of IL-6/STAT3 signaling were increased by A20 overexpression and decreased by A20 knockdown. In contrast, IL-6/STAT3 proinflammatory targets were increased in A20-deficient livers, and decreased or unchanged in A20 overexpressing livers. Upstream of SOCS3, levels of its microRNA regulator miR203 were significantly decreased in A20-deficient livers.

CONCLUSION

A20 enhances IL-6/STAT3 pro-proliferative signals in hepatocytes by down-regulating SOCS3, likely through a miR203-dependent manner. This finding together with A20 reducing the levels of the potent cell cycle brake p21 establishes its pro-proliferative properties in hepatocytes and prompts the pursuit of A20-based therapies to promote liver regeneration and repair.

Nuclear receptors in regenerating liver and hepatocellular carcinoma

A comprehensive understanding of the pathways underlying hepatocyte turnover and liver regeneration is essential for the development of innovative and effective therapies in the management of chronic liver disease, and the prevention of hepatocellular carcinoma (HCC) in cirrhosis. Nuclear receptors (NRs) are master transcriptional regulators of liver development, differentiation and function. NRs have been implicated in the modulation of hepatocyte priming and proliferation in regenerating liver, chronic hepatitis and HCC development. In this review, we focus on NRs and their pathways regulating hepatocyte proliferation and liver regeneration, with a perspective view on NRs as candidate biomarkers and novel pharmacological targets in the management of liver disease and HCC.

Gene methylation and silencing of SOCS3 in mantle cell lymphoma

The significance of loss of SOCS3, a negative regulator of signalling pathways including those of STAT3 and NF-κB, was examined in mantle cell lymphoma (MCL). The protein expression and gene methylation status of SOCS3 were detected using immunohistochemistry/Western blots and methylation-specific polymerase chain reaction, respectively. To evaluate its functional importance, SOCS3 was restored in two SOCS3-negative MCL cell lines using a lentiviral vector. Loss of SOCS3 protein expression was found in 3/4 MCL cell lines and 18/33 (54.5%) tumours. SOCS3 was found consistently methylated in cell lines (3/4) and tumours (7/7) negative for SOCS3, and was unmethylated in all SOCS3-positive cell line (1/1) and tumours (5/5) examined. Treatment of all three SOCS3-negative cell lines with 2'-deoxy-5-azacytidine restored SOCS3 expression. SOCS3 is biologically important in MCL, as lentiviral transfer of SOCS3 in SOCS3-negative cell lines increased their apoptotic activity, downregulated nuclear factor (NF)-κB-p65, cyclin D1 (CCND1), BCL2 and BCL-XL (BCL2L1), and substantially dampened interleukin 10-induced STAT3 activation. In 19 patients aged ≤ 69 years at time of diagnosis, we found that those that carried SOCS3-negative tumours showed a trend toward a worse outcome (P = 0.1, log-rank).

Interference of suppressor of cytokine signaling 3 promotes epithelial-mesenchymal transition in MHCC97H cells

AIM: To investigate the role of suppressor of cytokine signaling 3 (SOCS3) silencing in epithelial-mesenchymal transition (EMT) involved in a human hepatocellular carcinoma MHCC97H cell line.

METHODS: MHCC97H cells were transiently transfected with SOCS3 small-interfering RNA (siRNA). Morphological changes of the transfected cells were observed under microscope. Expressions of E-cadherin, Vimentin and α-smooth muscle actin (α-SMA) were identified with immunofluorescence. Furthermore, protein expressions and mRNA levels of characteristic markers of EMT (E-cadherin, Vimentin, α-SMA and Snail) were detected by Western blotting, quantitative real-time polymerase chain reaction. Transforming growth factor-β1 (TGF-β1) levels in the supernatant were measured with enzyme-linked immunosorbent assay.

RESULTS: The transfected cells with SOCS3 siRNA showed a morphological alteration from a typical cobblestone morphology to mesenchymal spindle-shaped and fusiform features. SOCS3 siRNA lessened immunofluorescent expression of E-cadherin, but elicited immunofluorescent expressions of Vimentin and α-SMA in MHCC97H cells. More importantly, compared with the negative control, depletion of SOCS3 resulted in the decrease of the epithelial marker E-cadherin (P < 0.05), and the increase of the mesenchymal markers Vimentin and α-SMA and the transcription factor Snail in MHCC97H cells (P < 0.05). Moreover, compared with the negative control, SOCS3 siRNA evidently enhanced TGF-β1 secretion in MHCC97H cells (200.20 ± 29.02 pg/mL vs 490.20 ± 92.43 pg/mL, P < 0.05).

