Epithelial-specific deletion of 11?-HSD2 hinders Apcmin/+ mouse tumorigenesis.
ABSTRACT: Cyclooxygenase-2 (COX-2)-derived prostaglandin E2 (PGE2) promotes colorectal tumorigenesis. Glucocorticoids are endogenous and potent COX-2 inhibitors, and their local actions are downregulated by 11?-hydroxysteroid dehydrogenase type II (11?-HSD2)-mediated metabolism. Previously, it was reported that 11?-HSD2 is increased in human colonic and Apc(min/+) mouse intestinal adenomas and correlated with increased COX-2, and 11?-HSD2 inhibition suppressed the COX-2 pathway and decreased tumorigenesis. Because 11?-HSD2 is expressed in Apc(min/+) mouse intestinal adenoma stromal and epithelial cells, Apc(min/+) mice were generated with selective deletion of 11?-HSD2 in intestinal epithelial cells (Vil-Cre-HSD2(-/-) Apc(min/+)). Deletion of 11?-HSD2 in intestinal epithelia led to marked inhibition of Apc(min/+) mouse intestinal tumorigenesis. Immunostaining indicated decreased 11?-HSD2 and COX-2 expression in adenoma epithelia, whereas stromal COX-2 expression was intact in Vil-Cre-HSD2(-/-) Apc(min/+) mice. In Vil-Cre-HSD2(-/-) Apc(min/+) mouse intestinal adenomas, both p53 and p21 mRNA and protein were increased, with a concomitant decrease in pRb, indicating glucocorticoid-mediated G1-arrest. Further study revealed that REDD1 (regulated in development and DNA damage responses 1), a novel stress-induced gene that inhibits mTOR signaling, was increased, whereas the mTOR signaling pathway was inhibited. Therefore, in Vil-Cre-HSD2(-/-) Apc(min/+) mice, epithelial cell 11?-HSD2 deficiency leads to inhibition of adenoma initiation and growth by attenuation of COX-2 expression, increased cell-cycle arrest, and inhibition of mTOR signaling as a result of increased tumor intracellular active glucocorticoids.Inhibition of 11?-HSD2 may represent a novel approach for colorectal cancer chemoprevention by increasing tumor glucocorticoid activity, which in turn inhibits tumor growth by multiple pathways.
Project description:Genetic deletion or pharmacological inhibition of cyclooxygenase (COX)-2 abrogates intestinal adenoma development at early stages of colorectal carcinogenesis. COX-2 is localised to stromal cells (predominantly macrophages) in human and mouse intestinal adenomas. Therefore, we tested the hypothesis that paracrine Cox-2-mediated signalling from macrophages drives adenoma growth and progression in vivo in the Apc Min/+ mouse model of intestinal tumorigenesis. Using a transgenic C57Bl/6 mouse model of Cox-2 over-expression driven by the chicken lysozyme locus (cLys-Cox-2), which directs integration site-independent, copy number-dependent transgene expression restricted to macrophages, we demonstrated that stromal macrophage Cox-2 in colorectal (but not small intestinal) adenomas from cLys-Cox-2 x Apc Min/+ mice was associated with significantly increased tumour size (P?=?0.025) and multiplicity (P?=?0.025), compared with control Apc Min/+ mice. Transgenic macrophage Cox-2 expression was associated with increased dysplasia, epithelial cell Cox-2 expression and submucosal tumour invasion, as well as increased nuclear ?-catenin translocation in dysplastic epithelial cells. In vitro studies confirmed that paracrine macrophage Cox-2 signalling drives catenin-related transcription in intestinal epithelial cells. Paracrine macrophage Cox-2 activity drives growth and progression of Apc Min/+ mouse colonic adenomas, linked to increased epithelial cell ?-catenin dysregulation. Stromal cell (macrophage) gene regulation and signalling represent valid targets for chemoprevention of colorectal cancer.
