Molecular pathways underlying IBD-associated colorectal neoplasia: therapeutic implications

Uncoupled nitric oxide synthase activity promotes colorectal cancer progression

Increased levels of reactive oxygen/nitrogen species are one hallmark of chronic inflammation contributing to the activation of pro-inflammatory/proliferative pathways. In the cancers analyzed, the tetrahydrobiopterin:dihydrobiopterin ratio is lower than that of the corresponding normal tissue, leading to an uncoupled nitric oxide synthase activity and increased generation of reactive oxygen/nitrogen species. Previously, we demonstrated that prophylactic treatment with sepiapterin, a salvage pathway precursor of tetrahydrobiopterin, prevents dextran sodium sulfate-induced colitis in mice and associated azoxymethane-induced colorectal cancer. Herein, we report that increasing the tetrahydrobiopterin:dihydrobiopterin ratio and recoupling nitric oxide synthase with sepiapterin in the colon cancer cell lines, HCT116 and HT29, inhibit their proliferation and enhance cell death, in part, by Akt/GSK-3β-mediated downregulation of β-catenin. Therapeutic oral gavage with sepiapterin of mice bearing azoxymethane/dextran sodium sulfate-induced colorectal cancer decreased metabolic uptake of [18F]-fluorodeoxyglucose and enhanced apoptosis nine-fold in these tumors. Immunohistochemical analysis of both mouse and human tissues indicated downregulated expression of key enzymes in tetrahydrobiopterin biosynthesis in the colorectal cancer tumors. Human stage 1 colon tumors exhibited a significant decrease in the expression of quinoid dihydropteridine reductase, a key enzyme involved in recycling tetrahydrobiopterin suggesting a potential mechanism for the reduced tetrahydrobiopterin:dihydrobiopterin ratio in these tumors. In summary, sepiapterin treatment of colorectal cancer cells increases the tetrahydrobiopterin:dihydrobiopterin ratio, recouples nitric oxide synthase, and reduces tumor growth. We conclude that nitric oxide synthase coupling may provide a useful therapeutic target for treating patients with colorectal cancer.

The immunomodulatory role of matrix metalloproteinases in colitis-associated cancer

Matrix metalloproteinases (MMPs) are an important class of enzymes in the body that function through the extracellular matrix (ECM). They are involved in diverse pathophysiological processes, such as tumor invasion and metastasis, cardiovascular diseases, arthritis, periodontal disease, osteogenesis imperfecta, and diseases of the central nervous system. MMPs participate in the occurrence and development of numerous cancers and are closely related to immunity. In the present study, we review the immunomodulatory role of MMPs in colitis-associated cancer (CAC) and discuss relevant clinical applications. We analyze more than 300 pharmacological studies retrieved from PubMed and the Web of Science, related to MMPs, cancer, colitis, CAC, and immunomodulation. Key MMPs that interfere with pathological processes in CAC such as MMP-2, MMP-3, MMP-7, MMP-9, MMP-10, MMP-12, and MMP-13, as well as their corresponding mechanisms are elaborated. MMPs are involved in cell proliferation, cell differentiation, angiogenesis, ECM remodeling, and the inflammatory response in CAC. They also affect the immune system by modulating differentiation and immune activity of immune cells, recruitment of macrophages, and recruitment of neutrophils. Herein we describe the immunomodulatory role of MMPs in CAC to facilitate treatment of this special type of colon cancer, which is preceded by detectable inflammatory bowel disease in clinical populations.

The mycobiota of the human body: a spark can start a prairie fire

Mycobiota are inseparable from human health, shaking up the unique position held by bacteria among microorganisms. What is surprising is that this seemingly small species can trigger huge changes in the human body. Dysbiosis and invasion of mycobiota are confirmed to cause disease in different parts of the body. Meanwhile, our body also produces corresponding immune changes upon mycobiota infection. Several recent studies have made a connection between intestinal mycobiota and the human immune system. In this review, we focus on questions related to mycobiota, starting with an introduction of select species, then we summarize the typical diseases caused by mycobiota in different parts of the human body. Moreover, we constructed a framework for the human anti-fungal immune system based on genetics and immunology. Finally, the progression of fungal detection methods is also reviewed.

Colorectal cancer in inflammatory bowel disease: review of the evidence

Inflammatory bowel disease (IBD)-related colorectal cancer (CRC) is responsible for approximately 2% of the annual mortality from CRC overall, but 10-15% of the annual deaths in IBD patients. IBD-related CRC patients are also affected at a younger age than sporadic CRC patients, and have a 5-year survival rate of 50%. Despite optimal medical treatment, the chronic inflammatory state inherent in IBD increases the risk for high-grade dysplasia and CRC, with additional input from genetic and environmental risk factors and the microbiome. Recognizing risk factors, implementing appropriate surveillance, and identifying high-risk patients are key to managing the CRC risk in IBD patients. Chemoprevention strategies exist, and studies evaluating their efficacy are underway. Once dysplasia or invasive cancer is diagnosed, appropriate surgical resection and postoperative treatment and surveillance are necessary. Here, we discuss the current state of IBD-related CRC, prevalence, risk factors, and evidence for surveillance, prophylaxis, and treatment recommendations.

