A specific inducible nitric oxide synthase inhibitor, ONO-1714 attenuates inflammation-related large bowel carcinogenesis in male Apc(Min/+) mice

Dietary Mixed Cereal Grains Ameliorate the Azoxymethane and Dextran Sodium Sulfate-Induced Colonic Carcinogenesis in C57BL/6J Mice

The chemopreventive effects of various mixed cereal grain (MCG) samples on azoxymethane (AOM, 10 mg/kg) and dextran sulfate sodium (DSS, 0.02 g/mL)-induced colorectal cancer (CRC) in C57BL/6J mice were studied. The main MCG preparation consisted of fermented brown rice (FBR), glutinous brown rice, glutinous Sorghum bicolor, glutinous Panicum miliaceum, Coix lacryma-jobi, and black soybean at an appropriate mixing ratio. Other MCG preparations contained rice coated with 5% Phellinus linteus and 5% Curcuma longa (MCG-PC) or 10% Phellinus linteus (MCG-P) or 10% Curcuma longa (MCG-C). Consumption of dietary MCG-PC by CRC mice significantly increased colon length, decreased the ratio of colon weight to length, and reduced the number of colon tumors. Similar effects, although to a lower extent, were observed in CRC mice fed with MCG-P, followed by those fed with MCG-C, MCG, FBR, or white rice. MCG-PC significantly suppressed colonic neoplasia and decreased the levels of various cytokines (tumor necrosis factor: Tnf, interleukin 1 beta: Il1b, interleukin 6: Il6, and interferon gamma: Ifnγ) in serum and colon tissue of the CRC mice. In addition, MCG-PC increased the mRNA expressions of tumor suppressor protein p53 (Tp53) and cyclin-dependent kinase inhibitor 1A (Cdkn1a), activated pro-apoptotic caspase 3 (Casp3), and reduced expressions of both mRNA and protein of inducible nitric oxide synthase 2 (Nos2), prostaglandin-endoperoxide synthase 2 (Ptgs2), and cyclin D1 (Ccnd1) in colon tissue. These findings suggest that compared with other cereal grain preparations, MCG-PC had a greater activity against AOM/DSS-induced CRC by reducing intestinal inflammation and modulating the expression of certain carcinogenesis related factors (Nos2, Ptgs2, Tp53, Cdkn1a, Ccnd1, and Casp3) in colon tissue of CRC mice.

TNF-α antagonist improves oxidative stress and lipid disorders induced by scorpion venom in the intestinal tissue

We previously reported that Androctonus australis hector (Aah) venom induces inflammation in several tissues, however limited information is available on its role in gastrointestinal tract. Here we evaluate the involvement of TNF-α in lipid metabolism in the small intestine after Aah envenomation. To address these issues, NMRI mice (3-month-old) were pre-treated with a TNF-α antagonist, 30 min prior to Aah venom injection. Redox status, cytotoxicity and histopathological changes were analyzed in small intestine 3 and 24 h after Aah injection. Lipid metabolism was evaluated through lipid tolerance test in sera. Lipid content in small intestine was also evaluated at different times after envenomation. Obtained results showed that Aah venom affects the intestinal integrity. This cytotoxicity could be associated with lipid peroxidation and altered or insufficient antioxidant system. These results also highlight the perturbation of lipid absorption in intestine tissue of envenomed mice. The use of TNF-α antagonist prior to Aah venom injection seems to be able to improve lipid profile, oxidative stress and antioxidant activity. These findings suggest that Aah venom induces lipid alterations in the intestinal tissue mechanisms involving of TNF- α.

