STAT3 activation regulates growth, inflammation, and vascularization in a mouse model of gastric tumorigenesis

The oncogenic mechanisms of the Janus kinase-signal transducer and activator of transcription pathway in digestive tract tumors

Digestive tract tumors are heterogeneous and involve the dysregulation of multiple signaling pathways. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway plays a notable role in the oncogenesis of digestive tract tumors. Typically activated by pro-inflammatory cytokines, it regulates important biological processes, such as cell growth, differentiation, apoptosis, immune responses, and inflammation. The aberrant activation of this pathway manifests in different forms, including mutations in JAKs, overexpression of cytokine receptors, and sustained STAT activation, and contributes to promoting the malignant characteristics of cancer cells, including uncontrolled proliferation, resistance to apoptosis, enhanced invasion and metastasis, angiogenesis, acquisition of stem-like properties, and drug resistance. Numerous studies have shown that aberrant activation of the JAK-STAT pathway is closely related to the development and progression of digestive tract tumors, contributing to tumor survival, angiogenesis, changes in the tumor microenvironment, and even immune escape processes. In addition, this signaling pathway also affects the sensitivity of digestive tract tumors to chemotherapy and targeted therapy. Therefore, it is crucial to comprehensively understand the oncogenic mechanisms underlying the JAK-STAT pathway in order to develop effective therapeutic strategies against digestive tract tumors. Currently, several JAK-STAT inhibitors are undergoing clinical and preclinical trials as potential treatments for various human diseases. However, further investigation is required to determine the role of this pathway, as well as the effectiveness and safety of its inhibitors, especially in the context of digestive tract tumors. In this review, we provide an overview of the structure, classic activation, and negative regulation of the JAK-STAT pathway. Furthermore, we discuss the pathogenic mechanisms of JAK-STAT signaling in different digestive tract tumors, with the aim of identifying potential novel therapeutic targets. Video Abstract.

Ciclopirox drives growth arrest and autophagic cell death through STAT3 in gastric cancer cells

Ciclopirox (CPX), an antifungal drug, has recently been identified as a promising agent for cancer treatment. However, the effects and underlying mechanism of CPX as an antitumor agent of gastric cancer (GC) remain largely unknown. Here, we found that CPX dramatically suppresses GC xenograft growth in vitro via inhibiting proliferation and stimulating autophagic cell death rather than apoptosis. Moreover, CPX (20 mg/kg, intraperitoneally) substantially inhibits GC xenograft tumor growth in vivo. Mechanistically, CPX promotes growth arrest and autophagic cell death through suppressing the phosphorylation of signal transducers and activators of transcription 3 (STAT3) at tyrosine 705 (Tyr705) and serine 727 (Ser727) sites, respectively. Additionally, CPX induces STAT3 ubiquitination, which subsequently leads to a decrease in the p-STAT3 (Ser727) level. On the other hand, CPX represses the p-STAT3 (Tyr705) level via p-Src (Tyr416) inhibition. Collectively, our findings unmask a novel mechanism by which CPX regulates growth and autophagic cell death in GC cells via regulating the phosphorylation of STAT3 both at Tyr705 and Ser727 residues, and suggest that CPX may be a potential treatment for GC.

IL-33 promotes gastric tumour growth in concert with activation and recruitment of inflammatory myeloid cells

Interleukin-33 (IL-33) is an IL-1 family cytokine known to promote T-helper (Th) type 2 immune responses that are often deregulated in gastric cancer (GC). IL-33 is overexpressed in human gastric tumours suggesting a role in driving GC progression although a causal link has not been proven. Here, we investigated the impact of IL-33 genetic deficiency in the well-characterized gp130^F/F mouse model of GC. Expression of IL-33 (and it’s cognate receptor, ST2) was increased in human and mouse GC progression. IL-33 deficient gp130^F/F/Il33^−/− mice had reduced gastric tumour growth and reduced recruitment of pro-tumorigenic myeloid cells including key mast cell subsets and type-2 (M2) macrophages. Cell sorting of gastric tumours revealed that IL-33 chiefly localized to gastric (tumour) epithelial cells and was absent from tumour-infiltrating immune cells (except modest IL-33 enrichment within CD11b⁺ CX3CR1⁺CD64⁺MHCII⁺ macrophages). By contrast, ST2 was absent from gastric epithelial cells and localized exclusively within the (non-macrophage) immune cell fraction together with mast cell markers, Mcpt1 and Mcpt2. Collectively, we show that IL-33 is required for gastric tumour growth and provide evidence of a likely mechanism by which gastric epithelial-derived IL-33 drives mobilization of tumour-promoting inflammatory myeloid cells.

Inhibition of STAT3-ferroptosis negative regulatory axis suppresses tumor growth and alleviates chemoresistance in gastric cancer

Chemotherapy is still one of the principal treatments for gastric cancer, but the clinical application of 5-FU is limited by drug resistance. Here, we demonstrate that ferroptosis triggered by STAT3 inhibition may provide a novel opportunity to explore a new effective therapeutic strategy for gastric cancer and chemotherapy resistance. We find that ferroptosis negative regulation (FNR) signatures are closely correlated with the progression and chemoresistance of gastric cancer. FNR associated genes (GPX4, SLC7A11, and FTH1) and STAT3 are upregulated in 5-FU resistant cells and xenografts. Further evidence demonstrates that STAT3 binds to consensus DNA response elements in the promoters of the FNR associated genes (GPX4, SLC7A11, and FTH1) and regulates their expression, thereby establishing a negative STAT3-ferroptosis regulatory axis in gastric cancer. Genetic inhibition of STAT3 activity triggers ferroptosis through lipid peroxidation and Fe²⁺ accumulation in gastric cancer cells. We further develop a potent and selective STAT3 inhibitor, W1131, which demonstrates significant anti-tumor effects in gastric cancer cell xenograft model, organoids model, and patient-derived xenografts (PDX) model partly by inducing ferroptosis, thus providing a new candidate compound for advanced gastric cancer. Moreover, targeting the STAT3-ferroptosis circuit promotes ferroptosis and restores sensitivity to chemotherapy. Our finding reveals that STAT3 acts as a key negative regulator of ferroptosis in gastric cancer through a multi-pronged mechanism and provides a new therapeutic strategy for advanced gastric cancer and chemotherapy resistance.

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Genetic and pharmacological inhibition of STAT3 triggers ferroptosis by transcriptionlly regulation of GPX4, SLC7A11, and FTH1 in gastric cancer.

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A potent and selective STAT3 inhibitor W1131, with strong anti-tumor effects, is developed.

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Ferroptosis plays a key role in the progression and chemoresistance of gastric cancer.

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Targeting the STAT3-ferroptosis circuit provides a new therapeutic strategy for advanced gastric cancer and chemotherapy resistance.

Leukaemia inhibitory factor in gastric cancer: friend or foe?

IL-6 family cytokine leukaemia inhibitory factor (LIF) study has deciphered a variety of effects, in physiology as well as pathology. Despite the sudden arousal in LIF interest in cancers, its study in the gastric cancer (GC) context has been put aside. Only few related studies can be found in literature, most of them investigating IL-6/STAT3 signalling in GC, and not the particular LIF/LIFRβ signalisation. LIF/LIFR has opposing effects depending on the signalling pathways involved. This review relates the pro- and anti-tumorigenic aspects of LIF/LIFR in GC, taking also into account facts from other types of cancer. A better understanding of these issues would undoubtedly help postulate interesting hypotheses and perspectives for future LIF/LIFR study and its use in GC therapies, where options tend to be limited in number and efficiency.

