Development Of Gastric Tumors Research Articles

56 Zinc Finger Protein 545 is a Functional Tumor Suppressor Through Inhibiting Ribosomal RNA Transcription in Gastric Cancer

Background: Trefoil factor 1 protein (TFF1) is a small secreted protein. It is constitutively and strongly expressed in the stomach, where it has a key role in maintaining mucosal integrity. Our previous studies using TFF1-knockout mice indicated a mucosal pro-inflammatory phenotype with a sequence of morphological and signaling changes leading to the development of gastric cancer. Methods and Results: In the current study, we hypothesized that the tumorigenic phenotype obtained in the TFF1-deficient gastric tissues is induced through regulation of b-catenin/TCF pathway. Using immunohistochemistry for b-catenin expression in the pyloric antrum region of the stomach in TFF1 wild type and TFF1 knockout mice, our results showed strong nuclear accumulation of b-catenin in the epithelial cells of TFF1 knockout mice; this accumulation was absent in TFF1 wild type. Using In Vitro cell models, we investigated the transcriptional regulation of b-catenin/TCF activity by TFF1 using the pTOP flash and its mutant pFOP flash luciferase reporter assays. MKN28 and SNU1 TFF1 stable cell lines showed 80% and 50% decrease in b-catenin activity, respectively, as compared to their corresponding pcDNA control cells (P<0.001). These results were confirmed using TFF1 adenovirus system inMKN28 cell line where transient TFF1 expression decreased b-catenin/TCF luciferase activity by 60% relative to control (P<0.01). Using quantitative real time PCR, we found that stable TFF1 expression led to a significant downregulation of b-catenin/TCF target genes, c-Myc and Cyclin D1 in MKN28 and SNU1 cell lines, as compared to their pcDNA control cells (P<.01). The immunofluorescence assay data indicated that reconstitution of TFF1 expression in MKN28 cell line by TFF1 adenovirus (5MOI) abrogated translocation of b-catenin to the nucleus and induced strong staining in the cell membrane as compared to the control cells where the b-catenin showed a strong staining in the nucleus. Conclusion: Our data suggest that b-catenin activation could play a role in the development of gastric neoplasms in TFF1 knockout mice. In addition, our In Vitro and In Vivo studies unveil a novel mechanism by which TFF1 regulates b-catenin/TCF activity, thereby implicating its tumor suppressor function in gastric cancer. Ongoing studies using In Vivo, ex-vivo and In Vitromodels are underway to dissect the regulatory mechanisms that mediate TFF1 suppression of b-catenin/TCF.

Genetic instability and CpG methylation in the 5'-flanking region of the PAI-1 gene in Chinese patients with gastric cancer

We explored a possible correlation of genetic instability and CpG methylation in the 5'-flanking region of the PAI-1 gene with clinicopathologic features of gastric cancer in Chinese patients and looked for molecular markers for diagnosing gastric tumor development. Microsatellite instability and loss of heterozygosity of the PAI-1 gene locus D7S515, D7S471 and pai-1 in 50 specimens of gastric cancer and relevant pericancerous tissues were detected by PCR-single strand conformation polymorphism (PCR-SSCP) with sliver staining. Methylation-specific PCR was used to detect CpG methylation in the 5'-flanking region of the PAI-1 gene. Microsatellite instability was significantly more common in the negative than in the positive serosa infiltration group of gastric cancer (42.86 vs 2.33%). The frequency of microsatellite instability was significantly lower in the cases with lymph node metastasis than in those without metastasis (18.18 vs 2.56%); however, it was significantly higher in the low differentiation group than that in the middle or high differentiation groups (21.05 vs 0.00%). CpG methylation in the 5'-flanking region of the PAI-1 gene did not differ significantly. Microsatellite instability and loss of heterozygosity of the PAI-1 gene apparently regulates the development of gastric cancer through different pathways. Microsatellite instability could be used as a molecular marker for the development of gastric cancer. CpG methylation in the 5'-flanking region of the PAI-1 gene appears not to be involved in the development of gastric cancer.

