Colon Tumor Development Research Articles

A20 regulates canonical wnt-signaling through an interaction with RIPK4.

A20 is a ubiquitin-editing enzyme that is known to regulate inflammatory signaling and cell death. However, A20 mutations are also frequently found in multiple malignancies suggesting a potential role as a tumor suppressor as well. We recently described a novel role for A20 in regulating the wnt-beta-catenin signaling pathway and suppressing colonic tumor development in mice. The underlying mechanisms for this phenomenon are unclear. To study this, we first generated A20 knockout cell lines by genome-editing techniques. Using these cells, we show that loss of A20 causes dysregulation of wnt-dependent gene expression by RNAseq. Mechanistically, A20 interacts with a proximal signaling component of the wnt-signaling pathway, receptor interacting protein kinase 4 (RIPK4), and regulation of wnt-signaling by A20 occurs through RIPK4. Finally, similar to the mechanism by which A20 regulates other members of the receptor interacting protein kinase family, A20 modifies ubiquitin chains on RIPK4 suggesting a possible molecular mechanism for A20’s control over the wnt-signaling pathway.

MK2 contributes to tumor progression by promoting M2 macrophage polarization and tumor angiogenesis

Chronic inflammation is a major risk factor for colorectal cancer. The p38/MAPKAP Kinase 2 (MK2) kinase axis controls the synthesis of proinflammatory cytokines that mediate both chronic inflammation and tumor progression. Blockade of this pathway has been previously reported to suppress inflammation and to prevent colorectal tumorigenesis in a mouse model of inflammation-driven colorectal cancer, by mechanisms that are still unclear. Here, using whole-animal and tissue-specific MK2 KO mice, we show that MK2 activity in the myeloid compartment promotes tumor progression by supporting tumor neoangiogenesis in vivo. Mechanistically, we demonstrate that MK2 promotes polarization of tumor-associated macrophages into protumorigenic, proangiogenic M2-like macrophages. We further confirmed our results in human cell lines, where MK2 chemical inhibition in macrophages impairs M2 polarization and M2 macrophage-induced angiogenesis. Together, this study provides a molecular and cellular mechanism for the protumorigenic function of MK2.

Crosstalk between gut microbiota and Sirtuin-3 in colonic inflammation and tumorigenesis

Colorectal cancer (CRC) is a disease involving a variety of genetic and environmental factors. Sirtuin-3 (Sirt3) is expressed at a low level in cancer tissues of CRC, but it is unclear how Sirt3 modulates colonic tumorigenesis. In this study, we found that gut microbiota play a central role in the resistance to CRC tumor formation in wild-type (WT) mice through APC (Adenomatous Polyposis Coli)-mutant mouse microbiota transfer via Wnt signaling. We also found that Sirt3-deficient mice were hypersusceptible to colonic inflammation and tumor development through altered intestinal integrity and p38 signaling, respectively. Furthermore, susceptibility to colorectal tumorigenesis was aggravated by initial commensal microbiota deletion via Wnt signaling. Mice with Sirt3-deficient microbiota transfer followed by chemically induced colon tumorigenesis had low Sirt3 expression compared to WT control microbiome transfer, mainly due to a decrease in Escherichia/Shigella, as well as an increase in Lactobacillus reuteri and Lactobacillus taiwanensis. Collectively, our data revealed that Sirt3 is an anti-inflammatory and tumor-suppressing gene that interacts with the gut microbiota during colon tumorigenesis.

Interleukin 33 Signaling Restrains Sporadic Colon Cancer in an Interferon-γ-Dependent Manner.

