Helicobacter pyloriInduces Plasminogen Activator Inhibitor 2 in Gastric Epithelial Cells through Nuclear Factor-κB and RhoA

RHOA in Gastric Cancer: Functional Roles and Therapeutic Potential

The well-known signal mediator and small GTPase family member, RHOA, has now been associated with the progression of specific malignancies. In this review, we appraise the biomedical literature regarding the role of this enzyme in gastric cancer (GC) signaling, suggesting potential clinical significance. To that end, we examined RHOA activity, with regard to second-generation hallmarks of cancer, finding particular association with the hallmark "activation of invasion and metastasis." Moreover, an abundance of studies show RHOA association with Lauren classification diffuse subtype, in addition to poorly differentiated GC. With regard to therapeutic value, we found RHOA signaling to influence the activity of specific widely used chemotherapeutics, and its possible antagonism by various dietary constituents. We also review currently available targeted therapies for GC. The latter, however, showed a paucity of such agents, underscoring the urgent need for further investigation into treatments for this highly lethal malignancy.

Chemerin acts via CMKLR1 and GPR1 to stimulate migration and invasion of gastric cancer cells: putative role of decreased TIMP-1 and TIMP-2

The chemokine-like peptide, chemerin, stimulates chemotaxis in several cell types. In this study we examined the expression of putative chemerin receptors in gastric cancer and the action of chemerin on cancer cell migration and invasion. Immunohistochemical studies of gastric tumors identified expression of two putative receptors, chemokine-like receptor-1 (CMKLR1) and G-protein coupled receptor 1(GPR1), in cancer cells; there was also some expression in stromal myofibroblasts although generally at a lower intensity. The expression of both receptors was detected in a gastric cancer cell line, AGS; chemerin itself was expressed in cultured gastric cancer myofibroblasts but not AGS cells. Chemerin stimulated (a) morphological transformation of AGS cells characterized by extension of processes and cell scattering, (b) migration in scratch wound assays and (c) both migration and invasion in Boyden chamber chemotaxis assays. These responses were inhibited by two putative receptor antagonists CCX832 and α-NETA. Inhibition of receptor expression by siRNA selectively reduced CMKLR1 or GPR1 and inhibited the action of chemerin indicating that both receptors contributed to the functional response. Using a proteomic approach employing stable isotope dynamic labeling of secretomes (SIDLS) to selectively label secreted proteins, we identified down regulation of tissue inhibitors of metalloproteinease (TIMP)1 and TIMP2 in media in response to chemerin. When cells were treated with chemerin and TIMP1 or TIMP2 the migration response to chemerin was reduced. The data suggest a role for chemerin in promoting the invasion of gastric cancer cells via CMKLR1 and GPR1at least partly by reducing TIMP1 and TIMP2 expression. Chemerin receptor antagonists have potential in inhibiting gastric cancer progression.

The effects of starter microbiota and the early life feeding of medium chain triglycerides on the gastric transcriptome profile of 2- or 3-week-old cesarean delivered piglets

Background

The stomach is an underestimated key interface between the ingesta and the digestive system, affecting the digestion and playing an important role in several endocrine functions. The quality of starter microbiota and the early life feeding of medium chain triglycerides may affect porcine gastric maturation. Two trials (T1, T2) were carried out on 12 and 24 cesarean-delivered piglets (birth, d0), divided over two microbiota treatments, but slaughtered and sampled at two or three weeks of age, respectively. All piglets were fed orally: sow serum (T1) or pasteurized sow colostrum (T2) on d0; simple starter microbiota (Lactobacillus amylovorus, Clostridium glycolicum and Parabacteroides spp.) (d1-d3); complex microbiota inoculum (sow diluted feces, CA) or a placebo (simple association, SA) (d3-d4) and milk replacer ad libitum (d0-d4). The The T1 piglets and half of the T2 piglets were then fed a moist diet (CTRL); the remaining half of the T2 piglets were fed the CTRL diet fortified with medium chain triglycerides and 7% coconut oil (MCT). Total mRNA from the oxyntic mucosa was analyzed using Affymetrix©Porcine Gene array strips. Exploratory functional analysis of the resulting values was carried out using Gene Set Enrichment Analysis.

Results

Complex microbiota upregulated 11 gene sets in piglets of each age group vs. SA. Of these sets, 6 were upregulated at both ages, including the set of gene markers of oxyntic mucosa. In comparison with the piglets receiving SA, the CA enriched the genes in the sets related to interferon response when the CTRL diet was given while the same sets were impoverished by CA with the MCT diet.

Conclusions

Early colonization with a complex starter microbiota promoted the functional maturation of the oxyntic mucosa in an age-dependent manner. The dietary fatty acid source may have affected the recruitment and the maturation of the immune cells, particularly when the piglets were early associated with a simplified starter microbiota.

Cell cycle dependent expression of the CCK2 receptor by gastrointestinal myofibroblasts: putative role in determining cell migration

The well‐known action of the gastric hormone gastrin in stimulating gastric acid secretion is mediated by activation of cholecystokinin‐2 receptors (CCK2R). The latter are expressed by a variety of cell types suggesting that gastrin is implicated in multiple functions. During wound healing in the stomach CCK2R may be expressed by myofibroblasts. We have now characterized CCK2R expression in cultured myofibroblasts. Immunocytochemistry showed that a relatively small proportion (1–6%) of myofibroblasts expressed the receptor regardless of the region of the gut from which they were derived, or whether from cancer or control tissue. Activation of CCK2R by human heptadecapeptide gastrin (hG17) increased intracellular calcium concentrations in a small subset of myofibroblasts indicating the presence of a functional receptor. Unexpectedly, we found over 80% of cells expressing CCK2R were also labeled with 5‐ethynyl‐2′‐deoxyuridine (EdU) which is incorporated into DNA during S‐phase of the cell cycle. hG17 did not stimulate EdU incorporation but increased migration of both EdU‐labeled and unlabelled myofibroblasts; the migratory response was inhibited by a CCK2R antagonist and by an inhibitor of IGF receptor tyrosine kinase; hG17 also increased IGF‐2 transcript abundance. The data suggest myofibroblasts express CCK2R in a restricted period of the cell cycle during S‐phase, and that gastrin accelerates migration of these cells; it also stimulates migration of adjacent cells probably through paracrine release of IGF. Together with previous findings, the results raise the prospect that gastrin controls the position of dividing myofibroblasts which may be relevant in wound healing and cancer progression in the gastrointestinal tract.

Metaplasia in the Stomach-Precursor of Gastric Cancer?

Despite a significant decrease in the incidence of gastric cancer in Western countries over the past century, gastric cancer is still one of the leading causes of cancer-related deaths worldwide. Most human gastric cancers develop after long-term Helicobacter pylori infection via the Correa pathway: the progression is from gastritis, atrophy, intestinal metaplasia, dysplasia, to cancer. However, it remains unclear whether metaplasia is a direct precursor of gastric cancer or merely a marker of high cancer risk. Here, we review human studies on the relationship between metaplasia and cancer in the stomach, data from mouse models of metaplasia regarding the mechanism of metaplasia development, and the cellular responses induced by H. pylori infection.

Glucagon-like petide-2 acts on colon cancer myofibroblasts to stimulate proliferation, migration and invasion of both myofibroblasts and cancer cells via the IGF pathway

Glucagon-like peptide (GLP)-2 stimulates intestinal epithelial proliferation by acting, in part, via IGF release from sub-epithelial myofibroblasts. The response of myofibroblasts to GLP-2 remains incompletely understood. We studied the action of GLP-2 on myofibroblasts from colon cancer and adjacent tissue, and the effects of conditioned medium from these cells on epithelial cell proliferation, migration and invasion. GLP-2 stimulated proliferation, migration and invasion of myofibroblasts and the proliferative and invasive responses of cancer-associated myofibroblasts were greater than those of myofibroblasts from adjacent tissue. The responses were inhibited by an IGF receptor inhibitor, AG1024. Conditioned medium from GLP-2 treated myofibroblasts increased proliferation, migration and invasion of SW480, HT29, LoVo epithelial cells and these responses were inhibited by AG1024; GLP-2 alone had no effect on these cells. In addition, when myofibroblasts and epithelial cells were co-cultured in Ibidi chambers there was mutual stimulation of migration in response to GLP-2. The latter increased both IGF-1 and IGF-2 transcript abundance in myofibroblasts. Moreover, a number of IGF binding proteins (IGFBP-4, -5, -7) were identified in myofibroblast medium; in the presence of GLP-2 there was increased abundance of the cleavage products of IGBBP-4 and IGFBP-5 suggesting activation of a degradation mechanism that might increase IGF bioavailability. The data suggest that GLP-2 stimulates cancer myofibroblast proliferation, migration and invasion; GLP-2 acts indirectly on epithelial cells partly via increased IGF expression in myofibroblasts and partly, perhaps, by increased bioavailability through degradation of IGFBPs.