Stomach – Genetic and epigenetic alterations of preneoplastic and neoplastic lesions

Gastric cancer is one of the most common neoplasias in the world and remains an important cause of cancer-related mortality. Vast resources have been invested in the study of the molecular events driving the development and progression of gastric tumors. Gastric cancer is known to result from an interaction between host and environmental factors. The present review will discuss the most how genetic and epigenetic changes contribute to gastric carcinogenesis and their potential for developing novel diagnostic and therapeutic tools.

TFF1 Modulates NfκB Signaling and the Development of Gastric Neoplasms

TFF1 Modulates NfκB Signaling and the Development of Gastric Neoplasms

Abstract 1970: SOCS-1,-3 gene delivery in gastric cancer cells induces a potent anti-proliferative effect via the suppression of JAK/STAT and P38 MAPK signaling pathways

Abstract BACKGROUND:Enhanced activation of inflammatory cytokines signaling transductions have been suggested as a driving force in the development of gastric tumors. The suppressor of cytokine signaling (SOCS) family proteins are important negative regulator of proinflammatory cytokine signals and have been reported to be frequently silenced by DNA methylation of CpG islands in gastric cancer (GC). The aim of this in vitro assessment was to evaluate the role of SOCS-1 and SOCS-3 in the proliferation of GC cell through regulating cytokine signaling pathways. MATERIAL AND METHODS:Six GC cell lines (NUGC3, AGS, MKN45, NUGC4, MKN7, and MKN74) were used in this study. Methylation status of SOCS-1/-3 was assessed by methylation specific PCR. The concentrations of IL-6 in the cell culture supernatant was measured by ELISA. Adenovirus vectors encoding either SOCS-1 or SOCS-3 were constructed for gene delivery to GC cells. The status of activated kinases and downstream proteins were determined by Western blot analysis. Anti-proliferative effects in GC cells were assessed by WST-8 assay. RESULTS: In six GC cell lines used in our study, SOCS-1 and SOCS-3 genes were methylated except one cell line, and two cell lines (NUGC3, AGS) showed elevated endogenous IL-6 production with constitutively phosphorylated STAT3. Unexpectedly, anti-IL-6R antibody did not affect both of the cell proliferation and the status of phosphorylated STAT3 in these two cell lines. In contrast, adenovirus-mediated SOCS-1 /-3 gene delivery markedly reduced cell proliferation of these cells. The anti-proliferative effect of SOCS-1/-3 correlated with decreased levels of the activation of STAT3 and p38 MAPK. Cell proliferation assay confirmed that the blockade of JAK/STAT and p38 MAPK signaling pathways also reduced cell proliferation of these cell lines. CONCLUSIONS: Our results indicated that the DNA methylation of SOCS-1/-3 may be associated with GC proliferation, and highlighted an anti-proliferative potential of SOCS-1/-3 through the inhibition of JAK/STAT and p38 MAPK signaling pathways independently IL-6 signaling. Thus, DNA methylation of SOCS-1/-3 can be a molecular marker of GC progression, and their forced expression may represent a novel therapeutic application as a multi-growth signal inhibitor for GC treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1970. doi:10.1158/1538-7445.AM2011-1970

Abstract 2796: Suppressive effect of DNA hypomethylation on gastric carcinogenesis