Project description:To analyse roles of HAI-1/Spint1 in intestinal tumorigenesis, we examined the effect of intestine-specific deletion of Spint1 gene on Apc(Min/+) mice. The loss of Hai-1/Spint1 significantly accelerated tumor formation in ApcMin/+ mice and shortened their survival periods. Mouse small intestine tumor tissue or background mucosa lacking macroscopically visible tumors were proceeded to RNA extraction and hybridization on microarrays (Affymetrix Mouse Genome 430 2.0 Array). Non-tumor or tumor intestinal mucosa tissues of Apc (Min/+)/Spint1 (flox/flox) mice and non-tumor or tumor intestinal mucosa tissues of Apc (Min/+)/Spint1 (flox/flox)/Vil-Cre mice were analysed. The experiment was repeated respectively.
Project description:Two important protein-protein interactions establish E-cadherin (Cdh1) in the adhesion complex; homophilic binding via the extra-cellular (EC1) domain and cytoplasmic tail binding to ?-catenin. Here, we evaluate whether E-cadherin binding can inhibit ?-catenin when there is loss of Adenomatous polyposis coli (APC) from the ?-catenin destruction complex. Combined conditional loss of Cdh1 and Apc were generated in the intestine, intestinal adenoma and adenoma organoids. Combined intestinal disruption (Cdh1fl/flApcfl/flVil-CreERT2) resulted in lethality, breakdown of the intestinal barrier, increased Wnt target gene expression and increased nuclear ?-catenin localization, suggesting that E-cadherin inhibits ?-catenin. Combination with an intestinal stem cell Cre (Lgr5CreERT2) resulted in Apc?/? recombination and adenoma, but intact Cdh1fl/fl alleles. Cultured Apc?/?Cdh1fl/fl adenoma cells infected with adenovirus-Cre induced Cdh1fl/fl recombination (Cdh1?/?), disruption of organoid morphology, nuclear ?-catenin localization, and cells with an epithelial-mesenchymal phenotype. Complementation with adenovirus expressing wild-type Cdh1 (Cdh1-WT) rescued adhesion and ?-catenin membrane localization, yet an EC1 specific double mutant defective in homophilic adhesion (Cdh1-MutW2A, S78W) did not. These data suggest that E-cadherin inhibits ?-catenin in the context of disruption of the APC-destruction complex, and that this function is also EC1 domain dependent. Both binding functions of E-cadherin may be required for its tumour suppressor activity.
Project description:Nuclear factor-?B is a critical regulator of cell-survival genes and the host inflammatory response. The purpose of this study was to investigate the role of enterocyte-specific NF-kB in sepsis through selective ablation of IkB kinase.Prospective, randomized controlled study.Animal laboratories in university medical centers.Mice lacking functional NF-kB in their intestinal epithelium (Vil-Cre/Ikk?) and wild-type mice were subjected to sham laparotomy or cecal ligation and puncture. Animals were killed at 24 hours or followed 7 days for survival.Septic wild-type mice had decreased villus length compared with sham mice, whereas villus atrophy was further exacerbated in septic Vil-Cre/Ikk? mice. Sepsis induced an increase in intestinal epithelial apoptosis compared with sham mice, which was further exacerbated in Vil-Cre/Ikk? mice. Sepsis induced intestinal hyperpermeability in wild-type mice compared with sham mice, which was further exacerbated in septic Vil-Cre/Ikk? mice. This was associated with increased intestinal expression of claudin-2 in septic wild-type mice, which was further increased in septic Vil-Cre/Ikk? mice. Both, pro-inflammatory and anti-inflammatory cytokines were increased in serum following cecal ligation and puncture, and interleukin 10 and monocyte chemoattractant protein-1 levels were higher in septic Vil-Cre/Ikk? mice than in septic wild-type mice. All septic mice were bacteremic, but no differences in bacterial load were identified between wild-type and Vil-Cre/Ikk? mice. To determine the functional significance of these results, animals were followed for survival. Septic wild-type mice had lower mortality than septic Vil-Cre/Ikk? mice (47% vs 80%, p<0.05). Antitumor necrosis factor administration decreased intestinal apoptosis, permeability, and mortality in wild-type septic mice, and a similar improvement in intestinal integrity and survival were seen when antitumor necrosis factor was given to Vil-Cre/Ikk? mice.Enterocyte-specific NF-kB has a beneficial role in sepsis by partially preventing sepsis-induced increases in apoptosis and permeability, which are associated with worsening mortality.