Inhibition of nuclear factor-κB signaling suppresses Spint1-deletion-induced tumor susceptibility in the ApcMin/+ model

Hepatocyte growth factor activator inhibitor type 1 (HAI-1), encoded by the Spint1 gene, is a membrane-bound serine protease inhibitor expressed on the epithelial cell surface. We have previously reported that the intestine-specific Spint1-deleted ApcMin/+ mice showed accelerated formation of intestinal tumors. In this study, we focused on the role of nuclear factor-κB (NF-κB) signaling in the HAI-1 loss-induced tumor susceptibility. In the HAI-1-deficient intestine, inflammatory cytokines, such as tumor necrosis factor-α and interleukin-6, were upregulated in normal mucosa. Furthermore, increased nuclear translocation of NF-κB was observed in both normal mucosa and tumor tissues of HAI-1-deficient ApcMin/+ intestines, and an NF-κB target gene, such as urokinase-type plasminogen activator, was upregulated in the HAI-1-deficient tumor tissues. Thus, we investigated the effect of dehydroxymethylepoxyquinomicin (DHMEQ), a synthetic inhibitor of NF-κB, on intestinal HAI-1-deficient ApcMin/+ mice. Treatment with DHMEQ reduced the formation of intestinal tumors compared with vehicle control in the HAI-1-deficient ApcMin/+ mice. These results suggested that insufficient HAI-1 function promotes intestinal carcinogenesis by activating NF-κB signaling.

Vancomycin-sensitive bacteria trigger development of colitis-associated colon cancer by attracting neutrophils

Inflammatory bowel disease confers an increased risk of developing colitis-associated colon cancer (CAC). During the active colitis or developing tumor stage, commensal bacteria show dynamic translocation. However, whether alteration of the bacterial composition in the gut causes CAC is still unclear. To clarify the effect of commensal bacteria on CAC development, we employed an azoxymethane (AOM) and dextran sodium sulfate (DSS)-induced murine CAC model treated with or without antibiotics. In addition, we analyzed the effects of antibiotics on infiltration of myeloid cells, colonic inflammatory responses, and colorectal cancer formation. We found that vancomycin treatment dramatically suppressed tumor development. In addition, AOM/DSS treatment greatly induced the infiltration of Gr-1^high/CD11b^high neutrophils to the colon, which led to the production of tumor necrosis factor α and inducible nitric oxide synthase. Vancomycin treatment suppressed the infiltration of neutrophils induced by AOM/DSS. Moreover, vancomycin treatment greatly reduced the colon injury and DNA damage caused by AOM/DSS-induced NO radicals. Our results indicate that vancomycin-sensitive bacteria induced colon inflammation and DNA damage by attracting neutrophils into damaged colon tissue, thus promoting tumor formation.

P53-dependent miRNAs mediate nitric oxide-induced apoptosis in colonic carcinogenesis

Both miRNAs and nitric oxide (NO) play important roles in colonic inflammation and tumorigenesis. Resistance of colonic epithelial cells to apoptosis may contribute to tumor development. We hypothesized that some miRNAs could increase the resistance of colonic cancer cells to nitric oxide-induced apoptotic cell death. Here we show that NO induced apoptosis and stimulated expression of some miRNAs. Loss of p53 not only blocked NO-induced apoptosis but also dramatically inhibited the expression of NO-related miRNAs, such as miR-34, miR-203, and miR-1301. In addition, blockage of p53-dependent miRNAs significantly reduced NO-induced apoptosis. Furthermore, forced expression of these miRNAs rendered HT-29 cells, which are resistant to apoptosis with mutant p53, more sensitive to NO-induced apoptotic cell death. Most interestingly, in a colitis-associated colon cancer mouse model, the level of miRNAs dropped significantly, accompanied by downregulation of p21, which is a key target gene of p53. In human colorectal cancer samples, the expression of miR-34 significantly correlated with the level of inducible nitric oxide synthase (iNOS). We contend that increased NO production may select cells with low levels of p53-dependent miRNAs which contributes to human colonic carcinogenesis and tumor progression.

