Regulation of stromal cell cyclooxygenase-2 in the Apc Min/+ mouse model of intestinal tumorigenesis

Effect of NETs/COX-2 pathway on immune microenvironment and metastasis in gastric cancer

Background

Neutrophil extracellular traps (NETs) are crucial in the progression of several cancers. The formation of NETs is closely related to reactive oxygen species (ROS), and the granule proteins involved in nucleosome depolymerization under the action of ROS together with the loosened DNA compose the basic structure of NETs. This study aims to investigate the specific mechanisms of NETs promoting gastric cancer metastasis in order to perfect the existing immunotherapy strategies.

Methods

In this study, the cells and tumor tissues of gastric cancer were detected by immunological experiments, real-time polymerase chain reaction and cytology experiments. Besides, bioinformatics analysis was used to analyze the correlation between cyclooxygenase-2 (COX-2) and the immune microenvironment of gastric cancer, as well as its effect on immunotherapy.

Results

Examination of clinical specimens showed that NETs were deposited in tumor tissues of patients with gastric cancer and their expression was significantly correlated with tumor staging. Bioinformatics analysis showed that COX-2 was involved in gastric cancer progression and was associated with immune cell infiltration as well as immunotherapy. In vitro experiments, we demonstrated that NETs could activate COX-2 through Toll-like receptor 2 (TLR2) and thus enhance the metastatic ability of gastric cancer cells. In addition, in a liver metastasis model of nude mice we also demonstrated the critical role of NETs and COX-2 in the distant metastasis of gastric cancer.

Conclusion

NETs can promote gastric cancer metastasis by initiating COX-2 through TLR2, and COX-2 may become a target for gastric cancer immunotherapy.

Tanshinone IIA attenuates AOM/DSS-induced colorectal tumorigenesis in mice via inhibition of intestinal inflammation

CONTEXT

Tanshinone IIA is a natural extract derived from a Chinese medicinal herb with multiple bioactivities; however, whether and how tanshinone IIA protects against colorectal cancer (CRC) are uncertain.

OBJECTIVE

We investigated the potential beneficial effects of tanshinone IIA in a colitis-associated colorectal tumorigenesis mouse model and its underlying mechanisms.

MATERIALS AND METHODS

Male C57BL/6 mice were treated with azoxymethane (AOM) 10 mg/kg body weight and dextran sulphate sodium (2.5% DSS) to induce a colitis-associated cancer model. Tanshinone IIA (200 mg/kg body weight) was given to the mice intraperitoneally. After 12 weeks, all mice were sacrificed to measure tumour formation, intestinal permeability, neutrophil infiltration, and colonic inflammation. In addition, whether tanshinone IIA has inhibitory effects on neutrophil activation was determined through in vitro investigations.

RESULTS

We observed that tanshinone IIA significantly decreased tumour formation in AOM/DSS-treated mice compared to AOM/DSS-treated alone mice (0.266 ± 0.057 vs. 0.78 ± 0.153, p = 0.013). Tanshinone IIA also decreased intestinal permeability compared to that in AOM/DSS-treated alone mice (3.12 ± 0.369 vs. 5.06 ± 0.597, p = 0.034) and consequently reduced neutrophil infiltration of the colonic mucosa (53.25 ± 8.85 vs. 107.6 ± 13.09, p = 0.014) as well as intestinal inflammation in mice. Mechanistically, tanshinone IIA downregulated the NF-κB signalling pathway in the colonic tumours of AOM/DSS-treated mice. In vitro assays further validated that tanshinone IIA suppressed LPS-induced neutrophil activation.

CONCLUSION

These data suggest that tanshinone IIA alleviates colorectal tumorigenesis through inhibition of intestinal inflammation. Tanshinone IIA may have a therapeutic potential for CRC in clinical practice.

Reduction in the resident intestinal myelomonocytic cell population occurs during ApcMin/+ mouse intestinal tumorigenesis

