Inflammation-associated Tumorigenesis Research Articles

The preventive role of breadfruit against inflammation‐associated epithelial carcinogenesis in mice

Artocarpus communis has been identified as a rich source of flavonoids and has been gaining attention for its potential chemopreventive abilities. In this study, methanol extracts from the fruit of A. communis (MEFA) and leaf of A. communis (MELA) were prepared, and their effects on inflammation-associated skin tumorigenesis were assessed using mouse models, including 12-O-tetradecanoylphorbol-13-acetate (TPA) induced cutaneous inflammation as well as 7,12-dimethylbenz[α]anthracene (DMBA) initiated and TPA-promoted skin tumorigenesis. According to the results, both MEFA and MELA decreased the intensity of leukocyte infiltration in mouse dorsal skin and cutaneous edema induced by TPA, which appeared to be mediated by inhibition of proinflammatory genes (inducible nitric oxide synthase, cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), IL-1β, and IL-6) and proinflammatory mediators (TNF-α, IL-1β, and Prostaglandin E2 ). In addition, topical application with MEFA or MELA effectively attenuated tumor incidence, multiplicity, volume, malignancy as well as angiogenesis of TPA-stimulated skin tumor promotion in DMBA-initiated mice. Notably, immunohistochemical stain showed that MEFA and MELA attenuated COX-2 expression of both skin and tumor tissues in different animal tests, which may be closely related to the suppression of nuclear factor kappa B/activator protein signaling networks. These findings first demonstrate that flavonoid-rich A. communis may exert potent anti-inflammatory activity through modulation of COX-2 in TPA-activated skin and tumor tissues.

Inhibitory effect of a formulated extract from multiple citrus peels on LPS-induced inflammation in RAW 246.7 macrophages

Background: Formulated Citrus Peel Extract (GL) made from the peels of six citrus fruits available in Japan, namely navel oranges, citrus hassaku, citrus limon, citrus natsudaidai, citrus miyauchi and satsuma, was initially developed as a cosmetic product to protect skin from UV irradiation. Anecdotal evidences of anti-cancer property of GL have been reported by consumers based on the cases such as topical application for melanoma, and oral ingestion for prostate, lung and liver cancers. Those anecdotal reports stimulated us to investigate anti-tumorigenesis activity of GL. In the previous study, we reported that the topical application of GL inhibited DMBA/TPA-induced skin tumor formation by decreasing inflammatory gene parameters.Objective: In this study, we mainly investigated the effect of GL on translocation of NF-kB together with production of nitric-oxide and TNF-α induced by LPS in RAW 264.7 cells.Results: This investigation showed that GL decreased the release of TNF-α and nitric oxide from macrophage RAW264.7 cells stimulated by LPS in a dose-dependent manner. In addition, GL suppressed the expression of iNOS and nuclear translocation of NF-kB in RAW264.7 cells, inhibited the degradation of IκB-α, and scavenged hydroxyl radicals (DMPO/OH adduct) in vitro.Conclusions: Our findings suggest that GL suppresses the inflammation in vitro, and exerts chemopreventive activity through the inhibition of production of TNF-α and iNOS proteins due to the inhibition of nuclear translocation of NF-kB and oxidative stress. GL appears to be a novel functional natural product capable of preventing inflammation and inflammation-associated tumorigenesis. Keywords: GL, Citrus peel extract, anti-inflammation, Nitric oxide, iNOS, NF-kB, TNF-α

Abstract 2866: Functional impairment of microRNAs induced by chronic inflammation is the cause of inflammation-associated colon tumorigenesis.