CD177+ neutrophils suppress epithelial cell tumourigenesis in colitis-associated cancer and predict good prognosis in colorectal cancer

Neutrophils are found to be infiltrated in tumour tissues of patients with colitis-associated cancer (CAC) and colorectal cancer (CRC), and CD177 is mainly expressed in neutrophils. In our study, expression of CD177 in tumour tissues from patients with CAC or CRC was analysed byquantitative real-time polymerase chain reaction, flow cytometry and immunohistochemistry. We recruited 378 patients with CRC, determined CD177 expression in tumours and examined its correlation with clinicopathological features. Moreover, CAC model was induced in wild-type and CD177-/- mice by azoxymethane/dextran sodium sulphate. CD177+ neutrophils were significantly increased in colon tumour tissues from patients with CRC or CAC compared with controls. Expression of CD177 mRNA and percentages of CD177+ neutrophils were also markedly increased in tumour tissues from CRC patients compared with controls. Patients with high density of CD177+ neutrophils had better overall survival and disease-free survival compared with controls. Multivariate analyses revealed that the density of CD177+ neutrophils was an independent factor in predicting overall survival and disease-free survival. Consistently, CD177 depletion aggravated azoxymethane/dextran sodium sulphate-induced CAC in mice. Expression of Ki67 and proliferating cell nuclear antigen was increased in tumour tissues from CD177-/- mice compared with wild-type counterparts. Moreover, CD177-/- neutrophils failed to migrate in response to fMLP[AU: Please expand fMLP, DN, TNM and HIF-1α.] stimulation compared with wild-type controls. Our data indicate that CD177+ neutrophils suppress epithelial cell tumourigenesis and act as an independent factor in predicting the prognosis in patients with CRC. CD177+ neutrophils may serve as a novel therapeutic target in the treatment and predict the prognosis of CAC and CRC.

Berberine inhibits colitis-associated tumorigenesis via suppressing inflammatory responses and the consequent EGFR signaling-involved tumor cell growth

The anti-inflammatory and anti-tumor effects of berberine, a traditional Chinese medicine, were separately discovered in pathological intestinal tissues. However, whether the anti-inflammatory effect of berberine contributes to its anti-tumor effect on colitis-associated colorectal cancer (CACRC) remains unknown. In the present study, we found that berberine effectively inhibited colitis-associated tumorigenesis and colonic epithelium hyperproliferation in dextran sulfate sodium (DSS)-treated Apc^Min/+ mice. A mechanistic study identified that these inhibitory effects of berberine occurred through blocking interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) expression in colonic macrophages. An in vitro study on cell lines identified that berberine treatment of Raw 264.7 macrophages resulted in conditioned media with fewer proliferative effects on a cell line with a heterozygous Apc mutation (Immorto-Min colonic epithelium, IMCE). EGFR-ERK signaling act downstream of berberine/pro-inflammatory cytokines axis to regulate CACRC cell proliferation. Furthermore, in vivo administration of IL-6 to DSS-treated Apc^Min/+ mice effectively weakened the inhibitory effects of berberine on tumorigenesis and EGFR-ERK signaling in colon tissues. Altogether, the results of our studies have revealed that berberine inhibits the development of CACRC by interfering with inflammatory response-driven EGFR signaling in tumor cell growth. The findings of this study support the possibility that berberine and other anti-inflammatory drugs may be beneficial in the treatment of CACRC.

Low HtrA1 expression in patients with long‑standing ulcerative colitis and colorectal cancer

The association between inflammatory bowel disease (IBD) and colorectal cancer (CRC) is being increasingly investigated. HtrA1 overexpression inhibits cell growth and proliferation by influencing apoptosis, invasiveness and migration of tumour cells. In the present study, HtrA1 expression was analysed in 228 colon tissue samples from patients with CRC, adenoma with high-grade dysplasia (AHD), adenoma with low-grade dysplasia (ALD), ulcerative colitis of >10 year duration (UCL), ulcerative colitis of <5 year duration (UCS) and colonic diverticulitis (D), and was compared with its expression in normal colon tissues (NCTs) collected 5 cm from the CRC lesion and in healthy colon mucosa (HC), to establish whether HtrA1 can serve as a biomarker for these conditions. All tissue specimens came from Italian Caucasian subjects. The main finding of the present study was that HtrA1 expression was significantly reduced in CRC and UCL tissues compared with that observed in both NCT and HC samples and with tissues from the other patients. In particular, a similar HtrA1 expression was detected in the stromal compartment of UCL and CRC samples. In contrast, the HtrA1 level was significantly lower (p=0.0008) in UCL compared with UCS tissues, suggesting an inverse relationship between HtrA1 expression and ulcerative colitis duration. HtrA1 immunostaining in the stromal compartment of AHD and ALD tissues showed no differences compared with the HC tissues. No data are available on the immunohistochemical localization of HtrA1 in CRC or IBD. The present findings suggest that HtrA1 could serve as a marker to identify UCL patients at high risk of developing CRC.