Abstract Global DNA hypomethylation and concomitant site-specific gene hypermethylation are among the most common molecular alterations in human neoplasia. Although site-specific DNA hypermethylation has been shown to be associated with the development of various tumors accompanied by transcriptional silencing of target genes, the functional significance of global DNA hypomethylation in tumorigenesis remains unclear. Previous studies have revealed that a genetic reduction of the DNA methylation levels leads to opposing effects on tumor development, depending on the tumor cell type and the stage of tumorigenesis. In the present study, we investigated the effect of DNA hypomethylation on gastric carcinogenesis in mice. DNA methyltransferase 1 (Dnmt1) hypomorphic mice, which showed that Dnmt1 hypomorphic alleles induced global DNA hypomethylation in the gastric mucosa, were used in this study. The genetic reduction of DNA methylation levels suppressed the incidence, number and size of gastric tumors in two different mouse models for gastric tumorigenesis: the N-methyl-N-nitrosourea (MNU)-induced model and the Apc (Min/+) mouse model that spontaneously develops gastric tumors with aging. Histological analyses revealed DNA hypomethylation to completely inhibit the development of invasive gastric tumors. In the MNU model, DNA hypomethylation reduced the persistent increase in the cell proliferative activity in the non-cancerous gastric mucosa exposed to MNU. However, the aberrant site-specific methylations were not found in MNU-induced mouse gastric tumors unlike in the case of human gastric tumors, thus indicating that the pattern of the site-specific aberrant methylations in mouse gastric tumors is distinctly different from that in human gastric cancers. Taken together, these findings indicate that the reduction of DNA methylation levels suppresses gastric carcinogenesis and suggest that DNA methylation is closely associated with gastric tumorigenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2796. doi:10.1158/1538-7445.AM2011-2796

Prostaglandin E 2 2 Signaling and Bacterial Infection Recruit Tumor-Promoting Macrophages to Mouse Gastric Tumors

Helicobacter pylori infection induces an inflammatory response, which can contribute to gastric tumorigenesis. Induction of cyclooxygenase-2 (COX-2) results in production of prostaglandin E(2) (PGE(2)), which mediates inflammation. We investigated the roles of bacterial infection and PGE(2) signaling in gastric tumorigenesis in mice. We generated a germfree (GF) colony of K19-Wnt1/C2mE mice (Gan mice); these mice develop gastric cancer. We examined tumor phenotypes, expression of cytokines and chemokines, and recruitment of macrophages. We also investigated PGE(2) signaling through the PGE(2) receptor subtype 4 (EP4) in Gan mice given specific inhibitors. Gan mice raised in a specific pathogen-free facility developed large gastric tumors, whereas gastric tumorigenesis was significantly suppressed in GF-Gan mice; reconstitution of commensal flora or infection with Helicobacter felis induced gastric tumor development in these mice. Macrophage infiltration was significantly suppressed in the stomachs of GF-Gan mice. Gan mice given an EP4 inhibitor had decreased expression of cytokines and chemokines. PGE(2) signaling and bacterial infection or stimulation with lipopolysaccharide induced expression of the chemokine C-C motif ligand 2 (CCL2) (which attracts macrophage) in tumor stromal cells or cultured macrophages, respectively. CCL2 inhibition suppressed macrophage infiltration in tumors, and depletion of macrophages from the tumors of Gan mice led to signs of tumor regression. Wnt signaling was suppressed in the tumors of GF-Gan and Gan mice given injections of tumor necrosis factor-α neutralizing antibody. Bacterial infection and PGE(2) signaling are required for gastric tumorigenesis in mice; they cooperate to up-regulate CCL2, which recruits macrophage to gastric tumors. Macrophage-derived tumor necrosis factor-α promotes Wnt signaling in epithelial cells, which contributes to gastric tumorigenesis.

Helicobacter pylori Infection Promotes Methylation and Silencing of Trefoil Factor 2, Leading to Gastric Tumor Development in Mice and Humans

Trefoil factors (TFFs) regulate mucosal repair and suppress tumor formation in the stomach. Tff1 deficiency results in gastric cancer, whereas Tff2 deficiency increases gastric inflammation. TFF2 expression is frequently lost in gastric neoplasms, but the nature of the silencing mechanism and associated impact on tumorigenesis have not been determined. We investigated the epigenetic silencing of TFF2 in gastric biopsy specimens from individuals with Helicobacter pylori-positive gastritis, intestinal metaplasia, gastric cancer, and disease-free controls. TFF2 function and methylation were manipulated in gastric cancer cell lines. The effects of Tff2 deficiency on tumor growth were investigated in the gp130(F/F) mouse model of gastric cancer. In human tissue samples, DNA methylation at the TFF2 promoter began at the time of H pylori infection and increased throughout gastric tumor progression. TFF2 methylation levels were inversely correlated with TFF2 messenger RNA levels and could be used to discriminate between disease-free controls, H pylori-infected, and tumor tissues. Genome demethylation restored TFF2 expression in gastric cancer cell lines, so TFF2 silencing requires methylation. In Tff2-deficient gp130(F/F)/Tff2(-/-) mice, proliferation of mucosal cells and release of T helper cell type-1 (Th-1) 1 cytokines increased, whereas expression of gastric tumor suppressor genes and Th-2 cytokines were reduced, compared with gp130(F/F)controls. The fundus of gp130(F/F)/Tff2(-/-) mice displayed glandular atrophy and metaplasia, indicating accelerated preneoplasia. Experimental H pylori infection in wild-type mice reduced antral expression of Tff2 by increased promoter methylation. TFF2 negatively regulates preneoplastic progression and subsequent tumor development in the stomach, a role that is subverted by promoter methylation during H pylori infection.