With its significant contribution to cancer mortality globally, advanced colorectal cancer (CRC) requires new treatment strategies. However, despite recent good results for mismatch repair (MMR)-deficient CRC and other malignancies, such as melanoma, the vast majority of MMR-proficient CRCs are resistant to checkpoint inhibitor (CKI) therapy. MMR-proficient CRCs commonly develop from precursor adenomas with enhanced Wnt-signalling due to adenomatous polyposis coli (APC) mutations. In melanomas with enhanced Wnt signalling due to stabilized β-catenin, immune anergy and resistance to CKI therapy has been observed, which is dependent on micro-environmental myelomonocytic (MM) cell depletion in melanoma models. However, MM populations of colorectal adenomas or CRC have not been studied. To characterize resident intestinal MM cell populations during the early stages of tumorigenesis, the present study utilized the Apc^Min/+ mouse as a model of MMR-proficient CRC, using enhanced green fluorescent protein (EGFP) expression in the mouse lysozyme (M-lys) ^lys-EGFP/+ mouse as a pan-myelomonocytic cell marker and a panel of murine macrophage surface markers. Total intestinal lamina propria mononuclear cell (LPMNC) numbers significantly decreased with age (2.32±1.39×10⁷ [n=4] at 33 days of age vs. 1.06±0.24×10⁷ [n=8] at 109 days of age) during intestinal adenoma development in Apc^Min/+ mice (P=0.05; unpaired Student's t-test), but not in wild-type littermates (P=0.35). Decreased total LPMNC numbers were associated with atrophy of intestinal lymphoid follicles and the absence of MM/lymphoid cell aggregates in Apc^Min/+ mouse intestine, but not spleen, compared with wild-type mice. Furthermore, during the early stage of intestinal adenoma development, there was a two-fold reduction of M-lys expressing cells (P=0.05) and four-fold reduction of ER-HR3 (macrophage sub-set) expressing cells (P=0.05; two tailed Mann-Whitney U test) in mice with reduced total intestinal LPMNCs (n=3). Further studies are necessary to determine the relevance of these findings to immune-surveillance of colorectal adenomas or MMR-proficient CRC CKI therapy resistance.

Microbial Sensing by Intestinal Myeloid Cells Controls Carcinogenesis and Epithelial Differentiation

Physiologic microbe-host interactions in the intestine require the maintenance of the microbiota in a luminal compartment through a complex interplay between epithelial and immune cells. However, the roles of mucosal myeloid cells in this process remain incompletely understood. In this study, we identified that decreased myeloid cell phagocytic activity promotes colon tumorigenesis. We show that this is due to bacterial accumulation in the lamina propria and present evidence that the underlying mechanism is bacterial induction of prostaglandin production by myeloid cells. Moreover, we show that similar events in the normal colonic mucosa lead to reductions in Tuft cells, goblet cells, and the mucus barrier of the colonic epithelium. These alterations are again linked to the induction of prostaglandin production in response to bacterial penetration of the mucosa. Altogether, our work highlights immune cell-epithelial cell interactions triggered by the microbiota that control intestinal immunity, epithelial differentiation, and carcinogenesis.

COX-2 Signaling in the Tumor Microenvironment

Tumorigenesis is a multistep, complicated process, and many studies have been completed over the last few decades to elucidate this process. Increasingly, many studies have shifted focus toward the critical role of the tumor microenvironment (TME), which consists of cellular players, cell-cell communications, and extracellular matrix (ECM). In the TME, cyclooxygenase-2 (COX-2) has been found to be a key molecule mediating the microenvironment changes. COX-2 is an inducible form of the enzyme that converts arachidonic acid into the signal transduction molecules (thromboxanes and prostaglandins). COX-2 is frequently expressed in many types of cancers and has been closely linked to its occurrence, progression, and prognosis. For example, COX-2 has been shown to (1) regulate tumor cell growth, (2) promote tissue invasion and metastasis, (3) inhibit apoptosis, (4) suppress antitumor immunity, and (5) promote sustainable angiogenesis. In this chapter, we summarize recent advances of studies that have evaluated COX-2 signaling in TME.

Thrombospondin-1 interactions regulate eicosanoid metabolism and signaling in cancer-related inflammation

The metabolism of arachidonic acid and other polyunsaturated fatty acids produces eicosanoids, a family of biologically active lipids that are implicated in homeostasis and in several pathologies that involve inflammation. Inflammatory processes mediated by eicosanoids promote carcinogenesis by exerting direct effects on cancer cells and by affecting the tumor microenvironment. Therefore, understanding how eicosanoids mediate cancer progression may lead to better approaches and chemopreventive strategies for the treatment of cancer. The matricellular protein thrombospondin-1 is involved in processes that profoundly regulate inflammatory pathways that contribute to carcinogenesis and metastatic spread. This review focuses on interactions of thrombospondin-1 and eicosanoids in the microenvironment that promote carcinogenesis and how the microenvironment can be targeted for cancer prevention to increase curative responses of cancer patients.