Interleukin 33 (IL33) is an inflammatory cytokine released during necrotic cell death. The epithelium and stroma of the intestine express large amounts of IL33 and its receptor St2. IL33 is therefore continuously released during homeostatic turnover of the intestinal mucosa. Although IL33 can prevent colon cancer associated with inflammatory colitis, the contribution of IL33 signaling to sporadic colon cancer remains unknown. Here, we utilized a mouse model of sporadic colon cancer to investigate the contribution of IL33 signaling to tumorigenesis in the absence of preexisting inflammation. We demonstrated that genetic ablation of St2 enhanced colon tumor development. Conversely, administration of recombinant IL33 reduced growth of colon cancer cell allografts. In reciprocal bone marrow chimeras, the concurrent loss of IL33 signaling within radioresistant nonhematopoietic, and the radiosensitive hematopoietic, compartments was associated with increased tumor burden. We detected St2 expression within the radioresistant mesenchymal cell compartment of the colon whose stimulation with IL33 induced expression of bona fide NF-κB target genes. Mechanistically, we discovered that St2 deficiency within the nonhematopoietic compartment coincided with increased abundance of regulatory T cells and suppression of an IFNγ gene expression signature, whereas IL33 administration triggered IFNγ expression by tumor allograft-infiltrating T cells. The decrease of this IFNγ gene expression signature was associated with more aggressive disease in human colon cancer patients, suggesting that lack of IL33 signaling impaired the generation of a potent IFNγ-mediated antitumor immune response. Collectively, our data reveal that IL33 functions as a tumor suppressor in sporadic colon cancer. Cancer Immunol Res; 6(4); 409-21. ©2018 AACR.

CXCR4 inhibitor, MSX‐122 suppresses AOM‐induced colon cancer in Apc+/Min mouse

IntroductionIn prior studies, we showed that EGFR is required for tumor promotion by Western diet in the azoxymethane (AOM) model of sporadic colon cancer and the AOM/DSS model of inflammation‐associated colon cancer. We also demonstrated that ADAM17, the metalloprotease responsible for shedding membrane‐bound EGFR ligands, controls tumor development in both the AOM and the Apc+/mutant multiple intestinal neoplasia (Min) mouse model. Furthermore, we established that Sdf1a‐CXCR4 signals activated EGFR by an ADAM17‐dependent mechanism in colon cancer cells; and that Western diet up‐regulated Sdf1a‐CXCR4 and ADAM17 in colonic mucosa. We hypothesized that CXCR4 blockade might inhibit colon cancer development. The aim of this study was to test the ability of a novel CXCR4 antagonist, MSX‐122 (substituted benzylamine) to inhibit AOM‐promoted colon cancer in Apc+/Min mice. Min mice without AOM treatment mostly develop small intestinal tumors, whereas AOM‐treated Apc+/Min mice develop colon cancers (Suzui et al 2002).MethodsIn studies in cell culture, we examined the ability of MSX‐122 to block Sdf1a‐induced EGFR transactivation. In vivo, Apc+/Min mice were given AOM (10 mg i.p./kg body weight) and two weeks later mice were started on a Western diet (20% fat). Mice received MSX‐122 i.p. (2.5 mg/kg body weight, n=12) or vehicle (DMSO, n=13) three times weekly and were killed after 10 wks.ResultsMSX‐122 blocked EGFR transactivation by Sdf1a in HT29 colon cancer cells as assessed by reductions in pErbB2, pAKT and pERK. In vivo, MSX‐122 was well tolerated with mice showing comparable weight gain to vehicle‐treated mice. As expected, AOM induced colon tumors in Apc+/Min mice. MSX‐122 significantly reduced colon tumor incidence (92.3% vs. 50.0%, p=0.025) and cancer incidence (69.2% vs. 16.7%, p=0.015). MSX‐122 also reduced tumor burden as assessed by total tumor multiplicity (1.8 vs. 1.0 tumor per TBM; p=0.02), tumor volume (169.5 mm3 vs. 61.2 mm3, p<0.023) and tumor proliferation as assessed by Ki67 staining (37.2±3.6% vs. 25.3±5.8%, p<0.005). Cancer multiplicity also appeared to be decreased (1.6 vs. 1.0 tumor/TBM, p=0.17).ConclusionsMSX‐122 blocked EGFR transactivation by CXCR4 agonist Sdf1a in colon cancer cells. MSX‐122 also inhibited colon tumor development and progression in the AOM‐promoted Apc+/Min mouse model. We speculate that MSX‐122, which was well tolerated in a phase 1b clinical trial (Painter, W. 2015), could serve as a chemopreventive agent in individuals at increased risk for colon cancer.Support or Funding InformationNIH R01CA164124This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Vitamin D deficiency in the ApcPirc/+ rat does not exacerbate colonic tumorigenesis, while low dietary calcium might be protective.

