Overexpression of interleukin-1beta induces gastric inflammation and cancer and mobilizes myeloid-derived suppressor cells in mice

Histamine deficiency promotes inflammation-associated carcinogenesis through reduced myeloid maturation and accumulation of CD11b+Ly6G+ immature myeloid cells

Histidine decarboxylase (HDC), the unique enzyme responsible for histamine generation, is highly expressed in myeloid cells but its function is poorly understood. Here, we show that Hdc knockout mice exhibit a markedly increased rate of colon and skin carcinogenesis. Using Hdc-EGFP BAC transgenic mice, we demonstrate that Hdc is expressed primarily in CD11b⁺Ly6G⁺ immature myeloid cells (IMCs) that are recruited early on in chemical carcinogenesis. Transplant of Hdc-deficient bone marrow to wildtype recipients results in increased CD11b⁺Ly6G⁺ cell mobilization and reproduces the cancer susceptibility phenotype. In addition, IMCs from Hdc knockout mice promote the growth of cancer xenografts and colon cancer cells downregulate Hdc expression through promoter hypermethylation and inhibits myeloid cell maturation. Exogenous histamine induces the differentiation of IMCs and suppresses their ability to support the growth of xenografts. These data indicate key roles for Hdc and histamine in myeloid cell differentiation, and CD11b⁺Ly6G⁺ IMCs in early cancer development.

The inflammasome component NLRP3 impairs antitumor vaccine by enhancing the accumulation of tumor-associated myeloid-derived suppressor cells

The inflammasome is a proteolysis complex that generates the active forms of the proinflammatory cytokines interleukin (IL)-1β and IL-18. Inflammasome activation is mediated by NLR proteins that respond to microbial and nonmicrobial stimuli. Among NLRs, NLRP3 senses the widest array of stimuli and enhances adaptive immunity. However, its role in antitumor immunity is unknown. Therefore, we evaluated the function of the NLRP3 inflammasome in the immune response using dendritic cell vaccination against the poorly immunogenic melanoma cell line B16-F10. Vaccination of Nlrp3(-/-) mice led to a relative 4-fold improvement in survival relative to control animals. Immunity depended on CD8(+) T cells and exhibited immune specificity and memory. Increased vaccine efficacy in Nlrp3(-/-) hosts did not reflect differences in dendritic cells but rather differences in myeloid-derived suppressor cells (MDSC). Although Nlrp3 was expressed in MDSCs, the absence of Nlrp3 did not alter either their functional capacity to inhibit T cells or their presence in peripheral lymphoid tissues. Instead, the absence of Nlrp3 caused a 5-fold reduction in the number of tumor-associated MDSCs found in host mice. Adoptive transfer experiments also showed that Nlrp3(-/-) MDSCs were less efficient in reaching the tumor site. Depleting MDSCs with an anti-Gr-1 antibody increased the survival of tumor-bearing wild-type mice but not Nlrp3(-/-) mice. We concluded that Nlrp3 was critical for accumulation of MDSCs in tumors and for inhibition of antitumor T-cell immunity after dendritic cell vaccination. Our findings establish an unexpected role for Nlrp3 in impeding antitumor immune responses, suggesting novel approaches to improve the response to antitumor vaccines by limiting Nlrp3 signaling.

Helicobacter pylori infection promotes methylation and silencing of trefoil factor 2, leading to gastric tumor development in mice and humans

BACKGROUND & AIMS

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

TFF2 negatively regulates preneoplastic progression and subsequent tumor development in the stomach, a role that is subverted by promoter methylation during H pylori infection.

Role of virulence factors and host cell signaling in the recognition of Helicobacter pylori and the generation of immune responses

Helicobacter pylori colonizes a large proportion of the world's population, with infection invariably leading to chronic, lifelong gastritis. While the infection often persists undiagnosed and without causing severe pathology, there are a number of host, bacterial and environmental factors that can influence whether infection provokes a mild inflammatory response or results in significant morbidity. Intriguingly, the most virulent H. pylori strains appear to deliberately induce the epithelial signaling cascades responsible for activating the innate immune system. While the reason for this remains unclear, the resulting adaptive immune responses are largely ineffective in clearing the bacterium once infection has become established and, as a result, inflammation likely causes more damage to the host itself.

Molecular mechanisms regulating myeloid-derived suppressor cell differentiation and function

Myeloid-derived suppressor cells (MDSCs) are one of the main cell populations responsible for regulating immune responses. MDSCs accumulate during tumor progression, autoimmunity, chronic infection and other pathological conditions, and can potently suppress T cell function. Recent studies have demonstrated the ability of MDSCs to modulate the activity of NK and myeloid cells and have implicated MDSCs in the induction of regulatory T cells. Here, we discuss recent findings that describe the molecular mechanisms that regulate the expansion and function of MDSCs, as well as recent attempts to use MDSCs in cell therapy for different pathologic conditions.

K-ras mutation targeted to gastric tissue progenitor cells results in chronic inflammation, an altered microenvironment, and progression to intraepithelial neoplasia

Chronic infectious diseases, such as Helicobacter pylori infection, can promote cancer in a large part through induction of chronic inflammation. Oncogenic K-ras mutation in epithelial cells activates inflammatory pathways, which could compensate for a lack of infectious stimulus. Gastric histopathology and putative progenitor markers [doublecortin and calcium/calmodulin-dependent protein kinase-like 1 (Dcamkl1) and keratin 19 (K19)] in K19-K-ras-V12 (K19-kras) transgenic mice were assessed at 3, 6, 12, and 18 months of age, in comparison with Helicobacter felis-infected wild-type littermates. Inflammation was evaluated by reverse transcription-PCR of proinflammatory cytokines, and K19-kras mice were transplanted with green fluorescent protein (GFP)-labeled bone marrow. Both H. felis infection and K-ras mutation induced upregulation of proinflammatory cytokines, expansion of Dcamkl1(+) cells, and progression to oxyntic atrophy, metaplasia, hyperplasia, and high-grade dysplasia. K19-kras transgenic mice uniquely displayed mucous metaplasia as early as 3 months and progressed to high-grade dysplasia and invasive intramucosal carcinoma by 20 months. In bone marrow-transplanted K19-kras mice that progressed to dysplasia, a large proportion of stromal cells were GFP(+) and bone marrow-derived, but only rare GFP(+) epithelial cells were observed. GFP(+) bone marrow-derived cells included leukocytes and CD45(-) stromal cells that expressed vimentin or α smooth muscle actin and were often found surrounding clusters of Dcamkl1(+) cells at the base of gastric glands. In conclusion, the expression of mutant K-ras in K19(+) gastric epithelial cells can induce chronic inflammation and promote the development of dysplasia.