An increased CD25-positive intestinal regulatory T lymphocyte population is dependent upon Cox-2 activity in the Apcmin/+ model

Only mismatch repair (MMR)-deficient colorectal cancer (CRC) appears to respond well to programmed death (PD)-1 inhibition at the present time. Emerging evidence suggests a role for micro-environmental factors such as CD25⁺ cells modulating response to PD-1 inhibition. In the Apc^Min/+ model of familial adenomatous polyposis (MMR-proficient CRC), increased Cyclooxygenase-2 (Cox-2) expression by cells which include alternatively activated mononuclear phagocytes promotes intestinal tumorigenesis by mechanisms which may include immune suppression. To gain insight into this, we compared regulatory T cell (T_reg ) populations between Apc^Min/+ and wild-type mice prior to and after the phase of increased intestinal Cox-2-dependent prostaglandin E₂ (PGE₂ ) production. There was no difference in systemic T_reg function or numbers between Apc^Min/+ and wild-type mice. However, increased numbers of small intestinal CD25⁺ T_regs were observed with increased Cox-2 activity in the absence of any difference in the expression of Tgf-β or Tslp between Apc^Min/+ and wild-type mice. Cox-2 inhibitor therapy (Celecoxib) reversed the increase in Apc^Min/+ intestinal CD25⁺ T_reg numbers, without decreasing numbers of CD25⁺ systemic T_regs . Forkhead box protein 3 (FoxP3⁺ ) and Cox-2⁺ cells were co-localized to the interstitium of adenomas of Apc^min/+ mice. These results suggest selective dependence of an 'activated T_reg ' phenotype on paracrine Cox-2 activity in Apc^Min/+ small intestine. For therapeutic potential, further studies are required to evaluate the relevance of these findings to human cancer as well as the functional significance of CD25⁺ intestinal T_regs in cancer.

Paracrine cyclooxygenase-2 activity by macrophages drives colorectal adenoma progression in the Apc Min/+ mouse model of intestinal tumorigenesis

Genetic deletion or pharmacological inhibition of cyclooxygenase (COX)-2 abrogates intestinal adenoma development at early stages of colorectal carcinogenesis. COX-2 is localised to stromal cells (predominantly macrophages) in human and mouse intestinal adenomas. Therefore, we tested the hypothesis that paracrine Cox-2-mediated signalling from macrophages drives adenoma growth and progression in vivo in the Apc^Min/+ mouse model of intestinal tumorigenesis. Using a transgenic C57Bl/6 mouse model of Cox-2 over-expression driven by the chicken lysozyme locus (cLys-Cox-2), which directs integration site-independent, copy number-dependent transgene expression restricted to macrophages, we demonstrated that stromal macrophage Cox-2 in colorectal (but not small intestinal) adenomas from cLys-Cox-2 x Apc^Min/+ mice was associated with significantly increased tumour size (P = 0.025) and multiplicity (P = 0.025), compared with control Apc^Min/+ mice. Transgenic macrophage Cox-2 expression was associated with increased dysplasia, epithelial cell Cox-2 expression and submucosal tumour invasion, as well as increased nuclear β-catenin translocation in dysplastic epithelial cells. In vitro studies confirmed that paracrine macrophage Cox-2 signalling drives catenin-related transcription in intestinal epithelial cells. Paracrine macrophage Cox-2 activity drives growth and progression of Apc^Min/+ mouse colonic adenomas, linked to increased epithelial cell β-catenin dysregulation. Stromal cell (macrophage) gene regulation and signalling represent valid targets for chemoprevention of colorectal cancer.

Dietary fat overcomes the protective activity of thrombospondin-1 signaling in the Apc(Min/+) model of colon cancer