Inhibitory effects of low-dose aloe-emodin on the development of colorectal tumors in min mice

Aloe-emodin (AE), a natural anthraquinone compound, has been reported to exhibit anticancer activity in various cancer cell lines and anti-inflammatory effects in murine macrophages. In the present study, we investigated the cancer chemopreventive effects of AE in an Apc-deficient Min mouse model. In the first experiment, male Min mice were fed a basal diet or diets containing 5 ppm AE and 10 ppm AE for 12 weeks. The dietary administration of 5 ppm AE significantly reduced the number of colorectal tumors. In a second experiment, we investigated the effects of AE on colitis-related colon carcinogenesis in Min mouse treated with dextran sodium sulfate (DSS). Female Min mice were administered 1% DSS in their drinking water for 7 days. AE was given to mice in their diet at a dose of 5 or 50 ppm for 5 weeks. Feeding with AE significantly reduced the number of colorectal tumors. When proliferation of cells in normal-appearing colonic mucosa was assessed by monoclonal anti-rat Ki-67 antibody (MIB-5) immunohistochemistry in experiments 1 and 2, the AE treatment significantly decreased the mean MIB-5-labeling index. These results suggest that the dietary administration of low-dose AE may have chemopreventive effects against development of colorectal tumors in Min mice, possibly in part by reducing cell proliferation in colorectal mucosa.

Cytokines, angiogenic, and antiangiogenic factors and bioactive lipids in preeclampsia

Preeclampsia is a low-grade systemic inflammatory condition in which oxidative stress and endothelial dysfunction occurs. Plasma levels of soluble receptor for vascular endothelial growth factor (VEGFR)-1, also known as sFlt1 (soluble fms-like tyrosine kinase 1), an antiangiogenic factor have been reported to be elevated in preeclampsia. It was reported that pregnant mice deficient in catechol-O-methyltransferase (COMT) activity show a preeclampsia-like phenotype due to a deficiency or absence of 2-methoxyoestradiol (2-ME), a natural metabolite of estradiol that is elevated during the third trimester of normal human pregnancy. Additionally, autoantibodies (AT1-AAs) that bind and activate the angiotensin II receptor type 1 a (AT1 receptor) also have a role in preeclampsia. None of these abnormalities are consistently seen in all the patients with preeclampsia and some of them are not specific to pregnancy. Preeclampsia could occur due to an imbalance between pro- and antiangiogenic factors. VEGF, an angiogenic factor, is necessary for the transport of polyunsaturated fatty acids (PUFAs) to endothelial cells. Hence reduced VEGF levels decrease the availability of PUFAs to endothelial cells. This leads to a decrease in the formation of anti-inflammatory and angiogenic factors: lipoxins, resolvins, protectins, and maresins from PUFAs. Lipoxins, resolvins, protectins, maresins, and PUFAs suppress insulin resistance; activation of leukocytes, platelets, and macrophages; production of interleukin-6 and tumor necrosis factor-α; and oxidative stress and endothelial dysfunction; and enhance production of prostacyclin and nitric oxide (NO). Estrogen enhances the formation of lipoxin A4 and NO. PUFAs also augment the production of NO and inhibit the activity of angiotensin-converting enzyme and antagonize the actions of angiotensin II. Thus, PUFAs can prevent activation of angiotensin II receptor type 1 a (AT1 receptor). Patients with preeclampsia have decreased plasma phospholipid concentrations of arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), the precursors of lipoxins (from AA), resolvins (from EPA and DHA), and protectins (from DHA) and prostaglandin E1 (PGE1 from DGLA: dihomo-γ-linolenic acid) and prostacyclin (PGI2 derived from AA). Based on these evidences, it is proposed that preeclampsia may occur due to deficiency of PUFAs and their anti-inflammatory products: lipoxins, resolvins, protectins, and maresins.