SerpinB2 Deficiency Results in a Stratum Corneum Defect and Increased Sensitivity to Topically Applied Inflammatory Agents

SerpinB2 (plasminogen activator inhibitor type 2) is constitutively expressed at high levels by differentiating keratinocytes in mice and humans; however, the physiological function of keratinocyte SerpinB2 remains unclear. Herein, we show that SerpinB2(-/-) mice are more susceptible to contact dermatitis after topical application of dinitrofluorobenzene, and show enhanced inflammatory lesions after topical applications of phorbol ester. Untreated SerpinB2(-/-) mice showed no overt changes in epithelial structure, and we were unable to find evidence for a role for keratinocyte SerpinB2 in regulating immunity, apoptosis, IL-1β production, proteasomal activity, or wound healing. Instead, the phenotype was associated with impaired skin barrier function and a defective stratum corneum, with SerpinB2(-/-) mice showing increased transepidermal water loss, increased overt loss of stratum corneum in inflammatory lesions, and impaired stratum corneum thickening after phorbol ester treatment. Immunoblotting suggested that SerpinB2 (cross-linked into the cornified envelope) is present in the stratum corneum and retains the ability to form covalent inhibitory complexes with urokinase. Data suggest that the function of keratinocyte SerpinB2 is protection of the stratum corneum from proteolysis via inhibition of urokinase, thereby maintaining the integrity and barrier function of the stratum corneum, particularly during times of skin inflammation. Implications for studies involving genetically modified mice treated with topical agents and human dermatological conditions, such as contact dermatitis, are discussed.

Statins Attenuate Helicobacter pylori CagA Translocation and Reduce Incidence of Gastric Cancer: In Vitro and Population-Based Case-Control Studies

Gastric cancer is the second leading cause of cancer-related death worldwide. The correlation of Helicobacter pylori and the etiology of gastric cancer was substantially certain. Cholesterol-rich microdomains (also called lipid rafts), which provide platforms for signaling, are associated with H. pylori-induced pathogenesis leading to gastric cancer. Patients who have been prescribed statins, inhibitors of 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase, have exhibited a reduced risk of several types of cancer. However, no studies have addressed the effect of statins on H. pylori-associated gastric cancer from the antineoplastic perspective. In this study, we showed that treatment of gastric epithelial cells with simvastatin reduced the level of cellular cholesterol and led to attenuation of translocation and phosphorylation of H. pylori cytotoxin-associated gene A (CagA), which is recognized as a major determinant of gastric cancer development. Additionally, a nationwide case-control study based on data from the Taiwanese National Health Insurance Research Database (NHIRD) was conducted. A population-based case-control study revealed that patients who used simvastatin exhibited a significantly reduced risk of gastric cancer (adjusted odds ratio (OR) = 0.76, 95% confidence interval (CI) = 0.70–0.83). In patients exhibiting H. pylori infection who were prescribed simvastatin, the adjusted OR for gastric cancer was 0.25 (95% CI = 0.12–0.50). Our results combined an in vitro study with a nationwide population analysis reveal that statin use might be a feasible approach to prevent H. pylori-associated gastric cancer.

Gastrin stimulates MMP-1 expression in gastric epithelial cells: putative role in gastric epithelial cell migration

The pyloric antral hormone gastrin plays a role in remodeling of the gastric epithelium, but the specific targets of gastrin that mediate these effects are poorly understood. Glandular epithelial cells of the gastric corpus express matrix metalloproteinase (MMP)-1, which is a potential determinant of tissue remodeling; some of these cells express the CCK-2 receptor at which gastrin acts. We have now examined the hypothesis that gastrin stimulates expression of MMP-1 in the stomach. We determined MMP-1 transcript abundance in gastric mucosal biopsies from Helicobacter pylori negative human subjects with normal gastric mucosal histology, who had a range of serum gastrin concentrations due in part to treatment with proton pump inhibitors (PPI). The effects of gastrin were studied on gastric epithelial AGS-GR cells using Western blot and migration assays. In human subjects with increased serum gastrin due to PPI usage, MMP-1 transcript abundance was increased 2-fold; there was also increased MMP-7 transcript abundance but not MMP-3. In Western blots, gastrin increased proMMP-1 abundance, as well that of a minor band corresponding to active MMP-1, in the media of AGS-GR cells, and the response was mediated by protein kinase C and p42/44 MAP kinase. There was also increased MMP-1 enzyme activity. Gastrin-stimulated AGS-GR cell migration in both scratch wound and Boyden chamber assays was inhibited by MMP-1 immunoneutralization. We conclude that MMP-1 expression is a target of gastrin implicated in mucosal remodeling.

Finding gene regulatory network candidates using the gene expression knowledge base

Background

Network-based approaches for the analysis of large-scale genomics data have become well established. Biological networks provide a knowledge scaffold against which the patterns and dynamics of ‘omics’ data can be interpreted. The background information required for the construction of such networks is often dispersed across a multitude of knowledge bases in a variety of formats. The seamless integration of this information is one of the main challenges in bioinformatics. The Semantic Web offers powerful technologies for the assembly of integrated knowledge bases that are computationally comprehensible, thereby providing a potentially powerful resource for constructing biological networks and network-based analysis.

Results

We have developed the Gene eXpression Knowledge Base (GeXKB), a semantic web technology based resource that contains integrated knowledge about gene expression regulation. To affirm the utility of GeXKB we demonstrate how this resource can be exploited for the identification of candidate regulatory network proteins. We present four use cases that were designed from a biological perspective in order to find candidate members relevant for the gastrin hormone signaling network model. We show how a combination of specific query definitions and additional selection criteria derived from gene expression data and prior knowledge concerning candidate proteins can be used to retrieve a set of proteins that constitute valid candidates for regulatory network extensions.

Conclusions

Semantic web technologies provide the means for processing and integrating various heterogeneous information sources. The GeXKB offers biologists such an integrated knowledge resource, allowing them to address complex biological questions pertaining to gene expression. This work illustrates how GeXKB can be used in combination with gene expression results and literature information to identify new potential candidates that may be considered for extending a gene regulatory network.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-014-0386-y) contains supplementary material, which is available to authorized users.

Increased expression of chemerin in squamous esophageal cancer myofibroblasts and role in recruitment of mesenchymal stromal cells

Stromal cells such as myofibroblasts influence tumor progression. The mechanisms are unclear but may involve effects on both tumor cells and recruitment of bone marrow-derived mesenchymal stromal cells (MSCs) which then colonize tumors. Using iTRAQ and LC-MS/MS we identified the adipokine, chemerin, as overexpressed in esophageal squamous cancer associated myofibroblasts (CAMs) compared with adjacent tissue myofibroblasts (ATMs). The chemerin receptor, ChemR23, is expressed by MSCs. Conditioned media (CM) from CAMs significantly increased MSC cell migration compared to ATM-CM; the action of CAM-CM was significantly reduced by chemerin-neutralising antibody, pretreatment of CAMs with chemerin siRNA, pretreatment of MSCs with ChemR23 siRNA, and by a ChemR23 receptor antagonist, CCX832. Stimulation of MSCs by chemerin increased phosphorylation of p42/44, p38 and JNK-II kinases and inhibitors of these kinases and PKC reversed chemerin-stimulated MSC migration. Chemerin stimulation of MSCs also induced expression and secretion of macrophage inhibitory factor (MIF) that tended to restrict migratory responses to low concentrations of chemerin but not higher concentrations. In a xenograft model consisting of OE21 esophageal cancer cells and CAMs, homing of MSCs administered i.v. was inhibited by CCX832. Thus, chemerin secreted from esophageal cancer myofibroblasts is a potential chemoattractant for MSCs and its inhibition may delay tumor progression.

Novel roles of gastrin

The existence of the hormone gastrin in the distal stomach (antrum) has been known for almost 110 years, and the physiological function of this amidated peptide in regulating gastric acid secretion via the CCK2 receptor is now well established. In this brief review we consider important additional roles of gastrin, including regulation of genes encoding proteins such as plasminogen activator inhibitors and matrix metalloproteinases that have important actions on extracellular matrix remodelling. These actions are, at least in part, effected by paracrine signalling pathways and make important contributions to maintaining functional integrity of the gastric epithelium. Recent studies also provide support for the idea that gastrin, in concert with other hormones, could potentially contribute a post-prandial incretin effect. We also review recent developments in the biology of other gastrin gene products, including the precursor progastrin, which causes proliferation of the colonic epithelium and in certain circumstances may induce cancer formation. Glycine-extended biosynthetic processing intermediates also have proliferative effects in colonic mucosa and in some oesophageal cancer cell lines. Whether these additional gene products exert their effects through the CCK2 receptor or a separate entity is currently a matter of debate.

SerpinB2 mediated regulation of macrophage function during enteric infection

Host defense is an orchestrated response involving changes in the expression of receptors and release of mediators from both immune and structural cells. There is a growing recognition of the important role of proteolytic pathways for the protective immune response to enteric pathogens. Enteric nematode infection induces a type 2 immune response with polarization of macrophages toward the alternatively activated phenotype (M2). The Th2 cytokines, IL-4, and IL-13, induce a STAT6-dependent upregulation of the expression of the protease inhibitor, serpinB2, which protects macrophages from apoptosis. M2 are critical to worm clearance and a novel role for serpinB2 is its regulation of the chemokine, CCL2, which is necessary for monocyte and/or macrophage influx into small intestine during infection. There is a growing list of factors including immune (LPS, Th2 cytokines) as well as hormonal (gastrin, 5-HT) that are linked to increased expression of serpinB2. Thus, serpinB2 represents an immune regulated factor that has multiple roles in the intestinal mucosa.