Thrombospondin 1 is a glycoprotein that regulates cellular phenotype through interactions with its cellular receptors and extracellular matrix-binding partners. Thrombospondin 1 locally regulates angiogenesis and inflammatory responses that contribute to colorectal carcinogenesis in Apc^Min/+ mice. The ability of thrombospondin 1 to regulate responses of cells and tissues to a variety of stresses suggested that loss of thrombospondin 1 may also have broader systemic effects on metabolism to modulate carcinogenesis. Apc^Min/+:Thbs1^−/− mice exhibited decreased survival and higher tumor multiplicities in the small and large intestine relative to Apc^Min/+ mice when fed a low (5%) fat western diet. However, the protective effect of endogenous thrombospondin 1 was lost when the mice were fed a western diet containing 21% fat. Biochemical profiles of liver tissue identified systemic metabolic changes accompanying the effects of thrombospondin 1 and dietary lipid intake on tumorigenesis. A high-fat western diet differentially regulated elements of amino acid, energy and lipid metabolism in Apc^Min/+:Thbs1^−/− mice relative to Apc^Min/+:Thbs1^+/+mice. Metabolic changes in ketone body and tricarboxylic acid cycle intermediates indicate functional interactions between Apc and thrombospondin 1 signaling that control mitochondrial function. The cumulative diet-dependent differential changes observed in Apc^Min/+:Thbs1^−/− versus Apc^Min/+ mice include altered amino acid and lipid metabolism, mitochondrial dysfunction, eicosanoids and ketone body formation. This metabolic profile suggests that the protective role of thrombospondin 1 to decrease adenoma formation in Apc^Min/+ mice results in part from improved mitochondrial function.

Prostaglandin E2 stimulates normal bronchial epithelial cell growth through induction of c-Jun and PDK1, a kinase implicated in oncogenesis

Background

Cyclooxygenase-2-derived prostaglandin E₂ (PGE₂), a bioactive eicosanoid, has been implicated in many biological processes including reproduction, inflammation and tumor growth. We previously showed that PGE₂ stimulated lung cancer cell growth and progression through PGE₂ receptor EP2/EP4-mediated kinase signaling pathways. However, the role of PGE₂ in controlling lung airway epithelial cell phenotype remains unknown. We evaluated the effects of c-Jun and 3-phosphoinositede dependent protein kinase-1 (PDK1) in mediating epithelial cell hyperplasia induced by PGE₂.

Method

The bronchial epithelial cell lines BEAS-2B and HBEc14-KT were cultured and then treated with PGE₂. PDK1 small interfering RNA (siRNA) and a PDK1 inhibitor, an antagonist of the PGE₂ receptor subtype EP4 and EP4 siRNA, c-Jun siRNA, and overexpressions of c-Jun and PDK1 have been used to evaluate the effects on cell proliferation.

Results

We demonstrated that PGE₂ increased normal bronchial epithelial cell proliferation through induction of PDK1, an ankyrin repeat-containing Ser/Thr kinase implicated in the induction of apoptosis and the suppression of tumor growth. PDK1 siRNA and a PDK1 inhibitor blocked the effects of PGE₂ on normal cell growth. The PGE₂-induced PDK1 expression was blocked by an antagonist of the PGE₂ receptor subtype EP4 and by EP4 siRNA. In addition, we showed that induction of PDK1 by PGE₂ was associated with induction of the transcription factor, c-Jun protein. Silencing of c-Jun using siRNA and point mutations of c-Jun sites in the PDK1 gene promoter resulted in blockade of PDK1 expression and promoter activity induced by PGE₂. In contrast, overexpression of c-Jun induced PDK1 gene promoter activity and expression followed increased cell proliferation.

Conclusion

PGE₂ increases normal bronchial epithelial cell proliferation through increased PDK1 gene expression that is dependent on EP4 and induction of c-Jun. Therewith, our data suggest a new role of c-Jun and PDK1 in mediating epithelial cell hyperplasia induced by PGE₂.

Prostaglandin E receptor 4 (EP4) promotes colonic tumorigenesis

Colorectal cancer (CRC) continues to be a major cause of morbidity and mortality. Although the factors underlying CRC development and progression are multifactorial, there is an important role for tumor-host interactions, especially interactions with myeloid cells. There is also increasing evidence that cyclooxygenase-derived prostaglandins are important mediators of CRC development and growth. Although prevention trials with either nonselective NSAIDs or COX-2 selective agents have shown promise, the gastrointestinal or cardiovascular side effects of these agents have limited their implementation. The predominant prostaglandin involved in CRC pathogenesis is PGE2. Since myeloid cells express high levels of the PGE2 receptor subtype, EP4, we selectively ablated EP4 in myeloid cells and studied adenoma formation in a mouse model of intestinal adenomatous polyposis, ApcMin/+ mice. ApcMin/+mice with selective myeloid cell deletion of EP4 had marked inhibition of both adenoma number and size, with associated decreases in mTOR and ERK activation. Either genetic or pharmacologic inhibition of EP4 receptors led to an anti-tumorigenic M1 phenotype of macrophages/dendritic cells. Therefore, PGE2-mediated EP4 signaling in myeloid cells promotes tumorigenesis, suggesting EP4 as a potentially attractive target for CRC chemoprevention or treatment.

