Colorectal carcinoma development in inducible nitric oxide synthase-deficient mice with dextran sulfate sodium-induced ulcerative colitis

Investigation of TLR2 (-196 to -174del) and TLR9 (T-1486C) Gene Polymorphisms Association with Inflammatory Bowel Diseases

BACKGROUND

Inflammatory bowel diseases (IBD), Crohn's disease (CD), and ulcerative colitis (UC) are diseases that result from the combined effects of a predisposing genetic background and several environmental factors, including smoking. Some genes can influence these diseases through genetic inheritance, and their regulation is explained by gene polymorphism. However, Toll-like receptor (TLR) genes have been identified as susceptibility genes for CD and UC.

METHODS

A case-control study was performed on a Turkish population composed of 105 healthy controls and  79 CD, 77 UC patients genotyped by Allele-specific PCR and PCR-RFLP for TLR9 (T-1486C) and TLR 2 (-196 to -174del) gene. Genotype and allele frequencies of TLR9 (T-1486C) and TLR 2 (-196 to -174del) gene polymorphisms compared to allele frequencies in CD and UC patients.

RESULTS

No statistically significant findings were found between the CD, UC patients, and the control group in terms of both genotype distributions and allele frequencies for TLR 9 (T-1486C; rs187084) and TLR 2 (-196 to -174del; rs111200466) gene polymorphisms in a Turkish population (P > 0.05).

CONCLUSION

No association was found between the TLR2 (rs111200466) and TLR 9 (rs187084) gene polymorphisms among IBD patients and the control groups in the Turkish population.

Mechanism of Fructus Mume Pills Underlying Their Protective Effects in Rats with Acetic Acid-Inducedulcerative Colitis via the Regulation of Inflammatory Cytokines and the VEGF-PI3K/Akt-eNOS Signaling Pathway

Background

Fructus mume pills (FMPs) have been clinically proven to be effective for treating ulcerative colitis (UC). However, the therapeutic and protective mechanisms have not been fully studied.

Aim

We aimed to explore the mechanism of FMPs in an acetic acid (AA)-induced ulcerative colitis rat model.

Methods

The targets, GO terms, and KEGG pathways for the FMPs and UC were screened and constructed using network pharmacology. A possible mechanism was verified in a 4% AA-induced colitis rat model. Colitis activity and state were evaluated using the disease activity index, and colon ulceration and intestinal mucosal damage were determined by histopathological observation through HE, AB-PAS, and Masson pathological staining. The concentrations of TNF-α, IL-6, IL-8, IL-10, MPO, MMP9, CXCR1, eNOS, and VEGF were measured to evaluate vascular permeability effects.

Results

The network pharmacology results showed 108 active compounds, and 139 FMP-related targets were identified. Twenty-nine targets were identified for FMPs against UC, which included MMP9, MMP3, ESR1, PTGS1, PPARA, MPO, and NOS2. A total of 1,536 GO terms and 41 pathways were associated with FMP treatment of UC. The pharmacological evaluation showed that FMPs attenuated inflammation in AA-induced colitis by reducing the serum concentrations of TNF-α, IL-6, IL-8, and IL-10 and the colonic concentrations of MPO, MMP9, and CXCR1. FMPs ameliorated hyperpermeability by reducing the colonic VEGF and eNOS concentrations. FMPs also significantly decreased the VEGFA, VEGFR2, Src, and eNOS protein expressions in colon tissue through the VEGF-PI3K/Akt-eNOS signaling pathway.

Conclusion

These results suggest that FMPs control UC inflammation by regulating inflammatory cytokine concentrations. FMPs alleviate AA-induced UC by regulating microvascular permeability through the VEGF-PI3K/Akt-eNOS signaling pathway.

