Mouse Model Of Colitis-associated Cancer Research Articles

Endoscopic Optical Biopsy of Experimental Colitis Associated Cancer Using a Gamma-Glutamyltransferase Activatable Fluorescence Imaging Probe

BACKGROUND & AIM: The diagnosis of colitis associated cancer (CAC) remains difficult despite technologic improvements in modern endoscopes. It can be challenging to see a tumor against a background of inflammation. Recently, we demonstrated that ovarian cancer peritoneal implants can be easily visualized In Vivo using a fast reacting gamma-glutamyltransferase (GGT) activatable optical probe, which only fluoresces in the presence of GGT activity. The aim of this study was to test this agent in the context of a colitis associated carcinogenesis model. METHODS: Expression of GGT in colon cancer cell lines was examined with the GGT activatable probe (1 μM) using a fluorescencemicroscopy and a flow cytometry. A mouse model of CAC induced by azoxymethane (AOM) and dextran sulfate sodium (DSS) was then used for the In Vivo experiment. The distal colon up to the splenic flexure was examined with conventional white light and fluorescence micro-colonoscopy before and after intrarectal administration (50 μM/400 μL) of the GGT activatable probe. RESULTS: The GGT activatable probe was activated as early as 5 min after application. Microscopy revealed localization predominantly in the cytosol. Expression of GGT was higher in colon cancer cells than in normal human colon cells. With In Vivo fluorescence micro-colonoscopy, it was possible to detect lesions as early as 5 minutes after intrarectal administration of the probe, and fluorescence lasted at least 30 minutes with high signal-to-background ratios. By switching to white light imaging, fluorescent lesions could be superimposed on sites of tumor. Fluorescence guided biopsy revealed that all fluorescent lesions contained cancer and/or low-to-high grade dysplasia (n = 16), whereas 3 out of 12 non-fluorescent lesions contained low grade dysplasia while the remainder showed no neoplasia/dysplasia. Furthermore, tumor progression in the same mouse could be followed by repeat micro-colonoscopy after application of the GGT activatable probe. CONCLUSIONS: These results indicate that it is possible to enhance the detection of CAC using a GGT activatable probe during endoscopy. This could have broad implications for the early detection of patients with long standing bowel inflammation who are at increased risk for the development of colon cancer.

The inflammasome protects?

The NLRP3 inflammasome protects against tumorigenesis in an experimental mouse model of colitis-associated cancer.

Inflammation and Colon Cancer

The connection between inflammation and tumorigenesis is well-established and in the last decade has received a great deal of supporting evidence from genetic, pharmacological, and epidemiological data. Inflammatory bowel disease is an important risk factor for the development of colon cancer. Inflammation is also likely to be involved with other forms of sporadic as well as heritable colon cancer. The molecular mechanisms by which inflammation promotes cancer development are still being uncovered and could differ between colitis-associated and other forms of colorectal cancer. Recent work has elucidated the role of distinct immune cells, cytokines, and other immune mediators in virtually all steps of colon tumorigenesis, including initiation, promotion, progression, and metastasis. These mechanisms, as well as new approaches to prevention and therapy, are discussed in this review.