Chemistry meets biology in colitis-associated carcinogenesis

The intestine comprises an exceptional venue for a dynamic and complex interplay of numerous chemical and biological processes. Here, multiple chemical and biological systems, including the intestinal tissue itself, its associated immune system, the gut microbiota, xenobiotics, and metabolites meet and interact to form a sophisticated and tightly regulated state of tissue homoeostasis. Disturbance of this homeostasis can cause inflammatory bowel disease (IBD)-a chronic disease of multifactorial etiology that is strongly associated with increased risk for cancer development. This review addresses recent developments in research into chemical and biological mechanisms underlying the etiology of inflammation-induced colon cancer. Beginning with a general overview of reactive chemical species generated during colonic inflammation, the mechanistic interplay between chemical and biological mediators of inflammation, the role of genetic toxicology, and microbial pathogenesis in disease development are discussed. When possible, we systematically compare evidence from studies utilizing human IBD patients with experimental investigations in mice. The comparison reveals that many strong pathological and mechanistic correlates exist between mouse models of colitis-associated cancer, and the clinically relevant situation in humans. We also summarize several emerging issues in the field, such as the carcinogenic potential of novel inflammation-related DNA adducts and genotoxic microbial factors, the systemic dimension of inflammation-induced genotoxicity, and the complex role of genome maintenance mechanisms during these processes. Taken together, current evidence points to the induction of genetic and epigenetic alterations by chemical and biological inflammatory stimuli ultimately leading to cancer formation.

Rodent intestinal epithelial carcinogenesis: pathology and preclinical models

Colon cancer is a major human malignancy that afflicts millions of people throughout the world each year. Genetics and diet play large roles in colon carcinogenesis although chemicals may also contribute. For the past 40 years, scientists have studied experimentally induced intestinal carcinogenesis in rodents in order to elucidate the etiology and mechanisms involved. Comparative histopathology has revealed many similarities of rodent and human intestinal cancers. Comparative molecular pathology has also shown genetic similarities. More recently, genetically engineered mice and inflammatory colon cancer models have been used for investigating mechanisms and potential chemopreventive and treatment modalities. This review will focus on comparative histopathology and nonclinical models.

Mast cells and inflammation-associated colorectal carcinogenesis

Close association between chronic inflammation and cancer has been recently highlighted. Indeed, inflammatory bowel disease (IBD) has been strongly linked with an increased risk of development of colorectal cancer (CRC). Inflammatory cell-produced inflammatory mediators, such as proinflammatory cytokines and inducible enzymes, contribute to this association. In an inflammatory microenvironment, infiltrating macrophages and mast cells mediate production of these inflammatory mediators to promote growth of tumors in target tissues. In contrast to macrophages, contribution of mast cells to CRC development in inflamed colon is not well understood. This study aimed to determine the role of mast cells in inflammation-associated colorectal carcinogenesis. CRC was induced by administration of the colonic carcinogen, azoxymethane (AOM), and the tumor promoter dextran sodium sulfate (DSS) in male mast cell-deficient WBBF(1)-kit (W/W-v) (W/W(v)) and mast cell-normal WBB6F(1)-+/+(WT) mice. At week 12, the W/W(v) mice had markedly lower inflammation scores in the colon when compared with WT mice. The mRNA levels of colonic proinflammatory cytokines and inducible enzymes were also decreased in W/W(V) mice at weeks 12 and 20, when compared with WT counterparts. Colorectal tumors, including CRC, were identified by histopathological analysis performed 20 weeks thereafter. Importantly, there were less neoplastic and preneoplastic colonic lesions in the W/W(v) mice compared with the WT mice. Thus, for the first time, our study shows that mice lacking mast cells are less susceptible to inflammation-associated colorectal carcinogenesis. Our findings also suggest that mast cells and their selected cytokines could play an important role in inflammation-mediated tumorigenesis through regulation of proinflammatory cytokines and inducible inflammatory enzymes.