Recruitment of M1 Macrophages May Not Be Critical for Protection against Colitis-Associated Tumorigenesis

A close connection between inflammation and the risk of developing colon cancer has been suggested in the last few years. It has been estimated that patients diagnosed with some types of inflammatory bowel disease, such as ulcerative colitis or Crohn's disease, have up to a 30% increased risk of developing colon cancer. However, there is also evidence showing that the activation of anti-inflammatory pathways, such as the IL-4 receptor-mediated pathway, may favor the development of colon tumors. Using an experimental model of colitis-associated colon cancer (CAC), we found that the decrease in tumor development in global IL4Rα knockout mice (IL4RαKO) was apparently associated with an inflammatory response mediated by the infiltration of M1 macrophages (F480+TLR2+STAT1+) and iNOS expression in colon tissue. However, when we developed mice with a specific deletion of IL4Rα in macrophages (LysMcreIL4Rα-/lox mice) and subjected them to CAC, it was found that despite presenting a large infiltration of M1 macrophages into the colon, these mice were as susceptible to colon-tumorigenesis as WT mice. These data suggest that in the tumor microenvironment the absence of IL4Rα expression on macrophages, as well as the recruitment of M1 macrophages, may not be directly associated with resistance to developing colon tumors. Therefore, it is possible that IL4Rα expression in other cell types, such as colonic epithelial cells, could have an important role in promoting the development of colitis-associated colon tumorigenesis.

Brusatol-Enriched Brucea javanica Oil Ameliorated Dextran Sulfate Sodium-Induced Colitis in Mice: Involvement of NF-κB and RhoA/ROCK Signaling Pathways

Brucea javanica oil (BJO) is beneficial for the treatment of ulcerative colitis (UC), and that quassinoids in particular brusatol are bioactive components. However, it is still uncertain whether or not other components in BJO, such as oleic acid and fatty acids, have an anti-UC effect. The present study is aimed at comparing the anti-UC effects between brusatol-enriched BJO (BE-BJO) and brusatol-free BJO (BF-BJO) and at exploring the effects and mechanisms of BE-BJO on colon inflammation and intestinal epithelial barrier function. Balb/C mice received 3% (wt/vol) DSS for one week to establish the UC model. Different doses of BE-BJO, BF-BJO, or BJO were treated. The result illustrated that BE-BJO alleviated DSS-induced loss of body weight, an increase of disease activity index (DAI), and a shortening of colon, whereas BF-BJO did not have these protective effects. BE-BJO treatment improved the morphology of colon tissue, inhibited the production and release of TNF-α, IFN-γ, IL-6, and IL-1β in the colon tissue, and reversed the decreased expressions of ZO-1, occludin, claudin-1, and E-cadherin induced by DSS but augmented claudin-2 expression. Mechanistically, BE-BJO repressed phosphorylation of NF-κB subunit p65, suppressed RhoA activation, downregulated ROCK, and prevented phosphorylation of myosin light chain (MLC) in DSS-treated mice, indicating that the protective effect of BE-BJO is attributed to suppression of NF-κB and RhoA/ROCK signaling pathways. These findings confirm that brusatol is an active component from BJO in the treatment of UC.

Melatonin-loaded chitosan nanoparticles endows nitric oxide synthase 2 mediated anti-inflammatory activity in inflammatory bowel disease model