Hec1/Ndc80 is overexpressed in human gastric cancer and regulates cell growth

BACKGROUND

Chromosomal instability caused by abnormal cell division is a major cause of heterogeneity which evokes highly complex and malignant features of gastric cancer. Hec1/Ndc80 is critical in regulating proper cell division at the G2/M phase. The aim of our study is to investigate the in vitro and in vivo effects of Hec1 on gastric cancer cell growth.

METHODS

The mRNA levels of Hec1 in human normal and cancer tissues were analyzed using the Oncomine database. Hec1 mRNA and protein levels in human gastric cancer tissues were analyzed by quantitative realtime-PCR and immunohistochemical staining, respectively. The effects of Hec1 on cell growth were explored by Hec1 knockdown and Hec1 overexpression. Apoptosis and cell cycle distributions were analyzed by flow cytometry. In vivo tumorigenicity was performed by engrafting tumor cells into nude mice.

RESULTS

Hec1 mRNA and protein were broadly overexpressed in many human cancers including gastric cancer. Hec1 knockdown dramatically suppressed gastric cancer cell growth in vitro and in vivo, induced apoptosis, and arrested cell division at the G2/M phase. On the contrary, Hec1 overexpression moderately promoted gastric cancer cell growth in vivo. Hec1 overexpression induced asymmetrical chromosome alignments, abnormal cell division, and thus rendered chromosomal instability.

CONCLUSIONS

Hec1 is critical in maintaining the in vitro and in vivo growth of gastric cancer cells. Elevated Hec1 levels may occur at the early stage of gastric tumorigenesis.

MicroRNA-362 induces cell proliferation and apoptosis resistance in gastric cancer by activation of NF-κB signaling

Background

According to cancer-related microRNA (miRNA) expression microarray research available in public databases, miR-362 expression is elevated in gastric cancer. However, the expression and biological role of miR-362 in gastric progression remain unclear.

Methods

miR-362 expression levels in gastric cancer tissues and cell lines were determined using real-time PCR. The roles of miR-362, in promoting gastric cancer cell proliferation and apoptosis resistance, were assessed by different biological assays, such as colony assay, flow cytometry and TUNEL assay. The effect of miR-362 on NF-κB activation was investigated using the luciferase reporter assay, fluorescent immunostaining.

Results

MiR-362 overexpression induced cell proliferation, colony formation, and resistance to cisplatin-induced apoptosis in BGC-823 and SGC-7901 gastric cancer cells. MiR-362 increased NF-κB activity and relative mRNA expression of NF-κB–regulated genes, and induced nuclear translocation of p65. Expression of the tumor suppressor CYLD was inhibited by miR-362 in gastric cancer cells; miR-362 levels were inversely correlated with CYLD expression in gastric cancer tissue. MiR-362 downregulated CYLD expression by binding its 3′ untranslated region. NF-κB activation was mechanistically associated with siRNA-mediated downregulation of CYLD. MiR-362 inhibitor reversed all the effects of miR-362.

Conclusion

The results suggest that miR-362 plays an important role in repressing the tumor suppressor CYLD and present a novel mechanism of miRNA-mediated NF-κB activation in gastric cancer.

Zerumbone inhibits tumor angiogenesis via NF-κB in gastric cancer

Zerumbone derived from a subtropical ginger, Zingiber zerumbet Smith, was previously reported to have antitumor growth and anti-inflammatory properties in some types of cancer. However, the effects of zerumbone against cancer angiogenesis have not been fully elucidated. In this study, we clarified the role of zerumbone in gastric cancer angiogenesis. We examined the expression of vascular endothelial growth factor (VEGF) in gastric cancer cell lines both in the basal state and following zerumbone treatment by real-time RT-PCR and enzyme-linked immunosorbent assay (ELISA). Changes in gastric cancer cell proliferation in response to zerumbone treatment were measured by WST-1 assay. Additionally, the effects of zerumbone on NF-κB activity were examined in AGS cells. Finally, the effects of zerumbone on angiogenesis in AGS cells were measured by in vitro angiogenesis assay in which human umbilical vein endothelial cells (HUVECs) and fibroblasts were cocultured with AGS cells. Among the 6 gastric cancer cell lines tested, AGS cells exhibited the highest expression of VEGF. Cell proliferation, VEGF expression and NF-κB activity in AGS cells were all significantly inhibited by zerumbone. Moreover, the tube formation area of HUVECs was increased by coculture with AGS cells, and this effect was inhibited by zerumbone. Both VEGF expression and NF-κB activity in AGS cells were reduced by treatment with zerumbone, thereby inhibiting angiogenesis. Thus, zerumbone may become a new anti-angiogenic and antitumor drug in the treatment of gastric cancer.

Selection of potential therapeutic human single-chain Fv antibodies against cholecystokinin-B/gastrin receptor by phage display technology

BACKGROUND AND OBJECTIVE

Gastric/gastrointestinal cancers are associated with high mortality worldwide. G-protein coupled receptor (GPCR) superfamily members such as gastrin/cholecystokinin-B receptor (CCK-BR) are involved in progression of gastric tumors, thus CCK-BR is considered as a potential target for immunotherapy. However, production of functional monoclonal antibodies (mAbs) against GPCR seems to be very challenging, in part due to its integration in cell membranes and inaccessibility for selection. To tackle this problem, we implemented phage display technology and a solution-phase biopanning (SPB) scheme for production of mAbs specific to the native conformation of CCK-BR.

METHODS

To perform the SPB process, we utilized a synthetic biotinylated peptide corresponding to the second extracellular loop (ECL2) of CCK-BR and a semi-synthetic phage antibody library. After enzyme-linked immunosorbent assay (ELISA) screening, the CCK-BR specificity of the selected single-chain variable fragments (scFvs) were further examined using immunoblotting, whole-cell ELISA, and flow cytometry assays.

RESULTS

After performing four rounds of selection, we identified nine antibody clones which showed positive reactivity with the CCK-BR peptide in an ELISA assay. Of these, eight clones were unique scFv antibodies and one was a V(L) single domain antibody. Specificity analysis of the selected scFvs revealed that five of the selected scFvs recognized a denatured form of CCK-BR, while the majority of the selected scFvs were able to recognize the native conformation of CCK-BR on the surface of human gastric adenocarcinoma cells and cervical carcinoma HeLa cells.

CONCLUSION

For the first time, we report on the establishment of a diverse panel of scFv antibody fragments that are specific to the native conformation of CCK-BR. Based on these results, we suggest the selected scFv antibody fragments as potential agents for diagnosis, imaging, targeting, and/or immunotherapy of cancers that overexpress CCK-BR.

Mapping proteolytic processing in the secretome of gastric cancer-associated myofibroblasts reveals activation of MMP-1, MMP-2, and MMP-3

Cancer progression involves changes in extracellular proteolysis, but the contribution of stromal cell secretomes to the cancer degradome remains uncertain. We have now defined the secretome of a specific stromal cell type, the myofibroblast, in gastric cancer and its modification by proteolysis. SILAC labeling and COFRADIC isolation of methionine containing peptides allowed us to quantify differences in gastric cancer-derived myofibroblasts compared with myofibroblasts from adjacent tissue, revealing increased abundance of several proteases in cancer myofibroblasts including matrix metalloproteinases (MMP)-1 and -3. Moreover, N-terminal COFRADIC analysis identified cancer-restricted proteolytic cleavages, including liberation of the active forms of MMP-1, -2, and -3 from their inactive precursors. In vivo imaging confirmed increased MMP activity when gastric cancer cells were xenografted in mice together with gastric cancer myofibroblasts. Western blot and enzyme activity assays confirmed increased MMP-1, -2, and -3 activity in cancer myofibroblasts, and cancer cell migration assays indicated stimulation by MMP-1, -2, and -3 in cancer-associated myofibroblast media. Thus, cancer-derived myofibroblasts differ from their normal counterparts by increased production and activation of MMP-1, -2, and -3, and this may contribute to the remodelling of the cancer cell microenvironment.