A molecular signature of normal breast epithelial and stromal cells from Li-Fraumeni syndrome mutation carriers

Specific changes in gene expression during cancer initiation should enable discovery of biomarkers for risk assessment, early detection and targets for chemoprevention. It has been previously demonstrated that altered mRNA and proteome signatures of morphologically normal cells bearing a single inherited "hit" in a tumor suppressor gene parallel many changes observed in the corresponding sporadic cancer. Here, we report on the global gene expression profile of morphologically normal, cultured primary breast epithelial and stromal cells from Li-Fraumeni syndrome (LFS) TP53 mutation carriers. Our analyses identified multiple changes in gene expression in both morphologically normal breast epithelial and stromal cells associated with TP53 haploinsufficiency, as well as interlocking pathways. Notably, a dysregulated p53 signaling pathway was readily detectable. Pharmacological intervention with the p53 rescue compounds CP-31398 and PRIMA-1 provided further evidence in support of the central role of p53 in affecting these changes in LFS cells and treatment for this cancer. Because loss of signaling mediated by TP53 is associated with the development and survival of many human tumors, identification of gene expression profiles in morphologically normal cells that carry "one-hit" p53 mutations may reveal novel biomarkers, enabling the discovery of potential targets for chemoprevention of sporadic tumors as well.

Type 1 T helper cells induce the accumulation of myeloid-derived suppressor cells in the inflamed Tgfb1 knockout mouse liver

Immune-mediated liver injury in hepatitis is due to activated T cells producing interferon-γ (IFN-γ). It is important to identify negative feedback immune mechanisms that can regulate T cell activity. In this study, we demonstrate that liver inflammation mediated by type 1 T helper (Th1) cells can induce the accumulation of myeloid-derived suppressor cells (MDSCs), pleiomorphic cells capable of modulating T cell-mediated immunity, that heretofore have been studied almost exclusively in the context of tumor-associated inflammation. Mice deficient in the gene encoding transforming growth factor-β1 (Tgfb1(-/-) mice) acutely develop liver necroinflammation caused by IFN-γ-producing clusters of differentiation 4-positive (CD4(+)) T cells. Liver Th1 cell accumulation was accompanied by myeloid cells expressing CD11b and Gr1, phenotypic hallmarks of MDSCs. Isolated Tgfb1(-/-) liver CD11b(+)Gr1(+) cells were functional MDSCs, readily suppressing T cell proliferation in vitro. Pharmacologic inhibitors of inducible nitric oxide (NO) synthase completely eliminated suppressor function. Suppressor function and the production of NO were dependent on cell-cell contact between MDSCs and T cells, and upon IFN-γ, and were specifically associated with the "monocytic" CD11b(+)Ly6G(-) Ly6C(hi) subset of liver Tgfb1(-/-) CD11b(+) cells. The rapid accumulation of CD11b(+)Gr1(+) cells in Tgfb1(-/-) liver was abrogated when mice were either depleted of CD4(+) T cells or rendered unable to produce IFN-γ, showing that Th1 activity induces MDSC accumulation.

CONCLUSION

Th1 liver inflammation mobilizes an MDSC response that, through the production of NO, can inhibit T cell proliferation. We propose that MDSCs serve an important negative feedback function in liver immune homeostasis, and that insufficient or inappropriate activity of this cell population may contribute to inflammatory liver pathology.

Cancer and inflammation: promise for biologic therapy

Cancers often arise as the end stage of inflammation in adults, but not in children. As such there is a complex interplay between host immune cells during neoplastic development, with both an ability to promote cancer and limit or eliminate it, most often complicit with the host. In humans, defining inflammation and the presence of inflammatory cells within or surrounding the tumor is a critical aspect of modern pathology. Groups defining staging for neoplasms are strongly encouraged to assess and incorporate measures of the presence of apoptosis, autophagy, and necrosis and also the nature and quality of the immune infiltrate. Both environmental and genetic factors enhance the risk of cigarette smoking, Helicobacter pylori, hepatitis B/C, human papilloma virus, solar irradiation, asbestos, pancreatitis, or other causes of chronic inflammation. Identifying suitable genetic polymorphisms in cytokines, cytokine receptors, and Toll-like receptors among other immune response genes is also seen as high value as genomic sequencing becomes less expensive. Animal models that incorporate and assess not only the genetic anlagen but also the inflammatory cells and the presence of microbial pathogens and damage-associated molecular pattern molecules are necessary. Identifying micro-RNAs involved in regulating the response to damage or injury are seen as highly promising. Although no therapeutic strategies to prevent or treat cancers based on insights into inflammatory pathways are currently approved for the common epithelial malignancies, there remains substantial interest in agents targeting COX2 or PPARgamma, ethyl pyruvate and steroids, and several novel agents on the horizon.

Dual roles for immunity in gastrointestinal cancers

Histopathologic examination reveals that most human tumors are associated with diverse immune cell infiltrates, but the roles of host reactions in disease pathogenesis and prognosis remain to be fully clarified. Recent investigations in genetically engineered murine tumor models have uncovered dual functions for immune responses during cancer development and progression. Alterations in tumor cell gene expression profiles and coding sequences may trigger the activation of cytotoxic lymphocytes, which act to restrain tumor growth. In contrast, persistent inflammatory reactions, which may be driven by infection, environmental toxins, or impaired immune regulation, create a microenvironment that fosters tumor cell growth, survival, invasion, and dissemination. The dynamic interplay of these competing responses appears to be a critical event in cancer pathogenesis, with tumor promotion and immune evasion proving dominant in clinically evident disease. Nonetheless, longitudinal studies of patient cohorts have demonstrated that particular histopathologic and genetic signatures of cytotoxic lymphocyte reactions provide important prognostic information. Here, we discuss the dual roles of immunity in cancer development, focusing on gastrointestinal malignancies, given the depth of recent insights into the mechanisms underlying these tumors.

TLR2-mediated expansion of MDSCs is dependent on the source of tumor exosomes

Exosomes released from tumor cells having been shown to induce interleukin-6 release from myeloid-derived suppressor cells in a Toll-like receptor 2/Stat3-dependent manner. In this study, we show that exosomes released from tumor cells re-isolated from syngeneic mice are capable of inducing interleukin-6 in a Toll-like receptor 2-independent manner, whereas the data generated from exosomes of tumor cells having undergone numerous in vitro passages induce interleukin-6 in a Toll-like receptor 2-dependent manner. This discrepancy may be due to the source of tumor cells used to generate the exosomes for this study. These results suggest that exosomes released from tumor cells that are not within a tumor microenvironment may not realistically represent the role of tumor exosomes in vivo. This is an important consideration since frequently passing tumor cells in vivo is an accepted practice for studying tumor exosome-mediated inflammatory responses.

Whole blood-derived miRNA profiles as potential new tools for ovarian cancer screening

BACKGROUND

Screening is an unsolved problem for ovarian cancer (OvCA). As late detection is equivalent to poor prognosis, we analysed whether OvCA patients show diagnostically meaningful microRNA (miRNA) patterns in blood cells.