ABSTRACTHuman studies have shown that individuals with colon cancer tend to have lower serum 25-hydroxy-vitamin D3 [25(OH)D3] levels compared with healthy controls, but whether this link is causative, a result of the disease or an indicator of another factor altogether has yet to be demonstrated. In humans, vitamin D, calcium and UV exposure are inextricably linked; therefore, understanding the individual and combined roles of each of these will require animal models specifically designed to address these questions. To begin to untangle this network, our group has employed the ApcPirc/+ rat, which contains a truncating mutation in the Apc gene, leading to the development of colonic tumors. Our group previously utilized this model to demonstrate that vitamin D supplementation above normal does not reduce colonic tumor burden and, in fact, increased tumor multiplicity in a dose-dependent manner. In the current study, we tested whether vitamin D deficiency plays a causative role in tumor development using two strains which differ in their susceptibility to intestinal tumorigenesis. In the colon, vitamin D deficiency did not increase the development of tumors in either strain, and was actually protective in one strain. Unexpectedly, low dietary calcium combined with vitamin D deficiency significantly suppressed tumor development in the small intestine and colon of both strains. The vast majority of tumors in the human intestine occur in the colon, and we find no evidence to support a direct role of vitamin D deficiency in increasing colonic tumorigenesis, and low calcium might protect against tumor development.This article has an associated First Person interview with the first author of the paper.

Enhancement of colon carcinogenesis by the combination of indole-3 carbinol and synbiotics in hemin-fed rats

The risk of developing colorectal cancer (CRC) could be associated with red and processed meat intake. Experimental data supports that hemin iron, found abundantly in red meat, promotes CRC in mice and rats, while indole-3 carbinol (I3C) and synbiotics (syn) exert anti-carcinogenic activities in most studies of colon carcinogenesis. This study aimed to investigate the modifying effects of I3C and syn (inulin + Bifidobacterium lactis), given separately or together, on dimethylhidrazine (DMH)-induced colon carcinogenesis in hemin-fed rats. All animals were given four subcutaneous DMH injections and then, two weeks after carcinogen exposure, they began a basal diet containing hemin, hemin + I3C, hemin + syn, or hemin + I3C + syn for 23 weeks. The combination of I3C + syn significantly increased fecal water genotoxicity, tumor volume and invasiveness when compared to the hemin-fed control group. The groups fed I3C or syn alone had a significant reduction in the number of preneoplastic aberrant crypt foci (ACF) lesions compared to the hemin-fed group. Dietary I3C also reduced fecal water genotoxicity. Gene expression analysis of colorectal tumors demonstrated that the combination of dietary I3C + syn increased transcript levels for Raf1 and decreased tumor progression and invasiveness related to the genes Cdh1 and Appl1. This analysis also revealed that the Tnf and Cdh1 genes were significantly up- and down-regulated, respectively, in tumors of rats that received I3C, in comparison with the hemin-fed group. These findings reveal that the joint administration of I3C and syn enhanced the development of colon tumors induced by DMH in hemin-fed rats, while they potentially reduced ACF development when given alone.

IL-17A-Induced PLET1 Expression Contributes to Tissue Repair and Colon Tumorigenesis.

This study identifies a novel mechanism linking IL-17A with colon tissue repair and tumor development. Abrogation of IL-17A signaling in mice attenuated tissue repair of dextran sulfate sodium (DSS)-induced damage in colon epithelium and markedly reduced tumor development in an azoxymethane/DSS model of colitis-associated cancer. A novel IL-17A target gene, PLET1 (a progenitor cell marker involved in wound healing), was highly induced in DSS-treated colon tissues and tumors in an IL-17RC-dependent manner. PLET1 expression was induced in LGR5+ colon epithelial cells after DSS treatment. LGR5+PLET1+ marks a highly proliferative cell population with enhanced expression of IL-17A target genes. PLET1 deficiency impaired tissue repair of DSS-induced damage in colon epithelium and reduced tumor formation in an azoxymethane/DSS model of colitis-associated cancer. Our results suggest that IL-17A-induced PLET1 expression contributes to tissue repair and colon tumorigenesis.