Activation of Epidermal Growth Factor Receptor in Macrophages Mediates Feedback Inhibition of M2 Polarization and Gastrointestinal Tumor Cell Growth

EGF receptor (EGFR) in tumor cells serves as a tumor promoter. However, information about EGFR activation in macrophages in regulating M2 polarization and tumor development is limited. This study aimed to investigate the effects of EGFR activation in macrophages on M2 polarization and development of gastrointestinal tumors. IL-4, a cytokine to elicit M2 polarization, stimulated release of an EGFR ligand, HB-EGF, and transactivation and down-regulation of EGFR in Raw 264.7 cells and peritoneal macrophages from WT mice. Knockdown of HB-EGF in macrophages inhibited EGFR transactivation by IL-4. IL-4-stimulated STAT6 activation, Arg1 and YM1 gene expression, and HB-EGF production were further enhanced by inhibition of EGFR activity in Raw 264.7 cells using an EGFR kinase inhibitor and in peritoneal macrophages from Egfr(wa5) mice with kinase inactive EGFR and by knockdown of EGFR in peritoneal macrophages from Egfr(fl/fl) LysM-Cre mice with myeloid cell-specific EGFR deletion. Chitin induced a higher level of M2 polarization in peritoneal macrophages in Egfr(fl/fl) LysM-Cre mice than that in Egfr(fl/fl) mice. Accordingly, IL-4-conditioned medium stimulated growth and epithelial-to-mesenchymal transition in gastric epithelial and colonic tumor cells, which were suppressed by that from Raw 264.7 cells with HB-EGF knockdown but promoted by that from Egfr(wa5) and Egfr(fl/fl) LysM-Cre peritoneal macrophages. Clinical assessment revealed that the number of macrophages with EGFR expression became less, indicating decreased inhibitory effects on M2 polarization, in late stage of human gastric cancers. Thus, IL-4-stimulated HB-EGF-dependent transactivation of EGFR in macrophages may mediate inhibitory feedback for M2 polarization and HB-EGF production, thereby inhibiting gastrointestinal tumor growth.

IRAK-M Expression in Tumor Cells Supports Colorectal Cancer Progression through Reduction of Antimicrobial Defense and Stabilization of STAT3

Colorectal cancer (CRC) is associated with loss of epithelial barrier integrity, which facilitates the interaction of the immunological microenvironment with the luminal microbiome, eliciting tumor-supportive inflammation. An important regulator of intestinal inflammatory responses is IRAK-M, a negative regulator of TLR signaling. Here we investigate the compartment-specific impact of IRAK-M on colorectal carcinogenesis using a mouse model. We demonstrate that IRAK-M is expressed in tumor cells due to combined TLR and Wnt activation. Tumor cell-intrinsic IRAK-M is responsible for regulation of microbial colonization of tumors and STAT3 protein stability in tumor cells, leading to tumor cell proliferation. IRAK-M expression in human CRCs is associated with poor prognosis. These results suggest that IRAK-M may be a potential therapeutic target for CRC treatment.

MGMT-B gene promoter hypermethylation in patients with inflammatory bowel disease - a novel finding

Inflammatory bowel disease (IBD) is a disease strongly associated with colorectal cancer (CRC) as a well-known precancerous condition. Alterations in DNA methylation and mutation in K-ras are believed to play an early etiopathogenic role in CRC and may also an initiating event through deregulation of molecular signaling. Epigenetic silencing of APC and SFRP2 in the WNT signaling pathway may also be involved in IBD-CRC. The role of aberrant DNA methylation in precancerous state of colorectal cancer (CRC) is under intensive investigation worldwide. The aim of this study was to investigate the status of promoter methylation of MGMT-B, APC1A and SFRP2 genes, in inflamed and normal colon tissues of patients with IBD compared with control normal tissues. A total of 52 IBD tissues as well as corresponding normal tissues and 30 samples from healthy participants were obtained. We determined promoter methylation status of MGMT-B, SFRP2 and APC1A genes by chemical treatment with sodium bisulfite and subsequent MSP. The most frequently methylated locus was MGMT-B (71%; 34 of 48), followed by SFRP2 (66.6 %; 32 of 48), and APC1A (43.7%; 21 of 48). Our study demonstrated for the first time that hypermethylation of the MGMT-B and the SFRP2 gene promoter regions might be involved in IBD development. Methylation of MGMT-B and SFRP2 in IBD patients may provide a method for early detection of IBD-associated neoplasia.