Abstract Background: A widespread downregulation of microRNAs is commonly observed in human cancers and is involved in cellular transformation and tumorigenesis. Because we previously reported that microRNA functions are inhibited under various kinds of cellular stresses including inflammatory cytokines in vitro, we hypothesized that chronic inflammation in vivo may also cause chronic functional impairment of microRNAs, which mimics a global reduction of microRNA abundance, resulting in a causal role in inflammation-associated tumorigenesis. Methods & Results: 1) To examine this hypothesis, we first confirmed the functional impairment of microRNAs under inflammatory stimuli in vitro using artificial reporter constructs. The derepression of microRNA-targeting reporter activities by inflammatory stimuli could also be observed using reporter constructs containing natural 3’UTR sequences of c-myc and Lin28B genes, which are targeted by endogenous let-7. 2) Next, we constructed reporter transgenic mice bearing CMV-promoter driven GFP construct carrying target sequences of microRNAs in its 3’UTR, and monitored the changes of microRNA functions in vivo during the course of a Dextran Sulfate Sodium (DSS) induced colitis-associated colon tumor model. The expression levels of GFP were significantly increased during colitis, suggesting that microRNA functions were impaired during the chronic inflammation in vivo. The expression levels of microRNA-target oncogenes such as c-myc and Lin28B in the colonic mucosa were indeed upregulated. 3) Lastly, to determine the consequences of the global functional impairment of microRNAs during the colitis, we examined Dicer-deficient mice, which have globally low levels of microRNA expression and may mimic the functional impairment of global microRNAs induced by chronic inflammation described above. As expected, Dicer deficient mice were more liable to have the colitis-associated tumors. This indicates that the global decrease of microRNAs leads to oncogenesis, suggesting that the functional impairment of global miRNAs during chronic inflammation can also be a cause of the inflammation-associated carcinogenesis. Conclusion: In conclusion, we propose a novel concept that the attenuation of global microRNA functions by chronic inflammation is the cause of inflammation-associated tumorigenesis. Citation Format: Takeshi Yoshikawa. Functional impairment of microRNAs induced by chronic inflammation is the cause of inflammation-associated colon tumorigenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2866. doi:10.1158/1538-7445.AM2013-2866

Topoisomerase II-Mediated DNA Cleavage and Mutagenesis Activated by Nitric Oxide Underlie the Inflammation-Associated Tumorigenesis

Both cancer-suppressing and cancer-promoting properties of reactive nitrogen and oxygen species (RNOS) have been suggested to play a role in tumor pathology, particularly those activities associated with chronic inflammation. Here, we address the impact of nitric oxide (NO) on the induction of DNA damage and genome instability with a specific focus on the involvement of topoisomerase II (TOP2). We also investigate the contribution of NO to the formation of skin melanoma in mice. Similar to the TOP2-targeting drug, etoposide (VP-16), the NO-donor, S-nitrosoglutathione (GSNO), induces skin melanomas formation in 7,12-dimethyl- benz[a]anthracene (DMBA)-initiated mice. To explore the mechanism(s) underlying this NO-induced tumorigenesis, we use a co-culture model system to demonstrate that inflamed macrophages with inducible NO synthase (iNOS) expression cause γ-H2AX activation, p53 phosphorylation, and chromosome DNA breaks in the target cells. Inhibitor experiments revealed that NO and TOP2 isozymes are responsible for the above described cellular phenotypes. Notably, NO, unlike VP-16, preferentially induces the formation of TOP2β cleavable complexes (TOP2βcc) in cells. Moreover, GSNO induced TOP2-dependent DNA sequence rearrangements and cytotoxicity. Furthermore, the incidences of GSNO- and VP-16-induced skin melanomas were also observed to be lower in the skin-specific top2β-knockout mice. Our results suggest that TOP2 isozymes contribute to NO-induced mutagenesis and subsequent cancer development during chronic inflammation. We provide the first experimental evidence for the functional role of TOP2 in NO-caused DNA damage, mutagenesis, and carcinogenesis. Notably, these studies contribute to our molecular understanding of the cancer-promoting actions of RNOS during chronic inflammation.

The role of pattern recognition receptors in intestinal inflammation.