Inflammatory Bowel Disease (IBD) is a complex inflammatory condition arising due to interactions of environmental and genetic factors that lead to dysregulated immune response and inflammation in intestine. Complementary and alternative medicine approaches have been utilized to treat IBD. However, chronic inflammatory diseases are not medically curable. Hence, potent anti-inflammatory therapeutic agents are urgently warranted. Melatonin has emerged as a potent anti-inflammatory and neuroprotective candidate. Although, it's therapeutic efficacy is compromised due to less solubility and rapid clearance. Hence, we have synthesized melatonin loaded chitosan nanoparticle (Mel-CSNPs) to improve drug release profile and evaluate its in-vitro and in-vivo therapeutic efficacy. Mel-CSNPs exhibited better anti-inflammatory response in an in-vitro and in-vivo IBD model. Significant anti-inflammatory activity of Mel-CSNPs is attributed to nitric oxide (NO) reduction, inhibited nuclear translocation of NF-kB p65 and reduced IL-1β and IL-6 expression. In-vivo biodistribution study has shown a good distribution profile. Effective in-vivo therapeutic efficiency of Mel-CSNPs has been confirmed with reduced disease activity index parameters and inhibited neutrophilic infiltration. Histological evaluation has further proved the protective effect of Mel-CSNPs by preventing crypt damage and immune cells infiltration against Dextran Sodium Sulphate induced insults. Immuno-histochemical analysis has confirmed anti-inflammatory action of Mel-CSNPs with reduction of inflammatory markers, Nitric Oxide Synthase-2 (NOS2) and Nitro-tyrosine. Indeed, this study divulges anti-inflammatory activity of Mel-CSNPs by improving the therapeutic potential of melatonin.

Protease-activated receptor 2 signaling modulates susceptibility of colonic epithelium to injury through stabilization of YAP in vivo

Hippo signaling plays critical roles in intestinal regeneration. However, the mechanisms which regulate its activity in vivo are largely unknown. We hypothesize that protease-activated receptor 2 (PAR2) signaling, which could be activated by trypsin, might affect YAP activity in the setting of tissue damage and regeneration. It is found that knockout of PAR2 severely aggravates the mucosal damage induced by dextran sodium sulfate (DSS) in mouse, which correlated with notable repression of YAP protein in colonic epithelial cells. Although the cytokine expression is reduced, the damage of colonic crypt is more severe after DSS-induced colitis in PAR2-/- mouse. In vitro, PAR2 activation causes the accumulation of YAP, while knockdown of PAR2 with shRNA dramatically represses the expression of YAP protein in different intestinal epithelial cell lines. Moreover, forced expression of YAP significantly reduces the production of reactive oxygen species (ROS) and the sensitivity to nitric oxide-induced apoptosis in PAR2-deficient condition. Further studies show that PAR2 signaling stabilizes YAP protein but independent of Lats. Nevertheless PAR2 activation increased the binding of YAP with protein phosphatase PP1. Inhibition of PP1 with specific siRNA blocked PAR2-induced dephosphorylation of YAP. Taken together, PAR2 signaling might modulate susceptibility of colonic epithelium to injury through stabilization of YAP.

Interleukin-22 drives nitric oxide-dependent DNA damage and dysplasia in a murine model of colitis-associated cancer

The risk of colon cancer is increased in patients with Crohn's disease and ulcerative colitis. Inflammation-induced DNA damage could be an important link between inflammation and cancer, although the pathways that link inflammation and DNA damage are incompletely defined. RAG2-deficient mice infected with Helicobacter hepaticus (Hh) develop colitis that progresses to lower bowel cancer. This process depends on nitric oxide (NO), a molecule with known mutagenic potential. We have previously hypothesized that production of NO by macrophages could be essential for Hh-driven carcinogenesis, however, whether Hh infection induces DNA damage in this model and whether this depends on NO has not been determined. Here we demonstrate that Hh infection of RAG2-deficient mice rapidly induces expression of iNOS and the development of DNA double-stranded breaks (DSBs) specifically in proliferating crypt epithelial cells. Generation of DSBs depended on iNOS activity, and further, induction of iNOS, the generation of DSBs, and the subsequent development of dysplasia were inhibited by depletion of the Hh-induced cytokine IL-22. These results demonstrate a strong association between Hh-induced DNA damage and the development of dysplasia, and further suggest that IL-22-dependent induction of iNOS within crypt epithelial cells rather than macrophages is a driving force in this process.