NVP-BEZ235 or JAKi Treatment leads to decreased survival of examined GBM and BBC cells

Cancer cells almost universally harbor constitutively active Phosphatidylinositol-3 Kinase (PI3K) Pathway activity via mutation of key signaling components and/or epigenetic mechanisms. Scores of PI3K Pathway inhibitors are currently under investigation as putative chemotherapeutics. However, feedback and stem cell mechanisms induced by PI3K Pathway inhibition can lead to reduced treatment efficacy. To address therapeutic barriers, we examined whether JAKi would reduce stem gene expression in a setting of PI3K Pathway inhibition in order to improve treatment efficacy. We targeted the PI3K Pathway with NVP-BEZ235 (dual PI3K and mTOR inhibitor) in combination with the Janus Kinase inhibitor JAKi in glioblastoma (GBM) and basal-like breast cancer (BBC) cell lines. We examined growth, gene expression, and apoptosis in cells treated with NVP-BEZ235 and/or JAKi. Growth and recovery assays showed no significant impact of dual treatment with NVP-BEZ235/JAKi compared to NVP-BEZ235 treatment alone. Gene expression and flow cytometry revealed that single and dual treatments induced apoptosis. Stem gene expression was retained in dual NVP-BEZ235/JAKi treatment samples. Future in vivo studies may give further insight into the impact of combined NVP-BEZ235/JAKi treatment in GBM and BBC.

New Actors Driving the Epithelial-Mesenchymal Transition in Cancer: The Role of Leptin

Leptin is a hormone secreted mainly by adipocytes; physiologically, it participates in the control of appetite and energy expenditure. However, it has also been linked to tumor progression in different epithelial cancers. In this review, we describe the effect of leptin on epithelial-mesenchymal transition (EMT) markers in different study models, including in vitro, in vivo, and patient studies and in various types of cancer, including breast, prostate, lung, and ovarian cancer. The different studies report that leptin promotes the expression of mesenchymal markers and a decrease in epithelial markers, in addition to promoting EMT-related processes such as cell migration and invasion and poor prognosis in patients with cancer. Finally, we report that leptin has the greatest biological relevance in EMT and tumor progression in breast, lung, prostate, esophageal, and ovarian cancer. This relationship could be due to the key role played by the enriched tumor microenvironment in adipose tissue. Together, these findings demonstrate that leptin is a key biomolecule that drives EMT and metastasis in cancer.

Molecular biology and immunology of gastric cancer peritoneal metastasis

Peritoneal metastases occur in 55-60% of patients with gastric cancer (GC) and are associated with a 2% 5-year overall survival rate. There are limited treatment options for these patients, and no targeted therapy or immunotherapy is available. Rational therapeutic targets remain to be found. In this review, we present the published literature and our own recent experience in molecular biology to identify important molecules and signaling pathways as well as cellular immunity involved in the peritoneal metastasis of GC. We also suggest potential novel strategies for improving the outcomes of GC patients with peritoneal metastasis.

Gastro-Protective Effects of Calycosin Against Precancerous Lesions of Gastric Carcinoma in Rats

Aim

Gastric cancer is a leading cause of cancer death worldwide. In-depth research of precancerous lesions of gastric carcinoma (PLGC) with malignant transformation potential is a key measure to prevent the development of gastric carcinoma. Recently, calycosin has been shown to have anticancer effects in vitro and in vivo. The molecular mechanism by which calycosin affects PLGC, however, has not yet been elucidated. The purpose of this study was to evaluate the effect and mechanism of calycosin in N‐methyl‐Nʹ‐nitro‐N‐nitrosoguanidine (MNNG)-induced PLGC rats.

Methods

The effects of calycosin in the gastric mucosa of rats with PLGC were evaluated using histopathology and transmission electron microscopy (TEM). For further characterization, the expression levels of integrin β1, nuclear factor kappa B (NF-κB), p-NF-κB, DARPP-32 and signal transducer and activator of transcription 3 (STAT3) were determined by Western blot assay and immunohistochemistry.

Results

Hematoxylin–eosin and high iron diamine–Alcian blue–periodic acid-Schiff (HID-AB-PAS) staining showed that intestinal metaplasia and dysplasia were significantly ameliorated in the calycosin intervention groups compared with the model group. Further, TEM results showed that calycosin intervention tempered microvascular abnormalities and cell morphology of primary and parietal cells in PLGC tissues. The results suggested that calycosin had gastro-protective effects in MNNG-induced PLGC rats. Western blot and immunohistochemistry analysis showed that the increased protein expression levels of NF-κB, p-NF-κB, DARPP-32 and STAT3 in the model group were downregulated by calycosin. The upregulation of integrin β1 expression induced by MNNG was decreased in the calycosin groups.

Conclusion

Collectively, calycosin protected against gastric mucosal injury in part via regulation of the integrin β1/NF-κB/DARPP-32 pathway and suppressed the expression of STAT3 in PLGC. The elucidation of this effect and mechanism of calycosin in PLGC provides a potential therapeutic strategy for treatment of gastric precancerous lesions.

Trillin prevents proliferation and induces apoptosis through inhibiting STAT3 nuclear translocation in hepatoma carcinoma cells

Trillin is a constituent of total Trillium Tschonoskii Maxim (TTM), which is extracted from TTM and displayed anti-tumor effect in many tumor cell lines. However, the anti-tumor mechanism of trillin is still unclear. This study demonstrated that trillin could dramatically inhibit hepatoma carcinoma cell proliferation, induce apoptosis and decrease migration and invasion through suppressing phosphorylated STAT3 translocated to nucleus. Trillin could down-regulate Bcl-2 and Survivin, up-regulate cleaved PRAP, leading to dramatically apoptosis; trillin could also down-regulate MMP1, MMP2, MucI and VEGF, which displayed an inhibition effect on hepatocellular tumor cells invasion and development. The results of this study indicated the potential utility of trillin as a STAT3 inhibitor for the treatment of cancers.

Phosphorylated STAT3 expression linked to SOCS3 methylation is associated with proliferative ability of gastric mucosa in patients with early gastric cancer

Gastric cancers (GCs) may develop in the gastric mucosa after elimination of Helicobacter pylori (H. pylori) using eradication therapy. Cytokine signaling is a key mechanism underlying GC development and progression, and STAT3 signaling may serve a central role in gastritis-associated tumorigenesis. In the present study, suppressor of cytokine signaling 3 (SOCS3) methylation was examined, as an activator of phosphorylated (p-)STAT3 expression in the non-neoplastic gastric mucosa (non-NGM) of patients with early GC. The methylation status of the SOCS3 gene promoter was analyzed using methylation-specific PCR in the non-NGM of patients with or without early GC. Expression levels of p-STAT3 and Ki67 were investigated immunohistochemically in non-NGM with early GC before and after H. pylori eradication. In non-NGM, SOCS3 promoter methylation was detected in 17/51 patients (33.3%) with early GC. In those patients, the non-NGM labeling indices of both Ki67 and p-STAT3 were significantly higher compared with that in patients with early GC without SOCS3 methylation. A significant correlation between Ki67 and p-STAT3 expression levels was demonstrated in the non-NGM of patients with early GC. In patients with early GC without SOCS3 methylation, the labeling indices of both Ki67 and p-STAT3 in non-NGM were significantly reduced after H. pylori eradication, whereas no such change was observed in patients with early GC with SOCS3 methylation. SOCS3 methylation is associated with continuous p-STAT3 overexpression and enhanced epithelial cell proliferation in non-NGM of patients with early GC.