SerpinB2 is critical to Th2 immunity against enteric nematode infection

SerpinB2, a member of the serine protease inhibitor family, is expressed by macrophages and is significantly upregulated by inflammation. Recent studies implicated a role for SerpinB2 in the control of Th1 and Th2 immune responses, but the mechanisms of these effects are unknown. In this study, we used mice deficient in SerpinB2 (SerpinB2(-/-)) to investigate its role in the host response to the enteric nematode, Heligmosomoides bakeri. Nematode infection induced a STAT6-dependent increase in intestinal SerpinB2 expression. The H. bakeri-induced upregulation of IL-4 and IL-13 expression was attenuated in SerpinB2(-/-) mice coincident with an impaired worm clearance. In addition, lack of SerpinB2 in mice resulted in a loss of the H. bakeri-induced smooth muscle hypercontractility and a significant delay in infection-induced increase in mucosal permeability. Th2 immunity is generally linked to a CCL2-mediated increase in the infiltration of macrophages that develop into the alternatively activated phenotype (M2). In H. bakeri-infected SerpinB2(-/-) mice, there was an impaired infiltration and alternative activation of macrophages accompanied by a decrease in the intestinal CCL2 expression. Studies in macrophages isolated from SerpinB2(-/-) mice showed a reduced CCL2 expression, but normal M2 development, in response to stimulation of Th2 cytokines. These data demonstrate that the immune regulation of SerpinB2 expression plays a critical role in the development of Th2-mediated protective immunity against nematode infection by a mechanism involving CCL2 production and macrophage infiltration.

The role of proteasome beta subunits in gastrin-mediated transcription of plasminogen activator inhibitor-2 and regenerating protein1

The hormone gastrin physiologically regulates gastric acid secretion and also contributes to maintaining gastric epithelial architecture by regulating expression of genes such as plasminogen activator inhibitor 2 (PAI-2) and regenerating protein 1(Reg1). Here we examine the role of proteasome subunit PSMB1 in the transcriptional regulation of PAI-2 and Reg1 by gastrin, and its subcellular distribution during gastrin stimulation. We used the gastric cancer cell line AGS, permanently transfected with the CCK2 receptor (AGS-GR) to study gastrin stimulated expression of PAI-2 and Reg1 reporter constructs when PSMB1 was knocked down by siRNA. Binding of PSMB1 to the PAI-2 and Reg1 promoters was assessed by chromatin immunoprecipitation (ChIP) assay. Subcellular distribution of PSMB1 was determined by immunocytochemistry and Western Blot. Gastrin robustly increased expression of PAI-2 and Reg1 in AGS-GR cells, but when PSMB1 was knocked down the responses were dramatically reduced. In ChIP assays, following immunoprecipitation of chromatin with a PSMB1 antibody there was a substantial enrichment of DNA from the gastrin responsive regions of the PAI-2 and Reg1 promoters compared with chromatin precipitated with control IgG. In AGS-GR cells stimulated with gastrin there was a significant increase in the ratio of nuclear:cytoplasmic PSMB1 over the same timescale as recruitment of PSMB1 to the PAI-2 and Reg1 promoters seen in ChIP assays. We conclude that PSMB1 is part of the transcriptional machinery required for gastrin stimulated expression of PAI-2 and Reg1, and that its change in subcellular distribution in response to gastrin is consistent with this role.

Expression of plasminogen activator inhibitor-2 is negatively associated with invasive potential in hepatocellular carcinoma cells

OBJECTIVE

To investigate the association between plasminogen activator inhibitor (PAI)-2 expression and invasive potential in hepatocellular carcinoma (HCC) cells.

METHODS

The HCC cell lines with high, low, and non-metastatic potentials, namely MHCC97-H, MHCC97-L, and SMMC-7721 respectively, were cultured in vitro. Matrigel invasion assay and Western blot of PAI-2 protein expression were conducted.

RESULTS

The number of invaded cells in MHCC97-L was significantly higher than that in SMMC-7721 (P=0.005), whereas that in MHCC97-H was higher than in MHCC97-L (P=0.017) and SMMC-7721 (P=0.001). Contrarily, PAI-2 protein expression was gradually reducing from SMMC-7721, MHCC97-L, to MHCC97-H (MHCC97-H vs. MHCC97-L, P<0.001; MHCC97-H vs. SMMC-7721, P=0.001; MHCC97-L vs. SMMC-7721, P=0.001). The Pearson's correlation analysis revealed a significant negative association between invaded cell number and PAI-2 expression (r=-0.892, P=0.001).

CONCLUSION

PAI-2 expression may be negatively associated with the invasive potential of HCC.

The transcription factor C/EBP-β mediates constitutive and LPS-inducible transcription of murine SerpinB2

SerpinB2 or plasminogen activator inhibitor type 2 (PAI-2) is highly induced in macrophages in response to inflammatory stimuli and is linked to the modulation of innate immunity, macrophage survival, and inhibition of plasminogen activators. Lipopolysaccharide (LPS), a potent bacterial endotoxin, can induce SerpinB2 expression via the toll-like receptor 4 (TLR4) by ∼1000-fold over a period of 24 hrs in murine macrophages. To map the LPS-regulated SerpinB2 promoter regions, we transfected reporter constructs driven by the ∼5 kb 5'-flanking region of the murine SerpinB2 gene and several deletion mutants into murine macrophages. In addition, we compared the DNA sequence of the murine 5′ flanking sequence with the sequence of the human gene for homologous functional regulatory elements and identified several regulatory cis-acting elements in the human SERPINB2 promoter conserved in the mouse. Mutation analyses revealed that a CCAAT enhancer binding (C/EBP) element, a cyclic AMP response element (CRE) and two activator protein 1 (AP-1) response elements in the murine SerpinB2 proximal promoter are essential for optimal LPS-inducibility. Electrophoretic mobility shift (EMSA) and chromatin immunoprecipitation (ChIP) assays demonstrated that LPS induces the formation of C/EBP-β containing complexes with the SerpinB2 promoter. Importantly, both constitutive and LPS-induced SerpinB2 expression was severely abrogated in C/EBP-β-null mouse embryonic fibroblasts (MEFs) and primary C/EBP-β-deficient peritoneal macrophages. Together, these data provide new insight into C/EBP-β-dependent regulation of inflammation-associated SerpinB2 expression.

Bacterial plasminogen receptors utilize host plasminogen system for effective invasion and dissemination

In order for invasive pathogens to migrate beyond the site of infection, host physiological barriers such as the extracellular matrix, the basement membrane, and encapsulating fibrin network must be degraded. To circumvent these impediments, proteolytic enzymes facilitate the dissemination of the microorganism. Recruitment of host proteases to the bacterial surface represents a particularly effective mechanism for enhancing invasiveness. Plasmin is a broad spectrum serine protease that degrades fibrin, extracellular matrices, and connective tissue. A large number of pathogens express plasminogen receptors which immobilize plasmin(ogen) on the bacterial surface. Surface-bound plasminogen is then activated by plasminogen activators to plasmin through limited proteolysis thus triggering the development of a proteolytic surface on the bacteria and eventually assisting the spread of bacteria. The host hemostatic system plays an important role in systemic infection. The interplay between hemostatic processes such as coagulation and fibrinolysis and the inflammatory response constitutes essential components of host defense and bacterial invasion. The goal of this paper is to highlight mechanisms whereby pathogenic bacteria, by engaging surface receptors, utilize and exploit the host plasminogen and fibrinolytic system for the successful dissemination within the host.

Release of TGFβig-h3 by gastric myofibroblasts slows tumor growth and is decreased with cancer progression

Tumor progression has been linked to changes in the stromal environment. Myofibroblasts are stromal cells that are often increased in tumors but their contribution to cancer progression is not well understood. Here, we show that the secretomes of myofibroblasts derived from gastric cancers [cancer-associated myofibroblasts (CAMs)] differ in a functionally significant manner from those derived from adjacent tissue [adjacent tissue myofibroblasts (ATMs)]. CAMs showed increased rates of migration and proliferation compared with ATMs or normal tissue myofibroblasts (NTMs). Moreover, conditioned medium (CM) from CAMs significantly stimulated migration, invasion and proliferation of gastric cancer cells compared with CM from ATMs or NTMs. Proteomic analysis of myofibroblast secretomes revealed decreased abundance of the extracellular matrix (ECM) adaptor protein like transforming growth factor-β-induced gene-h3 (TGFβig-h3) in CAMs, which was correlated with lymph node involvement and shorter survival. TGFβig-h3 inhibited IGF-II-stimulated migration and proliferation of both cancer cells and myofibroblasts, and suppressed IGF-II activation of p42/44 MAPkinase; TGFβig-h3 knockdown increased IGF-II- and CM-stimulated migration. Furthermore, administration of TGFβig-h3 inhibited myofibroblast-stimulated growth of gastric cancer xenografts. We conclude that stromal cells exert inhibitory as well as stimulatory effects on tumor cells; TGFβig-h3 is a stromal inhibitory factor that is decreased with progression of gastric cancers.