Mouse models of gastric tumors: Wnt activation and PGE2 induction

Accumulating evidence has suggested that cooperation of oncogenic activation and the host responses is important for cancer development. In gastric cancer, activation of Wnt signaling appears to be a major oncogenic pathway that causes tumorigenesis. In the chronic gastritis caused by Helicobacter pylori infection, cyclooxigenase-2 induces prostaglandin E(2) (PGE(2)) biosythesis, which plays an important role in tumorigenesis. We constructed a series of mouse models and investigated the role of each pathway in the gastric tumorigenesis. Wnt activation in gastric epithelial cells suppresses differentiation, and induces development of preneoplastic lesions. On the other hand, induction of the PGE(2) pathway in gastric mucosa induces development of spasmolytic polypeptide-expressing metaplasia (SPEM), which is a possible preneoplastic metaplasia. Importantly, simultaneous activation of Wnt and PGE(2) pathways leads to dysplastic gastric tumor development. Moreover, induction of the PGE(2) pathway also promotes gastric hamartoma development when bone morphogenetic protein (BMP) signaling is suppressed. These results indicate that alteration in the Wnt or BMP signaling impairs epithelial differentiation, and the PGE(2) pathway accelerates tumor formation regardless of the types of oncogenic pathways. We review the phenotypes and gene expression profiles of the respective models, and discuss the cooperation of oncogenic pathways and host responses in gastric tumorigenesis.

Suppressive effect of global DNA hypomethylation on gastric carcinogenesis

Global DNA hypomethylation and concomitant site-specific gene hypermethylation are among the most common molecular alterations in human neoplasia. Although site-specific DNA hypermethylation has been shown to be associated with the development of various tumors accompanied by transcriptional silencing of target genes, the functional significance of global DNA hypomethylation in tumorigenesis remains unclear. Previous studies have revealed that a genetic reduction of the DNA methylation levels leads to opposing effects on tumor development, depending on the tumor cell type and the stage of tumorigenesis. In the present study, we investigated the effect of DNA hypomethylation on gastric carcinogenesis in mice. The genetic reduction of DNA methylation levels suppressed the incidence, number and size of gastric tumors in two different mouse models for gastric tumorigenesis: the N-methyl-N-nitrosourea-induced model and the Apc(Min/+) mouse model that spontaneously develops gastric tumors with aging. Histological analyses revealed DNA hypomethylation to completely inhibit the development of invasive gastric tumors. These findings indicate that the reduction of DNA methylation levels suppresses gastric carcinogenesis and suggest that DNA methylation is closely associated with gastric tumorigenesis.

Abstract 958: Recruitment of tumor-associated macrophages by cooperation of PGE2 pathway and infectious stimulation