Recognition of microorganisms by pattern-recognition receptors (PRRs) is the primary component of innate immunity that is responsible for the maintenance of host–microbial interactions in intestinal mucosa. Dysregulation in host–commensal interactions has been implicated as the central pathogenesis of inflammatory bowel disease (IBD), which predisposes to developing colorectal cancer. Recent animal studies have begun to outline some unique physiology and pathology involving each PRR signaling in the intestine. The major roles played by PRRs in the gut appear to be the regulation of the number and the composition of commensal bacteria, epithelial proliferation, and mucosal permeability in response to epithelial injury. In addition, PRR signaling in lamina propria immune cells may be involved in induction of inflammation in response to invasion of pathogens. Because some PRR-deficient mice have shown variable susceptibility to colitis, the outcome of intestinal inflammation may be modified depending on PRR signaling in epithelial cells, immune cells, and the composition of commensal flora. Through recent findings in animal models of IBD, this review will discuss how abnormal PRR signaling may contribute to the pathogenesis of inflammation and inflammation-associated tumorigenesis in the intestine.Supplementary informationThe online version of this article (doi:10.1038/mi.2013.13) contains supplementary material, which is available to authorized users.

MTORC1 inhibition restricts inflammation-associated gastrointestinal tumorigenesis in mice

Gastrointestinal cancers are frequently associated with chronic inflammation and excessive secretion of IL-6 family cytokines, which promote tumorigenesis through persistent activation of the GP130/JAK/STAT3 pathway. Although tumor progression can be prevented by genetic ablation of Stat3 in mice, this transcription factor remains a challenging therapeutic target with a paucity of clinically approved inhibitors. Here, we uncovered parallel and excessive activation of mTOR complex 1 (mTORC1) alongside STAT3 in human intestinal-type gastric cancers (IGCs). Furthermore, in a preclinical mouse model of IGC, GP130 ligand administration simultaneously activated mTORC1/S6 kinase and STAT3 signaling. We therefore investigated whether mTORC1 activation was required for inflammation-associated gastrointestinal tumorigenesis. Strikingly, the mTORC1-specific inhibitor RAD001 potently suppressed initiation and progression of both murine IGC and colitis-associated colon cancer. The therapeutic effect of RAD001 was associated with reduced tumor vascularization and cell proliferation but occurred independently of STAT3 activity. We analyzed the mechanism of GP130-mediated mTORC1 activation in cells and mice and revealed a requirement for JAK and PI3K activity but not for GP130 tyrosine phosphorylation or STAT3. Our results suggest that GP130-dependent activation of the druggable PI3K/mTORC1 pathway is required for inflammation-associated gastrointestinal tumorigenesis. These findings advocate clinical application of PI3K/mTORC1 inhibitors for the treatment of corresponding human malignancies.

Effective suppression of azoxymethane‐induced aberrant crypt foci formation in mice with citrus peel flavonoids

Citrus peel or its extract has been reported to exhibit a broad spectrum of biological activity. Herein, we report the first investigation of inhibitory effects of a formulated product from citrus peel extract, gold lotion (GL), on azoxymethane-induced colonic tumorigenesis. We have demonstrated that oral feeding of GL decreased the number of aberrant crypt foci (ACF), particularly large size of ACF in colonic tissues of mice. Both gene and protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were suppressed by GL treatment. The in vivo data have revealed for the first time that the citrus peel extract-GL-is an effective antitumor agent mechanistically downregulating the protein levels of iNOS, COX-2, ornithine decarboxylase, vascular endothelial growth factor, and matrix metallopeptidase 9 in colonic tissues of mice, suggesting that GL is a novel functional natural product capable of preventing inflammation-associated colon tumorigenesis.

Reduced group IVA phospholipase A2 expression is associated with unfavorable outcome for patients with gastric cancer