The pathological role of microRNAs and inflammation in colon carcinogenesis

Evidence of an association between inflammation, microRNAs (miRNAs) and tumorigenesis has emerged in recent years. Patients with inflammatory bowel disease (IBD) are at an increased risk for colorectal cancer (CRC) development, suggesting that inflammatory mediators play a causative role in colon carcinogenesis. MiRNAs are small (19-22 nucleotides) non-coding RNA molecules that regulate gene expression at the post-transcriptional level by base-pairing to specific messenger RNAs (mRNAs), promoting their degradation or suppressing translation. MiRNAs can act as inflammatory mediators, oncogenes or tumor suppressors in different cellular environments. MiRNAs also serve as biomarkers and therapeutic targets in CRC. The risk of CRC is also influenced by miRNA polymorphisms and binding sites. Their functions as early diagnostic biomarkers or prognostic classifiers has been demonstrated. Here, we reviewed recent findings on miRNAs and inflammation in colon carcinogenesis and discussed the potential for miRNAs and inflammation-related genes as biomarkers and therapeutic targets in CRC.

Apple polysaccharide reduces NF-Kb mediated colitis-associated colon carcinogenesis

Nuclear factor-kappa B (NF-κB) is an important molecule in mediating inflammatory colitis, which can lead to colorectal cancer (CRC). The aim of this study was to evaluate the chemopreventive efficacy of apple polysaccharide extract (AP) in inhibiting NF-κB-mediated inflammation pathways in CRC. We evaluated AP in vitro in HT-29 and SW620 human CRC cells. We also used the azoxymethane and dextran sodium sulphate (AOM/DSS) model to induce colon carcinogenesis in vivo. The chemoprotective effects of AP were assessed using Western blot, immunofluorescence assay, real-time PCR, electrophoretic mobility shift assay, and flow cytometry. AP reduced AOM/DSS-associated toxicities, prevented carcinogenesis, and decreased the expression of TLR4, MD2, MyD88, TRAM, TRIF-related adapter molecule, interferon-β, tumor necrosis factor-α, and interleukin-6. The protective effects of AP may be related to the inhibition of TLR4/MD2-mediated signaling, including MyD88 and TRIF, as well as the inhibition of NF-κB-mediated inflammatory signaling pathways. Therefore, AP could be used in combination therapy for the prevention of colitis-associated colon cancer.

Predictive proteomic biomarkers for inflammatory bowel disease-associated cancer: Where are we now in the era of the next generation proteomics?

Recent advances in genomic medicine have opened up the possibility of tailored medicine that may eventually replace traditional “one-size-fits all” approaches to the treatment of inflammatory bowel disease (IBD). In addition to exploring the interactions between hosts and microbes, referred to as the microbiome, a variety of strategies that can be tailored to an individual in the coming era of personalized medicine in the treatment of IBD are being investigated. These include prompt genomic screening of patients at risk of developing IBD, the utility of molecular discrimination of IBD subtypes among patients diagnosed with IBD, and the discovery of proteome biomarkers to diagnose or predict cancer risks. Host genetic factors influence the etiology of IBD, as do microbial ecosystems in the human bowel, which are not uniform, but instead represent many different microhabitats that can be influenced by diet and might affect processes essential to bowel metabolism. Further advances in basic research regarding intestinal inflammation may reveal new insights into the role of inflammatory mediators, referred to as the inflammasome, and the macromolecular complex of metabolites formed by intestinal bacteria. Collectively, knowledge of the inflammasome and metagenomics will lead to the development of biomarkers for IBD that target specific pathogenic mechanisms involved in the spontaneous progress of IBD. In this review article, our recent results regarding the discovery of potential proteomic biomarkers using a label-free quantification technique are introduced and on-going projects contributing to either the discrimination of IBD subtypes or to the prediction of cancer risks are accompanied by updated information from IBD biomarker research.

Relationship between methylation and colonic inflammation in inflammatory bowel disease

AIM: To investigate the relationship between the methylation status in the SLIT2 and TGFB2 promoters and colonic inflammation in inflammatory bowel disease patients.

METHODS: We evaluated the methylation status of 2 genes (SLIT2 and TGFB2) in 226 biopsies taken from 62 colonoscopies of 38 patients (29 ulcerative colitis and 9 Crohn’s colitis) using methylation-specific melting curve analysis. The relationships between methylation status and clinical, biological, endoscopic and histological activities were evaluated. Twenty-three of the 38 patients had a second colonoscopy and were included in a longitudinal analysis. Numerical results were given as the means ± SD of the sample and range, except when specified. Student t analysis, U Mann Whitney and ANOVA factor were used to compare the means. Qualitative results were based on the χ² test.