METHODS

Blood-borne whole miRNome profiles from 24 patients with OvCA and 15 age- and sex-matched healthy controls were biostatistically evaluated.

RESULTS

Student's t-test revealed 147 significantly deregulated miRNAs before and 4 after Benjamini-Hochberg adjustment. Although these included miRNAs already linked to OvCA (e.g., miR-16, miR-155), others had never before been connected to specific diseases. A bioinformatically calculated miRNA profile allowed for discrimination between blood samples of OvCA patients and healthy controls with an accuracy of >76%. When only cancers of the serous subtype were considered and compared with an extended control group (n=39), accuracy, specificity and sensitivity all increased to >85%.

CONCLUSION

Our proof-of-principle study strengthens the hypothesis that neoplastic diseases generate characteristic miRNA fingerprints in blood cells. Still, the obtained OvCA-associated miRNA pattern is not yet sensitive and specific enough to permit the monitoring of disease progression or even preventive screening. Microarray-based miRNA profiling from peripheral blood could thus be combined with other markers to improve the notoriously difficult but important screening for OvCA.

Role of innate immunity in Helicobacter pylori-induced gastric malignancy

Helicobacter pylori colonizes the majority of persons worldwide, and the ensuing gastric inflammatory response is the strongest singular risk factor for peptic ulceration and gastric cancer. However, only a fraction of colonized individuals ever develop clinically significant outcomes. Disease risk is combinatorial and can be modified by bacterial factors, host responses, and/or specific interactions between host and microbe. Several H. pylori constituents that are required for colonization or virulence have been identified, and their ability to manipulate the host innate immune response will be the focus of this review. Identification of bacterial and host mediators that augment disease risk has profound ramifications for both biomedical researchers and clinicians as such findings will not only provide mechanistic insights into inflammatory carcinogenesis but may also serve to identify high-risk populations of H. pylori-infected individuals who can then be targeted for therapeutic intervention.

Helicobacter pylori infection, oncogenic pathways and epigenetic mechanisms in gastric carcinogenesis

Chronic colonization of the human stomach by Helicobacter pylori, a Gram-negative bacterium, is the major cause of chronic gastritis, peptic ulcers and gastric cancer. Recent progress has elucidated important bacterial and host factors that are responsible for H. pylori-induced gastric inflammation and gastric malignancy. H. pylori cytotoxin-associated antigen A is the major oncogenic factor injected into host cells from bacteria and it disrupts epithelial cell functions. Together with H. pylori cag pathogenicity island, it causes general inflammatory stress within gastric mucosa and activates multiple oncogenic pathways in epithelial cells. A growing list of these pathways includes NF-kappaB, activator protein-1, PI3K, signal transducers and activators of transcription 3, Wnt/beta-catenin and cyclooxygenase 2. H. pylori induces epigenetic alterations, such as DNA methylation and histone modification, which play critical roles in oncogenic transformation. In addition, investigations into gastric stem cell or progenitor cell biology have shed light on the mechanisms through which gastric cancer may originate. Continued investigation in these areas will yield novel insights and help to elucidate the mechanisms of bacteria-induced carcinogenesis.

Helicobacter pylori in the pathogenesis of gastric cancer and gastric lymphoma

Chronic gastric infection by the gram-negative bacterium Helicobacter pylori is strongly associated with the development of distal gastric carcinoma and gastric mucosal lymphoma in humans. Eradication of H. pylori with combination antibiotic therapy cures most cases of gastric lymphoma and slows progression to gastric adenocarcinoma. H. pylori promotes gastric neoplasia, principally via the induction of an intense gastric inflammatory response that lasts over decades. This persistent inflammatory state produces chronic oxidative stress and adaptive changes in gastric epithelial and immune cell pathobiology that in a minority of infected subjects eventually proceeds to frank neoplastic transformation.

Inhibitor of kappaB kinase beta regulates gastric carcinogenesis via interleukin-1alpha expression

BACKGROUND & AIMS

Nuclear factor-kappaB (NF-kappaB) is an important transcription factor involved in various biological processes, including carcinogenesis. However, it is unknown whether NF-kappaB activation is involved in gastric carcinogenesis.

METHODS

To explore the roles of inhibitor of kappaB kinase (IKKbeta), the key kinase for NF-kappaB activation, in gastric epithelium, we established a conditional gastric mucosal epithelium knockout mouse (Ikkbeta(DeltaST)). Gastric cancer was induced using N-methyl-N-nitrosourea (MNU). After 8 months, the number of tumors and their sizes were evaluated. Apoptosis was analyzed by terminal deoxynucleotidyl transferase-mediated deoxyuridine nick-end labeling staining, and levels of inflammatory cytokines were measured.

RESULTS

No phenotypical or histologic difference was observed between untreated Ikkbeta(DeltaST) and controls (Ikkbeta(F/F)). The number of tumors was significantly less in the MNU-treated Ikkbeta(DeltaST) group than in the Ikkbeta(F/F) group (mean +/- standard error, 2.21 +/- 0.48 vs 0.80 +/- 0.23), and the size of the tumors did not differ (2.75 +/- 0.99 vs 2.89 +/- 1.12 mm). After a single oral dose of MNU, interleukin (IL)-1alpha was up-regulated significantly in control mice compared with Ikkbeta(DeltaST) mice, whereas the levels of IL-1beta, IL-6, and tumor necrosis factor-alpha were unchanged. MNU significantly increased apoptotic cell death in Ikkbeta(DeltaST) mice compared with Ikkbeta(F/F) mice, and apoptosis was dependent on decreased IL-1alpha expression. IL-1alpha also induced the proliferation of gastric cancer cells. Fewer tumors were observed in IL-1-receptor knockout mice (Il-1r(-/-); 1.17 +/- 0.44) than in control mice (2.42 +/- 0.52).

CONCLUSIONS

IKKbeta regulates gastric carcinogenesis via IL-1alpha expression, which is associated with anti-apoptotic signaling and cell proliferation.

Tim-3/galectin-9 pathway: regulation of Th1 immunity through promotion of CD11b+Ly-6G+ myeloid cells

IFN-gamma plays a central role in antitumor immunity. T cell Ig and mucin domain (Tim-3) is expressed on IFN-gamma-producing Th1 cells; on interaction with its ligand, galectin-9, Th1 immunity is terminated. In this study, we show that transgenic overexpression of Tim-3 on T cells results in an increase in CD11b(+)Ly-6G(+) cells and inhibition of immune responses. Molecular characterization of CD11b(+)Ly-6G(+) cells reveals a phenotype consistent with granulocytic myeloid-derived suppressor cells. Accordingly, we find that modulation of the Tim-3/galectin-9 (Gal-9) pathway impacts on tumor growth. Similarly, overexpression of Tim-3 ligand, Gal-9, results in an increase in CD11b(+)Ly-6G(+) cells and inhibition of immune responses. Loss of Tim-3 restores normal levels of CD11b(+)Ly-6G(+) cells and normal immune responses in Gal-9 transgenic mice. Our data uncover a novel mechanism by which the Tim-3/Gal-9 pathway regulates immune responses and identifies this pathway as a therapeutic target in diseases where myeloid-derived suppressor cells are disadvantageous.