DDB2 Is a Novel Regulator of Wnt Signaling in Colon Cancer.

Deregulation of the Wnt/β-catenin signaling pathway drives the development of colorectal cancer, but understanding of this pathway remains incomplete. Here, we report that the damage-specific DNA-binding protein DDB2 is critical for β-catenin-mediated activation of RNF43, which restricts Wnt signaling by removing Wnt receptors from the cell surface. Reduced expression of DDB2 and RNF43 was observed in human hyperplastic colonic foci. DDB2 recruited EZH2 and β-catenin at an upstream site in the Rnf43 gene, enabling functional interaction with distant TCF4/β-catenin-binding sites in the intron of Rnf43 This novel activity of DDB2 was required for RNF43 function as a negative feedback regulator of Wnt signaling. Mice genetically deficient in DDB2 exhibited increased susceptibility to colon tumor development in a manner associated with higher abundance of the Wnt receptor-expressing cells and greater activation of the downstream Wnt pathway. Our results identify DDB2 as both a partner and regulator of Wnt signaling, with an important role in suppressing colon cancer development. Cancer Res; 77(23); 6562-75. ©2017 AACR.

MiR-148a inhibits colitis and colitis-associated tumorigenesis in mice.

miR-148a has been shown to regulate inflammation, immunity and the growth of certain tumors, but its roles in colitis and colorectal tumorigenesis remain largely undetermined. Here we found miR-148a-deficient mice to be more susceptible to colitis and colitis-associated tumorigenesis. Both were associated with increased nuclear factor κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) signaling. Bone marrow- and non-bone marrow-derived miR-148a contributed to colitis and colitis-associated tumorigenesis. miR-148a loss of heterozygosity exacerbated Apcmin/+ colon and small intestinal spontaneous tumor development. Restoring miR-148a expression prevented both spontaneous and carcinogen-induced colon tumor development. miR-148a was downregulated in human inflammatory bowel disease (IBD) and colorectal cancer patient tissues. This correlated with a high degree of miR-148a promoter methylation mediated by a complex comprised of P65 and DNA methyltransferase 3 alpha (DNMT3A). miR-148a directly targets several well-accepted upstream regulators of NF-κB and STAT3 signaling, including GP130, IKKα, IKKβ, IL1R1 and TNFR2, which leads to decreased NF-κB and STAT3 activation in macrophages and colon tissues. Our findings reveal that miR-148a is an indirect tumor suppressor that modulates colitis and colitis-associated tumorigenesis by suppressing the expression of signaling by NF-κB and STAT3 and their pro-inflammatory consequences.

Ca2+/calmodulin-dependent protein kinase II regulates colon cancer proliferation and migration via ERK1/2 and p38 pathways.

AIMTo investigate the role of calmodulin-dependent protein kinase II (CaMKII) in colon cancer growth, migration and invasion.METHODSCaMKII expression in colon cancer and paracancerous tissues was evaluated via immunochemistry. Transcriptional and posttranscriptional levels of CaMKIIin tissue samples and MMP2, MMP9 and TIMP-1 expression in the human colon cancer cell line HCT116 were assessed by qRT-PCR and western blot. Cell proliferation was detected with the MTT assay. Cancer cell migration and invasion were investigated with the Transwell culture system and wound-healing assay.RESULTSWe first demonstrated that CaMKII was over-expressed in human colon cancers and was associated with cancer differentiation. In the human colon cancer cell line HCT116, the CaMKII-specific inhibitor KN93, but not its inactive analogue KN92, decreased cancer cell proliferation. Furthermore, KN93 also significantly prohibited HCT116 cell migration and invasion. The specific inhibition of ERK1/2 or p38 decreased the proliferation and migration of colon cancer cells.CONCLUSIONOur findings highlight CaMKII as a potential critical mediator in human colon tumor development and metastasis.