Abstract Gastric cancer development is tightly associated with Helicobacter infection, which induces expression of COX-2 and mPGES-1 resulting in activation of PGE2 pathway in gastric mucosa. It has been established that PGE2 pathway plays a key role in chronic inflammation and tumorigenesis in the stomach. However, mechanisms of PGE2 or PGE2-induced inflammation underlying tumorigenesis have not been fully understood yet. On the other hand, tumor associated macrophages play an important role in tumorigenesis through expression of growth factors, induction of angiogenesis, remodeling and suppression of acquired immunity. We previously showed that macrophage infiltration was enhanced in K19-C2mE transgenic mouse stomach, in which PGE2 pathway is induced by expression of COX-2 and mPGES-1. Moreover, accumulated macrophages in gastric mucosa were activated, which was suppressed by treatment of the mice with antibiotics. These results suggested that both PGE2 pathway and infectious stimulation are important for macrophage infiltration and activation during tumorigenesis. To investigate the effect of PGE2 and infectious stimuli in gastric tumorigenesis, we generated germfree colony of K19-Wnt1/C2mE transgenic mice and examined gastric phenotypes. K19-Wnt1/C2mE mice develop dysplastic gastric tumors caused by simultaneous activation of Wnt signaling and PGE2 pathway. Importantly, germfree K19-Wnt1/C2mE mice showed significant suppression of gastric tumor development with decreased macrophage infiltration. Moreover, Helicobacter infection to germfree K19-Wnt1/C2mE mice induced gastric tumor development. These results indicate that infectious stimuli to gastric mucosa are required for tumor formation. We also found that PGE2 pathway together with bacterial infection induced expression of monocyte-attractant chemokine CCL2 in the gastric mucosa and macrophage cell line. Notably, infiltrated macrophages showed “alternatively” activated M2 properties, which are characteristics of tumor-associated macrophages. Finally, inhibition of COX-2/PGE2 pathway in K19-Wnt1/C2mE mice caused significant suppression of macrophage infiltration and gastric tumorigenesis. These results suggest that PGE2 signaling and bacterial infectious stimulation cooperatively recruit protumorigenic macrophages through induction of chemokines, and that recruitment of tumor-associated macrophages is one of the important mechanisms of PGE2 signaling in tumorigenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 958.

CD44+ slow‐cycling tumor cell expansion is triggered by cooperative actions of Wnt and prostaglandin E2 in gastric tumorigenesis

Similar to normal tissue stem cells, cancer stem cells (CSCs) are thought to be quiescent or slow-cycling and, thereby, insensitive to chemo- and radiotherapies. CD44, a cell surface component that interacts with the extracellular matrix, has been found to be highly expressed in CSCs of several solid tumors. However, the relevancy between CD44(+) cells and slow-cycling cells and the underlying mechanisms for the emergence of CD44(+) CSCs during tumorigenesis have not been elucidated. Here we show that a gastric gland residing at the squamo-columnar junction (SCJ) in normal mouse stomach contains CD44(+) stem cell-like slow-cycling cells and that this characteristic CD44(+) gland was expanded by prostaglandin E2 (PGE(2)) and Wnt signaling in K19-Wnt1/C2mE mouse, a genetic mouse model for gastric tumorigenesis. The analysis of three transgenic mouse lines, K19-Wnt1, K19-C2mE and K19-Wnt1/C2mE, revealed that the expansion of CD44(+) SCJ cells is triggered by PGE(2)-mediated signaling and is prominently enhanced by the addition of Wnt activation. Furthermore, each expanded CD44(+) gland in gastric tumor of K19-Wnt1/C2mE mouse contains a few BrdU label-retaining quiescent or slow-cycling cells, suggesting that the CD44(+) SCJ cells in normal mouse are candidates for the cell-of-origin of gastric CSCs. These observations suggest that PGE(2)-mediated inflammatory signaling and Wnt signaling cooperatively trigger the expansion of CD44(+) slow-cycling stem-like cells in SCJ, leading to development of lethal gastric tumors in mice.