CONCLUSION: SOCS3 silencing is able to promote EMT in MHCC97H cells via changing the phenotypic characteristics and modulating the characteristic markers.

Tumor-associated macrophage promotes tumor progression via STAT3 signaling in hepatocellular carcinoma

OBJECTIVE

Signal transducer and activator of transcription 3 (STAT3) is activated in hepatocellular carcinoma (HCC), and tumor-associated macrophage plays an important role in tumor progression. Therefore, we examined STAT3 activation, cytokine expression and infiltration of tumor-associated macrophages in resected HCCs as well as the alteration of cell growth and migration by cytokine stimulation in HCC cell lines.

METHODS

Immunohistochemical staining of phosphorylated STAT3 (pSTAT3), CD163, interleukin (IL)-6, Ki-67 and Bcl-XL was performed for 101 cases of resected HCC, and correlations between pSTAT3 staining and clinicopathological findings were analyzed. In HCC cell lines (PLC/PRF/5 and Huh7), cell proliferation and migration by IL-6 stimulation and S3I-201 (STAT3 inhibitor) treatment were analyzed.

RESULTS

In HCC specimens, the pSTAT3-positive group showed high levels of α-fetoprotein (p = 0.0276), large tumor size (p = 0.0092), frequent intrahepatic metastasis (p = 0.0214), high Ki-67 (p = 0.0002) and Bcl-XL (p = 0.0001), poor prognosis (p = 0.0234), and high recurrence rate (p = 0.0003). CD163-positive cells were frequently observed in the pSTAT3-positive group (p = 0.0013). In two HCC cell lines, IL-6 stimulation promoted cell proliferation and migration via the STAT3 phosphorylation, and S3I-201 inhibited this activation.

CONCLUSIONS

STAT3 activation was correlated with aggressive behavior of HCC and may be mediated via tumor-associated macrophage. We expect that STAT3 signaling and tumor-associated macrophages can be attractive therapeutic targets in HCC patients.

The inflammatory microenvironment in hepatocellular carcinoma: a pivotal role for tumor-associated macrophages

Hepatocellular carcinoma (HCC) is one of the most common and aggressive human cancers worldwide. HCC is an example of inflammation-related cancer and represents a paradigm of the relation occurring between tumor microenvironment and tumor development. Tumor-associated macrophages (TAMs) are a major component of leukocyte infiltrate of tumors and play a pivotal role in tumor progression of inflammation-related cancer, including HCC. Several studies indicate that, in the tumor microenvironment, TAMs acquire an M2-polarized phenotype and promote angiogenesis, metastasis, and suppression of adaptive immunity through the expression of cytokines, chemokines, growth factors, and matrix metalloproteases. Indeed, an established M2 macrophage population has been associated with poor prognosis in HCC. The molecular links that connect cancer cells and TAMs are not completely known, but recent studies have demonstrated that NF-κB, STAT-3, and HIF-1 signaling pathways play key roles in this crosstalk. In this paper, we discuss the current knowledge about the role of TAMs in HCC development, highlighting the role of TAM-derived cytokines, chemokines, and growth factors in the initiation and progression of liver cancer and outlining the signaling pathways involved in the interplay between cancer cells and TAMs.

STAT3-driven upregulation of TLR2 promotes gastric tumorigenesis independent of tumor inflammation

Gastric cancer (GC) is associated with chronic inflammation; however, the molecular mechanisms promoting tumorigenesis remain ill defined. Using a GC mouse model driven by hyperactivation of the signal transducer and activator of transcription (STAT)3 oncogene, we show that STAT3 directly upregulates the epithelial expression of the inflammatory mediator Toll-like receptor (TLR)2 in gastric tumors. Genetic and therapeutic targeting of TLR2 inhibited gastric tumorigenesis, but not inflammation, characterized by reduced proliferation and increased apoptosis of the gastric epithelium. Increased STAT3 pathway activation and TLR2 expression were also associated with poor GC patient survival. Collectively, our data reveal an unexpected role for TLR2 in the oncogenic function of STAT3 that may represent a therapeutic target in GC.