Leukotriene B4-receptor-1 mediated host response shapes gut microbiota and controls colon tumor progression

ABSTRACTInflammation and infection are key promoters of colon cancer but the molecular interplay between these events is largely unknown. Mice deficient in leukotriene B4 receptor1 (BLT1) are protected in inflammatory disease models of arthritis, asthma and atherosclerosis. In this study, we show that BLT1−/− mice when bred onto a spontaneous tumor (ApcMin/+) model displayed an increase in the rate of intestinal tumor development and mortality. A paradoxical increase in inflammation in the tumors from the BLT1−/−ApcMin/+ mice is coincidental with defective host response to infection. Germ-free BLT1−/−ApcMin/+ mice are free from colon tumors that reappeared upon fecal transplantation. Analysis of microbiota showed defective host response in BLT1−/− ApcMin/+ mice reshapes the gut microbiota to promote colon tumor development. The BLT1−/−MyD88−/− double deficient mice are susceptible to lethal neonatal infections. Broad-spectrum antibiotic treatment eliminated neonatal lethality in BLT1−/−MyD88−/− mice and the BLT1−/−MyD88−/−ApcMin+ mice are protected from colon tumor development. These results identify a novel interplay between the Toll-like receptor mediated microbial sensing mechanisms and BLT1-mediated host response in the control of colon tumor development.

Sphingosine kinase 1 expression enhances colon tumor growth

BackgroundAccumulating evidence suggests that sphingosine kinase 1 (SphK1)/sphingosine 1-phosphate pathway plays a pivotal role in colon carcinogenesis.MethodsTo further support the evidence, we investigated the effects of SphK1 using three separate animal models: SphK1 knockout mice, SphK1 overexpressing transgenic mice, and SphK1 overexpression in human colon cancer xenografts. Using azoxymethane (AOM, colon carcinogen), we analyzed colon tumor development in SphK1 KO and SphK1 overexpression in intestinal epithelial cells regulated by a tet-on system. Then, we analyzed subcutaneous tumor growth using xenografts of HT-29 human colon cancer cell. Finally, immunohistochemical analyses for SphK1 and COX-2 were performed on human colon cancer tissue microarray.ResultsSphK1 KO mice, compared to wild-type mice, demonstrated a significant inhibition in colon cancer development induced by AOM (58.6% vs. 96.4%, respectively, P < 0.005). Tumor multiplicity (1.00 vs. 1.64 per colon, respectively, P < 0.05) and tumor volume (14.82 mm3 vs. 29.10 mm3, P < 0.05) were both significantly reduced in SphK1 KO mice compared to wild-type mice. Next, SphK1 overexpression in HT-29 enhanced tumor growth as compared to GFP control in nude mice (229.5 mm3 vs. 90.9 mm3, respectively, P < 0.05). Furthermore, overexpression of SphK1 in intestinal epithelial cells significantly enhances AOM-induced colon tumor formation (P < 0.05). Lastly, SphK1 and COX-2 intensity tended to reduce overall survival of late stage colon cancer patients.ConclusionsSphK1 expression regulates the early stage of colon carcinogenesis and tumor growth, thus inhibition of SphK1 may be an effective strategy for colon cancer chemoprevention.

Lactobacillus casei Zhang and vitamin K2 prevent intestinal tumorigenesis in mice via adiponectin-elevated different signaling pathways.