Gastrin stimulates expression of plasminogen activator inhibitor-1 in gastric epithelial cells

Plasminogen activator inhibitor (PAI)-1 is associated with cancer progression, fibrosis and thrombosis. It is expressed in the stomach but the mechanisms controlling its expression there, and its biological role, are uncertain. We sought to define the role of gastrin in regulating PAI-1 expression and to determine the relevance for gastrin-stimulated cell migration and invasion. In gastric biopsies from subjects with elevated plasma gastrin, the abundances of PAI-1, urokinase plasminogen activator (uPA), and uPA receptor (uPAR) mRNAs measured by quantitative PCR were increased compared with subjects with plasma concentrations in the reference range. In patients with hypergastrinemia due to autoimmune chronic atrophic gastritis, there was increased abundance of PAI-1, uPA, and uPAR mRNAs that was reduced by octreotide or antrectomy. Immunohistochemistry revealed localization of PAI-1 to parietal cells and enterochromaffin-like cells in micronodular neuroendocrine tumors in hypergastrinemic subjects. Transcriptional mechanisms were studied by using a PAI-1-luciferase promoter-reporter construct transfected into AGS-G(R) cells. There was time- and concentration-dependent increase of PAI-1-luciferase expression in response to gastrin that was reversed by inhibitors of the PKC and MAPK pathways. In Boyden chamber assays, recombinant PAI-1 inhibited gastrin-stimulated AGS-G(R) cell migration and invasion, and small interfering RNA treatment increased responses to gastrin. We conclude that elevated plasma gastrin concentrations are associated with increased expression of gastric PAI-1, which may act to restrain gastrin-stimulated cell migration and invasion.

Down-regulation of Bcl-2 is mediated by NF-κB activation in Helicobacter pylori-induced apoptosis of gastric epithelial cells

OBJECTIVE

Bcl-2 family is involved in the regulation of apoptosis. NF-κB activation is associated with either the expression of Bcl-2 or down-regulation of Bcl-2 depending on cell types and stimuli. Previously, we showed NF-κB activation, decrease in the level of Bcl-2, and apoptosis in Helicobacter pylori (H. pylori)-infected gastric epithelial cells. The present study aims to investigate the relation of Bcl-2 expression and NF-κB activation in H. pylori-induced apoptotic cell death of AGS (gastric adenocarcinoma) cells.

MATERIAL AND METHODS

AGS cells were transfected with mutant IκBα to suppress NF-κB activation or Bcl-2 gene to induce overexpression of Bcl-2. mRNA expression of Bcl-2, p53 and Bax, DNA fragmentation, cell viability, and the numbers of apoptotic cells were determined.

RESULTS

H. pylori induced decrease in Bcl-2, but increase in p53 and Bax at the levels of mRNA and protein in AGS cells. H. pylori-induced increment of apoptotic cells and decrease in Bcl-2 level were inhibited in the cells transfected with mutant IκBα gene as compared with the cells transfected with control vector. H. pylori-induced apoptosis determined by apoptotic cells, DNA fragmentation, and cell viability was inhibited in the cells transfected with Bcl-2 gene.

CONCLUSION

Down-regulation of Bcl-2 is mediated by NF-κB activation, which may be the underlying mechanism of apoptosis in H. pylori-infected gastric epithelial cells.

The plasminogen activator inhibitor 2 transcript is destabilized via a multi-component 3' UTR localized adenylate and uridylate-rich instability element in an analogous manner to cytokines and oncogenes

Plasminogen activator inhibitor type 2 (PAI-2; SERPINB2) is a highly-regulated gene that is subject to both transcriptional and post-transcriptional control. For the latter case, inherent PAI-2 mRNA instability was previously shown to require a nonameric adenylate-uridylate element in the 3' UTR. However, mutation of this site was only partially effective at restoring complete mRNA stabilization. In the present study, we have identified additional regulatory motifs within the 3' UTR that cooperate with the nonameric adenylate-uridylate element to promote mRNA destabilization. These elements are located within a 74 nucleotide U-rich stretch (58%) of the 3' UTR that flanks the nonameric motif; deletion or substitution of this entire region results in complete mRNA stabilization. These new elements are conserved between species and optimize the destabilizing capacity with the nonameric element to ensure complete mRNA instability in a manner analogous to some class I and II adenylate-uridylate elements present in transcripts encoding oncogenes and cytokines. Hence, post-transcriptional regulation of the PAI-2 mRNA transcript involves an interaction between closely spaced adenylate-uridylate elements in a manner analogous to the post-transcriptional regulation of oncogenes and cytokines.

Gastrin activates paracrine networks leading to induction of PAI-2 via MAZ and ASC-1

The gastric hormone gastrin regulates the expression of a variety of genes involved in control of acid secretion and also in the growth and organization of the gastric mucosa. One putative target is plasminogen activator inhibitor-2 (PAI-2), which is a component of the urokinase activator system that acts extracellularly to inhibit urokinase plasminogen activator (uPA) and intracellularly to suppress apoptosis. Previous studies have demonstrated that gastrin induces PAI-2 both in gastric epithelial cells expressing the gastrin (CCK-2) receptor and, via activation of paracrine networks, in adjacent cells that do not express the receptor. We have now sought to identify the response element(s) in the PAI-2 promoter targeted by paracrine mediators initiated by gastrin. Mutational analysis identified two putative response elements in the PAI-2 promoter that were downstream of gastrin-activated paracrine signals. One was identified as a putative MAZ site, mutation of which dramatically reduced both basal and gastrin-stimulated responses of the PAI-2 promoter by a mechanism involving PGE(2) and the small GTPase RhoA. Yeast one-hybrid screening identified the other as binding the activating signal cointegrator-1 (ASC-1) complex, which was shown to be the target of IL-8 released by gastrin. RNA interference (RNAi) knockdown of two subunits of the ASC-1 complex (p50 and p65) inhibited induction of PAI-2 expression by gastrin. The data reveal previously unsuspected transcriptional mechanisms activated as a consequence of gastrin-triggered paracrine networks and emphasize the elaborate and complex cellular control mechanisms required for a key component of tissue responses to damage and infection.

The role of plasminogen-plasmin system in cancer

Components of the plasminogen-plasmin system participate in a wide variety of physiologic and pathologic processes, including tumor growth, invasion and metastasis, through their effect on angiogenesis and cell migration. These components are found in most tumors and their expression not only signifies their function but also carries a prognostic value. Their expression is in turn modulated by cytokines and growth factors, many of which are up-regulated in cancer. Though both tPA and uPA are expressed in tumor cells, uPA with its receptor (uPAR) is mostly involved in cellular functions, while tPA with its receptor Annexin II on endothelial surface, regulates intravascular fibrin deposition. Among the inhibitors of fibrinolysis, PAI-1 is a major player in the pathogenesis of many vascular diseases as well as in cancer. Therapeutic interventions, either using plasminogen activators or experimental inhibitor agents against PAI-1, have shown encouraging results in experimental tumors but not been verified clinically.

Gastrin increases mcl-1 expression in type I gastric carcinoid tumors and a gastric epithelial cell line that expresses the CCK-2 receptor

Elevated serum concentrations of the hormone gastrin are associated with the development of gastric carcinoid tumors, but the mechanisms of tumor development are not fully understood. We hypothesized that the antiapoptotic effects of gastrin may be implicated and have therefore investigated the role of antiapoptotic members of the bcl-2 family of proteins. AGS-G(R) human gastric carcinoma cells stably transfected with the CCK-2 receptor were used to assess changes in the expression of bcl-2 family members following gastrin treatment and the function of mcl-1 during apoptosis was investigated by use of small-interfering RNA (siRNA). Treatment of AGS-G(R) cells with 10 nM gastrin for 6 h caused maximally increased mcl-1 protein abundance. Gastrin-induced mcl-1 expression was inhibited by the transcription inhibitor actinomycin D and by the protein synthesis inhibitor cycloheximide. Downstream signaling of mcl-1 expression occurred via the CCK-2 receptor, protein kinase C, and MAP kinase pathways, but not via PI 3-kinase. Transfection with mcl-1 siRNA significantly suppressed mcl-1 protein expression and abolished the antiapoptotic effects of gastrin on serum starvation-induced apoptosis. Mcl-1 protein expression was also specifically increased in the type I enterochromaffin-like cell carcinoid tumors of 10 patients with autoimmune atrophic gastritis and hypergastrinemia. Gastrin therefore signals via the CCK-2 receptor, protein kinase C, and MAP kinase to induce expression of antiapoptotic mcl-1 in AGS-G(R) cells, and mcl-1 expression is also increased in human hypergastrinemia-associated type I gastric carcinoid tumors. Gastrin-induced mcl-1 expression may therefore be an important mechanism contributing toward type I gastric carcinoid development.

Apoptotic effect of Helicobacter pylori on oesophageal squamous-cell carcinoma cells in vitro

BACKGROUND

The relationship between Helicobacter pylori (Hp) infection and oesophageal squamous-cell carcinoma (ESCC) risk is still inconclusive. Our previous study found an inverse association between the two, but its mechanism is still unknown. Thus, we conducted in vitro studies to clarify the issue.

MATERIALS AND METHODS

One ESCC (CE 81T/VGH) cell line was co-cultured with Hp, using one gastric adenocarcinoma (AGS) cell line as the control. Hp-induced cell apoptosis was determined by flow cytometry, terminal transferase-mediated dUTP nick end labelling (TUNEL) assay and staining; caspase-3 protein expressions in cell lysates were detected by Western immunoblot.

RESULTS

Increased apoptosis was found in CE 81T/VGH, but not in AGS cells, by flow cytometry and TUNEL assay after being co-cultured with Hp at the multiplicity of infection of 1/100 (but not at 1/400) for 36 h. The amount of activated caspase-3 (17/19 kDa) also increased in CE 81T/VGH, but not in AGS cells, after co-culturing with Hp at MOI of 1/100 for 36 h. The results were confirmed by triplicate experiments in which the different apoptotic assays remained consistent.