Intracellular colon cancer-associated Escherichia coli promote protumoral activities of human macrophages by inducing sustained COX-2 expression

Intestinal dysbiosis has been reported in patients with colorectal cancer, and there is a high prevalence of Escherichia coli belonging to B2 phylogroup and producing a genotoxin, termed colibactin. Macrophages are one of the predominant tumor-infiltrating immune cells supporting key processes in tumor progression by producing protumoral factors such as cyclooxygenase-2 (COX-2). Here, we investigated whether B2 E. coli colonizing colon tumors could influence protumoral activities of macrophages. In contrast to commensal or nonpathogenic E. coli strains that were efficiently and rapidly degraded by macrophages at 24 h after infection, colon cancer-associated E. coli were able to resist killing by human THP-1 macrophages, to replicate intracellularly, and to persist inside host cells until at least 72 h after infection. Significant increases in COX-2 expression were observed in macrophages infected with colon cancer E. coli compared with macrophages infected with commensal and nonpathogenic E. coli strains or uninfected cells at 72 h after infection. Induction of COX-2 expression required live bacteria and was not due to colibactin production, as similar COX-2 levels were observed in macrophages infected with the wild-type colon cancer-associated E. coli 11G5 strain or a clbQ mutant unable to produce colibactin. Treatment of macrophages with ofloxacin, an antibiotic with intracellular tropism, efficiently decreased the number of intracellular bacteria and suppressed bacteria-induced COX-2 expression. This study provides new insights into the understanding of how tumor- infiltrating bacteria could influence cancer progression through their interaction with immune cells. Manipulation of microbes associated with tumors could have a deep influence on the secretion of protumoral molecules by infiltrating macrophages.

Intracellular colon cancer-associated Escherichia coli promote protumoral activities of human macrophages by inducing sustained COX-2 expression

Intestinal dysbiosis has been reported in patients with colorectal cancer, and there is a high prevalence of Escherichia coli belonging to B2 phylogroup and producing a genotoxin, termed colibactin. Macrophages are one of the predominant tumor-infiltrating immune cells supporting key processes in tumor progression by producing protumoral factors such as cyclooxygenase-2 (COX-2). Here, we investigated whether B2 E. coli colonizing colon tumors could influence protumoral activities of macrophages. In contrast to commensal or nonpathogenic E. coli strains that were efficiently and rapidly degraded by macrophages at 24 h after infection, colon cancer-associated E. coli were able to resist killing by human THP-1 macrophages, to replicate intracellularly, and to persist inside host cells until at least 72 h after infection. Significant increases in COX-2 expression were observed in macrophages infected with colon cancer E. coli compared with macrophages infected with commensal and nonpathogenic E. coli strains or uninfected cells at 72 h after infection. Induction of COX-2 expression required live bacteria and was not due to colibactin production, as similar COX-2 levels were observed in macrophages infected with the wild-type colon cancer-associated E. coli 11G5 strain or a clbQ mutant unable to produce colibactin. Treatment of macrophages with ofloxacin, an antibiotic with intracellular tropism, efficiently decreased the number of intracellular bacteria and suppressed bacteria-induced COX-2 expression. This study provides new insights into the understanding of how tumor- infiltrating bacteria could influence cancer progression through their interaction with immune cells. Manipulation of microbes associated with tumors could have a deep influence on the secretion of protumoral molecules by infiltrating macrophages.

Design and synthesis of benzimidazole analogs endowed with oxadiazole as selective COX-2 inhibitor

New molecules of benzimidazole endowed with oxadiazole were designed and synthesized from 2-(2-((pyrimidin-2-ylthio)methyl)-1H-benzo[d]imidazol-1-yl)acetohydrazide as 1-((5-substituted alkyl/aryl-1,3,4-oxadiazol-2-yl)methyl)-2-((pyrimidin-2-ylthio)methyl)-1H-benzimidazoles (5a-r) with the aim to acquire selective cyclooxygenase (COX-2) inhibitor activity. The synthesized compounds were screened by in vitro cyclooxygenase assays to determine COX-1 and COX-2 inhibitory potency and the results showed that they had good-to-remarkable activity with an IC50 range of 11.6-56.1 µM. The most active compounds were further screened for their in vivo anti-inflammatory activity by using the carrageenan-induced rat paw edema model. In vitro anticancer activities of the hybrid compounds were assessed by the National Cancer Institute (NCI), USA, against 60 human cell lines, and the results showed a good spectrum. Compound 5l exhibited significant COX-2 inhibition with an IC50 value of 8.2 µM and a percent protection of 68.4%. Compound 5b evinced moderate cytotoxicity toward the UO-31 cell line of renal cancer. A docking study was performed using Maestro 9.0, to provide the binding mode into the binding sites of the cyclooxygenase enzyme. Hopefully, in the future, compound 5l could serve as a lead compound for developing new COX-2 inhibitors.