Mutational screening of the SOCS3 gene promoter in metastatic colorectal cancer patients

Cytokine-induced expression of suppressors of cytokine signalling (SOCS) molecules is important for the negative feedback control of STAT-dependent cytokine signalling. The aim of this study was to investigate possible association between the promoter region polymorphisms of the SOCS3 gene and metastatic colorectal carcinoma in a Turkish population. The DNA samples obtained from 103 patients and 109 healthy individuals were analyzed by polymerase chain reaction/single-strand conformation polymorphism (SSCP), and nucleotide sequence analysis. Five sets of primers designed for the SOCS3 gene were used, and we did not detect significant differences in genotype frequencies for any of these polymorphisms between the study groups. Only the S3P1 region showed polymorphism and displayed three (1,2,4, 2,3,4 and 2,4) genotypes. Interestingly, 2,3,4 genotype was observed in 3 patients, but not in controls. Moreover, the sequence analysis revealed that the nucleotides positioned at -914 and -1031 nt had the polymorphisms. Nucleotide sequence analysis of SSCP band 1 and band 3 revealed C-914A (rs12953258) and T-1031C (rs111033850) polymorphisms, respectively. The T-1031C polymorphism lies in the border of the STAT-binding site. The T-1031C polymorphism (rs111033850) is a newly identified single nucleotide polymorphism with this study, and we submitted this to the NCBI database. However, these results suggested that there is no marked association between SOCS3 gene promoter region polymorphisms and the risk of developing metastatic colorectal cancer.

Loss of expression and function of SOCS3 is an early event in HNSCC: altered subcellular localization as a possible mechanism involved in proliferation, migration and invasion

Background

Suppressor of cytokine signaling 3 (SOCS3) is an inducible endogenous negative regulator of signal transduction and activator of transcription 3 (STAT3). Epigenetic silencing of SOCS3 has been shown in head and neck squamous cell carcinoma (HNSCC), which is associated with increased activation of STAT3. There is scarce information on the functional role of the reduction of SOCS3 expression and no information on altered subcellular localization of SOCS3 in HNSCC.

Methodology/Principal Findings

We assessed endogenous SOCS3 expression in different HNSCC cell lines by RT-qPCR and western blot. Immunofluorescence and western blot were used to study the subcellular localization of endogenous SOCS3 induced by IL-6. Overexpression of SOCS3 by CMV-driven plasmids and siRNA-mediated inhibition of endogenous SOCS3 were used to verify the role of SOCS3 on tumor cell proliferation, viability, invasion and migration in vitro. In vivo relevance of SOCS3 expression in HNSCC was studied by quantitative immunohistochemistry of commercially-available tissue microarrays. Endogenous expression of SOCS3 was heterogeneous in four HNSCC cell lines and surprisingly preserved in most of these cell lines. Subcellular localization of endogenous SOCS3 in the HNSCC cell lines was predominantly nuclear as opposed to cytoplasmic in non-neoplasic epithelial cells. Overexpression of SOCS3 produced a relative increase of the protein in the cytoplasmic compartment and significantly inhibited proliferation, migration and invasion, whereas inhibition of endogenous nuclear SOCS3 did not affect these events. Analysis of tissue microarrays indicated that loss of SOCS3 is an early event in HNSCC and was correlated with tumor size and histological grade of dysplasia, but a considerable proportion of cases presented detectable expression of SOCS3.

Conclusion

Our data support a role for SOCS3 as a tumor suppressor gene in HNSCC with relevance on proliferation and invasion processes and suggests that abnormal subcellular localization impairs SOCS3 function in HNSCC cells.