Differential expression of STAT3 gene and its regulatory long non-coding RNAs, namely lnc-DC and THRIL, in two eastern Iranian ethnicities with multiple sclerosis

OBJECTIVE

Genome-wide association studies (GWASs) revealed that variants of STAT3 are associated with multiple sclerosis (MS) risk. There are several studies showing the effect of ethnicity and genetic background on the characteristics of MS. Here, we aimed to investigate STAT3 gene expression status along with its two regulatory long non-coding RNAs, lnc-DC and THRIL, in order to compare the expression of these target genes among two different ethnicities in the east of Iran.

METHODS

A case-control study was performed between two groups of MS populations in east of Iran. We recruited individuals with Kurdish ethnicity from North Khorasan and Sistani ethnicity from southeast of Iran. The peripheral blood mononuclear cells were obtained from all participants, and total RNA was extracted. The gene expression of the selected genes was evaluated by qPCR.

RESULTS

The expression of THRIL in North Khorasan MS patients was significantly higher than controls (P = 0.03). The results of simultaneous analysis of expression of the target genes (STAT3, THRIL, and lnc-DC) in both ethnic groups failed to show any significant difference between the MS patients and controls (P > 0.05). In addition, the expression of STAT3 and THRIL genes in Sistani MS patients was statistically meaningful lower than healthy controls (P < 0.05).

CONCLUSION

To our knowledge, this is the first study that compared the expression of the STAT3 gene and its regulatory molecules between two ethnic groups of Iranian MS patients. We suggested that STAT3 and its associated molecules might be differentially expressed and regulated in MS patients with different genetic background.

Proton pump inhibitor: The dual role in gastric cancer

Proton pump inhibitors (PPIs) are one of the most frequently used medications for upper gastrointestinal diseases. However, a number of physicians have raised concern about the serious side effects of long-term use of PPIs, including the development of gastric cancer. Recent epidemiological studies have reported a significant association between long-term PPI intake and the risk of gastric cancer, even after successful Helicobacter pylori eradication. However, the effects of PPIs on the development of pre-malignant conditions such as atrophic gastritis or intestinal metaplasia are not fully known, suggesting the need for comprehensive and confirmative studies are needed in the future. Meanwhile, several experimental studies have demonstrated the effects of PPIs in reducing chemoresistance in gastric cancer cells by modulating the acidic microenvironment, cancer stemness and signal transducer and activator of transcription 3 (STAT3) signaling pathway. The inhibitory effects of PPIs on STAT3 activity may overcome drug resistance and enhance the efficacy of conventional or targeted chemotherapeutic agents. Taken together, PPIs may “play dual role” in gastric carcinogenesis and treatment of gastric cancer.

Overexpression of IL-11 promotes premalignant gastric epithelial hyperplasia in isolation from germline gp130-JAK-STAT driver mutations

Expression of the cytokine IL-11 is elevated in human Helicobacter pylori infection and progressively increases with worsening gastric pathology. Additionally, IL-11 is required for tumor development in STAT3-dependent murine models of gastric cancer (GC) and, when administered acutely, causes resolving atrophic gastritis. However, it is unclear whether locally elevated IL-11 ligand expression can, in isolation from oncogenic gp130-JAK-STAT pathway mutations, initiate GC pathogenesis. Here we developed a transgenic mouse model of stomach-specific (keratin 19 promoter) IL-11 ligand overexpression. Keratin 19 promoter-IL-11 transgenic ( K19-IL11^Tg) mice showed specific IL-11 overexpression in gastric corpus and antrum but not elsewhere in the gastrointestinal tract or in other tissues. K19-IL11^Tg mice developed spontaneous premalignant disease of the gastric epithelium, progressing from atrophic gastritis to TFF2-positive metaplasia and severe epithelial hyperplasia, including adenoma-like lesions in a subset of older (1 yr old) animals. Although locally advanced, the hyperplastic lesions remained noninvasive. H. pylori infection in K19-IL11^Tg mice accelerated some aspects of the premalignant phenotype. Finally, K19-IL11^Tg mice had splenomegaly in association with elevated serum IL-11, with spleens showing an expanded myeloid compartment. Our results provide direct in vivo functional evidence that stomach-specific overexpression of IL-11, in isolation from germline gp130-JAK-STAT3 genetic drivers, is sufficient for premalignant progression. These findings have important functional implications for human GC, in which frequent IL-11 overexpression occurs in the reported absence of somatic mutations in gp130 signaling components. NEW & NOTEWORTHY We provide direct in vivo functional evidence that stomach-specific overexpression of the cytokine IL-11, in isolation from gp130-JAK-STAT3 pathway mutations, can trigger spontaneous atrophic gastritis progressing to locally advanced epithelial hyperplasia (but not dysplasia or carcinoma), which does not require, but may be accelerated by, concomitant Helicobacter pylori infection.

BP‑1‑102 exerts an antitumor effect on the AGS human gastric cancer cell line through modulating the STAT3 and MAPK signaling pathways

BP-1-102, a novel inhibitor of signal transducer and activator of transcription 3 (STAT3), exhibits significant antitumor effects in several malignancies in vitro and in vivo. However, its role in gastric cancer (GC) remains to be elucidated. In the present study, the effect and potential molecular mechanisms of BP-102 in human GC cell lines were investigated. The results showed that BP-1-02 dose-dependently inhibited the proliferation of AGS cells, whereas it had little effect on HGC-27 cells. Flow cytometric analysis indicated that BP-1-102 induced apoptosis, but had minimal effect on cell cycle distribution. In addition, cells treated with BP-1-102 demonstrated markedly suppressed migration and invasion capacities. Western blot analysis revealed that BP-1-102 inhibited the phosphorylation of STAT3 and its target genes, including c-Myc, cyclin D1 and survivin, in a time- and dose-dependent manner. Furthermore, it was found that BP-1-102 induced the phosphorylation of c-Jun N-terminal kinase and p38 mitogen-activated protein kinase (MAPK) and inhibited the activation of extracellular signal-related kinases. Taken together, these results demonstrated that BP-1-102 may be a potent antitumor agent that acts through modulating the STAT3 and MAPK signaling pathways in GC cells.

HJC0152, a novel STAT3 inhibitor with promising anti-tumor effect in gastric cancer

Background

Aberrant activation of the signal transducer and activator of transcription 3 (STAT3) is frequently seen in patients with gastric cancer (GC), and is generally associated with worse prognosis. HJC0152, a novel STAT3 inhibitor, has shown significant anti-tumor effects in several cancers, although its role in GC remains to be clarified.

Methods

The effect of HJC0152 on STAT3 signaling pathway and the biological behaviors of GC cells were evaluated through in vitro and/or in vivo experiments. Meanwhile, RNA sequence analysis was used to further explore its potential anti-tumor mechanisms.

Results

HJC0152 inhibited the expression of activated STAT3 and its downstream target genes (c-Myc and clyclinD1) in GC cells, and restrained tumor growth in vivo. HJC0152 treatment induced apoptosis in the STAT3 hyper-activated AGS and MKN45 cell lines, along with down-regulation of survivin and Mcl1, and up-regulation of cleaved-poly(ADP-ribose) polymerase. Moreover, HJC0152 markedly inhibited migration and invasion of these cells. Finally, RNA sequence analysis and protein expression analyses showed that in addition to STAT3 suppression, HJC0152 also exerts its anti-tumor effects at least partly via the mitogen-activated protein kinases pathway.

Conclusion

Our findings highlight that HJC0152 is a promising therapeutic agent for GC.