Peripheral administration of morphine attenuates postincisional pain by regulating macrophage polarization through COX-2-dependent pathway

BACKGROUND

Macrophage infiltration to inflammatory sites promotes wound repair and may be involved in pain hypersensitivity after surgical incision. We recently reported that the development of hyperalgesia during chronic inflammation is regulated by macrophage polarity, often referred to as proinflammatory (M1) or anti-inflammatory (M2) macrophages. Although opioids such as morphine are known to alter the inflammatory milieu of incisional wounds through interactions with immunocytes, the macrophage-mediated effects of morphine on the development of postincisional pain have not been well investigated. In this study, we examined how morphine alters pain hypersensitivity through phenotypic shifts in local macrophages during the course of incision-induced inflammation.

RESULTS

Local administration of morphine in the early phase, but not in the late phase alleviated mechanical hyperalgesia, and this effect was reversed by clodronate-induced peripheral depletion of local macrophages. At the morphine-injected incisional sites, the number of pro-inflammatory F4/80+iNOS+M1 macrophages was decreased during the course of pain development whereas increased infiltration of wound healing F4/80+CD206+M2 macrophages was observed during the early phase. Morphine increased the gene expression of endogenous opioid, proenkephalin, and decreased the pronociceptive cytokine, interleukin-1β. Heme oxygenase (HO)-1 promotes the differentiation of macrophages to the M2 phenotype. An inhibitor of HO-1, tin protoporphyrin reversed morphine-induced analgesic effects and the changes in macrophage phenotype. However, local expression levels of HO-1 were not altered by morphine. Conversely, cyclooxygenase (COX)-2, primarily produced from peripheral macrophages in acute inflammation states, was up-regulated in the early phase at morphine-injected sites. In addition, the analgesic effects and a phenotype switching of infiltrated macrophages by morphine was reversed by local administration of a COX inhibitor, indomethacin.

CONCLUSIONS

Local administration of morphine alleviated the development of postincisional pain, possibly by altering macrophage polarity at the incisional sites. A morphine-induced shift in macrophage phenotype may be mediated by a COX-2-dependent mechanism. Therefore, μ-opioid receptor signaling in macrophages may be a potential therapeutic target during the early phase of postincisional pain development.

Cyclooxygenase-2 deficiency leads to intestinal barrier dysfunction and increased mortality during polymicrobial sepsis

Sepsis remains the leading cause of death in critically ill patients, despite modern advances in critical care. Intestinal barrier dysfunction may lead to secondary bacterial translocation and the development of the multiple organ dysfunction syndrome during sepsis. Cyclooxygenase (COX)-2 is highly upregulated in the intestine during sepsis, and we hypothesized that it may be critical in the maintenance of intestinal epithelial barrier function during peritonitis-induced polymicrobial sepsis. COX-2(-/-) and COX-2(+/+) BALB/c mice underwent cecal ligation and puncture (CLP) or sham surgery. Mice chimeric for COX-2 were derived by bone marrow transplantation and underwent CLP. C2BBe1 cells, an intestinal epithelial cell line, were treated with the COX-2 inhibitor NS-398, PGD(2), or vehicle and stimulated with cytokines. COX-2(-/-) mice developed exaggerated bacteremia and increased mortality compared with COX-2(+/+) mice following CLP. Mice chimeric for COX-2 exhibited the recipient phenotype, suggesting that epithelial COX-2 expression in the ileum attenuates bacteremia following CLP. Absence of COX-2 significantly increased epithelial permeability of the ileum and reduced expression of the tight junction proteins zonula occludens-1, occludin, and claudin-1 in the ileum following CLP. Furthermore, PGD(2) attenuated cytokine-induced hyperpermeability and zonula occludens-1 downregulation in NS-398-treated C2BBe1 cells. Our findings reveal that absence of COX-2 is associated with enhanced intestinal epithelial permeability and leads to exaggerated bacterial translocation and increased mortality during peritonitis-induced sepsis. Taken together, our results suggest that epithelial expression of COX-2 in the ileum is a critical modulator of tight junction protein expression and intestinal barrier function during sepsis.