Chronic epithelial NF-κB activation accelerates APC loss and intestinal tumor initiation through iNOS up-regulation

The role of NF-κB activation in tumor initiation has not been thoroughly investigated. We generated Ikkβ(EE)(IEC) transgenic mice expressing constitutively active IκB kinase β (IKKβ) in intestinal epithelial cells (IECs). Despite absence of destructive colonic inflammation, Ikkβ(EE)(IEC) mice developed intestinal tumors after a long latency. However, when crossed to mice with IEC-specific allelic deletion of the adenomatous polyposis coli (Apc) tumor suppressor locus, Ikkβ(EE)(IEC) mice exhibited more β-catenin(+) early lesions and visible small intestinal and colonic tumors relative to Apc(+/ΔIEC) mice, and their survival was severely compromised. IEC of Ikkβ(EE)(IEC) mice expressed high amounts of inducible nitric oxide synthase (iNOS) and elevated DNA damage markers and contained more oxidative DNA lesions. Treatment of Ikkβ(EE)(IEC)/Apc(+/ΔIEC) mice with an iNOS inhibitor decreased DNA damage markers and reduced early β-catenin(+) lesions and tumor load. The results suggest that persistent NF-κB activation in IEC may accelerate loss of heterozygocity by enhancing nitrosative DNA damage.

Preclinical cancer chemoprevention studies using animal model of inflammation-associated colorectal carcinogenesis

Inflammation is involved in all stages of carcinogenesis. Inflammatory bowel disease, such as ulcerative colitis and Crohn’s disease is a longstanding inflammatory disease of intestine with increased risk for colorectal cancer (CRC). Several molecular events involved in chronic inflammatory process are reported to contribute to multi-step carcinogenesis of CRC in the inflamed colon. They include over-production of free radicals, reactive oxygen and nitrogen species, up-regulation of inflammatory enzymes in arachidonic acid biosynthesis pathway, up-regulation of certain cytokines, and intestinal immune system dysfunction. In this article, firstly I briefly introduce our experimental animal models where colorectal neoplasms rapidly develop in the inflamed colorectum. Secondary, data on preclinical cancer chemoprevention studies of inflammation-associated colon carcinogenesis by morin, bezafibrate, and valproic acid, using this novel inflammation-related colorectal carcinogenesis model is described.

Emerging avenues linking inflammation and cancer

The role of inflammation in carcinogenesis has been extensively investigated and well documented. Many biochemical processes that are altered during chronic inflammation have been implicated in tumorigenesis. These include shifting cellular redox balance toward oxidative stress; induction of genomic instability; increased DNA damage; stimulation of cell proliferation, metastasis, and angiogenesis; deregulation of cellular epigenetic control of gene expression; and inappropriate epithelial-to-mesenchymal transition. A wide array of proinflammatory cytokines, prostaglandins, nitric oxide, and matricellular proteins are closely involved in premalignant and malignant conversion of cells in a background of chronic inflammation. Inappropriate transcription of genes encoding inflammatory mediators, survival factors, and angiogenic and metastatic proteins is the key molecular event in linking inflammation and cancer. Aberrant cell signaling pathways comprising various kinases and their downstream transcription factors have been identified as the major contributors in abnormal gene expression associated with inflammation-driven carcinogenesis. The posttranscriptional regulation of gene expression by microRNAs also provides the molecular basis for linking inflammation to cancer. This review highlights the multifaceted role of inflammation in carcinogenesis in the context of altered cellular redox signaling.

Development of an inflammation-associated colorectal cancer model and its application for research on carcinogenesis and chemoprevention

Chronic inflammation is a well-recognized risk factor for development of human cancer in several tissues, including large bowel. Inflammatory bowel disease, including ulcerative colitis and Crohn's disease, is a longstanding inflammatory disease of intestine with increased risk for colorectal cancer development. Several molecular events involved in chronic inflammatory process may contribute to multistep carcinogenesis of human colorectal cancer in the inflamed colon. They include overproduction of reactive oxygen and nitrogen species, overproduction and upregulation of productions and enzymes of arachidonic acid biosynthesis pathway and cytokines, and intestinal immune system dysfunction. In this paper, I will describe several methods to induce colorectal neoplasm in the inflamed colon. First, I will introduce a protocol of a novel inflammation-associated colon carcinogenesis in mice. In addition, powerful tumor-promotion/progression activity of dextran sodium sulfate in the large bowel of Apc^Min/+ mice will be described. Finally, chemoprevention of inflammation-associated colon carcinogenesis will be mentioned.