Arachidonic acid metabolic pathway has been implicated in the inflammation-associated tumorigenesis of gastrointestinal cancers. As the rate-limiting enzyme of arachidonic acid production, group IVA phospholipase A2 (PLA2G4A) is hypothesized to play a fundamental role in gastric tumorigenesis as well as cyclooxygenase-2 (COX-2). However, little is known about the expression and role of PLA2G4A in gastric cancer, and the association of PLA2G4A with COX-2 remains to be elucidated. In this study, the mRNA expression of PLA2G4A and COX-2 in 60 pairs of fresh gastric tumors and corresponding adjacent non-cancerous mucosa was detected by using real-time quantitative PCR and the immunostaining of the both proteins in paired samples from 866 gastric cancer patients were assessed by using immunohistochemistry method. The clinicopathological and the prognostic relevance of PLA2G4A and COX-2 expression were determined. The results revealed a significantly reduced expression of PLA2G4A in gastric tumors compared to in non-cancerous tissues, as opposite to the increased expression of COX-2. PLA2G4A was significantly associated with tumor size (P = 0.003), tumor grade (P < 0.001), intestinal type (P = 0.003), T classification (P < 0.001), N classification (P < 0.001), and thereby TNM stage (P < 0.001). PLA2G4A and COX-2 expression were both identified as independent prognostic factors in multivariate Cox model analysis (P = 0.024 for PLA2G4A and P < 0.001 for COX-2). Moreover, the reduced PLA2G4A and increased COX-2 expression was both associated with unfavorable survival for patients with gastric cancer. PLA2G4A might serve as a promising target for future therapeutic approaches to gastric cancer combined with COX-2 inhibitors.

Inhibition of citrus flavonoids on 12-O-tetradecanoylphorbol 13-acetate-induced skin inflammation and tumorigenesis in mice

The inhibitory effects of a formulated product from citrus peel extract, Gold Lotion (GL), on 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in mouse skin was reported in this study. It is found that in the TPA-induced skin inflammation model, the topical application of GL effectively inhibited the transcriptional activation of iNOS and its mRNA and protein in mouse skin. It is also discovered that GL significantly inhibited TPA-induced mouse skin inflammation by decreasing inflammatory gene parameters. Furthermore, GL dramatically inhibited 7,12-dimethylbenez[a]anthracene (DMBA)/TPA-induced skin tumor formation and reduced tumor incidence, tumor weight and tumor multiplicity of papillomas at 20 weeks. In essence, these in vivo data have revealed that GL is an effective anti-tumor agent that functions by down-regulating the protein levels of COX-2, ornithine decarboxylase (ODC), and vascular endothelial growth factor (VEGF) in mouse skin, suggesting that GL is a novel functional natural product capable of preventing inflammation-associated tumorigenesis.

Intestinal epithelial cell-specific CD98 expression regulates tumorigenesis in ApcMin/+ mice

The transmembrane glycoprotein CD98 regulates integrin signaling that in turn controls cell proliferation and survival. CD98 expression is upregulated in various carcinomas, including colorectal cancer. Recently, by generating gain- and loss-of-function mouse models featuring genetic manipulation of CD98 expression specifically in intestinal epithelial cells (IECs), we have explored the crucial role of CD98 in the regulation of intestinal homeostasis and inflammation-associated tumorigenesis. In the present study, we investigated the contribution of CD98 to intestinal tumorigenesis in ApcMin/+ mice and the underlying mechanism of action. Mice featuring IEC-specific CD98 overexpression (Tg animals) were crossed with ApcMin/+ mice, and the characteristics of intestinal adenoma formation were assessed. Compared with ApcMin/+ mice, Tg/ApcMin/+ animals exhibited increases in both intestinal tumor incidence and tumor size; these parameters correlated with enhanced proliferation and decreased apoptosis of IECs. IEC-specific CD98 overexpression resulted in increased synthesis of the oncogenic proteins c-myc and cyclin-D1 in ApcMin/+ mice, independently of the Wnt-APC-β-catenin pathway, suggesting the implication of CD98 overexpression-mediated Erk activation. IEC-specific CD98 overexpression enhanced the production of proinflammatory cytokines and chemokines that are crucial for tumorigenesis. We validated our results in mice exhibiting IEC-specific CD98 downregulation (CD98flox/+VillinCre animals). IEC-specific CD98 downregulation efficiently attenuated tumor incidence and growth in ApcMin/+ mice. The reduction of intestinal tumorigenesis upon IEC-specific CD98 downregulation was caused by the attenuation of IEC proliferation and cytokine/chemokine production. In conclusion, we show that CD98 exerts an oncogenic activity in terms of intestinal tumorigenesis, via an ability to regulate tumor growth and survival.