COX-2 inhibition alters the phenotype of tumor-associated macrophages from M2 to M1 in ApcMin/+ mouse polyps

Macrophages are a major component of tumor stroma. Tumor-associated macrophages (TAMs) show anti- (M1) or protumor (M2) functions depending on the cytokine milieu of the tumor microenvironment. Cyclooxygenase-2 (COX-2) is constitutively expressed in a variety of tumors including colorectal cancer. TAMs are known to be a major source of COX-2 in human and mice intestinal tumors. COX-2 inhibitor reduces the number and size of intestinal adenomas in familial adenomatous polyposis patients and Apc(Min/+) mice. Although COX-2 inhibitor is thought to regulate cancer-related inflammation, its effect on TAM phenotype remains unknown. Here, we examined the effects of COX-2 inhibition on TAM phenotype and cytokine expression both in vivo and in vitro. Firstly, the selective COX-2 inhibitor celecoxib changed the TAM phenotype from M2 to M1, in proportion to the reduction in number of Apc(Min/+) mouse polyps. Concomitantly, the expression of M1-related cytokine interfron (IFN)-γ was significantly upregulated by celecoxib, although the M2-related cytokines interleukin (IL)-4, IL-13 and IL-10 were not significantly altered. Secondly, IFN-γ treatment attenuated M2 phenotype of mouse peritoneal macrophages and oriented them to M1 even in the presence of M2-polarizing cytokines such as IL-4, IL-13 and IL-10. Thus, our results suggest that COX-2 inhibition alters TAM phenotype in an IFN-γ-dependent manner and subsequently may reduce intestinal tumor progression.

Suppression of tumorigenesis: modulation of inflammatory cytokines by oral administration of microencapsulated probiotic yogurt formulation

The objective of this study was to examine the ability of a novel microencapsulated probiotic yogurt formulation to suppress the intestinal inflammation. We assessed its anticancer activity by screening interleukin-1, 6, and 12 (IL-1, 6, 12), secretory levels of tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), prostaglandin E(2)  (PGE(2)), and thromboxane B2 in the digesta obtained from the duodenum, jejunum, proximal, and distal segments of the ileum of C57BL/6J-Apc(Min)/J mice. Formulation-receiving animals showed consistently lower proinflammatory cytokines' levels when compared to control group animals receiving empty alginate-poly-L-lysine-alginate (APA) microcapsules suspended in saline. The concentrations of IL-12 found in serum in control and treatment group animals were significant: 46.58 ± 16.96 pg/mL and 158.58 ± 28.56 pg/mL for control and treatment animals, respectively. We determined a significant change in plasma C-reactive protein: 81.04 ± 23.73 ng/mL in control group and 64.21 ± 16.64 ng/mL in treatment group. Western blots showed a 71% downregulation of cyclooxygenase-2 (COX-2) protein in treatment group animals compared to control. These results point to the possibility of using this yogurt formulation in anticancer therapies, in addition to chronic gut diseases such as Crohn's disease, irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD) thanks to its inflammation lowering properties.

p120-catenin is essential for maintenance of barrier function and intestinal homeostasis in mice

Epithelial-cadherin (E-cadherin) is a master organizer of the epithelial phenotype. Its function is regulated in part by p120-catenin (referred to herein as p120), a cytoplasmic binding partner that directly regulates cadherin stability. As it has been suggested that cadherins have a role in inflammatory bowel disease (IBD), we sought to investigate this further by assessing the effect of p120 deficiency in mouse small intestine and colon. p120 conditional KO mice were superficially normal at birth but declined rapidly and died within 21 days. Cell-cell adhesion defects and inflammation led to progressive mucosal erosion and terminal bleeding, similar to what is observed in a dominant-negative cadherin mouse model of IBD. Additionally, selective loss of adherens junctions and accumulation of atypical COX-2-expressing neutrophils in p120-null areas of the colon were observed. To elucidate the mechanism, direct effects of p120 deficiency were assessed in vitro in a polarizing colon cancer cell line. Notably, transepithelial electrical resistance was dramatically reduced, neutrophil binding was increased 30 fold, and levels of COX-2, an enzyme associated with IBD, were markedly increased in neutrophils. Our data suggest that p120 loss disrupts the neonatal intestinal barrier and amplifies neutrophil engagement and that these changes lead to catastrophic inflammation during colonization of the neonatal gut with bacteria and other luminal antigens. Thus, we conclude that p120 has an essential role in barrier function and epithelial homeostasis and survival in the intestine.