Development and function of myeloid-derived suppressor cells generated from mouse embryonic and hematopoietic stem cells

Emerging evidence suggests that myeloid-derived suppressor cells (MDSCs) have great potential as a novel immune intervention modality in the fields of transplantation and autoimmune diseases. Thus far, efforts to develop MDSC-based therapeutic strategies have been hampered by the lack of a reliable source of MDSCs. Here we show that functional MDSCs can be efficiently generated from mouse embryonic stem (ES) cells and bone marrow hematopoietic stem (HS) cells. In vitro-derived MDSCs encompass two homogenous subpopulations: CD115(+)Ly-6C(+) and CD115(+)Ly-6C(-) cells. The CD115(+)Ly-6C(+) subset is equivalent to the monocytic Gr-1(+)CD115(+)F4/80(+) MDSCs found in tumor-bearing mice. In contrast, the CD115(+)Ly-6C(-) cells, a previously unreported population of MDSCs, resemble the granulocyte/macrophage progenitors developmentally. In vitro, ES- and HS-MDSCs exhibit robust suppression against T-cell proliferation induced by polyclonal stimuli or alloantigens via multiple mechanisms involving nitric oxide synthase-mediated NO production and interleukin (IL)-10. Impressively, they display even stronger suppressive activity and significantly enhance ability to induce CD4(+)CD25(+)Foxp3(+) regulatory T-cell development compared with tumor-derived MDSCs. Furthermore, adoptive transfer of ES-MDSCs can effectively prevent alloreactive T-cell-mediated lethal graft-versus-host disease, leading to nearly 82% long-term survival among treated mice. The successful in vitro generation of MDSCs may represent a critical step toward potential clinical application of MDSCs.

Role of interleukin polymorphisms in gastric cancer: "Pros and cons"

Helicobacter pylori (H. pylori) infection is the leading cause of gastric cancer worldwide. Infection with this bacterium causes a chronic active immune response that persists for the life of the host. The combination of bacterial factors, environmental insults, and the host immune response drives the initiation and progression of mucosal atrophy, metaplasia, and dysplasia toward GC. Among the host factors, IL-1 gene cluster polymorphisms (IL-1B encoding IL-1β and IL-1RN encoding IL-1ra, its naturally occurring receptor antagonist) play a decisive role in modulating the risk of developing hypochlorhydria, gastric atrophy and GC in the presence of H. pylori infection. In particular, one single nucleotide polymorphism in the IL-1B promoter (IL-1B-511C⁄T), and the short allele of a 86-bp variable number of tandem repeats polymorphism in the IL-1RN second intron (IL-1RN*2) are associated with an increased risk for GC. However this hypothesis is still to be fully confirmed. This review focuses on the divergent results obtained by several epidemiological and functional in vitro and in vivo studies and show that IL-1 genotyping has still no role in the clinical management of patients with H. pylori infection.

Interleukin-1beta promotes the expression of monocyte chemoattractant protein-1 in human aorta smooth muscle cells via multiple signaling pathways

Monocyte chemoattractant protein-1 (MCP1) plays a key role in monocyte/macrophage infiltration to the sub-endothelial space of the blood vessel wall, which is a critical initial step in atherosclerosis. In this study, we examined the intracellular signaling pathway of IL-1beta-induced MCP1 expression using various chemical inhibitors. The pretreatment of a phosphatidylcholine (PC)-specific PLC (PC-PLC) inhibitor (D609), PKC inhibitors, or an NF-kapaB inhibitor completely suppressed the IL-1beta-induced MCP1 expression through blocking NF-gammaB translocation to the nucleus. Pretreatment with inhibitors of tyrosine kinase or PLD partially suppressed MCP1 expression and failed to block nuclear NF-kappaB translocation. These results suggest that IL-1beta induces MCP1 expression through activation of NF-kappaB via the PC-PLC/PKC signaling pathway.

Helicobacter pylori: gastric cancer and beyond

Helicobacter pylori is the dominant species of the human gastric microbiome, and colonization causes a persistent inflammatory response. H. pylori-induced gastritis is the strongest singular risk factor for cancers of the stomach; however, only a small proportion of infected individuals develop malignancy. Carcinogenic risk is modified by strain-specific bacterial components, host responses and/or specific host-microbe interactions. Delineation of bacterial and host mediators that augment gastric cancer risk has profound ramifications for both physicians and biomedical researchers as such findings will not only focus the prevention approaches that target H. pylori-infected human populations at increased risk for stomach cancer but will also provide mechanistic insights into inflammatory carcinomas that develop beyond the gastric niche.

Inflammation and colon cancer

The connection between inflammation and tumorigenesis is well-established and in the last decade has received a great deal of supporting evidence from genetic, pharmacological, and epidemiological data. Inflammatory bowel disease is an important risk factor for the development of colon cancer. Inflammation is also likely to be involved with other forms of sporadic as well as heritable colon cancer. The molecular mechanisms by which inflammation promotes cancer development are still being uncovered and could differ between colitis-associated and other forms of colorectal cancer. Recent work has elucidated the role of distinct immune cells, cytokines, and other immune mediators in virtually all steps of colon tumorigenesis, including initiation, promotion, progression, and metastasis. These mechanisms, as well as new approaches to prevention and therapy, are discussed in this review.

The role of sonic hedgehog reemergence during gastric cancer

Sonic Hedgehog (Shh) signaling has been extensively studied for its role in developmental biology and cancer biology. The association between Shh and cancer development in general is well established but the functional role of Shh in the development and progression of gastric cancer specifically is largely unknown. Bone marrow-derived stem cells, specifically mesenchymal stem cells (MSCs) infiltrate and engraft into the gastric mucosa in response to the chronic inflammatory environment of Helicobacter infection. In this review, MSC infiltration and changes in the cytokine and cellular profiles of later-stage chronic environments will be tied into their interactions with the Shh pathway. We will discuss how these changes shape tumorigenesis and tumor progression in the gastric mucosa. The current review focuses on the Shh signaling pathway and its role in the development of gastric cancer, specifically in response to Helicobacter pylori infection. We follow with an in-depth discussion of the regulation of the Hedgehog pathway during acute and chronic gastric inflammation with a focus on signaling within the MSC compartment.

Helicobacter pylori: gastric cancer and beyond

Helicobacter pylori is the dominant species of the human gastric microbiome, and colonization causes a persistent inflammatory response. H. pylori-induced gastritis is the strongest singular risk factor for cancers of the stomach; however, only a small proportion of infected individuals develop malignancy. Carcinogenic risk is modified by strain-specific bacterial components, host responses and/or specific host-microbe interactions. Delineation of bacterial and host mediators that augment gastric cancer risk has profound ramifications for both physicians and biomedical researchers as such findings will not only focus the prevention approaches that target H. pylori-infected human populations at increased risk for stomach cancer but will also provide mechanistic insights into inflammatory carcinomas that develop beyond the gastric niche.