Epithelial interleukin-4 receptor expression promotes colon tumor growth

Inflammatory mediators are of considerable interest as potential therapeutic targets in various cancers. Here we investigate whether interleukin (IL)-4 receptor alpha (IL4Ralpha), a component of the receptor complex for the T helper 2 cytokines IL4 and IL13, plays a role in colonic tumorigenesis. IL4Ralpha protein expression was seen in tumor cells of 28/48 human colon adenocarcinomas on a tissue microarray. In human and murine colon tumor cell lines analyzed in vitro, all of which expressed IL4Ralpha, treatment with exogenous ligand resulted in dose-dependent increases in proliferation. IL4 decreased apoptosis only in HCT116 cells. An orthotopic allograft model was used to determine in vivo effects of tumor cell-specific IL4Ra ablation. MC38 murine tumor cells with the IL4Ra gene knocked down showed reduced proliferation but no difference in apoptosis compared with controls after implantation in ceca of syngeneic mice. Mice null for IL4Ra and wild-type controls were treated with azoxymethane and dextran sulfate sodium to induce tumor formation. Mice with global deletion of IL4Ra had significantly fewer and smaller tumors. Reduced tumorigenicity correlated with decreased proliferation and increased apoptosis. Systemic blockade of IL4Ralpha-IL4 interactions with a chimeric soluble receptor protein gave similar results in the cecal implant model. Thus, IL4Ralpha, a component of the IL4R and IL13R, contributes to tumor formation in a mouse model of colitis-associated cancer. Proliferation appears to be directly mediated via IL4Ralpha on the epithelial tumor cells. Survival may be an indirect response mediated via other host cells. Our results support therapeutic targeting of IL4Ralpha in colon cancer.

A Novel Mouse Model of Inflammatory Bowel Disease Links Mammalian Target of Rapamycin-Dependent Hyperproliferation of Colonic Epithelium to Inflammation-Associated Tumorigenesis

Inflammatory bowel disease (IBD) is a high-risk condition for human colorectal cancer. However, our mechanistic understanding of the link between inflammation and tumorigenesis in the colon is limited. Here we established a novel mouse model of colitis-associated cancer by genetically inactivating signal transducer and activator of transcription 3 (Stat3) in macrophages, with partial deletion in other myeloid and lymphoid cells. Inflammation developed in the colon of mutant mice spontaneously, and tumor lesions, including invasive carcinoma, arose in the inflamed region of the intestine with a frequency similar to that observed in human IBD patients. The development of both inflammation and tumors in the mutant mice required the presence of microflora. Indeed, inflammation was associated with disruption of colonic homeostasis, fulminant epithelial/tumor cell proliferation, and activation of the mammalian target of rapamycin (mTOR)-Stat3 pathway in epithelial and tumor cells. The activation of this pathway was essential for both the excess proliferation of epithelial/tumor cells and the disruption of colonic homeostasis in the mutant mice. Notably, a similar abnormal up-regulation of mTOR-Stat3 signaling was consistently observed in the colonic epithelial cells of human IBD patients with active disease. These studies demonstrate a novel mouse model of IBD-colorectal cancer progression in which disrupted immune regulation, mTOR-Stat3 signaling, and epithelial hyperproliferation are integrated and simultaneously linked to the development of malignancy.

Tumor formation in a mouse model of colitis-associated colon cancer does not require COX-1 or COX-2 expression

Cyclooxygenase-2 (COX-2), a key enzyme of prostanoid biosynthesis, plays an important role in both hereditary and spontaneous colon cancer. Individuals with ulcerative colitis are also at high risk for colorectal cancer. To investigate the role of Cox-2 in colitis-associated colon cancer, we subjected Cox-2 luciferase-knock-in mice and Cox-2-knockout mice to a well-known mouse model of colitis-associated cancer in which animals are treated with a single-azoxymethane (AOM) injection followed by dextran sulfate sodium (DSS) administration. Tumors induced by AOM and DSS expressed significantly higher Cox-2 levels when compared with surrounding areas of colon, as detected both by luciferase reporter gene expression driven from the endogenous Cox-2 promoter and by western blotting of COX-2 protein in Cox-2 luciferase heterozygous knock-in mice. Immunofluorescence revealed that tumor stromal fibroblasts, macrophages and endothelial cells express COX-2 protein. In contrast, little COX-2 expression was observed in myofibroblasts or epithelial cells. Despite a significant elevation of COX-2 expression in AOM/DSS-induced colon tumors in wild-type mice, similar tumors developed in AOM/DSS-treated Cox-2(-/-)- and Cox-1(-/-)-knockout mice. These results indicate that cyclooxygenase-derived prostanoids are not major players in colitis-associated cancer. In contrast, tumor formation induced by multiple injections of AOM (with no DSS-induced colitis) did not occur in Cox-2(-/-)-knockout mice. Our data suggest that the mechanism of colorectal tumor promotion in colitis-associated cancer differs from the mechanism of tumor promotion for hereditary and sporadic colorectal cancer.