Anti-miR-203 Upregulates SOCS3 Expression in Breast Cancer Cells and Enhances Cisplatin Chemosensitivity

Breast cancer is one of the most common cancers among women in the United States. Although there are effective drugs, such as cisplatin, for treating advanced cancers, many patients eventually develop resistance. MicroRNAs (miRNAs) have emerged to play important roles in tumorigenesis and drug resistance. In this study, the authors observed a significant upregulation of miR-203 expression in human breast cancer tissues as compared to patient-matched nontumor breast tissues. Knockdown of miR-203 following cisplatin treatment enhances p53, p21, and Bax protein expression. Furthermore, knockdown of miR-203 sensitized human breast cancer MCF-7 cells to cisplatin-mediated apoptotic cell death, as evident from caspase-9 and caspase-7 activation, and poly(ADP-ribose) polymerase (PARP) cleavage. Moreover, the authors have demonstrated that suppressor of cytokine signaling 3 (SOCS3) is a novel target of miR-203, and cisplatin treatment in miR-203 knockdown MCF-7 cells enhanced SOCS3 expression. Exogenous expression of SOCS3 in MCF-7 cells increased sensitization to cisplatin-mediated apoptosis. Together, the results suggested a novel role of miR-203 in conferring cisplatin resistance through suppression of SOCS3, implicating an additional therapeutic strategy may be helpful to overcome cisplatin resistance for breast cancer patients.

Inflammation- and stress-related signaling pathways in hepatocarcinogenesis

It has been established that cancer can be promoted and exacerbated by inflammation. Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide, and its long-term prognosis remains poor. Although HCC is a complex and heterogeneous tumor with several genomic mutations, it usually develops in the context of chronic liver damage and inflammation, suggesting that understanding the mechanism(s) of inflammation-mediated hepatocarcinogenesis is essential for the treatment and prevention of HCC. Chronic liver damage induces a persistent cycle of necro-inflammation and hepatocyte regeneration, resulting in genetic mutations in hepatocytes and expansion of initiated cells, eventually leading to HCC development. Recently, several inflammation- and stress-related signaling pathways have been identified as key players in these processes, which include the nuclear factor-κB, signal transducer and activator of transcription, and stress-activated mitogen- activated protein kinase pathways. Although these pathways may suggest potential therapeutic targets, they have a wide range of functions and complex crosstalk occurs among them. This review focuses on recent advances in our understanding of the roles of these signaling pathways in hepatocarcinogenesis.

Serine 727 phosphorylation of STAT3: an early change in mouse hepatocarcinogenesis induced by neonatal treatment with diethylnitrosamine

STAT3 activation is involved in development and progression of hepatocellular carcinoma (HCC). We investigated STAT3 activation during hepatocarcinogenesis induced by neonatal diethylnitrosamine (DEN) treatment in mice. Nuclear accumulation and phosphorylation of STAT3 were detected in altered hepatocyte foci in the early stages as well as adenomas and HCCs in the late stages. Although total STAT3 levels were the same between the hepatic lesions and normal livers, S727-phosphorylated STAT3 was enhanced in adenomas and HCCs, whereas Y705-phosphorylated STAT3 was detected mainly in HCCs. In mouse HCC cell lines, although both S727 and Y705 remained un- or hypophosphorylated under serum-free conditions, fetal bovine serum (FBS) induced strong S727/weak Y705 phosphorylation, STAT3 nuclear accumulation and cell proliferation, whereas IL-6 treatment without FBS caused Y705 phosphorylation without S727 phosphorylation, STAT3 nuclear accumulation or cell proliferation. When HCCs were simultaneously treated with FBS/IL-6, selective suppression of S727 phosphorylation by an MEK inhibitor prevented STAT3 nuclear accumulation and cell proliferation. Furthermore, an S727 phosphorylation-deficient STAT3 mutant (S727A) had a diminished capacity to accumulate in the nucleus when compared with wild-type (WT) or the phosphorylation-mimic mutant (S727D) following treatment with FBS/IL-6. After treatment with FBS/IL-6, the cells expressing the S727A mutant proliferated more slowly than those expressing WT or S727D mutant. In contrast, suppression of Y705 phosphorylation by a JAK inhibitor in the FBS/IL-6 treated cells did not affect STAT3 nuclear accumulation or cell proliferation. Taken together, these data demonstrate that STAT3 activation, mainly through S727 phosphorylation, contributes to the DEN-induced hepatocarcinogenesis at the earliest stages.

STAT proteins - key regulators of anti-viral responses, inflammation, and tumorigenesis in the liver

Since its discovery in the early 1990s, the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway has been found to play key roles in regulating many key cellular processes such as survival, proliferation, and differentiation. There are seven known mammalian STAT family members: STAT1, 2, 3, 4, 5a, 5b, and 6. In the liver, activation of these STAT proteins is critical for anti-viral defense against hepatitis viral infection and for controlling injury, repair, inflammation, and tumorigenesis. The identification of functions for these STAT proteins has increased our understanding of liver disease pathophysiology and treatments, while also suggesting new therapeutic modalities for managing liver disease.

