SHP-2 (Src homology-2 domain-containing phosphatase 2) is a tyrosine phosphatase ubiquitously expressed. Previous work done in SHP-2-/- fibroblasts demonstrated its implication in proliferation and migration as well as in the regulation of many signaling pathways including the Ras-Raf/MEK/ERK, the PI3K/AKT and the Jak/STAT pathways(1). Importantly, gain-of-function mutations were discovered in some colorectal cancers (CRCs)(2). However, the role of SHP-2 in intestinal tumorigenesis has never been investigated. Methods: SHP-2 expression and catalytic activity were analyzed by Western blot, qPCR and immunohistochemistry in human CRC cells and in human tumours from different stages. SHP-2 expression was also analyzed in polyps (adenomas) from mice bearing a mutation in Apc gene (APCMin/+ mice). To elucidate the role of SHP-2, RNA interference was used to specifically downregulate its expression in intestinal epithelial cells transformed or not by the oncogenic form of KRASG12V (IEC/KRas). Proliferation (cell counting), invasion (through Matrigel in Boyden chamber), anchorage-independent growth (soft agar) and tumor formation in nude mice (xenograft assays) were analyzed. Results: 1- SHP-2 mRNA and protein levels were significantly increased in human CRC cells and tumors, especially in adenomas, in comparison to healthy adjacent tissues. 2- Interestingly, polyps from APCMin/+ mice also exhibited marked increase in SHP-2 protein expression in comparison to normal adjacent intestinal epithelium. 3- SHP-2 silencing in IEC/KRAS cells markedly reduced their proliferation rate, their growth in soft agar, their capacity to migrate and invade Matrigel and finally, their capacity to form tumor in vivo, in nude mice. 4- Of note, phosphorylated and activated levels of MEK and ERK kinases were significantly decreased following SHP-2 silencing in IECs particularly in those expressing the mutated form of KRAS. Conclusion: Our data suggest that SHP-2 promotes malignancy of intestinal epithelial cells by sustaining the oncogenic activation of MEK/ERK signalling during intestinal tumorigenesis. (1)Shi ZQ, Lu W, Feng GS., J Biol Chem. 1998 Feb 27;273(9):4904-8. (2)Bentires-Alj M. et al., Cancer Res. 2004 Dec 15;64(24):8816-20. Citation Format: Jessica Gagne Sansfacon, Geneviève Coulombe, Nadia Bourdages, Nathalie Rivard. Role of SHP-2 tyrosine phosphatase in colorectal carcinogenesis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5281. doi:10.1158/1538-7445.AM2014-5281

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Background High-fat/high-cholesterol diets are a well established risk factor for cardiovascular and metabolic diseases, given their propensity to trigger perturbations ranging from altering whole body lipid profile to the induction of intestinal dysbiosis. However much less is known about their effects on the host’s susceptibility to enteric infections. Aims To determine the effects of high-fat/high-cholesterol diets over the host’s susceptibility to enteric bacterial infections and identify the underlying molecular mechanisms. Methods C57BL/6 mice were given two different high-fat/high-cholesterol diets; HFHC (40% kcal fat, 1.25% cholesterol) or HFHCC (40% kcal fat, 1.25% cholesterol, 0.5% sodium cholate) and a control, normal diet (ND, 10% kcal fat, 0% cholesterol, 0% sodium cholate). After four weeks of administration, animals were euthanized and colonic tissue samples taken for histology, immunofluorescence, gene expression analyses, total protein lysates and microbiome sequencing (16S). A separated group of animals was gavaged with FITC-dextran to measure intestinal permeability. Mice fed with the diets for three weeks were infected with ~5x108 cfu of Citrobacter rodentium DBS100/StrpR by oral gavage, and kept on the corresponding diets after the infections. Bacterial shedding in the feces was followed for up to 30 days after infection. Results Administration of the HFHC and HFHCC diets caused an increase in intestinal permeability. Colonic sections stained with H&E and alcian blue evidenced a decreased in the number of mucin-filled goblet cells and a thinner mucus layer, suggesting a defect in the assembly and/or stability of the mucus layer. Expression analyses revealed a drop in the mRNA levels of Muc1 and Muc2, suggesting reduced mucin production. The concentration of IgA was slightly reduced in colon lysates and the transcript levels of the antimicrobial peptide genes Ang4, Leap2 and Cramp were also significantly reduced. Immunofluorescent microscopy showed that goblet cell granules of HFHC- and HFHCC-fed mice were devoid of Relmβ and Tff3, indicating defective production of those two factors critical for intestinal epithelial defense and homeostasis. Collectively, our results suggest that HFHC and HFHCC diets induce differentiation and functional defects in goblet cells. Fecal shedding of C. rodentium showed an increased bacterial burden in HFHC- and HFHCC-fed animals, indicating a more aggressive bacterial infection, accompanied by increased epithelial damage. Conclusions Consumption of high-fat/high cholesterol diets perturb the colonic homeostasis and alter intestinal defenses and the integrity of the intestinal barrier, predisposing the host to a higher susceptibility to enteric infections. Funding Agencies CIHRNSERC