CONCLUSIONS

Our study provides indirect evidence of the inverse association between Hp infection and ESCC risk, which is possibly due to Hp-induced apoptosis in ESCC cells. A further in vivo study is necessary to confirm our findings.

Increased expression of the urokinase plasminogen activator system by Helicobacter pylori in gastric epithelial cells

The gastric pathogen Helicobacter pylori (H. pylori) is linked to peptic ulcer and gastric cancer, but the relevant pathophysiological mechanisms are unclear. We now report that H. pylori stimulates the expression of plasminogen activator inhibitor (PAI)-1, urokinase plasminogen activator (uPA), and its receptor (uPAR) in gastric epithelial cells and the consequences for epithelial cell proliferation. Real-time PCR of biopsies from gastric corpus, but not antrum, showed significantly increased PAI-1, uPA, and uPAR in H. pylori-positive patients. Transfection of primary human gastric epithelial cells with uPA, PAI-1, or uPAR promoters in luciferase reporter constructs revealed expression of all three in H+/K+ATPase- and vesicular monoamine transporter 2-expressing cells; uPA was also expressed in pepsinogen- and uPAR-containing trefoil peptide-1-expressing cells. In each case expression was increased in response to H. pylori and for uPA, but not PAI-1 or uPAR, required the virulence factor CagE. H. pylori also stimulated soluble and cell surface-bound uPA activity, and both were further increased by PAI-1 knockdown, consistent with PAI-1 inhibition of endogenous uPA. H. pylori stimulated epithelial cell proliferation, which was inhibited by uPA immunoneutralization and uPAR knockdown; exogenous uPA also stimulated proliferation that was further increased after PAI-1 knockdown. The proliferative effects of uPA were inhibited by immunoneutralization of the EGF receptor and of heparin-binding EGF (HB-EGF) by the mutant diphtheria toxin CRM197 and an EGF receptor tyrosine kinase inhibitor. H. pylori induction of uPA therefore leads to epithelial proliferation through activation of HB-EGF and is normally inhibited by concomitant induction of PAI-1; treatments directed at inhibition of uPA may slow the progression to gastric cancer.

SerpinB2 protection of retinoblastoma protein from calpain enhances tumor cell survival

The tumor suppressor retinoblastoma protein (Rb) plays a pivotal role in the regulation of cell proliferation and sensitivity to apoptosis through binding to E2F transcription factors. Loss of Rb in response to genotoxic stress or inflammatory cytokines can enhance cell death, in part, by eliminating Rb-mediated repression of proapoptotic gene transcription. Here we show that calpain cleavage of Rb facilitates Rb loss by proteasome degradation and that this may occur during tumor necrosis factor alpha-induced apoptosis. The cytoprotective, Rb-binding protein SerpinB2 (plasminogen activator inhibitor type 2) protects Rb from calpain cleavage, increasing Rb levels and enhancing cell survival. Chromatin immunoprecipitation assays show that the increased Rb levels selectively enhance Rb repression of proapoptotic gene transcription. This cytoprotective role of SerpinB2 is illustrated by reduced susceptibility of SerpinB2-deficient mice to multistage skin carcinogenesis, where Rb-dependent cell proliferation competes with apoptosis during initiation of papilloma development. These data identify SerpinB2 as a cell survival factor that modulates Rb repression of proapoptotic signal transduction and define a new posttranslational mechanism for selective regulation of the intracellular levels of Rb.

Changes in gene expression of gastric mucosa during therapeutic acid inhibition

BACKGROUND

Long-term therapy with potent acid inhibitors is a common treatment for gastro-esophageal reflux disease. Administration of proton pump inhibitors (PPIs) causes profound and continuous hypochlorhydria by inhibition of the proton pump in gastric parietal cells. Long-term hypergastrinaemia increases mucosal thickness and enterochromaffin-like cell density in oxyntic mucosa.

OBJECTIVE

The aim of this study was to see whether this very common clinical intervention induces significant changes in the gastric mucosal gene expression pattern.

METHODS

Seven patients suffering from gastro-esophageal reflux disease were included in this study. Endoscopic biopsies were taken from the corpus mucosa before and toward the end of a 3-month treatment with the PPI esomeprazole.

RESULTS

Microarray analysis identified 186 differentially expressed genes. A high proportion of genes with changed gene expression levels during PPI treatment are involved in proliferation, apoptosis, and stress response.

CONCLUSION

This study identified many genes that were not previously known to be affected by inhibition of gastric acid secretion. Further characterization of the functional roles of genes whose expression is modulated by potent acid inhibition may give new insight into the biological responses to potent acid inhibition, including the mucosal response to the moderately increased gastrin levels encountered in clinical practice.

LC/MS identification of 12 intracellular cytoskeletal and inflammatory proteins from monocytes adherent on surface-adsorbed fibronectin-derived peptides

The extent and duration of the host response determines device efficacy, yet the mechanism is poorly understood. U937 promonocytic cells were cultured on peptide-adsorbed tissue-culture polystyrene to better understand surface-modulated intracellular events. Phosphotyrosine proteins were enriched by immunoprecipitation and analyzed by nanospray HPLC-coupled tandem mass spectrometry (LC/MS). Tyrosine-phosphorylated proteins were chosen based on physiological significance and previous densitometry results, which identified a set of proteins ranging from approximately 200 to approximately 23 kDa showing altered phosphorylation levels in response to various surface-adsorbed ligands and phosphorylation inhibitor AG18. Although LC/MS has been used for nearly a decade, its application to the field of biomaterials is relatively novel. Twelve intracellular proteins identified by nanospray LC/MS are potentially related to the host response. Eight of the twelve proteins are related to the cytoskeleton including: moesin, heat shock protein 90beta, alpha-tubulin, elongation factor 1alpha, beta actin, vimentin, plasminogen activator inhibitor 2, and heterogeneous ribonuclear protein A2. The remaining four proteins: high mobility group box 1, caspase recruitment domain 5, glycoprotein 96, and heterogeneous nuclear ribonucleoprotein D0 modulate inflammation. The specific effect each peptide has upon modulating the phosphorylation state of these proteins cannot be determined from this work; however, 12 viable targets have been identified for further investigation into the role each plays in the surface-mediated monocyte response.

Helicobacter pylori infection stimulates plasminogen activator inhibitor 1 production by gastric epithelial cells

Chronic infection with the gastric pathogen Helicobacter pylori significantly increases the risk of developing atrophic gastritis, peptic ulcer disease, and gastric adenocarcinoma. H. pylori strains that possess the cag pathogenicity island, which translocates CagA into the host cells, augment these risks. The aim of this study was to determine the molecular mechanisms through which H. pylori upregulates the expression of plasminogen activator inhibitor 1 (PAI-1), a member of the urokinase activator system that is involved in tumor metastasis and angiogenesis. Levels of PAI-1 mRNA and protein were examined in tissues from H. pylori-infected patients and in vitro using AGS gastric epithelial cells. In vitro, cells were infected with toxigenic cag-positive or nontoxigenic cag-negative strains of H. pylori or isogenic mutants. The amount of PAI-1 secretion was measured by enzyme-linked immunosorbent assay, and mRNA levels were determined using real-time PCR. The regulation of PAI-1 was examined using the extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor and small interfering RNA. Analysis of human biopsy samples revealed an increase in both PAI-1 mRNA and protein levels in patients with H. pylori gastritis compared to those of uninfected controls. Infection of AGS cells with H. pylori significantly increased PAI-1 mRNA expression and the secretion of PAI-1 protein. Moreover, PAI-1 mRNA and protein production was more pronounced when AGS cells were infected by H. pylori strains carrying a functional cag secretion system than when cells were infected by strains lacking this system. PAI-1 secretion was also reduced when cells were infected with either cagE-negative or cagA-negative mutants. The ectopic overexpression of CagA significantly increased the levels of PAI-1 mRNA and protein, whereas blockade of the ERK1/2 pathway inhibited H. pylori-mediated PAI-1 upregulation. These findings suggest that the upregulation of PAI-1 in H. pylori-infected gastric epithelial cells may contribute to the carcinogenic process.

The effects of cyclooxygenase2-prostaglandinE2 pathway on Helicobacter pylori-induced urokinase-type plasminogen activator system in the gastric cancer cells

BACKGROUND

Urokinase-type plasminogen activator (uPA) and its receptor (uPAR) play an important role in the destruction of the extracellular matrix and basement membrane. The induction of uPA and uPAR in the gastric cancer cells with H. pylori has been demonstrated previously. The involvement of COX-2-PGE2 pathway in the uPA system (uPA and uPAR) expression is unclear.