The biology and mechanism of action of suppressor of cytokine signaling 3

Suppressors of cytokine signaling 3 (SOCS3) has been shown to be an important and non-redundant feedback inhibitor of several cytokines including leukemia inhibitory factor, IL-6, IL-11, Ciliary neurotrophic factor (CNTF), leptin, and granulocyte colony-stimulating factor (G-CSF). Loss of SOCS3 in vivo has profound effects on placental development, inflammation, fat-induced weight gain, and insulin sensitivity. SOCS3 expression is induced by Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling and it then binds to specific cytokine receptors (including gp130, G-CSF, and leptin receptors). SOCS3 then inhibits JAK/STAT signaling in two distinct ways. First, SOCS3 is able to directly inhibit the catalytic activity of JAK1, JAK2, or TYK2 while remaining bound to the cytokine receptor. Second, SOCS3 recruits elongins B/C and Cullin5 to generate an E3 ligase that ubiquitinates both JAK and cytokine receptor targeting them for proteasomal degradation. Detailed in vivo studies have revealed that SOCS3 action not only limits the duration of cytokine signaling to prevent overactivity but it is also important in maintaining the specificity of cytokine signaling.

FXR ligands protect against hepatocellular inflammation via SOCS3 induction

Because of the anti-inflammatory actions of farnesoid X receptor (FXR) agonists, FXR has received much attention as a potential therapeutic target. However, the molecular mechanisms of actions have not yet been elucidated. In the present study, we reported that in the animal model of LPS-induced liver injury, administration of the FXR natural ligand CDCA could attenuate hepatocyte inflammatory damage, reduce transaminase activities, suppress inflammation mediators (IL-6, TNF-α and ICAM-1) expression and inhibit STAT3 phosphorylation. These protective effects of FXR were accompanied by an increased expression of suppressor of cytokine signaling 3 (SOCS3), which is a negative feedback regulator of cytokine-STAT3 signaling. We then demonstrated that the beneficial effects of FXR agonist in STAT3 activation were weakened by small interfering RNA-mediated SOCS3 knockdown in hepacytes. Moreover we observed both natural ligand CDCA and synthetic ligand GW4064 could upregulate SOCS 3 expression by enhancing the promoter activity in hepatocytes. These results suggest modulation of SOCS3 expression may represent a novel mechanism through which FXR activation could selectively affect cytokine bioactivity in inflammation response. FXR ligands may be potentially therapeutic in the treatment of liver inflammatory diseases via SOCS3 induction.

A novel obatoclax derivative, SC-2001, induces apoptosis in hepatocellular carcinoma cells through SHP-1-dependent STAT3 inactivation

We investigated the effects of a novel compound, SC-2001, on hepatocellular carcinoma (HCC). SC-2001, which is structurally related to the Mcl-1 inhibitor obatoclax, showed better antitumor effects than obatoclax in HCC cell lines, including HepG2, PLC5 and Huh-7. Like obatoclax, SC-2001 inhibited the protein-protein interactions between Mcl-1 and Bak. However, SC-2001 downregulated the protein levels of Mcl-1 by reducing its transcription whereas obatoclax had no significant effect on Mcl-1 expression. As Mcl-1 is regulated by signal transducers and activators of transcription 3 (STAT3), we found that SC-2001 downregulated the phosphorylation of STAT3 (Tyr 705) and subsequently inhibited transcriptional activities of STAT3 in a dose-dependent manner. In addition to Mcl-1, STAT3-regulated proteins, including survivin and cyclin D1, were also repressed by SC-2001. Notably, SC-2001 reduced IL-6-induced STAT3 activation in HepG2 and PLC5 cells. Ectopic expression of STAT3 abolished the prominent apoptotic death in SC-2001-treated PLC5 cells, indicating that STAT3 is indispensable in mediating the effects of SC-2001. Importantly, SC-2001 enhanced the expression of SHP1, a negative regulator of STAT3. Inhibition of SHP-1 by either specific inhibitor or small interference RNA reduced the apoptotic effects of SC-2001, indicating that SHP-1 plays a key role in mediating SC2001-induced cell death. SC-2001 enhanced the activity of SHP-1 in all tested HCC cells including HepG2, PLC5 and Huh-7. Finally, SC-2001 reduced PLC5 tumor growth, downregulated p-STAT3 and upregulated SHP-1 expression and activity in vivo. In conclusion, our results suggest that SC-2001 induces apoptosis in HCC, and that this effect is mediated through SHP-1-dependent STAT3 inactivation.