The incidence of colon cancer has increased considerably and the intestinal microbiota participate in the development of colon cancer. We showed that the L. casei Zhang or vitamin K2 (Menaquinone-7) intervention significantly alleviated intestinal tumor burden in mice. This was associated with increased serum adiponectin levels in both treatments. But osteocalcin level was only increased by L. casei Zhang. Furthermore, the anti-carcinogenic actions of L. casei Zhang were mediated by hepatic Chloride channel-3(CLCN3)/Nuclear Factor Kappa B(NF-κB) and intestinal Claudin15/Chloride intracellular channel 4(CLIC4)/Transforming Growth Factor Beta(TGF-β) signaling, while the vitamin K2 effect involved a hepatic Vitamin D Receptor(VDR)-phosphorylated AMPK signaling pathway. Fecal DNA sequencing by the Pacbio RSII method revealed there was significantly lower Helicobacter apodemus, Helicobacter mesocricetorum, Allobaculum stercoricanis and Adlercreutzia equolifaciens following both interventions compared to the model group. Moreover, different caecum acetic acid and butyric acid levels and enrichment of other specific microbes also determined the activity of the different regulatory pathways. Together these data show that L. casei Zhang and Vitamin K2 can suppress gut risk microbes and promote beneficial microbial metabolites to reduce colonic tumor development in mice.

ADAM17 is a Tumor Promoter and Therapeutic Target in Western Diet-associated Colon Cancer.

Epidermal growth factor receptors (EGFR) are required for tumor promotion by Western diet. The metalloprotease, ADAM17 activates EGFR by releasing pro-EGFR ligands. ADAM17 is regulated by G-protein-coupled receptors, including CXCR4. Here we investigated CXCR4-ADAM17 crosstalk and examined the role of ADAM17 in tumorigenesis. We used CXCR4 inhibitor, AMD3100 and ADAM17 inhibitor, BMS566394 to assess CXCR4-ADAM17 crosstalk in colon cancer cells. We compared the expression of CXCR4 ligand, CXCL2, and ADAM17 in mice fed Western diet versus standard diet. Separately, mice were treated with marimastat, a broad-spectrum ADAM17 inhibitor, or AMD3100 to assess EGFR activation by ADAM17 and CXCR4. Using Apc-mutant Min mice, we investigated the effects of ADAM17/10 inhibitor INCB3619 on tumorigenesis. To assess the effects of colonocyte ADAM17, mice with ADAM17 conditional deletion were treated with azoxymethane (AOM). ADAM17 expression was also compared in colonocytes from primary human colon cancers and adjacent mucosa. CXCL12 treatment activated colon cancer cell EGFR signals, and CXCR4 or ADAM17 blockade reduced this activation. In vivo, Western diet increased CXCL12 in stromal cells and TGFα in colonocytes. Marimastat or AMD3100 caused >50% reduction in EGFR signals (P < 0.05). In Min mice, INCB3619 reduced EGFR signals in adenomas and inhibited intestinal tumor multiplicity (P < 0.05). In the AOM model, colonocyte ADAM17 deletion reduced EGFR signals and colonic tumor development (P < 0.05). Finally, ADAM17 was upregulated >2.5-fold in human malignant colonocytes. ADAM17 is a Western diet-inducible enzyme activated by CXCL12-CXCR4 signaling, suggesting the pathway: Western diet→CXCL12→CXCR4→ADAM17→TGFα→EGFR. ADAM17 might serve as a druggable target in chemoprevention strategies. Clin Cancer Res; 23(2); 549-61. ©2016 AACR.

Covering the Cover

Covering the Cover

Repression of MicroRNA Function Mediates Inflammation-associated Colon Tumorigenesis

