High-Fat Diet-Induced Complement Activation Mediates Intestinal Inflammation and Neoplasia, Independent of Obesity.

Obesity and related metabolic disturbances are closely associated with pathologies that represent a significant burden to global health. Epidemiological and molecular evidence links obesity and metabolic status with inflammation and increased risk of cancer. Here, using a mouse model of intestinal neoplasia and strains that are susceptible or resistant to diet-induced obesity, it is demonstrated that high-fat diet-induced inflammation, rather than obesity or metabolic status, is associated with increased intestinal neoplasia. The complement fragment C5a acts as the trigger for inflammation and intestinal tumorigenesis. High-fat diet induces complement activation and generation of C5a, which in turn induces the production of proinflammatory cytokines and expression of proto-oncogenes. Pharmacological and genetic targeting of the C5a receptor reduced both inflammation and intestinal polyposis, suggesting the use of complement inhibitors for preventing diet-induced neoplasia. IMPLICATIONS: This study characterizes the relations between diet and metabolic conditions on risk for a common cancer and identifies complement activation as a novel target for cancer prevention. Mol Cancer Res; 14(10); 953-65. ©2016 AACR.

IL-33 activates tumor stroma to promote intestinal polyposis.

Tumor epithelial cells develop within a microenvironment consisting of extracellular matrix, growth factors, and cytokines produced by nonepithelial stromal cells. In response to paracrine signals from tumor epithelia, stromal cells modify the microenvironment to promote tumor growth and metastasis. Here, we identify interleukin 33 (IL-33) as a regulator of tumor stromal cell activation and mediator of intestinal polyposis. In human colorectal cancer, IL-33 expression was induced in the tumor epithelium of adenomas and carcinomas, and expression of the IL-33 receptor, IL1RL1 (also referred to as IL1-R4 or ST2), localized predominantly to the stroma of adenoma and both the stroma and epithelium of carcinoma. Genetic and antibody abrogation of responsiveness to IL-33 in the Apc(Min/+) mouse model of intestinal tumorigenesis inhibited proliferation, induced apoptosis, and suppressed angiogenesis in adenomatous polyps, which reduced both tumor number and size. Similar to human adenomas, IL-33 expression localized to tumor epithelial cells and expression of IL1RL1 associated with two stromal cell types, subepithelial myofibroblasts and mast cells, in Apc(Min/+) polyps. In vitro, IL-33 stimulation of human subepithelial myofibroblasts induced the expression of extracellular matrix components and growth factors associated with intestinal tumor progression. IL-33 deficiency reduced mast cell accumulation in Apc(Min/+) polyps and suppressed the expression of mast cell-derived proteases and cytokines known to promote polyposis. Based on these findings, we propose that IL-33 derived from the tumor epithelium promotes polyposis through the coordinated activation of stromal cells and the formation of a protumorigenic microenvironment.

PTPRT regulates high-fat diet-induced obesity and insulin resistance.

Obesity is a risk factor for many human diseases. However, the underlying molecular causes of obesity are not well understood. Here, we report that protein tyrosine phosphatase receptor T (PTPRT) knockout mice are resistant to high-fat diet-induced obesity. Those mice avoid many deleterious side effects of high-fat diet-induced obesity, displaying improved peripheral insulin sensitivity, lower blood glucose and insulin levels. Compared to wild type littermates, PTPRT knockout mice show reduced food intake. Consistently, STAT3 phosphorylation is up-regulated in the hypothalamus of PTPRT knockout mice. These studies implicate PTPRT-modulated STAT3 signaling in the regulation of high-fat diet-induced obesity.

Metabolomics of ApcMin/+ mice genetically susceptible to intestinal cancer.

BACKGROUND: To determine how diets high in saturated fat could increase polyp formation in the mouse model of intestinal neoplasia, ApcMin/+, we conducted large-scale metabolome analysis and association study of colon and small intestine polyp formation from plasma and liver samples of ApcMin/+ vs. wild-type littermates, kept on low vs. high-fat diet. Label-free mass spectrometry was used to quantify untargeted plasma and acyl-CoA liver compounds, respectively. Differences in contrasts of interest were analyzed statistically by unsupervised and supervised modeling approaches, namely Principal Component Analysis and Linear Model of analysis of variance. Correlation between plasma metabolite concentrations and polyp numbers was analyzed with a zero-inflated Generalized Linear Model. RESULTS: Plasma metabolome in parallel to promotion of tumor development comprises a clearly distinct profile in ApcMin/+ mice vs. wild type littermates, which is further altered by high-fat diet. Further, functional metabolomics pathway and network analyses in ApcMin/+ mice on high-fat diet revealed associations between polyp formation and plasma metabolic compounds including those involved in amino-acids metabolism as well as nicotinamide and hippuric acid metabolic pathways. Finally, we also show changes in liver acyl-CoA profiles, which may result from a combination of ApcMin/+-mediated tumor progression and high fat diet. The biological significance of these findings is discussed in the context of intestinal cancer progression. CONCLUSIONS: These studies show that high-throughput metabolomics combined with appropriate statistical modeling and large scale functional approaches can be used to monitor and infer changes and interactions in the metabolome and genome of the host under controlled experimental conditions. Further these studies demonstrate the impact of diet on metabolic pathways and its relation to intestinal cancer progression. Based on our results, metabolic signatures and metabolic pathways of polyposis and intestinal carcinoma have been identified, which may serve as useful targets for the development of therapeutic interventions.