SOCS, Inflammation, and Autoimmunity

Cytokines play essential roles in innate and adaptive immunity. However, excess cytokines or dysregulation of cytokine signaling will cause a variety of diseases, including allergies, autoimmune diseases, inflammation, and cancer. Most cytokines utilize the so-called Janus kinase–signal transducers and activators of transcription pathway. This pathway is negatively regulated by various mechanisms including suppressors of cytokine signaling (SOCS) proteins. SOCS proteins bind to JAK or cytokine receptors, thereby suppressing further signaling events. Especially, suppressor of cytokine signaling-1 (SOCS1) and SOCS3 are strong inhibitors of JAKs, because these two contain kinase inhibitory region at the N-terminus. Studies using conditional knockout mice have shown that SOCS proteins are key physiological as well as pathological regulators of immune homeostasis. Recent studies have also demonstrated that SOCS1 and SOCS3 are important regulators of helper T cell differentiation and functions. This review focuses on the roles of SOCS1 and SOCS3 in T cell mediated inflammatory diseases.

Chronic inflammation and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) invariably develops within a setting of chronic inflammation caused by either hepatotropic viruses, toxins, metabolic liver disease or autoimmunity. Mechanisms that link these two processes are not completely understood, but transcription factors of the NF-κB family and signal transducer and activator of transcription 3 (STAT3), cytokines such as IL-6 and IL-1α and ligands of the epidermal growth factor receptor (EGFR) family are clearly pivotal players. HCC may have its origins in either hepatocytes or hepatic progenitor cells (HPCs), and HCCs, like other solid tumours appear to be sustained by a minority population of cancer stem cells.

Context-Specific Growth Hormone Signaling through the Transcription Factor STAT5: Implications for the Etiology of Hepatosteatosis and Hepatocellular Carcinoma

Growth hormone (GH) controls hepatic physiology to a large extent through the transcription factor signal transducers and activators of transcription (STAT) 5. Here, we focus on lessons learned from the physiology and pathophysiology of mice with disrupted Ghr and Stat5 loci. We discuss that hepatosteatosis and hepatocellular carcinoma observed in the absence of STAT5 can be explained in part through an aberrant activation of STAT1 and STAT3, which in themselves promote cell proliferation and survival. We also argue that STAT5 can be a context-specific tumor suppressor as it negatively regulates cell cycle progression. Lastly, we discuss promiscuity between STAT members that permits a given cytokine receptor to activate different STATs and thereby elicit context-dependent biological responses.

Cytokine induction of tumor necrosis factor receptor 2 is mediated by STAT3 in colon cancer cells

The IL-6/STAT3 and TNFα/NFκB pathways are emerging as critical mediators of inflammation-associated colon cancer. TNF receptor (TNFR) 2 expression is increased in inflammatory bowel diseases, the azoxymethane/dextran sodium sulfate (AOM/DSS) model of colitis-associated cancer, and by combined interleukin (IL) 6 and TNFα. The molecular mechanisms that regulate TNFR2 remain undefined. This study used colon cancer cell lines to test the hypothesis that IL-6 and TNFα induce TNFR2 via STAT3 and/or NFκB. Basal and IL-6 + TNFα-induced TNFR2 were decreased by pharmacologic STAT3 inhibition. NFκB inhibition had little effect on IL-6 + TNFα-induced TNFR2, but did inhibit induction of endogenous IL-6 and TNFR2 in cells treated with TNFα alone. Chromatin immunoprecipitation (ChIP) revealed cooperative effects of IL-6 + TNFα to induce STAT3 binding to a -1,578 STAT response element in the TNFR2 promoter but no effect on NFκB binding to consensus sites. Constitutively active STAT3 was sufficient to induce TNFR2 expression. Overexpression of SOCS3, a cytokine-inducible STAT3 inhibitor, which reduces tumorigenesis in preclinical models of colitis-associated cancer, decreased cytokine-induced TNFR2 expression and STAT3 binding to the -1,578 STAT response element. SOCS3 overexpression also decreased proliferation of colon cancer cells and dramatically decreased anchorage-independent growth of colon cancer cells, even cells overexpressing TNFR2. Collectively, these studies show that IL-6- and TNFα-induced TNFR2 expression in colon cancer cells is mediated primarily by STAT3 and provide evidence that TNFR2 may contribute to the tumor-promoting roles of STAT3.