Long non‑coding RNA DILC is involved in sepsis by modulating the signaling pathway of the interleukin‑6/signal transducer and activator of transcription 3/Toll‑like receptor 4 axis

Sepsis is characterized by systemic inflammatory responses. In the present study, the role of deleted in liver cancer 1 (DILC), interleukin (IL)‑6, signal transducer and activator of transcription 3 (STAT3), and Toll‑like receptor 4 (TLR4) in the pathogenesis of sepsis was investigated. Reverse transcription‑quantitative polymerase chain reaction analysis and western blotting were performed to evaluate the effects of lipopolysaccharide (LPS) on the expression of DILC, IL‑6, STAT3, and TLR4, in addition to the effects of DILC and IL‑6 on the synthesis of tumor necrosis factor (TNF‑α), chemokine ligand 5 (CCL5), E‑selectin and C‑X‑C motif chemokine receptor 1 (CXCR1). In addition, the regulatory association between DILC, IL‑6, STAT3 and TLR4 was investigated. LPS reduced the expression level of DILC, and enhanced the expression of IL‑6, STAT3 and TLR4. DILC directly and negatively regulated the synthesis of IL‑6, as demonstrated by the markedly decreased luciferase activity in cells transfected with a wild‑type DILC plasmid. On the other hand, compared with the scramble control, DILC and IL‑6 small interfering (si)RNAs significantly suppressed the expression of IL‑6, STAT3 and TLR4. In addition, DILC siRNA enhanced the expression of IL‑6, STAT3 and TLR4, whereas the expression levels of TNF‑α, CCL5, E‑selectin and CXCR1 in LPS‑treated THP‑1 cells were downregulated following transfection with DILC and IL‑6 siRNAs. In patients with sepsis, DILC expression was inhibited, although the expression levels of IL‑6, STAT3 and TLR4 were upregulated. In addition, the expression levels of TNF‑α, CCL5, E‑selectin and CXCR1 in patients with sepsis were higher compared with normal subjects. Therefore, DILC may mediate the crosstalk between the cascades of IL‑6/STAT3 and TNF‑α signaling, indicating that DILC may act as a prognostic biomarker of sepsis, and may serve as a potential therapeutic target for the treatment of sepsis.

Interleukin-2 induces the in vitro maturation of human pluripotent stem cell-derived intestinal organoids

Human pluripotent stem cell (hPSC)-derived intestinal organoids (hIOs) form 3D structures organized into crypt and villus domains, making them an excellent in vitro model system for studying human intestinal development and disease. However, hPSC-derived hIOs still require in vivo maturation to fully recapitulate adult intestine, with the mechanism of maturation remaining elusive. Here, we show that the co-culture with human T lymphocytes induce the in vitro maturation of hIOs, and identify STAT3-activating interleukin-2 (IL-2) as the major factor inducing maturation. hIOs exposed to IL-2 closely mimic the adult intestinal epithelium and have comparable expression levels of mature intestinal markers, as well as increased intestine-specific functional activities. Even after in vivo engraftment, in vitro-matured hIOs retain their maturation status. The results of our study demonstrate that STAT3 signaling can induce the maturation of hIOs in vitro, thereby circumventing the need for animal models and in vivo maturation.

Negative Regulation of Cytokine Signaling in Immunity

Cytokines are key modulators of immunity. Most cytokines use the Janus kinase and signal transducers and activators of transcription (JAK-STAT) pathway to promote gene transcriptional regulation, but their signals must be attenuated by multiple mechanisms. These include the suppressors of cytokine signaling (SOCS) family of proteins, which represent a main negative regulation mechanism for the JAK-STAT pathway. Cytokine-inducible Src homology 2 (SH2)-containing protein (CIS), SOCS1, and SOCS3 proteins regulate cytokine signals that control the polarization of CD4+ T cells and the maturation of CD8+ T cells. SOCS proteins also regulate innate immune cells and are involved in tumorigenesis. This review summarizes recent progress on CIS, SOCS1, and SOCS3 in T cells and tumor immunity.

Activation of Signal Transduction and Activator of Transcription 3 Signaling Contributes to Helicobacter-Associated Gastric Epithelial Proliferation and Inflammation

Background/Aim

Although IL-6-mediated activation of the signal transduction and activator of transcription 3 (STAT3) axis is involved in inflammation and cancer, the role of STAT3 in Helicobacter-associated gastric inflammation and carcinogenesis is unclear. This study investigated the role of STAT3 in gastric inflammation and carcinogenesis and examined the molecular mechanism of Helicobacter-induced gastric phenotypes.

Methods

To evaluate the contribution of STAT3 to gastric inflammation and carcinogenesis, we used wild-type (WT) and gastric epithelial conditional Stat3-knockout (Stat3^Δgec) mice. Mice were infected with Helicobacter felis and euthanized at 18 months postinfection. Mouse gastric organoids were treated with recombinant IL-6 (rIL-6) or rIL-11 and a JAK inhibitor (JAKi) to assess the role of IL-6/STAT3 signaling in vitro.

Results

Inflammation and mucous metaplasia were more severe in WT mice than in Stat3^Δgec mice. The epithelial cell proliferation rate and STAT3 activation were increased in WT mice. Application of rIL-6 and rIL-11 induced expression of intestinal metaplasia-associated genes, such as Tff2; this induction was suppressed by JAKi administration.

Conclusions

Loss of STAT3 signaling in the gastric mucosa leads to decreased epithelial cell proliferation, atrophy, and metaplasia in the setting of Helicobacter infection. Therefore, activation of STAT3 signaling may play a key role in Helicobacter-associated gastric carcinogenesis.

Circulating SH2B1 is associated with an increased risk of gastric cancer

Gastric cancer (GC) is one of the most common types of cancer in humans and the second leading cause of cancer-associated mortality worldwide. Identifying novel risk factors will facilitate the development of therapeutic strategies to prevent and treat GC. Increased expression of the Src homology 2 B adaptor protein 1 (SH2B1) may stimulate the malignant progression of lung cancer, esophageal cancer and neuroblastoma. However, its function in GC has not yet been investigated. To identify whether increased serum SH2B1 is a risk factor for GC, the present study performed a nested case-control study of patients within the Chinese cohort study. Levels of serum SH2B1 were measured in 563 patients diagnosed with GC during the follow-up period and in 1,126 matched healthy controls. The results demonstrated that high levels of serum SH2B1 were associated with an increased GC risk (odds ratio, 3.23; 95% confidence interval, 2.45-5.65). When analyses were stratified further by sex, age and smoking, an association between increased levels of SH2B1 and GC was identified in males but not in females. Furthermore, the association between SH2B1 levels and GC was more evident in younger than in older participants, and statistically significant in current smokers but not in nonsmokers. These results were not altered following the exclusion of outliers. Furthermore, it was demonstrated that overexpression of SH2B1 contributes to the malignant transformation of normal gastric epithelial cells. Thus, the present study demonstrated that elevated serum SH2B1 levels may increase the risk of GC.

The role of lnc-DC long non-coding RNA and SOCS1 in the regulation of STAT3 in coronary artery disease and type 2 diabetes mellitus

AIMS

Coronary artery disease (CAD) can be classified as an inflammatory disease, which affected by type 2 diabetes mellitus (T2DM). Elevated levels of many inflammatory molecules were found in the serum of patients with CAD. STAT3 molecule as a transcription factor plays an important role in the cytokines expression. Here, we examined the expression levels of STAT3 and its important regulatory genes lnc-DC and SOCS1, in patients with CAD and T2DM.

METHODS

Blood samples were obtained from 37 CAD+ and 36 CAD- patients. These patients were enrolled in this study based on angiography findings and categorized based on T2DM status. The expression levels of STAT3, lnc-DC and SOCS1 genes were examined with Real time PCR method.