Mo1595 Farnesoid X Receptor Expression is Inversely Correlated With Neoplastic Progression in Colitis-Associated Colon Carcinogenesis

Background: A widespread downregulation of microRNAs is commonly observed in human cancers and is involved in cellular transformation and tumorigenesis. Because we previously reported that microRNA functions are inhibited under various kinds of cellular stresses including inflammatory cytokines In Vitro, we hypothesized that chronic inflammation In Vivo may also cause chronic functional impairment of microRNAs, which mimics a global reduction of microRNA abundance, resulting in a causal role in inflammation-associated tumorigenesis. Methods & Results: 1) To examine this hypothesis, we first confirmed the functional impairment of microRNAs under inflammatory stimuli In Vitro using artificial reporter constructs. The derepression of microRNA-targeting reporter activities by inflammatory stimuli could also be observed using reporter constructs containing natural 3'UTR sequences of c-myc and Lin28B genes, which are targeted by endogenous let-7. 2) Next, we constructed reporter transgenic mice bearing CMV-promoter driven GFP construct carrying target sequences of microRNAs in its 3'UTR, and monitored the changes of microRNA functions In Vivo during the course of a Dextran Sulfate Sodium (DSS) induced colitisassociated colon tumor model. The expression levels of GFP were significantly increased during colitis, suggesting that microRNA functions were impaired during the chronic inflammation In Vivo. The expression levels of microRNA-target oncogenes such as c-myc and Lin28B in the colonic mucosa were indeed upregulated. 3) Lastly, to determine the consequences of the global functional impairment of microRNAs during the colitis, we examined Dicer-deficient mice, which have globally low levels of microRNA expression and may mimic the functional impairment of global microRNAs induced by chronic inflammation described above. As expected, Dicer deficient mice were more liable to have the colitis-associated tumors. This indicates that the global decrease of microRNAs leads to oncogenesis, suggesting that the functional impairment of global microRNAs during chronic inflammation can also be a cause of the inflammation-associated carcinogenesis. Conclusion: In conclusion, we propose a novel concept that the attenuation of global microRNA functions by chronic inflammation is the cause of inflammation-associated tumorigenesis.

Mo1594 The Role Played by PepT1 in Colitis-Associated Cancer

Background: A widespread downregulation of microRNAs is commonly observed in human cancers and is involved in cellular transformation and tumorigenesis. Because we previously reported that microRNA functions are inhibited under various kinds of cellular stresses including inflammatory cytokines In Vitro, we hypothesized that chronic inflammation In Vivo may also cause chronic functional impairment of microRNAs, which mimics a global reduction of microRNA abundance, resulting in a causal role in inflammation-associated tumorigenesis. Methods & Results: 1) To examine this hypothesis, we first confirmed the functional impairment of microRNAs under inflammatory stimuli In Vitro using artificial reporter constructs. The derepression of microRNA-targeting reporter activities by inflammatory stimuli could also be observed using reporter constructs containing natural 3'UTR sequences of c-myc and Lin28B genes, which are targeted by endogenous let-7. 2) Next, we constructed reporter transgenic mice bearing CMV-promoter driven GFP construct carrying target sequences of microRNAs in its 3'UTR, and monitored the changes of microRNA functions In Vivo during the course of a Dextran Sulfate Sodium (DSS) induced colitisassociated colon tumor model. The expression levels of GFP were significantly increased during colitis, suggesting that microRNA functions were impaired during the chronic inflammation In Vivo. The expression levels of microRNA-target oncogenes such as c-myc and Lin28B in the colonic mucosa were indeed upregulated. 3) Lastly, to determine the consequences of the global functional impairment of microRNAs during the colitis, we examined Dicer-deficient mice, which have globally low levels of microRNA expression and may mimic the functional impairment of global microRNAs induced by chronic inflammation described above. As expected, Dicer deficient mice were more liable to have the colitis-associated tumors. This indicates that the global decrease of microRNAs leads to oncogenesis, suggesting that the functional impairment of global microRNAs during chronic inflammation can also be a cause of the inflammation-associated carcinogenesis. Conclusion: In conclusion, we propose a novel concept that the attenuation of global microRNA functions by chronic inflammation is the cause of inflammation-associated tumorigenesis.