Viral exploitation of host SOCS protein functions

Over the past decade, a family of host proteins known as suppressors of cytokine signaling (SOCS) have emerged as frequent targets of viral exploitation. Under physiologic circumstances, SOCS proteins negatively regulate inflammatory signaling pathways by facilitating ubiquitination and proteosomal degradation of pathway machinery. Their expression is tightly regulated to prevent excessive inflammation while maintaining protective antipathogenic responses. Numerous viruses, however, have developed mechanisms to induce robust host SOCS protein expression following infection, essentially "hijacking" SOCS function to promote virus survival. To date, SOCS proteins have been shown to inhibit protective antiviral signaling pathways, allowing viruses to evade the host immune response, and to ubiquitinate viral proteins, facilitating intracellular viral trafficking and progeny virus assembly. Importantly, manipulation of SOCS proteins not only facilitates progression of the viral life cycle but also powerfully shapes the presentation of viral disease. SOCS proteins can define host susceptibility to infection, contribute to peripheral disease manifestations such as immune dysfunction and cancer, and even modify the efficacy of therapeutic interventions. Looking toward the future, it is clear that a better understanding of the role of SOCS proteins in viral diseases will be essential in our struggle to modulate and even eliminate the pathogenic effects of viruses on the host.

Viral exploitation of host SOCS protein functions

Over the past decade, a family of host proteins known as suppressors of cytokine signaling (SOCS) have emerged as frequent targets of viral exploitation. Under physiologic circumstances, SOCS proteins negatively regulate inflammatory signaling pathways by facilitating ubiquitination and proteosomal degradation of pathway machinery. Their expression is tightly regulated to prevent excessive inflammation while maintaining protective antipathogenic responses. Numerous viruses, however, have developed mechanisms to induce robust host SOCS protein expression following infection, essentially "hijacking" SOCS function to promote virus survival. To date, SOCS proteins have been shown to inhibit protective antiviral signaling pathways, allowing viruses to evade the host immune response, and to ubiquitinate viral proteins, facilitating intracellular viral trafficking and progeny virus assembly. Importantly, manipulation of SOCS proteins not only facilitates progression of the viral life cycle but also powerfully shapes the presentation of viral disease. SOCS proteins can define host susceptibility to infection, contribute to peripheral disease manifestations such as immune dysfunction and cancer, and even modify the efficacy of therapeutic interventions. Looking toward the future, it is clear that a better understanding of the role of SOCS proteins in viral diseases will be essential in our struggle to modulate and even eliminate the pathogenic effects of viruses on the host.

Loss of SOCS3 expression is associated with an increased risk of recurrent disease in breast carcinoma

PURPOSE

Constitutive activation of JAK/STAT pathway is observed in various solid tumors and hematological malignancies. SOCS3 acts as a key negative regulator of JAK/STAT pathway and represents one of the candidate tumor suppressor genes. In the current study, we aimed to evaluate SOCS3 expression in breast carcinoma and to explore the prognostic significance of SOCS3.

METHODS

The expression of SOCS3 was measured by Western blot and immunohistochemistry in breast carcinoma cells and a large cohort of tissue microarray, respectively.

RESULTS

Among 367 human primary breast tumors, SOCS3 protein was detected in 103 patients. Deficient SOCS3 expression correlated significantly with lymph node metastasis (P = 0.003), blood vessel invasion (P = 0.029), VEGF (P = 0.001) and Ki-67 (P = 0.027). Univariate and multivariate analyses revealed that SOCS3 expression was an independent prognostic factor for disease-free survival (P < 0.0001). A positive SOCS3 protein expression correlated significantly with a low pSTAT3 protein expression in breast carcinoma (P = 0.015). The patients with a SOCS3 (+)/pSTAT3 (-) phenotype had a better prognosis than any other combination (DFI: P < 0.0001, BCSS: P = 0.013).