RESULTS

A significant increase was observed in expression of STAT3 and lnc-DC genes but not SOCS1 in CAD+ versus CAD- patients. These results replicated partially in some groups categorized based on T2DM and CAD status. However, severity of CAD had no effect on expressions of these genes. Moreover, we found some significant correlations between expressions of lnc-DC with SOCS1 and STAT3, which confirmed by in silico analysis.

CONCLUSION

Our results shed further light to the inflammatory aspects of CAD and T2DM with emphasis to JAK/STAT pathway and the regulatory role of long non-coding RNAs in the physiopathology of these diseases.

Mitochondrial GRIM-19 as a potential therapeutic target for STAT3-dependent carcinogenesis of gastric cancer

Aberrant STAT3 activation occurs in most human gastric cancers (GCs) and contributes to the malignant progression of GC, but mechanism(s) underlying aberrant STAT3 remain largely unknown. Here we demonstrated that the gene associated with retinoid interferon-induced mortality 19 (GRIM-19) was severely depressed or lost in GC and chronic atrophic gastritis (CAG) tissues and its loss contributed to GC tumorigenesis partly by activating STAT3 signaling. In primary human GC tissues, GRIM-19 was frequently depressed or lost and this loss correlated with advanced clinical stage, lymph node metastasis, H. pylori infection and poor overall survival of GC patients. In CAG tissues, GRIM-19 was progressively decreased along with its malignant transformation. Functionally, we indentified an oncogenic role of GRIM-19 loss in promoting GC tumorigenesis. Ectopic GRIM-19 expression suppressed GC tumor formation in vitro and in vivo by inducing cell cycle arrest and apoptosis. Moreover, we revealed that GRIM-19 inhibited STAT3 transcriptional activation and its downstream targets by reducing STAT3 nuclear distribution. Conversely, knockdown of GRIM-19 induced aberrant STAT3 activation and accelerated GC cell growth in vitro and in vivo, and this could be partly attenuated by the blockage of STAT3 activation. In addition, we observed subcellular redistributions of GRIM-19 characterized by peri-nuclear aggregates, non-mitochondria cytoplasmic distribution and nuclear invasion, which should be responsible for reduced STAT3 nuclear distribution. Our studies suggest that mitochondrial GRIM-19 could not only serve as an valuable prognostic biomarker for GC development, but also as a potential therapeutic target for STAT3-dependent carcinogenesis of GC.

E804, a derivative of indirubin, promotes autophagy of gastric cancer cells through Stat3 signaling pathway

AIM

To explore the pharmacological mechanism of E804, a derivative of indirubin, by investigating whether it can inhibit the viability of gastric cancer cells, alter the expression of markers of autophagy, and promote the autophagy activity.

METHODS

MGC-803 and MKN-45 cells were treated with different concentrations of E804. Non-treated MGC-803 and MKN-45 cells were used as negative controls, and those treated with interleukin-6 (100 ng/mL) for 2 h were used as a positive control. After treatment, cell viability was detected by MTT assay. The expression of autophagy markers was detected by Western blot. The diameter of transplantable tumor in a subcutaneous xenotransplanted tumor model was also measured.

RESULTS

The viability of both MGC-803 and MKN-45 cells declined significantly after treatment (P < 0.05). E804 increased the expression of LC3-B and Beclin-1, two markers of autophagy, in a dose-dependent manner. When comparing the maximal diameters of tumor in the control group (non-treated) and experimental group (treated with E804), the speed of tumor growth in the experimental group was significantly lower than that of the control group (P < 0.05).

CONCLUSION

E804 can promote autophagy of gastric cancer cells to suppress their growth, at least partly by inhibiting the activation of Stat3.

Genetic host factors in Helicobacter pylori-induced carcinogenesis: Emerging new paradigms

Helicobacter Pylori is a gram negative rod shaped microaerophilic bacterium that colonizes the stomach of approximately half the world's population. Infection with c may cause chronic gastritis which via a quite well described process known as Correas cascade can progress through sequential development of atrophic gastritis, intestinal metaplasia and dysplasia to gastric cancer. H. pylori is currently the only bacterium that is classified as a class 1 carcinogen by the WHO, although the exact mechanisms by which this bacterium contributes to gastric carcinogenesis are still poorly understood. Only a minority of H. pylori-infected patients will eventually develop gastric cancer, suggesting that host factors may be important in determining the outcome of H. pylori infection. This is supported by a growing body of evidence suggesting that the host genetic background contributes to risk of H. pylori infection and gastric carcinogenesis. In particular single nucleotide polymorphisms in genes that influence bacterial handling via pattern recognition receptors appear to be involved, further strengthening the link between host risk factors, H. pylori incidence and cancer. Many of these genes influence cellular pathways leading to inflammatory signaling, inflammasome formation and autophagy. In this review we summarize known carcinogenic effects of H. pylori, and discuss recent findings that implicate host genetic pattern recognition pathways in the development of gastric cancer and their relation with H. pylori.

Suppressors of cytokine signaling: Potential immune checkpoint molecules for cancer immunotherapy

Inhibition of immune checkpoint molecules, PD‐1 and CTLA4, has been shown to be a promising cancer treatment. PD‐1 and CTLA4 inhibit TCR and co‐stimulatory signals. The third T cell activation signal represents the signals from the cytokine receptors. The cytokine interferon‐γ (IFNγ) plays an important role in anti‐tumor immunity by activating cytotoxic T cells (CTLs). Most cytokines use the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway, and the suppressors of cytokine signaling (SOCS) family of proteins are major negative regulators of the JAK/STAT pathway. Among SOCS proteins, CIS, SOCS1, and SOCS3 proteins can be considered the third immunocheckpoint molecules since they regulate cytokine signals that control the polarization of CD4⁺ T cells and the maturation of CD8⁺ T cells. This review summarizes recent progress on CIS, SOCS1, and SOCS3 in terms of their anti‐tumor immunity and potential applications.

Regulation of Gastric Carcinogenesis by Inflammatory Cytokines

Chronic inflammation caused by infection with Helicobacter pylori and autoimmune gastritis increases an individual's risk of developing gastric cancer. More than 90% of gastric cancers are adenocarcinomas, which originate from epithelial cells in the chronically inflamed gastric mucosa. However, only a small subset of chronic gastritis patients develops gastric cancer, implying a role for genetic and environmental factors in cancer development. A number of DNA polymorphisms that increase gastric cancer risk have mapped to genes encoding cytokines. Many different cytokines secreted by immune cells and epithelial cells during chronic gastritis have been identified, but a better understanding of how cytokines regulate the severity of gastritis, epithelial cell changes, and neoplastic transformation is needed. This review summarizes studies in both human and mouse models, describing a number of different findings that implicate various cytokines in regulating the development of gastric cancer.

Shp2 Inhibits Proliferation of Esophageal Squamous Cell Cancer via Dephosphorylation of Stat3

Shp2 (Src-homology 2 domain-containing phosphatase 2) was originally reported as an oncogene in kinds of solid tumors and hematologic malignancies. However, recent studies indicated that Shp2 may act as tumor suppressors in several tumor types. We investigated the function of Shp2 in esophageal squamous cell cancer (ESCC). The expression level of Shp2 was analyzed in tumor tissues in comparison with adjacent normal tissues of ESCC patients by immunohistochemistry and Western blot. Shp2 was knocked down by Short hairpin RNA to evaluate its function in ESCC cell lines. The relationship between Shp2 and p-Stat3 (signal transducer and activator of transcription 3) in human ESCC tissues was statistically examined. A significant low expression of Shp2 was found in ESCC tissues. Low expression of Shp2 was related to poorer overall survival in patients from The Cancer Genome Atlas (TCGA) dataset. Knockdown of Shp2 increased the growth of ESCC cell lines both in vivo and vitro. Activation of Stat3 (p-Stat3) was induced by Shp2 depletion. Expression of p-Stat3 was negatively correlated with Shp2 expression in ESCC tissues. Furthermore, knockdown of Shp2 attenuated cisplatin-sensitivity of ESCC cells. Shp2 might suppress the proliferation of ESCC by dephosphorylation of p-Stat3 and represents a novel research field for targeted therapy.