Mo1593 Functional Impairment of MicroRNAs Induced by Chronic Inflammation is the Cause of Inflammation-Associated Colon Tumorigenesis

Mo1593 Functional Impairment of MicroRNAs Induced by Chronic Inflammation is the Cause of Inflammation-Associated Colon Tumorigenesis

Abstract 1519: Peroxisome proliferator-activated receptor ≤ promotes colonic inflammation and inflammation-associated tumorigenesis

Abstract Although epidemiologic and experimental evidence strongly indicates chronic inflammation as a risk factor for cancer, it remains unclear how chronic inflammation contributes carcinogenesis. Peroxisome proliferator-activated receptor ≤ (PPARδ) is one member of PPAR family that belongs to the nuclear hormone receptor superfamily and is also ligand-dependent transcription factor. Although PPARδ has been shown to be involved in chronic inflammation and the progression of hereditary and sporadic CRC, its role in inflammation-induced carcinogenesis is not defined. The aim of our present study was to determine whether PPARδ contributes to the pathogenesis of colonic inflammation and inflammation-associated carcinogenesis. Here we present genetic evidence demonstrating that deletion of PPARδ diminishes colonic inflammation accompanied with reducing infiltration of immune cells and the expression of pro-inflammatory chemokines and cytokines in a mouse model of colitis. These PPARδ-dependent chemokines are responsible for recruitment of leukocytes from the circulation to local inflammatory sites and the tumor microenvironment. Our results further reveal that activation of PPARδ induces COX-2 expression in colonic epithelial cells. Importantly, COX-2-derived PGE2 stimulates macrophages to produce pro-inflammatory chemokines and cytokines. More intriguingly, loss of PPARδ attenuated colonic chronic inflammation and colitis-associated adenoma growth via PGE2 signaling in two mouse models of colitis-associated tumorigenesis. Collectively, our results demonstrate that PPARδ promotes colonic chronic inflammation and colitis-associated tumor growth via a PGE2 signaling which mediates the crosstalk between tumor epithelial cells and macrophages. Our data further supports the notion that the existence of crosstalk between PPARδ and COX-2 signaling in CRC progression. These findings indicate that PPARδ plays a pivotal role in connecting colonic inflammation to cancer progression and may represent a potential therapeutic target for prevention or treatment of colorectal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1519. doi:1538-7445.AM2012-1519

Abstract 1339: The role of TNF-α in PGE2-induced tumorigenesis in gastric cancer mouse model

Abstract Accumulating evidence has indicated that chronic inflammation is associated with cancer development. Mouse genetic studies have shown that the proinflammatory mediator, PGE2, plays an essential role in gastrointestinal tumorigenesis. Moreover, the proinflammatory cytokine TNF-α also plays a key role in tumorigenesis, including colitis-associated colon cancer. However, the relationship between PGE2 and TNF-α in tumorigenesis has not yet been fully investigated. We previously constructed a gastric tumor mouse model, Gan mice, that recapitulates human intestinal-type gastric cancer, in which both the PGE2 pathway and Wnt signaling are activated simultaneously in the stomach by transgenic expression of the COX-2, mPGES-1, and Wnt1 genes. The induction of the PGE2 pathway triggers an inflammatory response in the Gan mouse stomach, and the expression of proinflammatory cytokines and chemokines is induced in gastric tumor tissues. We herein examined the role of TNF-α in the PGE2-induced inflammation-associated gastric tumorigenesis by crossing Gan mice with TNF-α knockout mice. Importantly, the gastric tumorigenesis in the Gan TNF-α (-/-) compound mice was significantly suppressed in comparison to the control Gan mice. Moreover, the β-catenin level decreased significantly in the gastric tumors of Gan TNF-α (-/-) mice, suggesting a role for TNF-α in the promotion of Wnt signaling. Interestingly, inflammatory cells, including macrophages and CD4+ T cells, still infiltrated into the Gan TNF-α (-/-) mouse tumors, and the expression levels of IL-1α and IL-6 were almost the same as those in the control Gan mouse tumors. Accordingly, it is possible that TNF-α is an important tumor-promoting factor for gastric tumorigenesis, although TNF-α is not essential for PGE2-induced inflammation in the stomach. Notably, macrophages in the Gan TNF-α (-/-) mouse tumors lost their expression of the M2 marker CD206. It has been suggested that macrophages polarized to the M2(-like) type are important for tissue remodeling and tumorigenesis. It is therefore possible that TNF-α is required for macrophage polarization to a pro-tumorigenic status, which may be important for Wnt activation and gastric tumor promotion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1339. doi:1538-7445.AM2012-1339