The CCK 2 receptor antagonist, YF476, inhibits Mastomys ECL cell hyperplasia and gastric carcinoid tumor development

YF476 is a potent and highly selective cholecystokin 2 (CCK 2) receptor antagonist of the benzodiazepine class. It inhibits gastric neuroendocrine enterochromaffin-like (ECL) cell secretion, proliferation and spontaneous formation of gastric neuroendocrine tumors (carcinoids) in cotton rats. The Mastomys rodent species exhibits a genetic predisposition to gastric ECL neuroendocrine tumor formation which can be accelerated by acid suppression and induction of hypergastrinemia. In this respect, it mimics the human condition of atrophic gastritis, hypergastrinemia and gastric carcinoid development. We investigated whether YF476 could inhibit acid suppression-induced ECL cell hyperplasia and neoplasia in this model. In addition, we examined whether YF476 could reverse established ECL cell hyperplasia and neoplasia. Targeting the CCK 2 receptor during Loxtidine-induced hypergastrinemia resulted in a reduction in ECL cell secretion (plasma and mucosal histamine, and histidine decarboxylase ( HDC) transcripts, p < 0.05) and proliferation (numbers of HDC-positive cells, connective tissue growth factor ( CTGF) and cyclin D1 transcription). This was associated with a decrease in ECL cell hyperplasia and a 60% reduction in gastric ECL cell microcarcinoid (tumors < 0.3 mm in size) formation. YF476 inhibited ECL cell neoplasia (gastric carcinoid) in animals with hyperplasia, inhibited the formation of ECL cell tumors when co-administered with Loxtidine and reversed the growth and developement of gastric ECL cell carcinoids in long-term acid suppressed Mastomys. Variable importance analysis using a logistic multinomial regression model indicated the effects of YF476 were specific to the ECL cell and alterations in ECL cell function reflected inhibition of transcripts for HDC, Chromogranin A ( CgA), CCK 2 and the autocrine growth factor, CTGF. We conclude that specifically targeting the CCK 2 receptor inhibits gastrin-mediated ECL cell secretion and ECL cell proliferation and tumor development in vivo.

Induction of metastatic gastric cancer by peroxisome proliferator-activated receptorδ activation.

Peroxisome proliferator-activated receptorδ (PPARδ) regulates a multiplicity of physiological processes associated with glucose and lipid metabolism, inflammation, and proliferation. One or more of these processes likely create risk factors associated with the ability of PPARδ agonists to promote tumorigenesis in some organs. In the present study, we describe a new gastric tumor mouse model that is dependent on the potent and highly selective PPARδ agonist GW501516 following carcinogen administration. The progression of gastric tumorigenesis was rapid as determined by magnetic resonance imaging and resulted in highly metastatic squamous cell carcinomas of the forestomach within two months. Tumorigenesis was associated with gene expression signatures indicative of cell adhesion, invasion, inflammation, and metabolism. Increased PPARδ expression in tumors correlated with increased PDK1, Akt, β-catenin, and S100A9 expression. The rapid development of metastatic gastric tumors in this model will be useful for evaluating preventive and therapeutic interventions in this disease.

1089 Promoter Hypermethylation Mediates Downregulation of Thiamin Receptor SLC19A3 But Not SLC19A2 in Gastric Cancer

G A A b st ra ct s cells. By transfection with miR-29c or after treatment with celecoxib, expression of Mcl-1, which is recently reported as one of the targets of miR-29 family (Oncogene 26: 6133, 2007), is suppressed and apoptosis is induced in gastric cancer cells. Conclusions. Since miR-29c suppresses Mcl-1 oncogene and is downregulated in early gastric cancers and gastric adenomas, miR-29c may play critical roles in the development of gastric tumors. These findings suggest that COX-2 inhibition is effective in the chemoprevention of gastric cancer via the activation of miR-29c.

Endocrine dysfunction in p27Kip1 deficient mice and susceptibility to Wnt-1 driven breast cancer

The cyclin-dependent kinase (Cdk) inhibitor p27(Kip1) (p27) is a marker of prognosis in many cancers, including breast cancer. Low p27 expression correlates with poor prognosis, especially in hormone receptor positive breast tumors. This association suggests a role for p27 in hormone-dependent cancer. We used the Wnt-1 transgenic mouse model to further explore the role of p27 in hormone-driven breast cancer. We found that p27 deficiency did not alter breast cancer rate in either male or female Wnt-1 mice. However, we did find p27-/- females had reduced levels of serum progesterone (P) and increased variability in estradiol (E), which could have affected their cancer susceptibility. To equalize hormone levels, an additional cohort of Wnt-1 female mice was ovariectomized and implanted with slow release pellets of E and P. Although this treatment did not alter the breast cancer rate, it did accelerate the development of pituitary and gastric tumors in p27-/- mice. This study shows that while not a significant inhibitor of Wnt-1-driven breast cancer, p27 inhibits gastric tumors, whose latency is modulated by sex steroids.