RESULTS: SLIT2 methylation was more frequent in samples with endoscopic activity than with endoscopic remission (55% vs 18%, P < 0.001). SLIT2 methylation was also higher in samples with acute inflammation (56.5%) than in samples with chronic (24%) or absent inflammation (15%) (P < 0.001). For TGFB2 methylation, the correlation was only significant with endoscopic activity. Methylation was higher in the distal colon for both genes (P < 0.001 for SLIT2 and P = 0.022 for TGFB2). In the multivariate analysis, only inflammation status (and not disease duration or extension) was independently associated with SLIT2 methylation [OR = 6.6 (95%CI: 1.65-27.36), P = 0.009]. In the longitudinal analysis, the maintenance of endoscopic remission was protective for methylation.

CONCLUSION: Endoscopic and histological inflammation are predictive for SLIT2 methylation.

Ulcerative colitis neoplasia is not associated with common inflammatory bowel disease single-nucleotide polymorphisms

BACKGROUND

Neoplasia complicating ulcerative colitis (UC-neoplasia) is a problem that is poorly addressed by present surveillance techniques. The association of greater than 300 single nucleotide polymorphisms (SNPs) with inflammatory bowel disease (IBD) suggests the possibility that certain genetic polymorphisms might identify patients with UC destined for malignant degeneration. This present study tested the hypothesis that presently known IBD-associated SNPs may correlate with UC-neoplasia.

MATERIALS AND METHODS

A total of 41 patients with UC-neoplasia (mean age 56 ± 2.1 years) were identified from our divisional IBD Biobank (low-grade dysplasia n = 13, high-grade dysplasia n = 8, colorectal cancer [CRC] n = 20). These patients were individually age, sex, and disease duration matched with UC patients without neoplasia. Primary sclerosing cholangitis and family history of CRC were recorded. Patients were genotyped for 314 of the most commonly IBD-associated SNPs by a custom SNP microarray. Logistic regression and Fischer exact test were used for statistical analysis.

RESULTS

After Bonferroni correction, none of the 314 IBD-associated SNPs correlated with UC-neoplasia when compared with matched UC controls. The incidence of primary sclerosing cholangitis was greater in the UC-neoplasia group (10/41, 24% vs 3/41, 7%; P = .03) compared with UC controls. The severity of neoplasia (low grade dysplasia versus high grade dysplasia versus CRC) correlated with disease duration (7.9 vs 13.4 vs 20.7 years, respectively).

CONCLUSION

The lack of correlation between well-known IBD-associated SNPs and UC-neoplasia demonstrated in this study suggests that the development of neoplasia in patients with UC is associated with genetic determinants other than those that predispose to inflammation or results from posttranslational modifications or epigenetic factors rather than germline polymorphisms.

Drug therapies and the risk of malignancy in Crohn's disease: results from the TREAT™ Registry

OBJECTIVES

We assessed potential associations between malignancy and antitumor necrosis factor therapy in patients with Crohn's disease (CD), as this relationship is currently poorly defined.

METHODS

Utilizing data from the Crohn's Therapy, Resource, Evaluation, and Assessment Tool (TREAT™) Registry, a prospective cohort study examining long-term outcomes of CD treatments in community and academic settings, influences of baseline patient/disease characteristics and medications were assessed by survival analysis and multivariate models. Standardized incidence ratios and exact 95 % confidence intervals were determined as the ratio of events observed (TREAT) vs. expected (general population of USA).

RESULTS

As of 23 February 2010, 6,273 CD patients (infliximab during registry=3,420 (during or within 1 year before registry=3,764); other-treatments-only: 2,509), were enrolled and, on average, had been followed for 5.2/7.6 years, respectively, for all/currently active patients. Crude cancer incidences were similar between infliximab- and other-treatments-only-exposed patients. Multivariate Cox regression analysis demonstrated that baseline age (hazard ratio (HR)=1.59/10 years; P<0.001), disease duration (HR=1.64/10 years; P=0.012), and smoking (HR=1.38; P=0.045) but neither immunosuppressive therapy alone (HR=1.43; P=0.11), infliximab therapy alone (HR=0.59; P=0.16), nor their combination (HR=1.22, P=0.34) were independently associated with the risk of malignancy. When compared with the general population, no significant increase in incidence was observed in any malignancy category. In an exposure-based analysis, use of immunosuppressants alone (odds ratio=4.19) or in combination with infliximab (3.33) seemed to be associated with a numerically, but not significantly, greater risk of malignancy than did treatment with infliximab alone (1.96) relative to treatment with neither.

CONCLUSIONS

In the TREAT Registry, age, disease duration, and smoking were independently associated with increased risk of malignancy. Although results for immunosuppressant use were equivocal, no significant association between malignancy and infliximab was observed.

Management of the elderly patients with inflammatory bowel disease: practical considerations

The aging U.S. population will approach 20% of the total population by 2030. The number of older patients with inflammatory bowel disease is anticipated to increase accordingly bringing the burden of multiple comorbidities, polypharmacy with drug interactions, the aging immune system, and extended social and financial issues to overall management of an already challenging management of these patients. Each of these concerns is measured by the metric of distinguishing the "fit versus frail" elderly and will be discussed in this review with an emphasis on a practical guide to therapy.