Thyroid cancer and inflammation

Some cancer types are strongly associated with chronic inflammatory or infectious diseases whereas others are not, but an inflammatory component is present in most human neoplastic lesions. This review focuses on various aspects of thyroid cancer and inflammation. The incidence of thyroid cancer, in particular of well-differentiated papillary thyroid carcinomas (PTCs), is increased in autoimmune thyroid diseases such as Hashimoto's thyroiditis. Thyroid cancer often has an inflammatory cell infiltrate, which includes lymphocytes, macrophages, dendritic cells and mast cells, whose role in thyroid cancer is still not completely understood. However, most experimental evidence suggests these cells exert a protumorigenic function. Moreover, oncoproteins typically expressed in human PTCs, such as RET/PTC, RAS, and BRAF, trigger a proinflammatory programme in thyreocytes. These data suggest that inflammatory molecules are promising targets for thyroid cancer therapy.

Immunity, inflammation, and cancer

Inflammatory responses play decisive roles at different stages of tumor development, including initiation, promotion, malignant conversion, invasion, and metastasis. Inflammation also affects immune surveillance and responses to therapy. Immune cells that infiltrate tumors engage in an extensive and dynamic crosstalk with cancer cells, and some of the molecular events that mediate this dialog have been revealed. This review outlines the principal mechanisms that govern the effects of inflammation and immunity on tumor development and discusses attractive new targets for cancer therapy and prevention.

Combination of Helicobacter pylori-iceA2 and proinflammatory interleukin-1 polymorphisms is associated with the severity of histological changes in Venezuelan chronic gastritis patients

Helicobacter pylori is a major cause of chronic gastritis (CG) and a firmly established carcinogen for gastric adenocarcinoma. However, the underlying pathogenic mechanisms are not fully understood. In this work we studied the association of the allelic variation of H. pylori-iceA virulence factor and human proinflammatory interleukin (IL)-1 polymorphisms (IL-1B-31, IL-1B-511, IL-1B+3954 and IL-1RN) with histopathological changes in the gastric mucosa of patients with CG in Venezuela, a country with a high incidence of and mortality from gastric cancer. Although in this work the iceA1 allele was found more frequently (69.7%), iceA2 allele prevalence was higher in samples with atrophic gastritis (AG) and more severe grades of granulocytic (G2/G3) [P=0.02; odds ratio (OR) 3.3] and lymphocytic infiltration (L2/L3). The carriage of iceA2 strains combined with proinflammatory IL-1 polymorphisms IL-1-31C or IL-1-511T allele carrier genotypes increased even more the risk of presenting G2/G3 with ORs of 5.1 and 5.4, respectively. Moreover, the iceA2/IL-1B-511T and iceA2/IL-1B-31C/-511T/IL-1RN(*)2 bacteria/host genotype combinations showed a significant association with AG and L2/L3, respectively. Despite not being well established, the bacterial risk factor iceA2 seems an important predictor of severe histological changes in CG, separately or in combination with host genetic factors in the Venezuelan population.

Contribution of MyD88 to the tumor exosome-mediated induction of myeloid derived suppressor cells

In this study we observed that mice pretreated with tumor exosomes had a significant acceleration of tumor metastasis in the lung. Tumor metastasis correlated significantly with an increase in recruitment of more Myeloid-derived suppressor cells (MDSCs) in the lung of C57BL/6j (B6) mice pretreated with tumor exosomes. These effects were blunted when MyD88 knockout (KO) mice were pretreated with tumor exosomes. MDSCs induced by tumor exosomes and isolated from wild-type B6 mice also more potently inhibited T cell activation and induction of interleukin-6 and tumor necrosis factor-alpha than MDSCs isolated from the lung of MyD88 KO mice. In vitro, addition of tumor exosomes to bone marrow-derived CD11b(+)Gr-1(+) cells isolated from wild-type B6 mice resulted in more cytokine production, including tumor necrosis factor-alpha, interleukin-6, and the chemokine CCL2, than CD11b(+)Gr-1(+) cells isolated from MyD88 KO mice. Moreover, lower levels of CCL2 were observed in the lungs in MyD88 KO mice pretreated with tumor exosomes than that in wild-type mice. Together these data demonstrate a pivotal role for MyD88 in tumor exosome-mediated expansion of MDSCs and tumor metastasis.

Conditional deletion of IkappaB-kinase-beta accelerates helicobacter-dependent gastric apoptosis, proliferation, and preneoplasia

BACKGROUND & AIMS

The nuclear factor kappaB (NF-kappaB)/IkappaB-kinase-beta (IKKbeta) pathway has been shown to represent a key link between inflammation and cancer, inducing pro-inflammatory cytokines in myeloid cells and anti-apoptotic pathways in epithelial cells. However, the role of NF-kappaB pathway in gastric carcinogenesis and injury has not been well-defined. We derived mice with a conditional knockout of IKKbeta in gastric epithelial cells (GECs) and myeloid cells, and examined responses to ionizing radiation (IR) and Helicobacter felis infection.

METHODS

Ikkbeta(Deltastom) mice were generated by crossing Foxa3-Cre mice to Ikkbeta(F/F) mice. Cellular stress was induced with IR and H felis in Ikkbeta(Deltastom), Ikkbeta(F/F), and cis-NF-kappaB-enhanced green fluorescent protein (GFP) reporter mice. Gastric histopathology, apoptosis, proliferation, necrosis, reactive oxygen species, and expression of cytokines, chemokines, and anti-apoptotic genes were assessed. The role of myeloid IKKbeta in these models was studied by crosses with LysM-Cre mice.

RESULTS

NF-kappaB activity was upregulated in myeloid cells with acute H felis infection, but in GECs by IR or long-term H felis infection during progression to dysplasia. Deletion of IKKbeta in GECs led to increased apoptosis, reactive oxygen species, and cellular necrosis, and resulted in up-regulation of interleukin-1alpha and down-regulation of anti-apoptotic genes. Loss of IKKbeta in GECs resulted in worse inflammation and more rapid progression to gastric preneoplasia, while loss of IKKbeta in myeloid cells inhibited development of gastric atrophy.

CONCLUSIONS

The loss of IKKbeta/NF-kappaB signaling in GECs results in increased apoptosis and necrosis in response to cellular stress, and accelerated development of dysplasia by Helicobacter infection.

Interleukin-1beta promotes gastric atrophy through suppression of Sonic Hedgehog

BACKGROUND & AIMS

In both human subjects and rodent models, Helicobacter infection leads to a decrease in Shh expression in the stomach. Sonic Hedgehog (Shh) is highly expressed in the gastric corpus and its loss correlates with gastric atrophy. Therefore, we tested the hypothesis that proinflammatory cytokines induce gastric atrophy by inhibiting Shh expression.