Project description:Sphingosine kinase (Sphk) enzymes are important in intracellular sphingolipid metabolism as well as in the biosynthesis of sphingosine 1-phosphate (S1P), an extracellular lipid mediator. Here, we show that Sphk1 is expressed and is required for small intestinal tumor cell proliferation in Apc Min/+ mice. Adenoma size but not incidence was dramatically reduced in Apc Min/+ Sphk(-/-) mice. Concomitantly, epithelial cell proliferation in the polyps was significantly attenuated, suggesting that Sphk1 regulates adenoma progression. Although the S1P receptors (S1P1R, S1P2R, and S1P3R) are expressed, polyp incidence or size was unaltered in Apc Min/+ S1p2r(-/-), Apc Min/+ S1p3r(-/-), and Apc Min/+ S1p1r(+/-) bigenic mice. These data suggest that extracellular S1P signaling via its receptors is not involved in adenoma cell proliferation. Interestingly, tissue sphingosine content was elevated in the adenomas of Apc Min/+ Sphk1(-/-) mice, whereas S1P levels were not significantly altered. Concomitantly, epithelial cell proliferation and the expression of the G1/S cell cycle regulator CDK4 and c-myc were diminished in the polyps of Apc Min/+ Sphk1(-/-) mice. In rat intestinal epithelial (RIE) cells in vitro, Sphk1 overexpression enhanced cell cycle traverse at the G1/S boundary. In addition, RIE cells treated with sphingosine but not C6-ceramide exhibited reduced cell proliferation, reduced retinoblastoma protein phosphorylation, and cyclin-dependent kinase 4 (Cdk4) expression. Our findings suggest that Sphk1 plays a critical role in intestinal tumor cell proliferation and that inhibitors of Sphk1 may be useful in the control of intestinal cancer.
Project description:Inactivation of the tumor suppressor adenomatous polyposis coli, with the resultant activation of beta-catenin, is the initiating event in the development of a majority of colorectal cancers. Krüppel-like factor 5 (KLF5), a proproliferative transcription factor, is highly expressed in the proliferating intestinal crypt epithelial cells. To determine whether KLF5 contributes to intestinal adenoma formation, we examined tumor burdens in Apc(Min/+) mice and Apc(Min/+)/Klf5(+/-) mice. Compared with Apc(Min/+) mice, Apc(Min/+)/Klf5(+/-) mice had a 96% reduction in the number of intestinal adenomas. Reduced tumorigenicity in the Apc(Min/+)/Klf5(+/-) mice correlated with reduced levels and nuclear localization of beta-catenin as well as reduced expression of two beta-catenin targets, cyclin D1 and c-Myc. In vitro studies revealed a physical interaction between KLF5 and beta-catenin that enhanced the nuclear localization and transcriptional activity of beta-catenin. Thus, KLF5 is necessary for the tumor-initiating activity of beta-catenin during intestinal adenoma formation in Apc(Min/+) mice, and reduced expression of KLF5 offsets the tumor-initiating activity of the Apc(Min) mutation by reducing the nuclear localization and activity of beta-catenin.