Genetic resistance to liver fibrosis on A/J mouse chromosome 17.

BACKGROUND: Because the histological and biochemical progression of liver disease is similar in alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH), we hypothesized that the genetic susceptibility to these liver diseases would be similar. To identify potential candidate genes that regulate the development of liver fibrosis, we studied a chromosome substitution strain (CSS-17) that contains chromosome 17 from the A/J inbred strain substituted for the corresponding chromosome on the C57BL/6J (B6) genetic background. Previously, we identified quantitative trait loci (QTLs) in CSS-17, namely obesity-resistant QTL 13 and QTL 15 (Obrq13 and Obrq15, respectively), that were associated with protection from diet-induced obesity and hepatic steatosis on a high-fat diet. METHODS: To test whether these or other CSS-17 QTLs conferred resistance to alcohol-induced liver injury and fibrosis, B6, A/J, CSS-17, and congenics 17C-1 and 17C-6 were either fed Lieber-DeCarli ethanol (EtOH)-containing diet or had carbon tetrachloride (CCl4 ) administered chronically. RESULTS: The congenic strain carrying Obrq15 showed resistance from alcohol-induced liver injury and liver fibrosis, whereas Obrq13 conferred susceptibility to liver fibrosis. From published deep sequencing data for chromosome 17 in the B6 and A/J strains, we identified candidate genes in Obrq13 and Obrq15 that contained single-nucleotide polymorphisms (SNPs) in the promoter region or within the gene itself. NADPH oxidase organizer 1 (Noxo1) and NLR family, CARD domain containing 4 (Nlrc4) showed altered hepatic gene expression in strains with the A/J allele at the end of the EtOH diet study and after CCl4 treatment. CONCLUSIONS: Aspects of the genetics for the progression of ASH are unique compared to NASH, suggesting that the molecular mechanisms for the progression of disease are at least partially distinct. Using these CSSs, we identified 2 candidate genes, Noxo1 and Nlrc4, which modulate genetic susceptibility in ASH.

Contrasting effects of Deadend1 (Dnd1) gain and loss of function mutations on allelic inheritance, testicular cancer, and intestinal polyposis.

BACKGROUND: Certain mutations in the Deadend1 (Dnd1) gene are the most potent modifiers of testicular germ cell tumor (TGCT) susceptibility in mice and rats. In the 129 family of mice, the Dnd1Ter mutation significantly increases occurrence of TGCT-affected males. To test the hypothesis that he Dnd1Ter allele is a loss-of-function mutation; we characterized the consequences of a genetically-engineered loss-of-function mutation in mice, and compared these results with those for Dnd1Ter. RESULTS: We found that intercrossing Dnd1+/KO heterozygotes to generate a complete loss-of-function led to absence of Dnd1KO/KO homozygotes and significantly reduced numbers of Dnd1+/KO heterozygotes. Further crosses showed that Dnd1Ter partially rescues loss of Dnd1KO mice. We also found that loss of a single copy of Dnd1 in Dnd1KO/+ heterozygotes did not affect baseline occurrence of TGCT-affected males and that Dnd1Ter increased TGCT risk regardless whether the alternative allele was loss-of-function (Dnd1KO) or wild-type (Dnd1⁺). Finally, we found that the action of Dnd1Ter was not limited to testicular cancer, but also significantly increased polyp number and burden in the Apc+/Min model of intestinal polyposis. CONCLUSION: These results show that Dnd1 is essential for normal allelic inheritance and that Dnd1Ter has a novel combination of functions that significantly increase risk for both testicular and intestinal cancer.

Kaiso is a bimodal modulator for Wnt/beta-catenin signaling.

The Wnt family of secreted ligands plays critical roles during embryonic development and tumorigenesis. Here we show that Kaiso, a dual specific DNA-binding protein, functions as a bimodal regulator of canonical Wnt signaling. Loss-of-function analysis of Kaiso abrogated Wnt-mediated reporter activity and axis duplication, whereas gain-of-function analysis of Kaiso dose-dependently resulted in synergistic and suppressive effects. Our analyses further suggest Kaiso can regulate TCF/LEF1-activity for these effects via modulating HDAC1 and beta-catenin-complex formation. Our studies together provide insights into why Kaiso null mice display resistance to intestinal tumors when crossed onto an Apc(Min/+) background.