Abstract 3341: Chronic TNFα treatment enhances cancer stem cell-like phenotype via Notch1 activation in oral squamous cell carcinoma cells

Abstract Although there is an increasing evidence of chronic inflammation-associated tumorigenesis, the molecular and cellular mechanisms linking chronic inflammation to tumorigenesis have not yet been fully understood. Recent studies have uncovered and validated the pathophysiological role of self-renewing cells, named cancer stem cells (CSC; also called tumor-initiating cells), in long-term sustenance of cancers. In this study, we investigated the effect of chronic inflammation on CSC phenotype of oral squamous cell carcinoma cells (OSCC). We treated OSCC cell lines with tumor necrosis factor alpha (TNFα), a major proinflammatory cytokine, for extended periods and examined the effect of chronic TNFα on CSC characteristics, i.e., undifferentiated tumor sphere forming ability, stem cell-associated genes expression and chemo-radioresistance. Chronic treatment of OSCC with TNFα enhanced CSC phenotype, which is shown by increased tumor sphere forming ability, greatly increased tumorigenicity and chemo-radioresistance, and increased expression of stemness-related genes. Moreover, activation of Notch1 signaling was detected in the TNFα treated cell, and suppression of Notch1 signaling inhibited CSC phenotype. Furthermore, we demonstrated that inhibition of Hes-1, the downstream target of Notch1, led to suppression of CSC phenotype. Taken together, the data suggest that proinflammatory cytokine exposure can generate or/and enrich OSCC CSC population, in part, by activation of the Notch1 signaling pathway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3341. doi:1538-7445.AM2012-3341

The inflammatory network in the gastrointestinal tumor microenvironment: lessons from mouse models

Accumulating evidence has indicated that inflammatory responses are important for cancer development. Epidemiological studies have shown that regular use of non-steroidal anti-inflammatory drugs (NSAIDs) reduces the risk of colon cancer development. Subsequently, mouse genetic studies have shown that cyclooxygenase (COX)-2, one of the target molecules of NSAIDs, and its downstream product, prostaglandin E(2) (PGE(2)), play an important role in gastrointestinal tumorigenesis. Bacterial infection stimulates the Toll-like receptor (TLR)/MyD88 pathway in tumor tissues, which leads to the induction of COX-2 in stromal cells, including macrophages. Induction of the COX-2/PGE(2) pathway in tumor stroma is important for the development and maintenance of an inflammatory microenvironment in gastrointestinal tumors. In such a microenvironment, tumor-associated macrophages express proinflammatory cytokines, including tumor necrosis factor (TNF)-α and interleukin (IL)-6, and these cytokines, respectively, activate the nuclear factor (NF)-κB and Stat3 transcription factors in epithelial cells, as well as in stromal cells. Recent mouse studies have uncovered the role of such an inflammatory network in the promotion of gastrointestinal tumor development. Genetically engineered and chemically induced mouse tumor models which mimic sporadic or inflammation-associated tumorigenesis were used in these studies. In this review article, we focus on mouse genetic studies using these tumor models, which have contributed to the elucidation of the molecular mechanisms associated with the inflammatory network in gastrointestinal tumors, and we also discuss the role of each pathway in cancer development. The involvement of immune cells such as macrophages, mast cells, and regulatory T cells in tumor promotion is also discussed.