TREM-1 inhibition attenuates inflammation and tumor within the colon

The role of myeloid cell receptor TREM-1 as an amplifier of inflammation has been widely accepted and more interestingly, TREM-1 has been implicated in tumorigenesis. However, it is not clear whether TREM-1 links colon inflammation and tumor in vivo. This study aimed to investigate whether inhibition of proinflammatory TREM-1 would prevent aberrant inflammation and tumor development within the colon. In the present study, the mouse model of DSS-induced colitis and colitis-associated tumorigenesis was used. In vivo, the treatment with the TREM-1 antagonist LP17 or control peptide was initiated at the beginning of or after induction of experimental colitis or colitis-associated tumorigenesis. As a result, TREM-1 inhibition by LP17 treatment ameliorated the development of inflammation and tumor within the colon through exerting anti-inflammatory effects. In addition, LP17 decreased intestinal epithelial proliferation in DSS-induced colitis. Taken together, TREM-1 plays critical roles in colon inflammation and tumor and targeting TREM-1 may represent a novel therapeutic strategy for colon inflammation and associated cancer.

Tying the knot between cytokine and toll-like receptor signaling in gastrointestinal tract cancers

Inflammation-associated malignancies of the gastrointestinal tract (GI), including those of the stomach and colon, collectively rank as the highest cause of cancer-related deaths worldwide. It has been well documented that the deregulated activation of the archetypal pro-inflammatory and oncogenic transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription (STAT)3 is a common feature of GI cancers that invariably correlates with poor prognosis. Signal transducer and activator of transcription 3 and NF-κB are key downstream signal transducers of the interleukin (IL)-6 cytokine and toll-like receptor (TLR) families, respectively, and until recently, the potential involvement of these two families in the pathogenesis of cancer has been investigated in isolation. However, there is now emerging evidence of the complex interplay between the IL-6 cytokine and TLR families in GI tract cancers, with a surprising twist in the identification of a non-immune role for specific TLR family members. In this review, we discuss the molecular mechanisms associated with cross-talk between the IL-6 cytokine family/STAT3 signaling network and the TLR family/NF-κB signaling network, and we address the potential benefit of their therapeutic targeting in gastric and colorectal cancers.

The surgical treatment of inflammatory bowel disease-associated dysplasia

Surgical management of colonic dysplasia discovered in the inflammatory bowel disease patient is controversial. Total proctocolectomy (TPC) is the most definitive treatment for the eradication of undiagnosed synchronous dysplasias and/or carcinomas and the prevention of subsequent metachronous lesions in both Crohn's disease (CD) and ulcerative colitis (UC). However, TPC is not always an attractive option owing to patient comorbidities and patient preference. Historically, dysplasia has been most studied in patients with UC, where the option of reconstruction without a stoma makes TPC more acceptable. Due to a relative lack of research on CD-related dysplasia, surveillance and treatment of CD dysplasia has followed paradigms based on UC data. However, due to pathophysiological differences in CD versus UC, options for surgical management in CD may be more varied than simple TPC, particularly in the less healthy surgical candidate and those who refuse end ileostomy.

Precancerous lesions in inflammatory bowel disease

Reduction of mortality from colorectal cancer is a prime goal in the clinical management of patients with extensive, longstanding ulcerative colitis and colonic Crohn's disease. The cornerstone of current cancer prevention efforts is endoscopic surveillance for colorectal dysplasia, or intraepithelial neoplasia, the direct histological precursor of cancer. A diagnosis of dysplasia provides a reliable indicator of heightened cancer risk and an end-point for colonoscopic surveillance allowing most patients to undergo prophylactic colectomy before the development of incurable cancer. This article reviews the classification, pathological criteria and clinical implications of colorectal dysplasia, current recommendations for the performance of surveillance colonoscopy, recent technical advances in colonoscopic imaging to enhance the detection of dysplasia, and a summary of the molecular genetic events implicated in its development.

Berberine inhibits proliferation and down-regulates epidermal growth factor receptor through activation of Cbl in colon tumor cells