METHODS

Shh-LacZ reporter mice were infected with Helicobacter felis for 3 and 8 weeks. Changes in Shh expression were monitored using beta-galactosidase staining and immunohistochemistry. Gastric acidity was measured after infection, and interleukin (IL)-1beta was quantified by quantitative reverse-transcription polymerase chain reaction. Mice were injected with either IL-1beta or omeprazole before measuring Shh mRNA expression and acid secretion. Organ cultures of gastric glands from wild-type or IL-1R1 null mice were treated with IL-1beta then Shh expression was measured. Primary canine parietal or mucous cells were treated with IL-1beta. Shh protein was determined by immunoblot analysis. Changes in intracellular calcium were measured by Fura-2.

RESULTS

All major cell lineages of the corpus including surface pit, mucous neck, zymogenic, and parietal cells expressed Shh. Helicobacter infection reduced gastric acidity and inhibited Shh expression in parietal cells by 3 weeks. IL-1beta produced during Helicobacter infection inhibited gastric acid, intracellular calcium, and Shh expression through the IL-1 receptor. Suppression of parietal cell Shh expression by IL-1beta and omeprazole was additive. IL-1beta did not suppress Shh expression in primary gastric mucous cells.

CONCLUSIONS

IL-1beta suppresses Shh gene expression in parietal cells by inhibiting acid secretion and subsequently the release of intracellular calcium.

Inflammation and oncogenesis: a vicious connection

Epidemiological and experimental data suggest a close connection between inflammation and tumorigenesis. Solid tumors are typically infiltrated with immune cells and inflammation impacts most, if not all, stages of tumorigenesis. Molecular and cellular pathways, which connect inflammation and cancer, have emerged as attractive targets for prevention and therapy. In this review we discuss general mechanisms and concepts of cancer promoting inflammation.

Membrane-associated Hsp72 from tumor-derived exosomes mediates STAT3-dependent immunosuppressive function of mouse and human myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) have been identified in humans and mice as a population of immature myeloid cells with the ability to suppress T cell activation. They accumulate in tumor-bearing mice and humans and have been shown to contribute to cancer development. Here, we have isolated tumor-derived exosomes (TDEs) from mouse cell lines and shown that an interaction between TDE-associated Hsp72 and MDSCs determines the suppressive activity of the MDSCs via activation of Stat3. In addition, tumor-derived soluble factors triggered MDSC expansion via activation of Erk. TDE-associated Hsp72 triggered Stat3 activation in MDSCs in a TLR2/MyD88-dependent manner through autocrine production of IL-6. Importantly, decreasing exosome production using dimethyl amiloride enhanced the in vivo antitumor efficacy of the chemotherapeutic drug cyclophosphamide in 3 different mouse tumor models. We also demonstrated that this mechanism is relevant in cancer patients, as TDEs from a human tumor cell line activated human MDSCs and triggered their suppressive function in an Hsp72/TLR2-dependent manner. Further, MDSCs from cancer patients treated with amiloride, a drug used to treat high blood pressure that also inhibits exosome formation, exhibited reduced suppressor functions. Collectively, our findings show in both mice and humans that Hsp72 expressed at the surface of TDEs restrains tumor immune surveillance by promoting MDSC suppressive functions.

Tobacco smoke promotes lung tumorigenesis by triggering IKKbeta- and JNK1-dependent inflammation

Chronic exposure to tobacco smoke, which contains over 60 tumor-initiating carcinogens, is the major risk factor for development of lung cancer, accounting for a large portion of cancer-related deaths worldwide. It is well established that tobacco smoke is a tumor initiator, but we asked whether it also acts as a tumor promoter once malignant initiation, such as caused by K-ras activation, has taken place. Here we demonstrate that repetitive exposure to tobacco smoke promotes tumor development both in carcinogen-treated mice and in transgenic mice undergoing sporadic K-ras activation in lung epithelial cells. Tumor promotion is due to induction of inflammation that results in enhanced pneumocyte proliferation and is abrogated by IKKbeta ablation in myeloid cells or inactivation of JNK1.

Mycobacterium bovis bacillus Calmette-Guérin vaccination mobilizes innate myeloid-derived suppressor cells restraining in vivo T cell priming via IL-1R-dependent nitric oxide production

Early immune response to the largely used Mycobacterium bovis bacillus Calmette-Guérin (BCG) intradermal vaccine remains ill defined. Three days after BCG inoculation into the mouse ear, in addition to neutrophils infiltrating skin, we observed CD11b(+)Ly-6C(int)Ly-6G(-) myeloid cells. Neutrophil depletion markedly enhanced their recruitment. These cells differed from inflammatory monocytes and required MyD88-dependent BCG-specific signals to invade skin, whereas neutrophil influx was MyD88 independent. Upon BCG phagocytosis, CD11b(+)Ly-6C(int)Ly-6G(-) cells produced NO, which required the IL-1 receptor. Despite NO production, they were unable to kill BCG or the nonpathogenic Mycobacterium smegmatis. However, they markedly impaired T cell priming in the draining lymph node. Their elimination by all-trans retinoid acid treatment increased the number of IFN-gamma-producing CD4 T cells. Thus, BCG vaccination recruits innate myeloid-derived suppressor cells, akin to mouse tumor-infiltrating cells. These propathogenic cells dampen the early T cell response and might facilitate BCG persistence.

A novel mechanism for inflammation-associated carcinogenesis; an important role of activation-induced cytidine deaminase (AID) in mutation induction

Inflammation is a risk for cancer development; however, its mechanism is unknown. Recent studies have revealed that activation-induced cytidine deaminase (AID), which plays essential roles in both class-switch recombination and somatic hypermutation of immunoglobulin gene in B lymphocytes, is aberrantly expressed in non-lymphoid cells not only by H.pylori and HCV infection but also by various proinflammatory cytokines, leading to the generation of gene mutations. These findings not only suggested a new mechanism of inflammation-associated carcinogenesis but has also opened up a new field of tumor biology.

Potential role of chitinase 3-like-1 in inflammation-associated carcinogenic changes of epithelial cells

The family of mammalian chitinases includes members both with and without glycohydrolase enzymatic activity against chitin, a polymer of N-acetylglucosamine. Chitin is the structural component of fungi, crustaceans, insects and parasitic nematodes, but is completely absent in mammals. Exposure to antigens containing chitin- or chitin-like structures sometimes induces strong T helper type-I responses in mammals, which may be associated with the induction of mammalian chitinases. Chitinase 3-like-1 (CHI3L1), a member of the mammalian chitinase family, is induced specifically during the course of inflammation in such disorders as inflammatory bowel disease, hepatitis and asthma. In addition, CHI3L1 is expressed and secreted by several types of solid tumors including glioblastoma, colon cancer, breast cancer and malignant melanoma. Although the exact function of CHI3L1 in inflammation and cancer is still largely unknown, CHI3L1 plays a pivotal role in exacerbating the inflammatory processes and in promoting angiogenesis and remodeling of the extracellular matrix. CHI3L1 may be highly involved in the chronic engagement of inflammation which potentiates development of epithelial tumorigenesis presumably by activating the mitogen-activated protein kinase and the protein kinase B signaling pathways. Anti-CHI3L1 antibodies or pan-chitinase inhibitors may have the potential to suppress CHI3L1-mediated chronic inflammation and the subsequent carcinogenic change in epithelial cells.