Increased sensitivity of African American triple negative breast cancer cells to nitric oxide-induced mitochondria-mediated apoptosis

Background

Breast cancer is a complex heterogeneous disease where many distinct subtypes are found. Younger African American (AA) women often present themselves with aggressive form of breast cancer with unique biology which is very difficult to treat. Better understanding the biology of AA breast tumors could lead to development of effective treatment strategies. Our previous studies indicate that AA but not Caucasian (CA) triple negative (TN) breast cancer cells were sensitive to nitrosative stress-induced cell death. In this study, we elucidate possible mechanisms that contribute to nitric oxide (NO)-induced apoptosis in AA TN breast cancer cells.

Methods

Breast cancer cells were treated with various concentrations of long-acting NO donor, DETA-NONOate and cell viability was determined by trypan blue exclusion assay. Apoptosis was determined by TUNEL and caspase 3 activity as well as changes in mitochondrial membrane potential. Caspase 3 and Bax cleavage, levels of Cu/Zn superoxide dismutase (SOD) and Mn SOD was assessed by immunoblot analysis. Inhibition of Bax cleavage by Calpain inhibitor, and levels of reactive oxygen species (ROS) as well as SOD activity was measured in NO-induced apoptosis. In vitro and in vivo effect of NO treatment on mammary cancer stem cells (MCSCs) was assessed.

Results and discussion

NO induced mitocondria-mediated apoptosis in all AA but not in CA TN breast cancer cells. We found significant TUNEL-positive cells, cleavage of Bax and caspase-3 activation as well as depolarization mitochondrial membrane potential only in AA TN breast cancer cells exposed to NO. Inhibition of Bax cleavage and quenching of ROS partially inhibited NO-induced apoptosis in AA TN cells. Increase in ROS coincided with reduction in SOD activity in AA TN breast cancer cells. Furthermore, NO treatment of AA TN breast cancer cells dramatically reduced aldehyde dehydrogenase1 (ALDH1) expressing MCSCs and xenograft formation but not in breast cancer cells from CA origin.

Conclusions

Ethnic differences in breast tumors dictate a need for tailoring treatment options more suited to the unique biology of the disease.

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.

Monocolonization of germ-free mice with Bacteroides fragilis protects against dextran sulfate sodium-induced acute colitis

Ulcerative colitis is inflammatory conditions of the colon caused by interplay of genetic and environmental factors. Previous studies indicated that the gut microflora may be involved in the colonic inflammation. Bacteroides fragilis (BF) is a Gram-negative anaerobe belonging to the colonic symbiotic. We aimed to investigate the protective role of BF in a colitis model induced in germ-free (GF) mice by dextran sulfate sodium (DSS). GF C57BL/6JNarl mice were colonized with BF for 28 days before acute colitis was induced by DSS. BF colonization significantly increased animal survival by 40%, with less reduction in colon length, and decreased infiltration of inflammatory cells (macrophages and neutrophils) in colon mucosa following challenge with DSS. In addition, BF could enhance the mRNA expression of anti-inflammatory-related cytokine such as interleukin 10 (IL-10) with polymorphism cytokine IL-17 and diminish that of proinflammatory-related tumor necrosis factor α with inducible nitric oxide synthase in the ulcerated colon. Myeloperoxidase activity was also decreased in BF-DSS mice. Taking these together, the BF colonization significantly ameliorated DSS-induced colitis by suppressing the activity of inflammatory-related molecules and inducing the production of anti-inflammatory cytokines. BF may play an important role in maintaining intestinal immune system homeostasis and regulate inflammatory responses.