Role of different inflammatory and tumor biomarkers in the development of ulcerative colitis-associated carcinogenesis

BACKGROUND

Colorectal cancer (CRC) is the most severe complication in inflammatory bowel disease (IBD). In the present study we investigated different mechanistic links between chronic colonic inflammation and its progression to adenocarcinoma. Along these lines, given that adrenomedullin (AM) has been implicated in carcinogenesis, we also analyzed changes in its colonic expression.

METHODS

Mice were exposed to 5, 10, and 15 cycles of dextran sulfate sodium (DSS); each cycle consisted of 0.7% DSS for 1 week followed by distilled water for 10 days. After each period, macroscopic and histological studies, as well as characterization of inflammatory and tumor biomarkers, were carried out.

RESULTS

The disease activity index (DAI) showed that the disease was present from the third cycle and it gradually increased during the course of DSS treatment. Macroscopic tumors were only seen after 15 cycles, and microscopic study showed that inflammation, dysplasia, and adenocarcinomas correlated with DSS cycles. β-Catenin and proliferating cell nuclear antigen expressions progressively increased in animals treated with the different cycles of DSS. TNF-α and IFN-γ showed the highest production at the tenth cycle. COX-2, mPGES-1, and iNOS levels were also appreciably higher at the fifth and tenth cycles. Moreover, we observed a progressive enhancement in AM expression and changes in its intracellular location during the progression of the disease.

CONCLUSIONS

Our results show an early induction of proinflammatory factors, which may contribute to the development of colon cancer, as well as demonstrate, for the first time, the expression of AM in IBD-derived CRC.

Sodium taurocholate inhibits intestinal adenoma formation in APCMin/+ mice, potentially through activation of the farnesoid X receptor

In light of clinical and biological evidence that bile constituents exert preventive effects against colorectal cancer, we evaluated the influence of oral bilirubin and sodium taurocholate (NaTC) on intestinal tumor formation in APC(Min/+) mice. Mice received bilirubin and/or bovine serum albumin (BSA) and NaTC in the drinking water for 8 weeks, after which the number, size and location of intestinal adenomas were determined. Tissue specimens were analyzed by light microscopy, TUNEL staining, immunohistochemistry for beta-catenin and Ki-67 and quantitative polymerase chain reaction for farnesoid X receptor (FXR)-dependent gene expression. Colon tumor formation also was assessed in azoxymethane (AOM)-treated hyperbilirubinemic Gunn (j/j) and wild-type (+/+) rats. Compared with untreated APC(Min/+) mice, the mean number of intestinal adenomas was markedly lower in both bilirubin (10.5 +/- 0.9 versus 37.0 +/- 5.2; +/-SEM; P < 0.001) and NaTC plus BSA (14.3 +/- 5.4; P = 0.01)-treated animals. Both treatment groups exhibited reduced levels of cellular proliferation in the ileum (by Ki-67 staining), but no differences in TUNEL staining or the percentage of beta-catenin-positive crypts. Bilirubin feeding reduced intestinal inducible nitric oxide synthase expression, but did not alter adenoma multiplicity in APC(Min/+) mice or in AOM-treated j/j versus +/+ rats. Mice receiving NaTC manifested increased intestinal expression of the FXR-regulated genes, Shp, FGF15 and IBABP, and a concomitant decrease in cyclin D1 message. Administering NaTC to APC(Min/+) mice causes a marked reduction in intestinal adenomas. We postulate that this effect is mediated through activation of FXR, leading to increased Shp expression and consequent downregulation of cyclin D1.