STAT3 signaling drives EZH2 transcriptional activation and mediates poor prognosis in gastric cancer

BACKGROUND

STAT3 signaling plays the pivotal role in tumorigenesis through EZH2 epigenetic modification, which enhanced STAT3 activity by increased tyrosine phosphorylation of STAT3. Here, another possible feedback mechanism and clinical significance of EZH2 and STAT3 were investigated in gastric cancer (GC).

METHODS

STAT3, p-STAT3 (Tyr 705) and EZH2 expression were examined in 63 GC specimens with matched normal tissues by IHC staining. EZH2 and STAT3 were also identified in five GC cell lines using RT-PCR and western blot analyses. p-STAT3 protein was detected by western blotting. In order to investigate whether EZH2 expression was directly regulated by STAT3, EZH2 expression was further detected using siRNA for STAT3 or IL-6 stimulation, with dual luciferase reporter analyses, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays. The clinical significance of STAT3, p-STAT3 and EZH2 expression was evaluated by multi-factor COX regression and Kaplan-Meier analyses.

RESULTS

Hyper-activation of STAT3, p-STAT3 and EZH2 expression were observed in GC cells and tissues. STAT3 signaling was correlated with EZH2 expression in GC (R = 0.373, P = 0.003), which was consistent with our data showing that STAT3 as the transcriptional factor enhanced EZH2 transcriptional activity by binding the relative promoter region (-214 ~ -206). STAT3 was an independent signature for poor survival (P = 0.002). Patients with STAT3⁺/EZH2⁺ or p-STAT3⁺/EZH2⁺ had a worse outcome than others (P < 0.001); Besides, high levels of STAT3 and EZH2 was associated with advanced TNM staging (P = 0.017). Moreover, treatment with a combination of siSTAT3 and EZH2-specific inhibitor, 3-deazaneplanocin A (DZNEP), increased the apoptotic ratio of cells. It is benefit for targeting STAT3-EZH2 interplay in GC treatment.

CONCLUSIONS

Our results indicate that STAT3 status mediated EZH2 upregulation, associated with advanced TNM stage and poor prognosis, suggesting that combination with knockdown of STAT3 and EZH2 inhibitor might be a novel therapy in GC treatment. Collectively, STAT3, p-STAT3 and EZH2 expression were provided for the precision medicine in GC patients.

Helicobacter pylori Activates IL-6-STAT3 Signaling in Human Gastric Cancer Cells: Potential Roles for Reactive Oxygen Species

BACKGROUND

Recent studies have shown that Helicobacter pylori (H. pylori) activates signal transducer and activator of transcription 3 (STAT3) that plays an important role in gastric carcinogenesis. However, the molecular mechanism underlying H. pylori-mediated STAT3 activation is still not fully understood. In this study, we investigated H. pylori-induced activation of STAT3 signaling in AGS human gastric cancer cells and the underlying mechanism.

MATERIALS AND METHODS

AGS cells were cocultured with H. pylori, and STAT3 activation was assessed by Western blot analysis, electrophoretic mobility shift assay and immunocytochemistry. To demonstrate the involvement of reactive oxygen species (ROS) in H. pylori-activated STAT3 signaling, the antioxidant N-acetylcysteine was utilized. The expression and production of interleukin-6 (IL-6) were measured by reverse-transcription polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA), respectively. The interaction between IL-6 and IL-6 receptor (IL-6R) was determined by the immunoprecipitation assay.

RESULTS

H. pylori activates STAT3 as evidenced by increases in phosphorylation on Tyr(705) , nuclear localization, DNA binding and transcriptional activity of this transcription factor. The nuclear translocation of STAT3 was also observed in H. pylori-inoculated mouse stomach. In the subsequent study, we found that H. pylori-induced STAT3 phosphorylation was dependent on IL-6. Notably, the increased IL-6 expression and the IL-6 and IL-6R binding were mediated by ROS produced as a consequence of H. pylori infection.

CONCLUSIONS

H. pylori-induced STAT3 activation is mediated, at least in part, through ROS-induced upregulation of IL-6 expression. These findings provide a novel molecular mechanism responsible for H. pylori-induced gastritis and gastric carcinogenesis.

Novel STAT 3 inhibitors for treating gastric cancer

INTRODUCTION

Advanced gastric cancer has a poor prognosis, with a median survival of approximately 12 months. There is a continued need to explore the use of novel treatments for this disease. STAT3 inhibitors are under evaluation in a number of early phase trials, some showing promise in gastric cancer.

AREAS COVERED

This article explores the role of STAT 3 in gastric cancer and highlights some early phase clinical trials on STAT3 inhibition. The STAT3 protein and signalling pathway are discussed. STAT3 in the pathogenesis of gastric cancer is reviewed; pre-clinical data on the role of STAT3 in the development of cancer is presented together with early and emerging data on STAT3 inhibitors under investigation in the clinical setting. In this review, the authors searched PubMed, clinicaltrials.gov and ASCO abstracts on STAT3 inhibitors, focusing on trials recruiting gastric cancer patients.

EXPERT OPINION

Activated STAT3 in gastric cancer is correlated with poor survival. It plays a critical role in regulating tumour growth and metastases. STAT3 inhibitors are emerging as an interesting drug in gastric cancer. However, trials utilising these agents remain in their early phase with one agent currently under evaluation in the phase III setting.

Expression of p-STAT3 and vascular endothelial growth factor in MNNG-induced precancerous lesions and gastric tumors in rats

AIM: To investigate the dynamic expression of p-signal transducer and activator of transcription 3 (STAT3) and vascular endothelial growth factor (VEGF) in the formation of gastric tumors induced by drinking water containing N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) in Wistar rats.

METHODS: One hundred and twenty Wistar rats were randomly divided into two groups (60 in each group): Control group and Model group. The rats in each group were then randomly divided into three groups (20 in each group): C/M15, C/M25 and C/M40 (15, 25 and 40 represent the number of feeding weeks from termination). Rats in the control group received normal drinking water and rats in the model group received drinking water containing 100 μg/mL MNNG. Stomach tissues were collected at the end of the 15^th, 25^th and 40^th week, respectively, for microscopic measurement using hematoxylin and eosin staining. The expression of p-STAT3 and VEGF in different pathological types of gastric tissue, including normal, inflammation, atrophy, hyperplasia and gastric stromal tumor, was observed by immunohistochemistry and Western blot, and the corelation between p-STAT3 and VEGF was analyzed.