Soluble epoxide hydrolase deficiency inhibits dextran sulfate sodium-induced colitis and carcinogenesis in mice

Soluble epoxide hydrolase (sEH) hydrolyses/inactivates anti-inflammatory epoxyeicosatrienoic acids (EETs) to their corresponding diols, and targeting sEH leads to strong anti-inflammatory effects. In the present study, using a tissue microarray and immunohistochemical approach, a significant increase of sEH expression was identified in ulcerative colitis (UC)-associated dysplasia and adenocarcinoma. The effects of deficiency in the sEH gene were determined on dextran sulfate sodium (DSS) colitis-induced carcinogenesis. The effects of EETs on lipopolysaccharide (LPS)-activated macrophages were analyzed in vitro. With extensive histopathological and immunohistochemical analyses, compared to wild-type mice, sEH(-/-) mice exhibited a significant decrease in tumor incidence (13/20 vs. 6/19, p<0.05) and a markedly reduced average tumor size (59.62±20.91 mm(3) vs. 22.42±11.22 mm(3)), and a significant number of pre-cancerous dysplasia (3±1.18 vs. 2±0.83, p<0.01). The inflammatory activity, as measured by the extent/proportion of erosion/ulceration/dense lymphoplasmacytosis (called active colitis index) in the colon, was significantly lower in sEH(-/-) mice (44.7%±24.9% vs. 20.2%±16.2%, p<0.01). The quantitative polymerase chain reaction (qPCR) assays demonstrated significantly low levels of cytokines/chemokines including monocyte chemoattractant protein (MCP-1), inducible nitric oxide synthase (iNOS), vasopressin-activated calcium-mobilizing (VCAM-1), interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α). In vitro, LPS-activated macrophages treated with 14,15-EET showed a significant reduction of LPS-triggered IL-1β and TNF-α expression. Eicosanoic acid metabolic profiling revealed a significant increase of the ratios of EETs/ dihydroeicosatrienoic acids (DHETs) and epoxyoctadecennoic acid/dihydroxyoctadecenoic acid (EpOMEs/DiHOMEs). These results indicate that sEH plays an important role in the development of colitis and in inducing carcinogenesis.

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.

Chronic inflammation-derived nitric oxide causes conversion of human colonic adenoma cells into adenocarcinoma cells

It has been suggested that nitric oxide (NO) derived from chronically inflamed tissues is a cause of carcinogenesis. We herein demonstrated that administration of an inducible NO synthase inhibitor, aminoguanidine, significantly suppressed the tumorigenic conversion of human colonic adenoma (FPCK-1-1) cells into adenocarcinoma (FPCK/Inflam) cells accelerated by foreign body-induced chronic inflammation in nude mice. To determine whether NO directly promotes carcinogenesis, we exposed FPCK-1-1 cells continuously to chemically generated NO (FPCK/NO), and periodically examined their tumorigenicity. FPCK/NO cells formed tumors, whereas vehicle-treated cells (FPCK/NaOH) did not. We selected a tumorigenic population from FPCK/NO cells kept it in three-dimensional (3D) culture where in vivo-like multicellular spheroidal growth was expected. FPCK/Inflam cells developed large spheroids whereas FPCK/NO cells formed tiny but growing compact aggregates in 3D culture. Meanwhile, FPCK-1-1 and FPCK/NaOH cells underwent anoikis (apoptotic cell death consequential on insufficient cell-to-substrate interactions) through activation of caspase 3. The survived cells in the 3D culture (FPCK/NO/3D), which were derived from FPCK/NO cells, showed a similar tumor incidence to that of FPCK/Inflam cells. These results showed that NO was one of the causative factors for the acceleration of colon carcinogenesis, especially in the conversion from adenoma to adenocarcinoma in the chronic inflammatory environment.

Sepiapterin ameliorates chemically induced murine colitis and azoxymethane-induced colon cancer