Little is known about the mechanisms by which chronic inflammation contributes to carcinogenesis, such as the development of colon tumors in patients with inflammatory bowel diseases. Specific microRNA (miRNAs) can function as suppressors or oncogenes, and widespread alterations in miRNA expression have been associated with tumorigenesis. We studied whether alterations in miRNA function contribute to inflammation-associated colon carcinogenesis. We studied the effects of inflammatory cytokines, such as tumor necrosis factor, interleukin-1α (IL1A), and IL1β (IL1B), on miRNA function, measured by activity of reporter constructs containing miRNA-binding sites in their 3' untranslated regions, in human 293T embryonic kidney, Caco-2, HT29, and HCT116 colon carcinoma cells, as well as dicer+/+ and dicer-/-, and Apobec3+/+ and Apobec3-/- mouse embryonic fibroblasts. Cells were analyzed by immunoblots, immunohistochemistry, and flow cytometry. We generated transgenic mice expressing reporter constructs regulated by LET7B, MIR122, and MIR29b response elements; some mice were given injections of miRNA inhibitors (anti-MIR122 or anti-LET7B), a negative control, or tumor necrosis factor. Liver tissues were collected and analyzed by immunoblotting. Reporter mice were given azoxymethane followed by dextran sulfate sodium to induce colitis and colon tumors; some mice were given the ROCK inhibitor fasudil along with these agents (ROCK inhibitors increase miRNA function). Colon tissues were collected and analyzed by immunohistochemistry, immunoblots, and fluorescence microscopy. Incubation of cell lines with inflammatory cytokines reduced the ability of miRNAs to down-regulate expression from reporter constructs; dicer was required for this effect, so these cytokines relieve miRNA-dependent reductions in expression. The cytokines promoted degradation of APOBEC3G, which normally promotes miRNA loading into argonaute 2-related complexes. Mice with colitis had reduced miRNA function, based on increased expression of reporter genes. Administration of fasudil to mice did not reduce the severity of colitis that developed but greatly reduced the numbers of colon tumors formed (mean 2 tumors/colon in mice given fasudil vs 9 tumors/colon in mice given control agent). We made similar observations in IL10-deficient mice. We found inflammatory cytokines to reduce the activities of miRNAs. In mice with colitis, activities of miRNAs are reduced; administration of an agent that increases miRNA function prevents colon tumor formation in these mice. This pathway might be targeted to prevent colon carcinogenesis in patients with inflammatory bowel diseases.

The role of Pygo2 for Wnt/ß-catenin signaling activity during intestinal tumor initiation and progression.

Pygo2 acts as a co-activator of Wnt signaling in a nuclear complex with ß-catenin/BCL9/BCL9-2 to increase target gene transcription. Previous studies showed that Pygo2 is upregulated in murine intestinal tumors and human colon cancer, but is apparently dispensable for normal intestinal homeostasis. Here, we have evaluated the in vivo role of Pygo2 during intestinal tumorigenesis using Pygo2 deficient mice. We analyzed chemically induced colon tumor development and conditional intestine specific mouse models harboring either Apc loss-of-function (LOF) or Ctnnb1 gain-of-function (ß-catenin GOF). Remarkably, the number and size of chemically induced tumors was significantly reduced in Pygo2 deficient mice, suggesting that Pygo2 has a tumor promoting function. Furthermore, loss of Pygo2 rescued early tumorigenesis of Ctnnb1 GOF mutants. In contrast, Pygo2 ablation was not sufficient to prevent tumor development of Apc LOF mice. The effect on tumor formation by Pygo2 knockout was linked to the repression of specific deregulated Wnt target genes, in particular of c-Myc. Moreover, the role of Pygo2 appears to be associated with the signaling output of deregulated Wnt signaling in the different tumor models. Thus, targeting Pygo2 might provide a novel strategy to suppress tumor formation in a context dependent manner.

Ultrasound imaging of splenomegaly as a proxy to monitor colon tumor development in Apc(min716/+) mice.

Animal models of colon cancer are widely used to understand the molecular mechanisms and pathogenesis of the disease. These animal models require a substantial investment of time and traditionally necessitate the killing of the animal to measure the tumor progression. Several in vivo imaging techniques are being used in both human clinics and preclinical studies, albeit at high cost and requiring particular expertise. Here, we report that the progression of splenomegaly coincides with and positively correlates to colon tumor development in Apc min716/+ mice expressing a mutant gene encoding an adenomatous polyposis coli protein truncated at amino acid 716. Ultrasound image‐based spleen size measurement precisely mirrors splenomegaly development in vivo in the tumor‐laden Apc min716/+ mice. Moreover, the spleen dimensions extracted from the ultrasound sonograms are positively correlated with normalized spleen weight and the number and area of colon tumors. Hence, we propose measuring the spleen size in vivo by ultrasound imaging as a novel approach to estimate splenomegaly development and to indirectly monitor colon tumor development in Apc min716/+ mice. The widespread use of ultrasound machines in the laboratory setting, coupled with the fact that it is a noninvasive method, make it a straightforward and useful tool for monitoring the experimental progress of colon cancer in mice and determining end points without killing animals strictly for diagnostics purposes.