Expression profiles of proliferative and antiapoptotic genes in sporadic and colitis-related mouse colon cancer models

Elevated levels of survivin, telomerase catalytic subunit (TERT), integrin-linked kinase (ILK), cyclooxygenase 2 (COX-2), inducible nitric oxide synthase (iNOS) and the regulatory factors c-MYB and Tcf-4 are often found in human cancers including colorectal cancer (CRC) and have been implicated in the development and progression of tumorigenesis. The aim of this study was to determine the expression of these genes in mouse models of sporadic and colitis-associated CRC. To address these issues, we used qRT-PCR approach to determine changes in gene expression patterns of neoplastic cells (high-grade dysplasia/intramucosal carcinoma) and surrounding normal epithelial cells in A/J and ICR mouse strains using laser microdissection. Both strains were injected with azoxymethane and ICR mice were also given drinking water that contained 2% dextran sodium sulphate. In both sporadic (A/J mice) and colitis-associated (ICR mice) models of CRC, the levels of TERT mRNA, COX-2 mRNA and Tcf-4 mRNA were higher in neoplastic cells than in surrounding normal epithelial cells. In contrast, survivin mRNA was upregulated only in neoplastic cells from A/J mice and ILK mRNA was upregulated only in neoplastic cells from ICR mice. However, the expression of iNOS mRNA was similar in normal and neoplastic cells in both models and c-MYB mRNA was actually downregulated in neoplastic cells compared with normal cells in both models. These findings suggest that the genetic background and/or the molecular mechanisms of tumorigenesis associated with genotoxic insults and colonic inflammation influence the gene expression of mTERT, COX-2, Tcf-4, c-MYB, ILK and survivin in colon epithelial neoplasia.

Citrus compounds inhibit inflammation- and obesity-related colon carcinogenesis in mice

Dietary polyphenols are important potential chemopreventive natural agents. Other agents, such as citrus compounds, are also candidates for cancer chemopreventives. They act on multiple key elements in signal transduction pathways related to cellular proliferation, differentiation, apoptosis, inflammation, and obesity. This short review article provides our findings of preclinical studies on potential chemopreventive activities of dietary citrus compounds, auraptene, collinin, and citrus unshiu segment membrane (CUSM), using clitis- and obesity-related colon tumorigenesis models. Dietary feeding with auraptene and collinin at dose levels of 0.01% and 0.05% significantly lowered the incidence (50-60% reduction) and multiplicity (67-80% reduction) of colonic adenocarcinomas induced by azoxymetahene [AOM, single intraperitoneal injection of 10 mg/kg body weight (bw)] and dextran sodium sulfate (1% in drinking water). Anti-inflammatory potency of aurapene and collinin may contribute to the effects. Administration with CUSM at 3 doses in diet significantly inhibited development of aberrant crypts foci induced by 5 weekly subcutaneous injections of AOM (15 mg/kg bw) in male db/db mice: 53% inhibition by 0.02% CUSM, 54% inhibition by 0.1% CUSM, and 59% inhibition by 0.5% CUSM. CUSM treatment also decreased serum level of triglycerides. Our findings suggest that certain citrus materials are capable of inhibiting clitis- and obesity-related colon carcinogenesis.

Chemopreventive effects of the standardized extract (DA-9601) of Artemisia asiatica on azoxymethane-initiated and dextran sulfate sodium-promoted mouse colon carcinogenesis

Dextran sulfate sodium (DSS) administration has been reported to cause inflammation in mouse colonic mucosa, which promotes colon carcinogenesis. When male ICR mice were treated with a single intraperitoneal dose (10 mg/kg body weight) of azoxymethane (AOM) followed by 2.5% DSS in drinking water for 7 consecutive days, all developed tumors at the 16th wk, mostly in the distal colon. Cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were markedly upregulated in the AOM-initiated and DSS-promoted colon tumors. The DNA binding activity of nuclear factor-kappaB (NF-kappa B) was also elevated in the colon tumors. In this study, we examined the chemopreventive effects of the standardized extract (DA-9601) of Artemisia asiatica that has been used in the traditional herbal medicine for the treatment of inflammatory disorders. Mice fed the chow diet containing 10% DA-9601 for 15 wk following DSS treatment displayed the significantly lower multiplicity of colon tumors. DA-9601 treatment suppressed the expression of COX-2 and iNOS as well as NF-kappa B DNA binding in the colonic tissues. It also downregulated the phosphorylation of extracellular, signal-regulated protein kinase and p38 mitogen-activated protein kinase that are upstream of NF-kappa B. Furthermore, DA-9601 reduced expression of beta-catenin in colonic mucosa of mice challenged with AOM plus DSS.