The Interleukin-6 Family Cytokine Interleukin-11 Regulates Homeostatic Epithelial Cell Turnover and Promotes Gastric Tumor Development

Gastric cancer is the second most common cause of cancer-related mortality worldwide, mainly as a result of late-stage detection. Interleukin (IL)-11 is a multifunctional cytokine reported to be up-regulated in human gastric cancer. We investigated the importance of IL-11 in gastric cancer progression by examining its role in a variety of mouse gastric tumor models, as well as in nonneoplastic and tumor tissues taken from gastric cancer patients. We then determined the transcriptional and translational outcomes of IL-11 overexpression in normal gastric mucosa and identified a novel gene signature important early in the progression toward gastric tumorigenesis. IL-11 was up-regulated significantly in 4 diverse mouse models of gastric pathology as well as in human biopsy specimens adjacent to and within gastric cancer. Removal of IL-11 co-receptor alpha significantly reduced HKbeta-/- mouse fundic hyperplasia and ablated gp130(757F/F) mouse tumorigenesis. Exogenous IL-11 but not IL-6 activated oncogenic signal transducer and activator of transcription-3, and altered expression of novel proliferative and cytoprotective genes RegIII-beta, RegIII-gamma, gremlin-1, clusterin, and growth arrest specific-1 in wild-type gastric mucosa, a gene signature common in gp130(757F/F) and HKbeta-/- tumors as well as nonneoplastic mucosa of gastric cancer patients. One week of chronic IL-11 administration in wild-type mice sustained the gene signature, causing pretumorigenic changes in both antrum and fundus. Increased gastric IL-11 alters expression of proliferative and cytoprotective genes and promotes pretumorigenic cellular changes.

Induction of follistatin precedes gastric transformation in gastrin deficient mice

We previously showed that antral gastric tumors develop in gastrin-deficient (Gas−/−) mice. Therefore Gas−/−mice were studied sequentially over 12 months to identify molecular mechanisms underlying gastric transformation. Fundic atrophy developed by 9 months in Gas−/− mice. Antral mucosal hyperplasia developed coincident with the focal loss of TFF1 and Muc5AC. Microarray analysis of 12 month Gas−/− tumors revealed an increase in follistatin, an activin/BMP antagonist. We found that elevated follistatin expression occurred in the proliferative neck zone of hyperplastic antrums, in antral tumors of Gas−/− mice, and also in human gastric cancers. Follistatin induced cyclin D1 and the trefoil factors TFF1 and TFF2 in a gastric cancer cell line. We concluded that antral hyperplasia in Gas−/− mice involves amplification of mucous cell lineages due to follistatin, suggesting its role in the development of antral gastric tumors.

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-GR 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-GR 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-GR 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.

Gastric Epithelial Cell Modality and Proton Pump Inhibitor

Proton pump inhibitors (PPIs) are now commonly used for the treatment of acid related diseases such as peptic ulcer and reflux esophagitis. Because of their ability to produce direct inhibition of the proton pump, PPIs provide more sustained increase of the gastric pH than H2-receptor (H2R) antagonists. Diverse reports have been published on gastric epithelial cell modality associated with PPI treatment both in animal models and clinical settings. The present review summarizes the recent accumulated evidence on gastric epithelial cell modality associated with PPI treatment, including the formation of gastric carcinoid tumors and fundic gland polyps, and the development of gastric mucosal atrophy. Long-term PPI treatment has been reported to cause enlargement of the parietal cells and enterochromaffin-like cells, and to decrease the number of chief cells without affecting A-like cell. Although the development of gastric carcinoid tumors after chronic PPI treatment has been reported in animal studies, no such occurrences have been demonstrated in humans. The effect of PPIs on the formation of fundic gland polyps and the development of atrophic gastritis should be investigated in future studies.