The effects of modulating tetrahydrobiopterin (BH4) levels with a metabolic precursor, sepiapterin (SP), on dextran sodium sulfate (DSS)-induced colitis and azoxymethane (AOM)-induced colorectal cancer were studied. SP in the drinking water blocks DSS-induced colitis measured as decreased disease activity index (DAI), morphologic criteria, and recovery of Ca(2+)-induced contractility responses lost as a consequence of DSS treatment. SP reduces inflammatory responses measured as the decreased number of infiltrating inflammatory macrophages and neutrophils and decreased expression of proinflammatory cytokines interleukin 1β (IL-1β), IL-6, and IL-17A. High-performance liquid chromatography analyses of colonic BH4 and its oxidized derivative 7,8-dihydrobiopterin (BH2) are inconclusive although there was a trend for lower BH4:BH2 with DSS treatment that was reversed with SP. Reduction of colonic cGMP levels by DSS was reversed with SP by a mechanism sensitive to 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a specific inhibitor of the NO-sensitive soluble guanylate cyclase (sGC). ODQ abrogates the protective effects of SP on colitis. This plus the finding that SP reduces DSS-enhanced protein Tyr nitration are consistent with DSS-induced uncoupling of NOS. The results agree with previous studies that demonstrated inactivation of sGC in DSS-treated animals as being important in recruitment of inflammatory cells and in altered cholinergic signaling and colon motility. SP also reduces the number of colon tumors in AOM/DSS-treated mice from 7 to 1 per unit colon length. Thus, pharmacologic modulation of BH4 with currently available drugs may provide a mechanism for alleviating some forms of colitis and potentially minimizing the potential for colorectal cancer in patients with colitis.

Using mice to unveil the genetics of cancer resistance

In the UK, four in ten people will develop some form of cancer during their lifetime, with an individual's relative risk depending on many factors, including age, lifestyle and genetic make-up. Much research has gone into identifying the genes that are mutated in tumorigenesis with the overwhelming majority of genetically-modified (GM) mice in cancer research showing accelerated tumorigenesis or recapitulating key aspects of the tumorigenic process. Yet if six out of ten people will not develop some form of cancer during their lifetime, together with the fact that some cancer patients experience spontaneous regression/remission, it suggests there are ways of 'resisting' cancer. Indeed, there are wildtype, spontaneously-arising mutants and GM mice that show some form of 'resistance' to cancer. Identification of mice with increased resistance to cancer is a novel aspect of cancer research that is important in terms of providing both chemopreventative and therapeutic options. In this review we describe the different mouse lines that display a 'cancer resistance' phenotype and discuss the molecular basis of their resistance.

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.

New paradigms in chronic intestinal inflammation and colon cancer: role of melatonin

In intestinal bowel disease (IBD), immune-mediated conditions exert their effects through various cells and proinflammatory mediators. Recent data support a participation of the endoplasmic reticulum stress and mitochondrial dysfunctions in IBD. Moreover, it is evident that chronic degenerative pathologies, including IBD, share comparable disease mechanisms with alteration in the autophagy mechanisms. Chronic inflammation in IBD exposes these patients to a number of signals known to have tumorigenic effects. This circuitry of inflammation and cancer modifies apoptosis and autophagy, and promotes cellular cycle progression, invasion, and angiogenesis. Melatonin has been shown as a specific antioxidant reducing oxidative damage in both lipid and aqueous cell environments. However, several studies provide further insight into the molecular mechanisms of melatonin action in the colon. In this line, recent data suggest that melatonin modulates autophagy and sirtuin activity. An anti-autophagic property of melatonin has been demonstrated, and it could contribute to its anti-oncogenic activity. Nevertheless, there is no information about whether antitumoral effects of melatonin on colon cancer are dependent on autophagy. Sirtuins have pleiotropic effects on cancer development, being reported both as facilitator and as suppressor of colon cancer development. Sirtuins and melatonin are connected through the circadian clock machinery, and melatonin seems able to correct the alterations in sirtuin activity associated with several pathological conditions. Autophagy and sirtuin activities are linked through 5'AMP-activated protein kinase (AMPK) activation, which switches on autophagy and increases sirtuin. The effect of melatonin on AMPK and the impact of this effect on IBD and colon cancer remain an open question.