Basic aspects of gastric cancer

Gastric cancer is a worldwide health burden, which is still the second most common cause of cancer related deaths with little improvement of long-term survival during the past decades. Understanding the molecular nature of this disease and its precursor lesions has been under intense investigation and our review attempts to highlight recent progress in this field of cancer research. First, host-related genetic susceptibility is dealt with genes involved in inflammation and carcinogen metabolism. Next, role of overexpression of a proinflammatory cytokine (interleukin-1beta) and deletion of a cell-cell adhesion molecule (E-cadherin) are described in experimental mouse models of gastric carcinogenesis. Finally, the role of stem cells in gastric cancer is covered.

Macrophage-derived IL-1beta stimulates Wnt signaling and growth of colon cancer cells: a crosstalk interrupted by vitamin D3

Tumor associated macrophages mediate the link between inflammation and cancer progression. Here we showed that macrophage-derived soluble factors induce canonical Wnt signaling in colon cancer cells and promote their growth. Tumor cells induced the release of IL-1β from macrophages, which induced phosphorylation of GSK3β, stabilized β-catenin, enhanced TCF-dependent gene activation, and induced the expression of Wnt target genes in tumor cells. Neutralization experiments using anti IL-1β specific antibodies, or silencing of IL-1β in THP1 macrophages, revealed that IL-1β was required for macrophages to induce Wnt signaling and to support the growth of tumor cells. Constitutive activation of STAT1 in THP1 macrophages was essential for the induction of IL-1β and thus for the activation of β–catenin signaling in tumor cells.

Vitamin D₃, an effective chemopreventive agent, interrupted this crosstalk by blocking the constitutive activation of STAT1 and the production of IL-1β in macrophages, and therefore- in a vitamin D receptor dependent manner- inhibited the ability of macrophages to activate Wnt signaling in colon carcinoma cells. Our data therefore established that vitamin D₃ exerts its chemopreventive activity by interrupting a cross-talk between tumor epithelial cells and the tumor microenvironment.

The role of bone-marrow-derived cells in tumor growth, metastasis initiation and progression

Emerging evidence from murine models suggests that tumor-specific endocrine factors systemically stimulate the quiescent bone marrow (BM) compartment, resulting in the expansion, mobilization and recruitment of BM progenitor cells. Discrete subsets of tumor-instigated BM-derived progenitor cells support tumor progression and metastasis by regulating angiogenesis, inflammation and immune suppression. Notably, clinical studies have begun to reveal that increased BM recruitment in tumors is associated with poor prognosis. Thus, the BM-derived tumor microenvironment is an attractive therapeutic target, and drugs targeting the components of the microenvironment are currently in clinical trials. Here, we focus on recent advances and emerging concepts regarding the intriguing role of BM-derived cells in tumor growth, metastasis initiation and progression, and we discuss future directions in the context of novel diagnostic and therapeutic opportunities.

Nature meets nurture: molecular genetics of gastric cancer

The immensity of genes and molecules implicated in gastric carcinogenesis is overwhelming and the relevant importance of some of these molecules is too often unclear. This review serves to bring us up-to-date with the latest findings as well as to look at the larger picture in terms of how to tackle the problem of solving this multi-piece puzzle. In this review, the environmental nurturing of intestinal cancer is discussed, beginning with epidemiology (known causative factors for inducing molecular change), an update of H. pylori research, including the role of inflammation and stem cells in premalignant lesions. The role of E-cadherin in the nature (genotype) of diffuse gastric cancer is highlighted, and finally the ever growing discipline of SNP analysis (including IL1B) is discussed.

Nature meets nurture: molecular genetics of gastric cancer

The immensity of genes and molecules implicated in gastric carcinogenesis is overwhelming and the relevant importance of some of these molecules is too often unclear. This review serves to bring us up-to-date with the latest findings as well as to look at the larger picture in terms of how to tackle the problem of solving this multi-piece puzzle. In this review, the environmental nurturing of intestinal cancer is discussed, beginning with epidemiology (known causative factors for inducing molecular change), an update of H. pylori research, including the role of inflammation and stem cells in premalignant lesions. The role of E-cadherin in the nature (genotype) of diffuse gastric cancer is highlighted, and finally the ever growing discipline of SNP analysis (including IL1B) is discussed.

Helicobacter pylori infection, host genetics and gastric cancer

Helicobacter pylori infects half the world's population and is responsible for a considerable global health burden, including peptic ulcer disease and gastric cancer. The infection causes a chronic gastritis, the severity and distribution of which determine the clinical outcome. Bacterial, environmental and host genetic factors combine to define the degree of gastric damage. Most patients have a limited mild pan-gastritis with no significant clinical consequences. Antral-predominant gastritis is associated with high gastric acid output and an increased risk of duodenal ulcers. Corpus-predominant gastritis is associated with a reduction in gastric acid, multifocal gastric atrophy and an increased risk of gastric cancer. Host genetic factors are particularly important in defining the severity and extent of Helicobacter-induced gastritis. The most relevant and consistent genetic factors uncovered thus far are in the interleukin-1 and tumor necrosis factor-A gene clusters. These cytokines appear to play a key role in the pathophysiology of gastric cancer and their roles have been confirmed in animal models that mimic human gastric neoplasia. More genetic factors have also been uncovered and, with advancing technology, there is every prospect of defining a full genetic risk profile in the next decade. This will aid in targeting the testing and treatment of Helicobacter pylori, which offers a true opportunity to prevent and defeat this global killer.

Gastrin is an essential cofactor for helicobacter-associated gastric corpus carcinogenesis in C57BL/6 mice

We have previously described a synergistic interaction between hypergastrinemia and Helicobacter felis infection on gastric corpus carcinogenesis in FVB/N mice housed under specific-pathogen-free conditions. However, gastrin-deficient (GAS-KO) mice on a mixed C57BL/6/129Sv genetic background maintained in conventional housing were reported to develop spontaneous gastric antral tumors. Therefore, we investigated the role of gastrin in Helicobacter-associated gastric carcinogenesis in H. felis-infected mice on a uniform C57BL/6 background housed in specific-pathogen-free conditions. Hypergastrinemic transgenic (INS-GAS) mice, GAS-KO mice, and C57BL/6 wild-type mice were infected with H. felis for either 12 or 18 months. At 12 months postinfection, INS-GAS mice had mild corpus dysplasia, while B6 wild-type mice had either severe gastritis or metaplasia, and GAS-KO mice had only mild to moderate gastritis. At 18 months postinfection, both INS-GAS and B6 wild-type mice had both severe atrophic gastritis and corpus dysplasia, while GAS-KO mice had severe gastritis with mild gastric atrophy, but no corpus dysplasia. In contrast, both GAS-KO and B6 wild-type mice had mild to moderate antral dysplasia, while INS-GAS mice did not. H. felis antral colonization remained stable over time among the three groups of mice. These results point to a distinct effect of gastrin on carcinogenesis of both the gastric corpus and antrum, suggesting that gastrin is an essential cofactor for gastric corpus carcinogenesis in C57BL/6 mice.