Pterostilbene, a natural analogue of resveratrol, potently inhibits 7,12-dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse skin carcinogenesis

We reported previously that pterostilbene, a natural analogue of resveratrol from blueberries, strongly suppressed lipopolysaccharide-induced up-expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in murine macrophages. In this study, we further investigated pterostilbene's molecular mechanism of action and its anti-tumor properties. Pretreatment with pterostilbene has resulted in the reduction of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced nuclear translocation of the nuclear factor-κB (NFκB) subunits. Pterostilbene also reduced TPA-induced phosphorylation of IκBα and p65 and caused subsequent degradation of IκBα. Moreover, pterostilbene markedly suppressed TPA-induced activation of extracellular signal-regulated kinase (ERK)1/2, p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK)1/2, phosphatidylinositol 3-kinase (PI3K) and Akt, which are upstream of NFκB and activator protein 1 (AP-1). Furthermore, pterostilbene significantly inhibited 7,12-dimethylbenz[a]anthracene (DMBA)/TPA-induced skin tumor formation measured by the tumor multiplicity of papillomas at 20 weeks. The presented data has, for the first time, revealed that pterostilbene is an effective anti-tumor agent that functions by downregulating inflammatory iNOS and COX-2 gene expression in mouse skin. It is suggested that pterostilbene is a novel functional agent capable of preventing inflammation-associated tumorigenesis.

Role of Natural Killer T Cells in the Mouse Colitis‐Associated Colon Cancer Model

Invariant natural killer T (iNKT) cells are considered innate-like lymphocytes, and regulate the immunity against inflammation and tumorigenesis. However, the impact of iNKT cells in inflammation-associated tumorigenesis remains unclear. In this study, we examined the physiological role of iNKT cells in a mouse colitis-associated colorectal cancer model. C57BL/6 (B6) and Jα18 NKT cell-deficient KO (KO) mice were used. Colitis-associated colorectal cancer was induced by azoxymethane (AOM) and dextran sodium sulfate (DSS). The resulting inflammation and tumours were examined. The surface markers of mononuclear cells from the liver and the colon were assessed by FACS. The levels of IL-13 from the colon were measured by ELISA. α-galactosylceramide (GC), or its close analog OCH, was administered intraperitoneally on the first day of each cycle of DSS-administration. In the AOM/DSS model, hepatic iNKT cells were significantly decreased. In KO mice there were significantly greater numbers of colon tumours and more severe inflammation than in B6 mice. FACS analysis revealed that the population of NK1.1 (+) T cells (non-invariant NKT cells) in the colon was increased when compared to B6 mice. The secretion of IL-13 was increased in the colon of KO mice after AOM/DSS. The number of colon tumours was significantly decreased in the GC-treated group compared to the control group. GC-treatment significantly inhibited IL-13 secretion from the colonic mononuclear cells and the number of colonic NK1.1 (+) T cells was significantly decreased. These results suggest that iNKT cells may play a critical role in the prevention of tumour progression and inflammation in the AOM/DSS model.

FAT10 mediates the effect of TNF-α in inducing chromosomal instability

Tumor necrosis factor-alpha (TNF-α) plays important roles in chronic inflammation-associated tumorigenesis but the mechanisms involved remain poorly understood. Previously, we reported that high levels of FAT10 led to chromosomal instability that is mediated by an abbreviated mitotic phase. Here, we show that TNF-α induces FAT10 gene expression through TNF receptor 1 (TNFR1) and activates the NF-κB pathway in HCT116 and SW620 cells. TNF-α treatment also leads to an abbreviated mitotic phase that can be reversed by inhibiting FAT10 expression. This abbreviated mitotic phase is correlated with a TNF-α-induced reduction in the kinetochore localization of MAD2 during prometaphase which, again, can be reversed by inhibiting FAT10 gene expression. There is greater variability of chromosome numbers in HCT116 and SW620 cells treated with TNF-α than in untreated cells, which can be reversed by the introduction of short hairpin RNA (shRNA) against FAT10. The more stable chromosome numbers in HCT116 cells expressing FAT10 shRNA can revert to greater variability with the addition of a mutant FAT10 that is not recognized by the FAT10 shRNA. Upon TNF-α stimulation, higher cell death is observed when FAT10 expression is inhibited by shRNA. These data strongly suggest that FAT10 plays an important role in mediating the function of TNF-α during tumorigenesis by inducing cell cycle deregulation and chromosomal instability, and by inhibiting apoptosis.