Berberine, an isoquinoline alkaloid, is an active component of Ranunculaceae and Papaveraceae plant families. Berberine has been found to suppress growth of several tumor cell lines in vitro through the cell-type-dependent mechanism. Expression and activation of epidermal growth factor receptor (EGFR) is increased in colonic precancerous lesions and tumours, thus EGFR is considered a tumour promoter. The aim of this study was to investigate the effects and mechanisms of berberine on regulation of EGFR activity and proliferation in colonic tumor cell lines and in vivo. We reported that berberine significantly inhibited basal level and EGF-stimulated EGFR activation and proliferation in the immorto Min mouse colonic epithelial (IMCE) cells carrying the APC(min) mutation and human colonic carcinoma cell line, HT-29 cells. Berberine acted to inhibit proliferation through inducing G1/S and G2/M cell cycle arrest, which correlated with regulation of the checkpoint protein expression. In this study, we also showed that berberine stimulated ubiquitin ligase Cbl activation and Cbl's interaction with EGFR, and EGFR ubiquitinylation and down-regulation in these two cell lines in the presence or absence of EGF treatment. Knock-down Cbl expression blocked the effects of berberine on down-regulation of EGFR and inhibition of proliferation. Furthermore, berberine suppressed tumor growth in the HT-29 cell xenograft model. Cell proliferation and EGFR expression level was decreased by berberine treatment in this xenograft model and in colon epithelial cells of APC(min/+) mice. Taken together, these data indicate that berberine enhances Cbl activity, resulting in down-regulation of EGFR expression and inhibition of proliferation in colon tumor cells.

Novel methylation panel for the early detection of neoplasia in high-risk ulcerative colitis and Crohn's colitis patients

BACKGROUND

Patients with ulcerative colitis and Crohn's colonic disease are at increased risk of developing colorectal cancer (CRC). The aim of the study was to analyze the methylation status of selected genes as a risk marker for CRC in inflammatory bowel disease (IBD) patients.

METHODS

We evaluated the methylation status of four genes (TGFB2, SLIT2, HS3ST2, and TMEFF2) in biopsies of four groups of patients: 60 patients with sporadic CRC, 32 patients with IBD-associated neoplasia, 85 patients with IBD without associated neoplasia (20 at high risk and 65 at low risk), and 28 healthy controls. Methylation-specific melting curve analysis (MS-MCA) was used. Methylation status of these genes was also assessed in stool DNA from 60 IBD patients without neoplasia.

RESULTS

Methylation of the panel of genes analyzed was a very common phenomenon (78%) in IBD-associated neoplasia. The prevalence of methylation in adjacent nonneoplastic mucosa was also high (12/30). This prevalence was higher than in mucosa from healthy controls (2/28;7.1%; P < 0.05). Methylation of SLIT2 and TMEFF2 was more frequently detected in the mucosa of IBD patients at high risk of dysplasia or cancer (15/20) than patients at low risk (32/63) (P = 0.05 and P = 0.03, respectively). When stool samples were assessed, only SLIT2 gene methylation was more frequently methylated in the group of patients at high risk of dysplasia or cancer (4/16) compared to low risk (0/37) (P = 0.006).

CONCLUSIONS

Analysis of a panel of methylation markers may help in the early identification of colorectal dysplasia or cancer in high-risk IBD patients.

PDCD4/miR-21 dysregulation in inflammatory bowel disease-associated carcinogenesis

Inflammatory bowel diseases (IBDs; both ulcerative colitis [UC] and Crohn's colitis [CC]) are well-established predisposing pathological conditions for colorectal cancer (CRC) development. In IBDs, both the endoscopy and the histology assessment of CRC precursors (i.e., dysplasia, also defined as intraepithelial neoplasia) are associated with low interobserver consistency, and no reliable dysplasia-specific biomarker is available. The programmed cell death 4 (PDCD4) tumor suppressor gene is involved in sporadic colorectal oncogenesis, but scanty information is available on its involvement in IBD-associated colorectal oncogenesis. One hundred twenty tissue samples representative of active and inactive IBD and of flat dysplasia were obtained from 30 cases of UC and 30 of CC who undergone colectomy. Twenty additional biopsy samples obtained from patients with irritable bowel syndrome acted as normal controls. PDCD4 expression was assessed by immunohistochemistry; the expression of miR-21 (a major PDCD4 regulator) was investigated by quantitative real-time PCR and in situ hybridization in different series of a hundred samples. Tissue specimens from both controls and inactive IBD consistently featured strong PDCD4 nuclear immunostain; conversely, lower PDCD4 nuclear expression was featured by both active IBD and IBD-associated dysplastic lesions. Significant PDCD4 down-regulation distinguished IBD-associated dysplasia (p < 0.001) versus active IBD. In both active IBD and dysplasia, PDCD4 down-regulation was significantly associated with miR-21 up-regulation. PDCD4 nuclear down-regulation (which parallels miR-21 up-regulation) is involved in the molecular pathway of IBD-associated carcinogenesis. PDCD4 nuclear expression may be usefully applied as ancillary maker in the histological assessment of IBD-associated dysplastic lesions.