15-hydroxyprostaglandin dehydrogenase is down-regulated in gastric cancer

PURPOSE

We have investigated the expression and regulation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in gastric cancer.

EXPERIMENTAL DESIGN

Clinical gastric adenocarcinoma samples were analyzed by immunohistochemistry and quantitative real-time PCR for protein and mRNA expression of 15-PGDH and for methylation status of 15-PGDH promoter. The effects of interleukin-1beta (IL-1beta) and epigenetic mechanisms on 15-PGDH regulation were assessed in gastric cancer cell lines.

RESULTS

In a gastric cancer cell line with a very low 15-PGDH expression (TMK-1), the 15-PGDH promoter was methylated and treatment with a demethylating agent 5-aza-2'-deoxycytidine restored 15-PGDH expression. In a cell line with a relatively high basal level of 15-PGDH (MKN-28), IL-1beta repressed expression of 15-PGDH mRNA and protein. This effect of IL-1beta was at least in part attributed to inhibition of 15-PGDH promoter activity. SiRNA-mediated knockdown of 15-PGDH resulted in strong increase of prostaglandin E(2) production in MKN-28 cells and increased cell growth of these cells by 31% in anchorage-independent conditions. In clinical gastric adenocarcinoma specimens, 15-PGDH mRNA levels were 5-fold lower in gastric cancer samples when compared with paired nonneoplastic tissues (n = 26) and 15-PGDH protein was lost in 65% of gastric adenocarcinomas (n = 210).

CONCLUSIONS

15-PGDH is down-regulated in gastric cancer, which could potentially lead to accelerated tumor progression. Importantly, our data indicate that a proinflammatory cytokine linked to gastric carcinogenesis, IL-1beta, suppresses 15-PGDH expression at least partially by inhibiting promoter activity of the 15-PGDH gene.

Modulating the expression of IFN regulatory factor 8 alters the protumorigenic behavior of CD11b+Gr-1+ myeloid cells

CD11b(+)Gr-1(+)-expressing cells, termed myeloid-derived suppressor cells, can mediate immunosuppression and tumor progression. However, the intrinsic molecular events that drive their protumorigenic behavior remain to be elucidated. Although CD11b(+)Gr-1(+) cells exist at low frequencies in normal mice, it also remains unresolved whether they are biologically distinct from those of tumor-bearing hosts. These objectives were investigated using CD11b(+)Gr-1(+) cells from both implantable (4T1) and autochthonous (mouse mammary tumor virus-polyomavirus middle T Ag (MMTV-PyMT)) mouse models of mammary carcinoma. Limited variation was observed in the expression of markers associated with immunoregulation between CD11b(+)Gr-1(+) cells of both tumor models, as well as with their respective controls (Cnt). Despite limited differences in phenotype, tumor-induced CD11b(+)Gr-1(+) cells were found to produce a more immunosuppressive cytokine profile than that observed by Cnt CD11b(+)Gr-1(+) cells. Furthermore, when admixed with tumor cells, CD11b(+)Gr-1(+) cells from tumor-bearing mice significantly enhanced neoplastic growth compared with counterpart cells from Cnt mice. However, the protumorigenic behavior of these tumor-induced CD11b(+)Gr-1(+) cells was significantly diminished when the expression of IFN regulatory factor 8, a key myeloid-associated transcription factor, was enhanced. The loss of this protumorigenic effect occurred independently of the host immune system and correlated with a CD11b(+)Gr-1(+) cytokine/chemokine production pattern that resembled cells from nontumor-bearing Cnt mice. Overall, our data indicate that 1) tumor-induced CD11b(+)Gr-1(+) cells from both cancer models were phenotypically similar, but biologically distinct from their nontumor-bearing counterparts and 2) modulation of IFN regulatory factor 8 levels in tumor-induced CD11b(+)Gr-1(+) cells can significantly abrogate their protumorigenic behavior, which may have important implications for cancer therapy.

Genetic aspects of inflammation

Chronic inflammation underlies many human diseases including cancer. The magnitude and direction of the inflammatory response is often directed by host genetic factors interacting with environmental exposures. Quite often, the environmental trigger is a microbial agent and the host's genetically determined response is crucial in setting the right tone for handling this threat. An inadequate response runs the risk of allowing the infection to become permanently established causing chronic damage, while too vigorous a response might cause collateral damage to the host's essential physiological pathways. Helicobacter pylori-induced gastric cancer is a paradigm for microbially induced and chronic inflammation-driven malignancy. In this review, we summarise current knowledge about the role of host genetic factors in the pathogenesis of this malignancy. The review illustrates the basic principles of genetic epidemiology and host-bacterial interactions and offers an example of how basic knowledge of the pathophysiology of a disease directed the search for the relevant host genetic factors. This contrasts with current approaches, driven by advanced technology, where genetic risk factors are being identified first with the hope that these will shed light on the pathogenesis of disease. Both approaches are necessary to make advances in reducing disease burden in society.

T-bet knockout prevents Helicobacter felis-induced gastric cancer

Helicobacter infection is the primary risk factor for gastric cancer, with the cytokine environment within the gastric mucosa the strongest predictor of disease risk. Elevated TNF-alpha, IL-1beta, and low IL-10 are associated with the highest risk. In this study, we used C57BL/6 mice to identify T-bet as a central regulator of the cytokine environment during Helicobacter felis infection. We infected male and female C57BL/6 and C57BL/6-T-bet knockout (KO) litter mates with H. felis and examined the bacterial colonization, immune response, and mucosal damage at varying time points. T-bet KO mice maintained infection for 15 mo at similar levels to wild-type mice. Infection and immune response did not differ between male and female mice. Despite sustained infection, T-bet KO mice respond with a blunted Th1 response associated with preservation of parietal and chief cells and protection from the development of gastric cancer. Unexpectedly, T-bet KO mice develop a gastric environment that would not be expected based on the phenotype of T-bet KO CD4 cells alone. T-bet KO mice respond to H. felis infection with a markedly blunted IL-1beta and TNF-alpha and elevated IL-10 levels. Activity of this one master regulator modulates the expression of the key gastric mucosal cytokines associated with gastric cancer and may be a target for therapy to restore immune balance clinically in patients at risk for gastric cancer.