RAGE, carboxylated glycans and S100A8/A9 play essential roles in colitis-associated carcinogenesis

Patients with inflammatory bowel diseases are at increased risk for colorectal cancer, but the molecular mechanisms linking inflammation and cancer are not well defined. We earlier showed that carboxylated N-glycans expressed on receptor for advanced glycation end products (RAGE) and other glycoproteins mediate colitis through activation of nuclear factor kappa B (NF-κB). Because NF-κB signaling plays a critical role in the molecular pathogenesis of colitis-associated cancer (CAC), we reasoned that carboxylated glycans, RAGE and its ligands might promote CAC. Carboxylated glycans are expressed on a subpopulation of RAGE on colon cancer cells and mediate S100A8/A9 binding to RAGE. Colon tumor cells express binding sites for S100A8/A9 and binding leads to activation of NF-κB and tumor cell proliferation. Binding, downstream signaling and tumor cell proliferation are blocked by mAbGB3.1, an anti-carboxylate glycan antibody, and by anti-RAGE. In human colon tumor tissues and in a mouse model of CAC, we found that myeloid progenitors expressing S100A8 and S100A9 infiltrate regions of dysplasia and adenoma. mAbGB3.1 administration markedly reduces chronic inflammation and tumorigenesis in the mouse model of CAC and RAGE-deficient mice are resistant to the onset of CAC. These findings show that RAGE, carboxylated glycans and S100A8/A9 play essential roles in tumor–stromal interactions, leading to inflammation-associated colon carcinogenesis.

IKKβ Links Inflammation and Tumorigenesis in a Mouse Model of Colitis-Associated Cancer

A link between inflammation and cancer has long been suspected, but its molecular nature remained ill defined. A key player in inflammation is transcription factor NF-κB whose activity is triggered in response to infectious agents and proinflammatory cytokines via the IκB kinase (IKK) complex. Using a colitis-associated cancer model, we show that although deletion of IKKβ in intestinal epithelial cells does not decrease inflammation, it leads to a dramatic decrease in tumor incidence without affecting tumor size. This is linked to increased epithelial apoptosis during tumor promotion. Deleting IKKβ in myeloid cells, however, results in a significant decrease in tumor size. This deletion diminishes expression of proinflammatory cytokines that may serve as tumor growth factors, without affecting apoptosis. Thus, specific inactivation of the IKK/NF-κB pathway in two different cell types can attenuate formation of inflammation-associated tumors. In addition to suppressing apoptosis in advanced tumors, IKKβ may link inflammation to cancer.

New safety standard for bike helmets

Chronic inflammation increases colorectal cancer (CRC) risk as seen in ulcerative colitis (UC). Proinflammatory cytokines play a critical role in mediating the development of colitis associated cancer (CAC). In this study, the therapeutic efficacy of anti-interleukin (IL)-17A by anti-IL-17A antibody injection on the development of CAC was assessed in 1,2-dimethylhydrazine (DMH) plus dextran sulfate sodium (DSS) induced CAC mouse model. The results showed that mice dosed with DMH plus DSS for 10 weeks evoked high degree dysplastic lesion in the large bowel that accompanied with significant increased IL-17A expression, proliferation index and inflammation degree in mice. After anti-IL-17A antibody injection for 2 weeks, the number of tumors, proliferation index and the expression level of IL-17A protein in the large bowel tissues were significantly decreased. Therefore, we concluded that the anti-IL-17A blockade can suppress the development of CAC and is a potential therapeutic agent for the prevention of CAC in colitis mice.