METHODS

Gastric cancer cells (MKN45) were co-cultured with H. pylori standard strain (NCTC11637). The specific inductions of uPA and uPAR mRNA were examined by reverse transcription-polymerase chain reaction amplification. The secreted uPA antigen was measured by ELISA. To evaluate the involvement of COX-2 and PGE2 pathway in H. pylori-induced uPA and uPAR expressions, we examined the effects of COX-2 inhibitor and PGE2 receptor antagonist on H. pylori-induced uPA and uPAR expression in the gastric cancer cells.

RESULTS

The expressions of both uPA and uPAR mRNAs in the gastric cancer cells increased obviously (12-fold and 3-fold, respectively) with H. pylori stimulation. The amount of uPA antigen into the culture medium increased dramatically with H. pylori stimulation. The COX-2 expression level in the gastric cancer cells increased remarkably with H. pylori stimulation. H. pylori-induced uPA and uPAR expression levels were suppressed with COX2 inhibitor treatment. The amount of PGE2 antigen into the culture medium increased dramatically 24 hours after H. pylori stimulation. The gastric cancer cells expressed EP2 and EP4 subtypes. EP2 receptor antagonist suppressed the H. pylori-induced uPA and uPAR expressions in the gastric cancer cells.

CONCLUSIONS

Our results indicated that COX2-PGE2 pathway may be involved in H. pylori-associated uPA and uPAR induction, and that COX-2 inhibitor or EP2 receptor antagonist may inhibit angiogenesis and tumor invasion via suppression of the uPA system.

Transactivation of the EGFR by AP-1 is induced by Helicobacter pylori in gastric cancer

BACKGROUND

Helicobacter pylori infection of the gastric mucosa is strongly associated with gastritis, peptic ulcer disease, and gastric cancer. However, the mechanisms by which H. pylori causes cancer are currently unknown. Binding of epidermal growth factor (EGF) to its receptor (EGFR) may be important in the development of gastric cancer. This interaction accelerates cell proliferation and migration, and triggers epithelial cell signaling. In this study, we investigated the effects of H. pylori on EGFR- and AP-1-mediated signal transduction pathways in the AGS gastric epithelial cell line and gastric tissue from humans.

METHODS

Cells were treated with H. pylori and cell death was examined at a variety of time points using cell viability and trypan blue exclusion dye assay. To investigate the effects on EGFR regulation, AGS cells were transfected with a full-length and truncated EGFR luciferase (luc) reporter. Tissue microarray containing 44 samples of gastric biopsies from H. pylori-positive patients was analyzed for protein expression level of EGFR by immunohistochemistry.

RESULTS

EGFR promoter activity was increased (twofold) 3 h after treatment with H. pylori commenced. Using a series of EGFR promoter deletion mutants, we identified a region that was crucial for transactivation of the EGFR by H. pylori. To determine whether AP-1 binding was altered, we transfected AGS cells with an AP-1 luciferase construct and then treated them with H. pylori for up to 6 h. We found that AP-1 activity was induced by H. pylori in gastric cells, while electrophoretic mobility shift assays confirmed that binding of AP-1 to the EGFR promoter site was increased following H. pylori treatment. Binding of c-Jun and c-Fos to the EGFR promoter region -1,062/-900 was induced eight- and six fold, respectively, using ChIP assay. Active EGFR staining was markedly increased in gastric mucosa from infected persons, compared to uninfected controls.

CONCLUSIONS

We conclude that exposure of gastric cells to H. pylori induces increased production of EGFR through various signal transduction pathways, including those mediated by the EGFR and AP-1. Distinct effects on EGFR activation may specify the subset of AP-1 target genes that are selected, including those involved in proliferation and apoptosis. This is consistent with EGFR activation that was found in the gastric mucosa of humans infected with H. pylori. Hence, the balance between apoptosis and proliferation in these cells may be altered in response to injury caused by H. pylori infection, leading to an increased risk of cancer.

Helicobacter and gastrin stimulate Reg1 expression in gastric epithelial cells through distinct promoter elements

The gastric pathogen Helicobacter pylori accelerates the progression to gastric cancer but the precise mechanisms that mediate carcinogenesis remain unidentified. We now describe how Helicobacter and gastrin stimulate the expression of a putative growth factor, Reg1, in primary gastric epithelial cells. RT-PCR and Western immunoblotting of human gastric corpus and antrum showed significantly increased Reg1alpha in H. pylori-infected patients. Similarly, Reg1 was increased in the stomachs of H. felis-infected INS-GAS mice. To study transcriptional regulation of the Reg1 gene, we transfected primary mouse gastric glands with -2111 bp and -104 bp Reg1 promoter-luciferase reporter constructs. Expression of both constructs was detected in pepsinogen- and VMAT-2-expressing cells, which corresponds to the normal pattern of expression of human and mouse endogenous Reg1. The expression of both constructs was increased in response to gastrin and H. pylori, and there were potentiating interactions between them; in contrast, only the -2111 bp construct responded to H. felis. Mutation of a C-rich putative regulatory element within the -104 bp sequence abolished the response to gastrin but not to H. pylori whereas mutation of the proximal -98 to -93 region of the promoter reduced the response to H. pylori but not to gastrin. Stimulation of Reg1 by H. pylori required the virulence factor CagA. These data indicate that expression of the putative growth factor Reg1 is controlled through separate promoter elements by gastrin and Helicobacter.

Attack and defence in the gastric epithelium - a delicate balance

The gastric epithelium is a complex structure formed into tubular branched gastric glands. The glands contain a wide variety of cell types concerned with the secretion of hydrochloric acid, proteases, mucus and a range of signalling molecules. All cell types originate from stem cells in the neck region of the gland, before migrating and differentiating to assume their characteristic positions and functions. Endocrine and local paracrine mediators are of crucial importance for maintaining structural and functional integrity of the epithelium, in the face of a hostile luminal environment. The first such mediator to be recognized, the hormone gastrin, was identified over a century ago and is now established as the major physiological stimulant of gastric acid secretion. Recent studies, including those using mice that overexpress or lack the gastrin gene, suggest a number of previously unrecognized roles for this hormone in the regulation of cellular proliferation, migration and differentiation. This review focuses on the identification of hitherto unsuspected gastrin-regulated genes and discusses the paracrine cascades that contribute to the maintenance of gastric epithelial architecture and secretory function. Helicobacter infection is also considered in cases where it shares targets and signalling mechanisms with gastrin.

Increased gastric expression of MMP-7 in hypergastrinemia and significance for epithelial-mesenchymal signaling

Chronic hypergastrinemia is associated with enterochromaffin-like (ECL) cell hyperplasia, which may progress to gastric carcinoid tumors. The latter consists of epithelial cells and stroma, and both compartments usually regress after normalization of hypergastrinemia. We previously showed that matrix metalloproteinase (MMP)-7 in gastric epithelial cells was upregulated by Helicobacter pylori and described MMP-7-dependent reciprocal signaling between the epithelium and a key stromal cell type, the myofibroblast. Here, we describe the regulation of gastric MMP-7 by gastrin and the potential significance for recruiting and maintaining myofibroblast populations. Biopsies of the gastric corpus and ECL cell carcinoid tumors were obtained from hypergastrinemic patients. Western blot analysis, ELISA, immunohistochemistry, and promoter-luciferase (luc) reporter assays were used to study MMP-7 expression. Gastric myofibroblasts were identified by alpha-smooth muscle actin (alpha-SMA) expression, and the effects of MMP-7 on myofibroblast proliferation were investigated. In hypergastrinemic patients, there was an increased abundance of MMP-7 and alpha-SMA in gastric corpus biopsies and ECL cell carcinoid tumors. In the latter, MMP-7 was localized to ECL cells but not stromal cells, which were nevertheless well represented. Gastrin stimulated MMP-7-luc expression in both AGS-G(R) and primary human gastric epithelial cells. Conditioned medium from gastrin-treated human gastric glands stimulated myofibroblast proliferation, which was inhibited by neutralizing antibodies to MMP-7. MMP-7 increased the proliferation of myofibroblasts via the MAPK and phosphatidylinositol 3-kinase (PI3K) pathways. In conclusion, stimulation of gastric MMP-7 by elevated plasma gastrin may activate epithelial-mesenchymal signaling pathways regulating myofibroblast function via MAPK and PI3K pathways and contribute to stromal deposition in ECL cell carcinoid tumors.

Inflammation and cancer: How hot is the link?

Although inflammation has long been known as a localized protective reaction of tissue to irritation, injury, or infection, characterized by pain, redness, swelling, and sometimes loss of function, there has been a new realization about its role in a wide variety of diseases, including cancer. While acute inflammation is a part of the defense response, chronic inflammation can lead to cancer, diabetes, cardiovascular, pulmonary, and neurological diseases. Several pro-inflammatory gene products have been identified that mediate a critical role in suppression of apoptosis, proliferation, angiogenesis, invasion, and metastasis. Among these gene products are TNF and members of its superfamily, IL-1alpha, IL-1beta, IL-6, IL-8, IL-18, chemokines, MMP-9, VEGF, COX-2, and 5-LOX. The expression of all these genes are mainly regulated by the transcription factor NF-kappaB, which is constitutively active in most tumors and is induced by carcinogens (such as cigarette smoke), tumor promoters, carcinogenic viral proteins (HIV-tat, HIV-nef, HIV-vpr, KHSV, EBV-LMP1, HTLV1-tax, HPV, HCV, and HBV), chemotherapeutic agents, and gamma-irradiation. These observations imply that anti-inflammatory agents that suppress NF-kappaB or NF-kappaB-regulated products should have a potential in both the prevention and treatment of cancer. The current review describes in detail the critical link between inflammation and cancer.