Vaccine prevention of cancer: can endogenous antigens be targeted?

This perspective on the report by Beatty et al. in this issue of the journal (beginning on page 438) discusses the prevention of cancer through vaccination strategies that target antigens associated with tumor promotion and progression. Such approaches were first developed for treating cancer. We address cancer vaccination in the context of a mouse model of inflammatory bowel disease expressing MUC1, an epithelial mucin aberrantly expressed during chronic inflammation and in colorectal carcinogenesis, and in a broader context that includes the potential of targeting the tumor microenvironment for immunoprevention in humans. Obstacles in developing effective cancer vaccines, including antigen selection, immunoediting, and tumor-mediated immunosuppression, are also discussed.

The COX-2/PGE2 pathway: key roles in the hallmarks of cancer and adaptation to the tumour microenvironment

It is widely accepted that alterations to cyclooxygenase-2 (COX-2) expression and the abundance of its enzymatic product prostaglandin E(2) (PGE(2)) have key roles in influencing the development of colorectal cancer. Deregulation of the COX-2/PGE(2) pathway appears to affect colorectal tumorigenesis via a number of distinct mechanisms: promoting tumour maintenance and progression, encouraging metastatic spread, and perhaps even participating in tumour initiation. Here, we review the role of COX-2/PGE(2) signalling in colorectal tumorigenesis and highlight its ability to influence the hallmarks of cancer--attributes defined by Hanahan and Weinberg as being requisite for tumorigenesis. In addition, we consider components of the COX-prostaglandin pathway emerging as important regulators of tumorigenesis; namely, the prostanoid (EP) receptors, 15-hydroxyprostaglandin dehydrogenase and the prostaglandin transporter. Finally, based on recent findings, we propose a model for the cellular adaptation to the hypoxic tumour microenvironment that encompasses the interplay between COX-2, hypoxia-inducible factor 1 and dynamic switches in beta-catenin function that fine-tune signalling networks to meet the ever-changing demands of a tumour.

Triptolide inhibits cyclooxygenase-2 and inducible nitric oxide synthase expression in human colon cancer and leukemia cells

Triptolide (TP), a traditional Chinese medicine, has been reported to be effective in the treatment of autoimmune diseases and exerting antineoplastic activity in several human tumor cell lines. This study investigates the antitumor effect of TP in human colon cancer cells (SW114) and myelocytic leukemia (K562), and elucidates the possible molecular mechanism involved. SW114 and K562 cells were treated with different doses of TP (0, 5, 10, 20, or 50 ng/ml). The cell viability was assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT). Results demonstrated that TP inhibited the proliferation of both tumor cell lines in a dose-dependent manner. To further investigate its mechanisms, the products prostaglandin E(2) (PGE(2)) and nitric oxide (NO) were measured by enzyme-linked immunosorbent assay (ELISA). Our data showed that TP strongly inhibited the production of NO and PGE(2). Consistent with these results, the expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) was up-regulated both at the mRNA level and the protein expression level, as shown by real-time RT-PCR and Western blotting. These results indicated that the inhibition of the inflammatory factor COX-2 and iNOS activity could be involved in the antitumor mechanisms of TP.

Polyclonal tumors in the mammalian intestine: are interactions among multiple initiated clones necessary for tumor initiation, growth, and progression?

Studies in both man and mouse indicate that the majority of familial intestinal tumors are polyclonal being composed of cells from at least two distinct progenitors. The formation of polyclonal tumors in the mouse can be explained by short-range interactions between multiple initiated clones within one or two crypt diameters of each other. These clonal interactions might be critical, if not necessary, for initiation, growth, progression, or all three stages of tumorigenesis. This view is diametrically opposed to the widely held view that intestinal tumors are monoclonal and progress by clonal expansion. The data supporting the latter are neither extensive nor definitive. In addition, the results from a recent study indicate that earlier studies of tumor clonality were heavily biased because lineage patches in the intestinal epithelium of humans resulting from X-inactivation are relatively large. Consequently, hundreds of tumors from familial and sporadic cases need to be analyzed to accurately assess tumor clonality. Investigators must keep an open mind regarding the clonality of tumors in the mammalian intestine as new experimental approaches are developed which will eventually provide a definitive answer to this fundamental question in the field of cancer biology.