Abstract 5248: ED-71, an analogue of Vitamin D3, blocks the promotion but not the initiation of colorectal tumors in the Apc+/Min-FCCC mouse model

Abstract Results from several studies demonstrate an inverse relationship between circulating levels of Vitamin D and risk of colorectal cancer. Eldecalcitol (1α,25-dihydroxy-2β-(3-hydroxypropyloxy) Vitamin D3; ED-71) is a novel analog of calcitriol, the most active form of Vitamin D3. ED-71 is more potent in stimulating bone remodeling and has been approved in Japan for the treatment of osteoporosis. The goal of this study was to assess the ability of ED-71 to inhibit spontaneous colorectal adenomas in a unique strain of multiple intestinal neoplasia (Apc+/Min-FCCC) mice. Male mice (6 wks of age) were randomized to treatment groups based on colon tumor status (endoscopic confirmation as tumor-free or -bearing) and body weight (bw) and administered: vehicle (MCT), calcitriol (0.25 μg/kg bw), or ED-71 (0.05 or 0.1 μg/kg bw) by gavage. Mice were treated every other day and bws were recorded weekly. After 14 wks of treatment, the small intestines and colons were excised and examined for gross tumors. Colorectal tumors &amp;gt;3 mm in diameter were frozen for gene expression analyses. The remaining tissue was fixed in formalin and processed for histological review. The multiplicity of gross small intestinal tumors in animals treated with ED-71 (both doses) was comparable to that of vehicle-treated controls. In contrast, the multiplicity of small intestinal tumors was elevated 34.6% over that of controls in animals treated with calcitriol (Mean ± SEM: 28.4 ± 2.6 vs. 21.1 ± 2.8, respectively; P = 0.034). The ability of ED-71 to inhibit colon tumorigenesis was evaluated independently in mice with vs. without tumors at treatment initiation. In tumor-bearing mice, neither calcitriol nor ED-71 (both doses) had any significant effect on the multiplicity of colorectal tumors as compared to control mice. However in tumor-free mice, ED-71 (0.1 μg/kg bw) reduced the mean incidence of adenomas (&amp;gt; 4 crypts) by 47% (ED-71 - 45.5%, controls 92.3%; P = 0.02) and the multiplicity by 47.6% (Mean ± SEM: ED-71 - 1.1 ± 0.39, controls - 2.1 ± 0.72; P &amp;gt; 0.05). In contrast, the multiplicity of microadenomas (≤ 4 crypts) was increased in mice treated with ED-71 (0.1 μg/kg bw) as compared to controls (0.9 ± 0.22 vs. 0.5 ± 0.25 P = 0.06, respectively). These findings suggest that ED-71 is effective in preventing the transition of microadenomas to mature adenomas. The lack of an effect of ED-71 on colon tumor development in mice bearing tumors at baseline could be due in part to loss of the Vitamin D receptor in colon adenomas, as confirmed by real-time PCR. Insight into the mechanism by which ED-71 inhibits adenoma development is being gained from analyses of Vitamin D signaling and microRNA expression in treated colonic epithelial cells. These promising data provide support for future studies to determine the potential utility of ED-71 in preventing colorectal cancer in high-risk patients found to be tumor-free during surveillance endoscopy. (Supported by NCI HHSN261201200015I) Citation Format: Wen-Chi L. Chang, Harry S. Cooper, Esther Kaunga, Lisa Vanderveer, Jing Peng, Suen S. Chen, Margie L. Clapper. ED-71, an analogue of Vitamin D3, blocks the promotion but not the initiation of colorectal tumors in the Apc+/Min-FCCC mouse model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5248.