RESULTS: (1) The expression of p-STAT3 in tissue with gastritis, atrophy, dysplasia and gastric stromal tumor were significantly increased in the model group compared with the control group (2.5 ± 1.0, 2.75 ± 0.36, 6.2 ± 0.45, 5.67 ± 0.55 vs 0.75 ± 0.36, P = 0.026, 0.035, 0.001, 0.002, respectively); the expression of p-STAT3 in tissue with dysplasia was higher than that in samples with gastritis or atrophy (6.2 ± 0.45 vs 2.5 ± 1.0, P = 0.006; 6.2 ± 0.45 vs 2.75 ± 0.36, P = 0.005, respectively); however, the expression of p-STAT3 in gastritis and atrophy was not significantly different (P > 0.05); (2) the expression of VEGF in tissue with gastritis, atrophy, dysplasia and gastric stromal tumor was significantly increased in the model group compared with normal gastric mucosa; and the expression of VEGF in tissue with dysplasia was higher than that in tissue with inflammation and atrophy (10.8 ± 1.96 vs 7.62 ± 0.25, P = 0.029; 10.8 ± 1.96 vs 6.26 ± 0.76, P = 0.033, respectively); similarly, the expression of VEGF in tissue with gastritis and atrophy was not significantly different (P > 0.05); and (3) the expression of VEGF was positively correlated with p-STAT3.

CONCLUSION: p-STAT3 plays an important role in gastric cancer formation by regulating the expression of VEGF to promote the progression of gastric tumor from gastritis.

Recapitulating Human Gastric Cancer Pathogenesis: Experimental Models of Gastric Cancer

This review focuses on the various experimental models to study gastric cancer pathogenesis, with the role of genetically engineered mouse models (GEMMs) used as the major examples. We review differences in human stomach anatomy compared to the stomachs of the experimental models, including the mouse and invertebrate models such as Drosophila and C. elegans. The contribution of major signaling pathways, e.g., Notch, Hedgehog, AKT/PI3K is discussed in the context of their potential contribution to foregut tumorigenesis. We critically examine the rationale behind specific GEMMs, chemical carcinogens, dietary promoters, Helicobacter infection, and direct mutagenesis of relevant oncogenes and tumor suppressor that have been developed to study gastric cancer pathogenesis. Despite species differences, more efficient and effective models to test specific genes and pathways disrupted in human gastric carcinogenesis have yet to emerge. As we better understand these species differences, "humanized" versions of mouse models will more closely approximate human gastric cancer pathogenesis. Towards that end, epigenetic marks on chromatin, the gut microbiota, and ways of manipulating the immune system will likely move center stage, permitting greater overlap between rodent and human cancer phenotypes thus providing a unified progression model.

miR-874 functions as a tumor suppressor by inhibiting angiogenesis through STAT3/VEGF-A pathway in gastric cancer

MicroRNAs are endogenously expressed, small non-coding RNAs that regulate gene expression by targeting mRNAs for translational repression or degradation. Our previous studies indicated that miR-874 played a suppressive role in gastric cancer (GC) development and progression. However, the role of miR-874 in tumor angiogenesis and the mechanisms underlying its function in GC remained to be clarified. Here, gain- and loss-of-function assays demonstrated that miR-874 inhibited the tumor angiogenesis of GC cells in vitro and in vivo. Through reporter gene and western blot assays, STAT3 was shown to be a direct target of miR-874. Overexpression of STAT3 rescued the loss of tumor angiogenesis caused by miR-874. Conversely, the STAT3-shRNA attenuated the increased tumor angiogenesis caused by the miR-874-inhibitor. Furthermore, the levels of miR-874 were inversely correlated with those of STAT3 protein in GC tissues. Taken together, these findings indicate that down-regulation of miR-874 contributes to tumor angiogenesis through STAT3 in GC, highlighting the potential of miR-874 as a target for human GC therapy.

STAT3: a critical component in the response to Helicobacter pylori infection

STAT3 imparts a profound influence on both the epithelial and immune components of the gastric mucosa, and through regulation of key intracellular signal transduction events, is well placed to control inflammatory and oncogenic outcomes in the context of Helicobacter (H.) pylori infection. Here we review the roles of STAT3 in the host immune response to H. pylori infection, from both gastric mucosal and systemic perspectives, as well as alluding more specifically to STAT3-dependent mechanisms that might be exploited as drug targets.

HDAC Inhibition Overcomes Acute Resistance to MEK Inhibition in BRAF-Mutant Colorectal Cancer by Downregulation of c-FLIPL

PURPOSE

Activating mutations in the BRAF oncogene are found in 8% to 15% of colorectal cancer patients and have been associated with poor survival. In contrast with BRAF-mutant (MT) melanoma, inhibition of the MAPK pathway is ineffective in the majority of BRAFMT colorectal cancer patients. Therefore, identification of novel therapies for BRAFMT colorectal cancer is urgently needed.

EXPERIMENTAL DESIGN

BRAFMT and wild-type (WT) colorectal cancer models were assessed in vitro and in vivo. Small-molecule inhibitors of MEK1/2, MET, and HDAC were used, overexpression and siRNA approaches were applied, and cell death was assessed by flow cytometry, Western blotting, cell viability, and caspase activity assays.

RESULTS

Increased c-MET-STAT3 signaling was identified as a novel adaptive resistance mechanism to MEK inhibitors (MEKi) in BRAFMT colorectal cancer models in vitro and in vivo. Moreover, MEKi treatment resulted in acute increases in transcription of the endogenous caspase-8 inhibitor c-FLIPL in BRAFMT cells, but not in BRAFWT cells, and inhibition of STAT3 activity abrogated MEKi-induced c-FLIPL expression. In addition, treatment with c-FLIP-specific siRNA or HDAC inhibitors abrogated MEKi-induced upregulation of c-FLIPL expression and resulted in significant increases in MEKi-induced cell death in BRAFMT colorectal cancer cells. Notably, combined HDAC inhibitor/MEKi treatment resulted in dramatically attenuated tumor growth in BRAFMT xenografts.

CONCLUSIONS

Our findings indicate that c-MET/STAT3-dependent upregulation of c-FLIPL expression is an important escape mechanism following MEKi treatment in BRAFMT colorectal cancer. Thus, combinations of MEKi with inhibitors of c-MET or c-FLIP (e.g., HDAC inhibitors) could be potential novel treatment strategies for BRAFMT colorectal cancer.

IL33 Is a Stomach Alarmin That Initiates a Skewed Th2 Response to Injury and Infection

BACKGROUND & AIMS

Interleukin (IL)33 is a recently described alarmin that is highly expressed in the gastric mucosa and potently activates Th2 immunity. It may play a pivotal role during Helicobacter pylori infection. Here, we delineate the role of IL33 in the normal gastric mucosa and in response to gastropathy.

METHODS

IL33 expression was evaluated in mice and human biopsy specimens infected with H pylori and in mice after dosing with aspirin. IL33 expression was localized in the gastric mucosa using immunofluorescence. Mice were given 1 or 7 daily doses of recombinant IL33 (1 μg/dose), and the stomach and the spleen responses were quantified morphologically, by flow cytometry and using quantitative reverse-transcription polymerase chain reaction and immunoblotting.

RESULTS

In mice, the IL33 protein was localized to the nucleus of a subpopulation of surface mucus cells, and co-localized with the surface mucus cell markers Ulex Europaeus 1 (UEA1), and Mucin 5AC (Muc5AC). A small proportion of IL33-positive epithelial cells also were Ki-67 positive. IL33 and its receptor Interleukin 1 receptor-like 1 (ST2) were increased 4-fold after acute (1-day) H pylori infection, however, this increase was not apparent after 7 days and IL33 expression was reduced 2-fold after 2 months. Similarly, human biopsy specimens positive for H pylori had a reduced IL33 expression. Chronic IL33 treatment in mice caused systemic activation of innate lymphoid cell 2 and polarization of macrophages to the M2 phenotype. In the stomach, IL33-treated mice developed transmural inflammation and mucous metaplasia that was mediated by Th2/signal transducer and activator of transcription 3 signaling. Rag-1^-/- mice, lacking mature lymphocytes, were protected from IL33-induced gastric pathology.