The AOM/DSS murine model for the study of colon carcinogenesis: From pathways to diagnosis and therapy studies

Colorectal cancer (CRC) is a major health problem in industrialized countries. Although inflammation-linked carcinogenesis is a well accepted concept and is often observed within the gastrointestinal tract, the underlying mechanisms remain to be elucidated. Inflammation can indeed provide initiating and promoting stimuli and mediators, generating a tumour-prone microenvironment. Many murine models of sporadic and inflammation-related colon carcinogenesis have been developed in the last decade, including chemically induced CRC models, genetically engineered mouse models, and xenoplants. Among the chemically induced CRC models, the combination of a single hit of azoxymethane (AOM) with 1 week exposure to the inflammatory agent dextran sodium sulphate (DSS) in rodents has proven to dramatically shorten the latency time for induction of CRC and to rapidly recapitulate the aberrant crypt foci–adenoma–carcinoma sequence that occurs in human CRC. Because of its high reproducibility and potency, as well as the simple and affordable mode of application, the AOM/DSS has become an outstanding model for studying colon carcinogenesis and a powerful platform for chemopreventive intervention studies. In this article we highlight the histopathological and molecular features and describe the principal genetic and epigenetic alterations and inflammatory pathways involved in carcinogenesis in AOM/DSS–treated mice; we also present a general overview of recent experimental applications and preclinical testing of novel therapeutics in the AOM/DSS model.

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.

Animal models of colitis-associated carcinogenesis

Inflammatory bowel disease (IBD) is a group of chronic inflammatory disorders that affect individuals throughout life. Although the etiology and pathogenesis of IBD are largely unknown, studies with animal models of colitis indicate that dysregulation of host/microbial interactions are requisite for the development of IBD. Patients with long-standing IBD have an increased risk for developing colitis-associated cancer (CAC), especially 10 years after the initial diagnosis of colitis, although the absolute number of CAC cases is relatively small. The cancer risk seems to be not directly related to disease activity, but is related to disease duration/extent, complication of primary sclerosing cholangitis, and family history of colon cancer. In particular, high levels and continuous production of inflammatory mediators, including cytokines and chemokines, by colonic epithelial cells (CECs) and immune cells in lamina propria may be strongly associated with the pathogenesis of CAC. In this article, we have summarized animal models of CAC and have reviewed the cellular and molecular mechanisms underlining the development of carcinogenic changes in CECs secondary to the chronic inflammatory conditions in the intestine. It may provide us some clues in developing a new class of therapeutic agents for the treatment of IBD and CAC in the near future.

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.

Inflammation and colorectal cancer

Patients with long-standing inflammatory bowel disease (IBD) have an increased risk of developing colorectal cancer (CRC). However, the underlying mechanisms are not entirely clear. A genetic basis for the increased risk of CRC in IBD patients is only a partial explanation. It is possible that high levels of inflammatory mediators that are produced in this setting may contribute to the development and progression of CRC. Growing evidence supports a role for various cytokines, released by epithelial and immune cells, in the pathogenesis of IBD-associated neoplasia. Two key genes in the inflammatory process, cyclooxygenase-2 (COX-2) and nuclear factor kappaB (NF-kappaB), provide a mechanistic link between inflammation and cancer while other factors such as, TNF-alpha and IL-6-induced signaling have been recently shown to promote tumor growth in experimental models of colitis-associated cancer. This article reviews the pathogenesis of IBD-related CRC and summarizes the molecular mechanisms underlying the development of intestinal neoplasia in the setting of chronic inflammation.

Consequences of cytoplasmic irradiation: studies from microbeam

The prevailing dogma for radiation biology is that genotoxic effects of ionizing radiation such as mutations and carcinogenesis are attributed mainly to direct damage to the nucleus. However, with the development of microbeam that can target precise positions inside the cells, accumulating evidences have shown that energy deposit by radiation in nuclear DNA is not required to trigger the damage, extra-nuclear or extra-cellular radiation could induce the similar biological effects as well. This review will summarize the biological responses after cytoplasm irradiated by microbeam, and the possible mechanisms involved in cytoplasmic irradiation.