Project description:Evidence suggests a relationship between dietary fat intake, obesity, and colorectal cancer, implying a role for fatty acid metabolism in intestinal tumorigenesis that is incompletely understood. Liver fatty acid-binding protein (L-Fabp), a dominant intestinal fatty acid-binding protein, regulates intestinal fatty acid trafficking and metabolism, and L-Fabp deletion attenuates diet-induced obesity. Here, we examined whether changes in intestinal fatty acid metabolism following L-Fabp deletion modify adenoma development in Apc(Min)(/+) mice. Compound L-Fabp(-/-)Apc(Min)(/+) mice were generated and fed a 10% fat diet balanced equally between saturated, monounsaturated, and polyunsaturated fat. L-Fabp(-/-)Apc(Min)(/+) mice displayed significant reductions in adenoma number and total polyp area compared with Apc(Min)(/+)controls, reflecting a significant shift in distribution toward smaller polyps. Adenomas from L-Fabp(-/-)Apc(Min)(/+) mice exhibited reductions in cellular proliferation, high-grade dysplasia, and nuclear ?-catenin translocation. Intestinal fatty acid content was increased in L-Fabp(-/-)Apc(Min)(/+) mice, and lipidomic profiling of intestinal mucosa revealed significant shifts to polyunsaturated fatty acid species with reduced saturated fatty acid species. L-Fabp(-/-)Apc(Min)(/+) mice also showed corresponding changes in mRNA expression of enzymes involved in fatty acid elongation and desaturation. Furthermore, adenomas from L-Fabp(-/-)Apc(Min)(/+) mice displayed significant reductions in mRNA abundance of nuclear hormone receptors involved in cellular proliferation and in enzymes involved in lipogenesis. These findings collectively implicate L-Fabp as an important genetic modifier of intestinal tumorigenesis, and identify fatty acid trafficking and metabolic compartmentalization as an important pathway linking dietary fat intake, obesity, and intestinal tumor formation.
Project description:STAT3 was recently reported to suppress tumor invasion in Apc(min)(/+) mice. We investigated the mechanisms by which STAT3 inhibits intestinal epithelial tumors using Apc(min)(/+)/Stat3(IEC-KO) mice (intestinal epithelial cell (IEC)-specific deletion of STAT3 in the Apc(min)(/+) background) to determine the role of STAT3 in carcinogenesis in vivo as well as colorectal cancer cell lines in vitro. To inhibit invasion of IEC tumors, STAT3 functions as a molecular adaptor rather than a transcription factor. Accordingly, the tumors in Apc(min)(/+)/Stat3(IEC-KO) mice undergo adenoma-to-carcinoma transition and acquire an invasive phenotype. Similarly, STAT3 knockdown in a colorectal cell line enhances IEC invasion. We demonstrate that STAT3 down-regulates SNAI (Snail-1) expression levels and hence suppresses epithelial-mesenchymal transition of colorectal cancer cells. Mechanistically, STAT3 facilitates glycogen synthase kinase (GSK) 3?-mediated degradation of SNAI by regulating phosphorylation of GSK3?. Our data identified a new role for STAT3 in the adenoma-to-carcinoma sequence of intestinal tumors.
Project description:Although Apc mutation is widely considered an initiating event in colorectal cancer, little is known about the earliest stages of tumorigenesis following sporadic Apc loss. Therefore, we have utilized a novel mouse model that facilitates the sporadic inactivation of Apc via frameshift reversion of Cre in single, isolated cells and subsequently tracks the fates of Apc-deficient intestinal cells. Our results suggest that consistent with Apc being a 'gatekeeper', loss of Apc early in life during intestinal growth leads to adenomas or increased crypt fission, manifested by fields of mutant but otherwise normal-appearing crypts. In contrast, Apc loss occurring later in life has minimal consequences, with mutant crypts being less prone to either increased crypt fission or adenoma formation. Using the stem cell-specific Lgr5-CreER mouse, we generated different sized fields of Apc-deficient crypts via independent recombination events and found that field size correlates with progression to adenoma. To evaluate this early stage prior to adenoma formation as a therapeutic target, we examined the chemopreventive effects of sulindac on Apc-deficient occult crypt fission. We found that sulindac treatment started early in life inhibits the morphologically occult spread of Apc-deficient crypts and thus reduces adenoma numbers. Taken together these results suggest that: (i) earlier Apc loss promotes increased crypt fission, (ii) a field of Apc-deficient crypts, which can form via occult crypt fission or independent neighboring events, is an important intermediate between loss of Apc and adenoma formation and (iii) normal-appearing Apc-deficient crypts are potential unappreciated targets for cancer screening and chemoprevention.