CONCLUSIONS

IL33 is highly expressed in the gastric mucosa and promotes the activation of T helper 2-cytokine-expressing cells. The loss of IL33 expression after prolonged H pylori infection may be permissive for the T helper 1-biased immune response observed during H pylori infection and subsequent precancerous progression.

Bidirectional regulation between TMEFF2 and STAT3 may contribute to Helicobacter pylori-associated gastric carcinogenesis

The transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is a single-pass transmembrane protein, and it is downregulated in human gastric cancer and levels correlate with tumor progression and time of survival. However, the mechanism of its dysregulation in gastric cancer is little known. Here we investigate its regulatory mechanism and the bidirectional regulation between TMEFF2 and STAT3 in gastric carcinogenesis. TMEFF2 expression was decreased after Helicobacter pylori (H. pylori) infection in vivo and in vitro. STAT3 directly binds to the promoter of TMEFF2 and regulates H. pylori-induced TMEFF2 downregulation in normal gastric GES-1 cells and gastric cancer AGS cells. Conversely, TMEFF2 may suppress the phosphorylation of STAT3 and TMEFF2-induced downregulation of STAT3 phosphorylation may depend on SHP-1. A highly inverse correlation between the expression of TMEFF2 and pSTAT3 was also revealed in gastric tissues. We now show the deregulation mechanism of TMEFF2 in gastric carcinogenesis and identify TMEFF2 as a new target gene of STAT3. The phosphorylation of STAT3 may be negatively regulated by TMEFF2, and the bidirectional regulation between TMEFF2 and STAT3 may contribute to H. pylori-associated gastric carcinogenesis.

Helicobacter pylori-induced STAT3 activation and signalling network in gastric cancer

Background

Helicobacter pylori (H. pylori) is the most important gastric carcinogen. However, the mechanisms of H. pylori induced gastric carcinogenesis through STAT3 activation are largely unknown. We evaluated the effects of H. pylori infection on STAT3 activation and dissected the signalling network of STAT3 in H. pylori- infected gastric carcinogenesis.

Methods

The expression of phospho-STAT3 (pSTAT3) was evaluated by immunohistochemistry and western blot. Gene expression array and chromatin immunoprecipitation were used to dissect the STAT3 signalling network on H. pylori co-cultured AGS.

Results

pSTAT3 was significantly higher in H. pylori -positive gastritis than in H. pylori -negative gastritis ( P = 0.003). In addition, 98% of H. pylori positive intestinal metaplasia specimens showed STAT3 activation, whereas pSTAT3 was significantly decreased in all 43 specimens one year after H. pylori eradication ( P < 0.001). Moreover, pSTAT3 was only detected in the H. pylori -infected gastric tissues of mice but not in control mice. We further identified 6 candidates ( BRUNOL4, FGFR1, SHOX2, JAK3, MAPK8, and PDPN ) were directly up-regulated by H. pylori induced STAT3 activation.

Conclusion

H. pylori infection triggers the activation of STAT3 and de-regulates multitude of tumorigenic genes which may contribute to the initiation and progression of gastric cancer.

Inhibition of the JAK2/STAT3 pathway reduces gastric cancer growth in vitro and in vivo

Signal Transducer and Activator of Transcription-3 (STAT3) is constitutively activated in many cancers where it promotes growth, inflammation, angiogenesis and inhibits apoptosis. We have shown that STAT3 is constitutively activated in human gastric cancer, and that chronic IL-11-driven STAT3 transcriptional activity induces gastric tumourigenesis in the gp130^757FF mouse model of gastric cancer development. Here we show that treatment of human AGS gastric cancer cells with the Janus Kinase (JAK) inhibitor WP1066 dose-, and time-dependently inhibits STAT3 phosphorylation, in conjunction with reduced JAK2 phosphorylation, reduced proliferation and increased apoptosis. In addition, application of intraperitoneal WP1066 for 2 weeks, reduced gastric tumour volume by 50% in the gp130^757FF mouse coincident with reduced JAK2 and STAT3 activation compared with vehicle-treated, littermate controls. Gastric tumours from WP1066- treated mice had reduced polymorphonuclear inflammation, coincident with inhibition of numerous proinflammatory cytokines including IL-11, IL-6 and IL-1β, as well as the growth factors Reg1 and amphiregulin. These results show that WP1066 can block proliferation, reduce inflammation and induce apoptosis in gastric tumour cells by inhibiting STAT3 phosphorylation, and that many cytokines and growth factors that promote gastric tumour growth are regulated by STAT3-dependent mechanisms. WP1066 may form the basis for future therapeutics against gastric cancer.

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.

Leptin signaling in skeletal muscle after bed rest in healthy humans

PURPOSE

This study aimed at determining the effects of bed rest on the skeletal muscle leptin signaling system.

METHODS

Deltoid and vastus lateralis muscle biopsies and blood samples were obtained from 12 healthy young men (mean ± SD, BMI 22.8 ± 2.7 kg/m(2)) before and after 7 days of bed rest. Leptin receptor isoforms (OB-Rs), suppressor of cytokine signaling 3 (SOCS3) and protein tyrosine phosphatase 1B (PTP1B) protein expression and signal transducer and activator of transcription 3 (STAT3) phosphorylation were analyzed by Western blot.

RESULTS

After bed rest basal insulin concentration was increased by 53% (P < 0.05), the homeostasis model assessment (HOMA) by 40% (P < 0.05), and serum leptin concentration by 35% (P < 0.05) with no changes in body fat mass. Although the soluble isoform of the leptin receptor (s-OBR) remained unchanged, the molar excess of leptin over sOB-R was increased by 1.4-fold after bed rest (P < 0.05). OB-Rs and SOCS3 protein expression, and STAT3 phosphorylation level remained unaffected in deltoid and vastus lateralis by bed rest, as PTP1B in the deltoid. PTP1B was increased by 90% with bed rest in the vastus lateralis (P < 0.05). There was a linear relationship between the increase in vastus lateralis PTP1B and the increase in both basal insulin concentrations (r = 0.66, P < 0.05) and HOMA (r = 0.68, P < 0.05) with bed rest.

CONCLUSIONS

One week of bed rest is associated with increased leptin levels without augmenting STAT3 phosphorylation indicating some degree of leptin resistance in skeletal muscle, which can be explained, at least in part, by an elevation of PTP1B protein content in the vastus lateralis muscle.

Tying the knot between cytokine and toll-like receptor signaling in gastrointestinal tract cancers

Inflammation-associated malignancies of the gastrointestinal tract (GI), including those of the stomach and colon, collectively rank as the highest cause of cancer-related deaths worldwide. It has been well documented that the deregulated activation of the archetypal pro-inflammatory and oncogenic transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription (STAT)3 is a common feature of GI cancers that invariably correlates with poor prognosis. Signal transducer and activator of transcription 3 and NF-κB are key downstream signal transducers of the interleukin (IL)-6 cytokine and toll-like receptor (TLR) families, respectively, and until recently, the potential involvement of these two families in the pathogenesis of cancer has been investigated in isolation. However, there is now emerging evidence of the complex interplay between the IL-6 cytokine and TLR families in GI tract cancers, with a surprising twist in the identification of a non-immune role for specific TLR family members. In this review, we discuss the molecular mechanisms associated with cross-talk between the IL-6 cytokine family/STAT3 signaling network and the TLR family/NF-κB signaling network, and we address the potential benefit of their therapeutic targeting in gastric and colorectal cancers.