Estrogen receptor-β protects against colitis-associated neoplasia in mice

Estrogen receptor-beta (ERβ) has been suggested to exert anti-inflammatory and anti-tumorigenic effects in the colon, providing a translational potential to prevent and/or treat inflammatory bowel disease (IBD) and its progression to colitis-associated colorectal cancer (CAC). However, the specific direct role of ERβ in CAC has not yet been tested. We assessed the effects of ERβ deficiency in the azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced CAC model using ERβ knockout (βERKO) mice and wild-type (WT) littermates. These mice were injected with AOM followed by 1 week of DSS treatment, and sacrificed on weeks 9 or 16. βERKO mice developed more severe clinical colitis compared to WT mice, as evidenced by significantly higher disease activity index after DSS treatment, weight to length ratio of the colons, inflammation score and grade of dysplasia. ERβ-deficient colons presented greater number and size of polyps at weeks 9 and 16, respectively, and were characterized by a significant increase in interleukin (IL)-6, IL-17, tumor necrosis factor alpha and interferon-gamma mRNA levels. Furthermore, higher protein expression levels of nuclear factor-kappa B, inducible nitric oxide synthase, β-catenin, proliferating cell nuclear antigen, mucin-1 and significantly lower caveolin-1 and mucin-2 protein levels were shown in βERKO mice compared to WT mice. These data suggest a possible anti-inflammatory and anti-neoplastic mechanism of action of ERβ in CAC. These results demonstrate for the first time that ERβ provides protection in the AOM/DSS-induced CAC model in mice, suggesting a preventive and/or therapeutic potential for the use of ERβ-selective agonists in IBD.

Potential avenues for immunotherapy of colitis-associated neoplasia

In patients with inflammatory bowel disease, chronic intestinal inflammation severely increases the risk for cancer development. In fact, various aspects of inflammation such as oxidative stress, cyclooxygenases and proinflammatory cytokines have been shown to support many aspects of cancer growth. During recent years, various experimental studies have increased our understanding of the molecular mechanisms leading to colitis-associated cancer. In particular, cytokines such as TNF-α or IL-6, which are involved in the pathogenesis of inflammation and cancer development, could be promising targets for the molecular prevention of colitis-associated cancer.

Colorectal cancer in patients with inflammatory bowel disease: Can we predict risk?

The inflammatory bowel diseases (IBD), Crohn’s disease (CD) and ulcerative colitis (UC), may be complicated by colorectal cancer (CRC). In a recent population-based cohort study of 47 347 Danish patients with IBD by Tine Jess and colleagues 268 patients with UC and 70 patients with CD developed CRC during 30 years of observation. The overall risk of CRC among patients with UC and CD was comparable with that of the general population. However, patients diagnosed with UC during childhood or as adolescents, patients with long duration of disease and those with concomitant primary sclerosing cholangitis were at increased risk. In this commentary, we discuss the mechanisms underlying carcinogenesis in IBD and current investigations of genetic susceptibility in IBD patients. Further advances will depend on the cooperative work by epidemiologist and molecular geneticists in order to identify genetic polymorphisms involved in IBD-associated CRC. The ultimate goal is to incorporate genotypes and clinical parameters into a predictive model that will refine the prediction of risk for CRC in colonic IBD. The challenge will be to translate these new findings into clinical practice and to determine appropriate preventive strategies in order to avoid CRC in IBD patients. The achieved knowledge may also be relevant for other inflammation-associated cancers.

Major signaling pathways in intestinal stem cells

BACKGROUND

The discovery of markers to identify the intestinal stem cell population and the generation of powerful transgenic mouse models to study stem cell physiology have led to seminal discoveries in stem cell biology.

SCOPE OF REVIEW

In this review we give an overview of the current knowledge in the field of intestinal stem cells (ISCs) highlighting the most recent progress on markers defining the ISC population and pathways governing intestinal stem cell maintenance and differentiation. Furthermore we review their interaction with other stem cell related pathways. Finally we give an overview of alteration of these pathways in human inflammatory gastrointestinal diseases.

MAJOR CONCLUSIONS

We highlight the complex network of interactions occurring among different pathways and put in perspective the many layers of regulation that occur in maintaining the intestinal homeostasis.

GENERAL SIGNIFICANCE

Understanding the involvement of ISCs in inflammatory diseases can potentially lead to new therapeutic approaches to treat inflammatory GI pathologies such as IBD and celiac disease and could reveal the molecular mechanisms leading to the pathogenesis of dysplasia and cancer in inflammatory chronic conditions. This article is part of a Special Issue entitled Biochemistry of Stem Cells.

Immune responses triggering colitis and colitis-associated carcinoma

Inflammatory bowel diseases compromise of two forms of chronic intestinal inflammatory disorders: Crohn's disease and ulcerative colitis. Both forms of inflammatory bowel disease result from inappropriate inflammatory responses to the intestinal microbiota, but have different underlying immune responses. The connection between inflammation and cancer has long been established and longstanding inflammatory bowel diseases are an important risk factor for developing colorectal cancer. Colitis-associated colorectal cancer pathogenesis is highly influenced by specific inflammatory processes during inflammatory bowel disease. This article reviews the immunological responses affecting Crohn's disease and ulcerative colitis as well as the linkage of inflammatory bowel disease to the development of colitis-associated cancer. Finally, we discuss the prospects of using new research efforts to devise new immunotherapeutic approaches.