CONCLUSIONS

Deficient expression of SOCS3 is associated with an aggressive phenotype and portends a poor clinical outcome in breast carcinoma.

SOCS1, a Negative Regulator of Cytokine Signals and TLR Responses, in Human Liver Diseases

Toll-like receptor (TLR) signaling pathways are strictly coordinated by several mechanisms to regulate adequate innate immune responses. Recent lines of evidence indicate that the suppressor of cytokine signaling (SOCS) family proteins, originally identified as negative-feedback regulators in cytokine signaling, are involved in the regulation of TLR-mediated immune responses. SOCS1, a member of SOCS family, is strongly induced upon TLR stimulation. Cells lacking SOCS1 are hyperresponsive to TLR stimulation. Thus, SOCS1 is an important regulator for both cytokine and TLR-induced responses. As an immune organ, the liver contains various types of immune cells such as T cells, NK cells, NKT cells, and Kupffer cells and is continuously challenged with gut-derived bacterial and dietary antigens. SOCS1 may be implicated in pathophysiology of the liver. The studies using SOCS1-deficient mice revealed that endogenous SOCS1 is critical for the prevention of liver diseases such as hepatitis, cirrhosis, and cancers. Recent studies on humans suggest that SOCS1 is involved in the development of various liver disorders in humans. Thus, SOCS1 and other SOCS proteins are potential targets for the therapy of human liver diseases.

Regulator of calcineurin 1 controls growth plasticity of adult pancreas

BACKGROUND & AIMS

Growth of exocrine pancreas is regulated by gastrointestinal hormones, notably cholecystokinin (CCK). CCK-driven pancreatic growth requires calcineurin (CN), which activates Nuclear Factor of Activated T cells (NFATs), but the genetic underpinnings and feedback mechanisms that regulate this response are not known.

METHODS

Pancreatic growth was stimulated by protease inhibitor (PI)-containing chow, which induces secretion of endogenous CCK. Expression profiling of PI stimulation was performed on Affymetrix 430A chips, and CN was inhibited via FK506. Exocrine pancreas-specific overexpression of CN inhibitor Regulator of Calcineurin 1 (Rcan1) was achieved by breeding elastase-Cre(estrogen receptor [ER]) transgenics with "flox-on" Rcan1 mice.

RESULTS

CN inhibitor FK506 blocked expression of 38 genes, as confirmed by quantitative polymerase chain reaction. The CN-dependent genes were linked to growth-related processes, whereas their promoters were enriched in NFAT and NFAT/AP1 sites. Multiple NFAT targets, including Rcan1, Rgs2, HB-EGF, Lif, and Gem, were validated by chromatin immunoprecipitation. One of these, a CN feedback inhibitor Rcan1, was induced >50 fold during 1-8 hours course of pancreatic growth and strongly inhibited (>99%) by FK506. To examine its role in pancreatic growth, we overexpressed Rcan1 in an inducible, acinar-specific fashion. Rcan1 overexpression inhibited CN-NFAT signaling, as shown using an NFAT-luciferase reporter and quantitative polymerase chain reaction. Most importantly, the increase in exocrine pancreas size, protein/DNA content, and acinar proliferation were all blocked in Rcan1 overexpressing mice.

CONCLUSIONS

We profile adaptive pancreatic growth, identify Rcan1 as an important new feedback regulator, and firmly establish that CN-NFAT signaling is required for this response.

Hepatocyte IKKbeta/NF-kappaB inhibits tumor promotion and progression by preventing oxidative stress-driven STAT3 activation

The NF-kappaB activating kinase IKKbeta suppresses early chemically induced liver tumorigenesis by inhibiting hepatocyte death and compensatory proliferation. To study IKKbeta's role in late tumor promotion and progression, we developed a transplant system that allows initiated mouse hepatocytes to form hepatocellular carcinomas (HCC) in host liver after a long latency. Deletion of IKKbeta long after initiation accelerated HCC development and enhanced proliferation of tumor initiating cells. These effects of IKKbeta/NF-kappaB were cell autonomous and correlated with increased accumulation of reactive oxygen species that led to JNK and STAT3 activation. Hepatocyte-specific STAT3 ablation prevented HCC development. The negative crosstalk between NF-kappaB and STAT3, which is also evident in human HCC, is a critical regulator of liver cancer development and progression.