Increased expression of inducible nitric oxide synthase (iNOS) in N-nitrosobis(2-oxopropyl)amine-induced hamster pancreatic carcinogenesis and prevention of cancer development by ONO-1714, an iNOS inhibitor

Elevated protein expression of inducible nitric oxide synthase (iNOS) has been observed in human pancreatic cancers and therefore, iNOS may play important roles in pancreatic carcinogenesis. This was examined in the present study, using an experimental model with N-nitrosobis(2-oxopropyl)amine (BOP)-treated hamsters. Reverse transcription-polymerase chain reaction analysis demonstrated iNOS expression in a hamster pancreatic cancer cell line as well as in human pancreatic cancer cell lines. Immunohistochemical analysis revealed increased expression of iNOS protein in atypical hyperplasia and ductal adenocarcinomas of the pancreas in BOP-treated hamsters. In addition, iNOS expression was also observed in macrophages and islet cells in pancreatic tissue surrounding tumors. In order to assess the role of iNOS expression in carcinogenesis in the pancreas, the effects of ONO-1714 [(1S, 5S, 6R, 7R)-7-chloro-3-imino-5-methyl-2-azabicyclo[4.1.0]heptane], an iNOS inhibitor, on hamster pancreatic ductal carcinogenesis were investigated. Female Syrian golden hamsters were treated with BOP at 10 mg/kg body wt, four times for 1 week, and 1 week after the last carcinogen treatment, ONO-1714 was administered at doses of 100 and 200 p.p.m. in the diet for 15 weeks. The incidences and multiplicities of atypical hyperplasia and invasive adenocarcinoma and total adenocarcinomas (non-invasive and invasive adenocarcinomas) in the pancreas were significantly lowered by treatment with 200 p.p.m. ONO-1714. Treatment with 100 p.p.m. ONO-1714 also significantly decreased the multiplicities of invasive and total adenocarcinomas. Moreover, treatment with 200 p.p.m. ONO-1714 reduced the number of BOP-induced cholangiocellular tumors. These results suggest that iNOS plays roles in promoting pancreatic carcinogenesis in both early and late stages in hamsters.

Cancer chemopreventive and therapeutic potential of resveratrol: mechanistic perspectives

A plant kingdom is considered as a gold mine for the discovery of many biologically active substances with therapeutic values. Resveratrol (3,5,4'-trihydroxystilbene), a naturally occurring polyphenol, exhibits pleiotropic health beneficial effects including anti-oxidant, anti-inflammatory, cardioprotective and anti-tumor activities. Currently, numerous preclinical findings suggest resveratrol as a promising nature's arsenal for cancer prevention and treatment. A remarkable progress in dissecting the molecular mechanisms underlying anti-cancer properties of resveratrol has been achieved in the past decade. As a potential anti-cancer agent, resveratrol has been shown to inhibit or retard the growth of various cancer cells in culture and implanted tumors in vivo. The compound significantly inhibits experimental tumorigenesis in a wide range of animal models. Resveratrol targets many components of intracellular signaling pathways including pro-inflammatory mediators, regulators of cell survival and apoptosis, and tumor angiogenic and metastatic switches by modulating a distinct set of upstream kinases, transcription factors and their regulators. This review summarizes the diverse molecular targets of resveratrol with a special focus on those involved in fine-tuning of orchestrated intracellular signal transduction.