Reciprocal upregulation of urokinase plasminogen activator and its inhibitor, PAI-2, by Borrelia burgdorferi affects bacterial penetration and host-inflammatory response

The mammalian plasminogen activation system (PAS) is a complex system involved in multiple physiological and pathological processes. Borrelia burgdorferi interacts with certain components of the PAS. Here we further investigate this interaction to determine its effect on bacterial dissemination and host cell migration in vitro. We show that stimulation of monocytic cells with B. burgdorferi induces the transient production and secretion of urokinase plasminogen activator (uPA), shortly followed by its physiological inhibitor, plasminogen activator inhibitor-2 (PAI-2). Mono Mac 6 (MM6) cells as well as peripheral blood monocytes enhanced transmigration of B. burgdorferi across a barrier coated with fibronectin mediated by uPA. Moreover, the induction of PAI-2 or the addition of recombinant PAI-2 did not have a significant effect on the uPA-potentiated transmigration of B. burgdorferi. In contrast, the induction of PAI-2 by B. burgdorferi resulted in significantly diminished invasion by monocytic cells across a reconstituted basement membrane (matrigel), which could be partially restored by treatment with purified uPA. These results show that the PAS plays a twofold role in the pathogenesis of B. burgdorferi infection, both by enhancing bacterial dissemination and by diminishing host-cell inflammatory migration.

Latest insights into the effects of Helicobacter pylori infection on gastric carcinogenesis

There appears to be the strong association between Helicobacter pylori (H pylori) and gastric cancer. We reviewed the latest evidences about the effects of H pylori infection on gastric carcinogenesis, classified into epidemiology, dynamics of gastric mucosal changes, DNA damages, virulence factors, host factors, and source of gastric malignancy. Through the considerable progress made in research into virulence factors resulting from differences between H pylori strains, such as cagA positivity, as well as into host factors, such as gene polymorphisms, a diverse spectrum of H pylori-associated diseases, including gastric cancer, is beginning to lend itself to elucidation. The impact of the novel hypothesis advanced by Houghton et al proposing bone-marrow derived stem cells (BMDC) as a potential source of gastric malignancy on evolving research remains to be seen with interest. Further progress in research into H pylori eradication as a viable prophylaxis of gastric cancer, as well as into the mechanisms of gastric carcinogenesis, is to be eagerly awaited for the current year and beyond.

The role of matrix metalloproteinase-7 in redefining the gastric microenvironment in response to Helicobacter pylori

BACKGROUND & AIMS

Interactions between epithelial and stromal cells are important determinants of mucosal organization, but the signaling mechanisms are understood incompletely. Matrix metalloproteinase (MMP)-7 is produced uniquely in epithelia, may act on growth factors and matrix proteins, and in the stomach is increased with Helicobacter pylori infection. We have studied the role of MMP-7 in signaling between epithelial cells and a key stromal cell type, the myofibroblast.

METHODS

Immunohistochemistry and Western blotting were applied to gastric corpus biopsy specimens; primary cultures of human gastric glands and myofibroblasts were used to study the role of MMP-7 in regulating proliferation and migration of the latter, and MMP-7 substrates were identified by proteomic methods.

RESULTS

Increased abundance of the myofibroblast marker alpha-smooth muscle actin was identified in H. pylori-positive biopsy specimens. Media from H pylori-infected gastric epithelial cultures stimulated proliferation and migration of primary human gastric myofibroblasts and antisense oligonucleotide treatment indicated a role for MMP-7. Proteomic methods identified insulin-like growth factor binding protein (IGFBP)-5 as a substrate for MMP-7 in medium from gastric myofibroblasts. Knockdown of IGFBP-5 by small interfering RNA or immunoneutralization of IGF-II, abolished myofibroblast responses to MMP-7. Proliferation of gastric epithelial cells also was stimulated by MMP-7-treated myofibroblasts via IGF-II.

CONCLUSIONS

MMP-7 acts as an epithelial-derived signal increasing the bioavailability of IGF-II released from myofibroblasts. Because IGF-II acts on both stromal and epithelial cells, the findings suggest that increased MMP-7 expression contributes to redefining the niche occupied by dividing cells and leading to hyperproliferation in H pylori infection.

Gene expression and protein profiling of AGS gastric epithelial cells upon infection with Helicobacter pylori

Helicobacter pylori, one of the most common bacterial pathogens, colonizes the human stomach and causes a variety of gastric diseases. This pathogen elicits a range of phenotypic responses in infected cultured AGS gastric epithelial cells, including expression of proinflammatory genes and changes in the actin cytoskeleton. Some of these responses are mediated by the type IV secretion system (T4SS) encoded by the cag pathogenicity island. We have used two global approaches, namely 2-DE combined with PMF and cDNA expression array analyses, to study in both a comprehensive and quantitative manner the protein profile and the temporal patterns of mRNA accumulation in AGS cells upon infection with H. pylori and isogenic T4SS mutants. We identified 140 transcripts and detected 190 protein species that were differentially regulated upon infection. Infection with wild-type H. pylori induced expression of a variety of host genes and changes in protein pattern involved in transcriptional responses, cell shape regulation and signal transduction. Among them, some were differentially regulated in a cag PAI-dependent manner, as shown by both the proteomic and cDNA expression array approaches. While 2-DE and PMF allowed us to examine the protein profiles in the infected host, array analysis enabled us to demonstrate dynamic temporal changes in host gene expression profile. In conclusion, our combined application of the two global approaches provides further molecular details on how the host cell responds to infection by H. pylori and its isogenic T4SS mutants on both transcriptional and protein levels. The findings pinpoint host proteins such as serine/threonine and tyrosine kinases, transcription factors, cell cycle related components and actin cytoskeletal signaling molecules as potential targets of individual H. pylori virulence determinants. This study serves as a basis for future work on transcription and proteome analyses of the H. pylori infection model.

Insulin-like growth factor binding protein-5 is a target of matrix metalloproteinase-7: implications for epithelial-mesenchymal signaling

Matrix metalloproteinase-7 (MMP-7) is localized to epithelial cells and is up-regulated in many cancers and in inflammation. We now report that MMP-7 targets a key mesenchymal cell type, the myofibroblast. Recombinant MMP-7 stimulated the proliferation and migration of human colonic myofibroblasts. These responses were partly attributable to activation of other MMPs, notably MMP-3 and MMP-8, and to stimulation of the mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling pathways. Using a proteomic approach, we identified insulin-like growth factor binding protein-5 (IGFBP-5) as a previously unsuspected target of MMP-7 produced by colonic myofibroblasts. We present evidence that the MMP-7 cleavage of IGFBP-5 liberates IGF-II that functions as an autocrine myofibroblast growth factor. Thus, MMP-7 may act as a signal from epithelial cells for local recruitment of myofibroblasts and stimulation of their proliferation. Similar effects of MMP-7 produced in epithelial tumors might account for the expansion of stroma through activation of myofibroblasts.

Nuclear factor-kappaB activation correlates with better prognosis and Akt activation in human gastric cancer

PURPOSE

Because the biological significance of constitutive nuclear factor-kappaB (NF-kappaB) activation in human gastric cancer is unclear, we undertook this study to clarify the regulatory mechanism of NF-kappaB activation and its clinical significance.

EXPERIMENTAL DESIGN

Immunohistochemistry for NF-kappaB/RelA was done on 290 human gastric carcinoma specimens placed on tissue array slides. The correlations between NF-kappaB activation and clinicopathologic features, prognosis, Akt activation, tumor suppressor gene expression, or Bcl-2 expression were analyzed. We also did luciferase reporter assay, Western blot analysis, and reverse transcription-PCR using the SNU-216 human gastric cancer cell line transduced with retroviral vectors containing constitutively active Akt or the NF-kappaB repressor mutant of IkappaBalpha.

RESULTS

Nuclear expression of RelA was found in 18% of the gastric carcinomas and was higher in early-stage pathologic tumor-node-metastasis (P = 0.019). A negative correlation was observed between NF-kappaB activation and lymphatic invasion (P = 0.034) and a positive correlation between NF-kappaB activation and overall survival rate of gastric cancer patients (P = 0.0228). In addition, NF-kappaB activation was positively correlated with pAkt (P = 0.047), p16 (P = 0.004), adenomatous polyposis coli (P < 0.001), Smad4 (P = 0.002), and kangai 1 (P < 0.001) expression. An in vitro study showed that NF-kappaB activity in gastric cancer cells is controlled by and controls Akt.

CONCLUSIONS

NF-kappaB activation was frequently observed in early-stage gastric carcinoma and was significantly correlated with better prognosis and Akt activation. These findings suggest that NF-kappaB activation is a valuable prognostic variable in gastric carcinoma.