Induced nitric oxide synthase as a major player in the oncogenic transformation of inflamed tissue

Nitric oxide (NO) is a free radical that is involved in the inflammatory process and carcinogenesis. There are four nitric oxide synthase enzymes involved in NO production: induced nitric oxide synthase (iNOS), endothelial NO synthase (eNOS), neural NO synthase (nNOS), and mitochondrial NOS. iNOS is an inducible and key enzyme in the inflamed tissue. Recent literatures indicate that NO as well as iNOS and eNOS can modulate cancer-related events including nitro-oxidative stress, apoptosis, cell cycle, angio-genesis, invasion, and metastasis. This chapter focuses on linking NO/iNOS/eNOS to inflammation and carcinogenesis from experimental evidence to potential targets on cancer prevention and treatment.

Mitochondrial function and nuclear factor-kappaB-mediated signaling in radiation-induced bystander effects

Although radiation-induced bystander effects have been well described over the past decade, the mechanisms of the signaling processes involved in the bystander phenomenon remain unclear. In the present study, using the Columbia University charged particle microbeam, we found that mitochondrial DNA-depleted human skin fibroblasts (rho(o)) showed a higher bystander mutagenic response in confluent monolayers when a fraction of the same population were irradiated with lethal doses compared with their parental mitochondrial-functional cells (rho(+)). However, using mixed cultures of rho(o) and rho(+) cells and targeting only one population of cells with a lethal dose of alpha-particles, a decreased bystander mutagenesis was uniformly found in nonirradiated bystander cells of both cell types, indicating that signals from one cell type can modulate expression of bystander response in another cell type. In addition, we found that Bay 11-7082, a pharmacologic inhibitor of nuclear factor-kappaB (NF-kappaB) activation, and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a scavenger of nitric oxide (NO), significantly decreased the mutation frequency in both bystander rho(o) and rho(+) cells. Furthermore, we found that NF-kappaB activity and its dependent proteins, cyclooxygenase-2 (COX-2) and inducible NO synthase (iNOS), were lower in bystander rho(o) cells when compared with their rho(+) counterparts. Our results indicated that mitochondria play an important role in the regulation of radiation-induced bystander effects and that mitochondria-dependent NF-kappaB/iNOS/NO and NF-kappaB/COX-2/prostaglandin E2 signaling pathways are important to the process.

Dextran sulfate sodium-induced colitis-associated neoplasia: a promising model for the development of chemopreventive interventions

Individuals diagnosed with ulcerative colitis face a significantly increased risk of developing colorectal dysplasia and cancer during their lifetime. To date, little attention has been given to the development of a chemopreventive intervention for this high-risk population. The mouse model of dextran sulfate sodium (DSS) - induced colitis represents an excellent preclinical system in which to both characterize the molecular events required for tumor formation in the presence of inflammation and assess the ability of select agents to inhibit this process. Cyclic administration of DSS in drinking water results in the establishment of chronic colitis and the development of colorectal dysplasias and cancers with pathological features that resemble those of human colitis-associated neoplasia. The incidence and multiplicity of lesions observed varies depending on the mouse strain used (ie, Swiss Webster, C57BL/6J, CBA, ICR) and the dose (0.7%-5.0%) and schedule (1-15 cycles with or without a subsequent recovery period) of DSS. The incidence of neoplasia can be increased and its progression to invasive cancer accelerated significantly by administering DSS in combination with a known colon carcinogen (azoxymethane (AOM), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-1- methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)) or iron. More recent induction of colitis-associated neoplasia in genetically defined mouse strains has provided new insight into the role of specific genes (ie, adenomatous polyposis coli (Apc), p53, inducible nitric oxide synthase (iNOS), Msh2) in the development of colitis-associated neoplasias. Emerging data from chemopreventive intervention studies document the efficacy of several agents in inhibiting DSS-induced neoplasia and provide great promise that colitis-associated colorectal neoplasia is a preventable disease.