The Src homology‐2 domain‐containing tyrosine phosphatase 2 (SHP‐2) regulates many cellular processes, including proliferation, differentiation and survival. Polymorphisms in the gene encoding SHP‐2 are associated with an increased susceptibility to develop ulcerative colitis. We recently reported that intestinal epithelial cell (IEC)‐specific deletion of Shp‐2 in mice ( Shp‐2 IEC‐KO ) leads to chronic colitis and colitis‐associated cancer. This suggests that SHP‐2‐dependent signaling protects the colonic epithelium against inflammation and colitis‐associated cancer development. To verify this hypothesis, we generated mice expressing the Shp‐2 E76K activated form specifically in IEC. Our results showed that sustained Shp‐2 activation in IEC increased intestine and crypt length, correlating with increased cell proliferation and migration. Crypt regeneration capacity was also markedly enhanced, as revealed by ex vivo organoid culture. Shp‐2 activation alters the secretory cell lineage, as evidenced by increased goblet cell numbers and mucus secretion. Notably, these mice also demonstrated elevated ERK signaling in IEC and exhibited resistance against both chemical‐ and Citrobacter rodentium ‐induced colitis. In contrast, mice with IEC‐specific Shp‐2 deletion displayed reduced ERK signaling and rapidly developed chronic colitis. Remarkably, expression of an activated form of Braf in Shp‐2‐deficient mice restored ERK activation, goblet cell production and prevented colitis. Altogether, our results indicate that chronic activation of Shp‐2/ERK signaling in the colonic epithelium confers resistance to mucosal erosion and colitis. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

A major risk factor of developing colorectal cancer (CRC) is the presence of chronic inflammation in the colon. In order to understand how inflammation contributes to CRC development, the present study focused on SHP-2, a tyrosine phosphatase encoded by PTPN11 gene in which polymorphisms have been shown to be markers of colitis susceptibility. Conversely, gain-of-function mutations in PTPN11 gene (E76 residue) have been found in certain sporadic CRC. Results shown herein demonstrate that SHP-2 expression was markedly increased in sporadic human adenomas but not in advanced colorectal tumors. SHP-2 silencing inhibited proliferative, invasive and tumoral properties of both intestinal epithelial cells (IECs) transformed by oncogenic KRAS and of human CRC cells. IEC-specific expression of a SHP-2E76K activated mutant in mice was not sufficient to induce tumorigenesis but markedly promoted tumor growth under the ApcMin/+ background. Conversely, mice with a conditional deletion of SHP-2 in IECs developed colitis-associated adenocarcinomas with age, associated with sustained activation of Wnt/β-catenin, NFκB and STAT3 signalings in the colonic mucosae. Moreover, SHP-2 epithelial deficiency considerably increased tumor load in ApcMin/+ mice, shifting tumor incidence toward the colon. Overall, these results reveal that SHP-2 can exert opposing functions in the large intestine: it can promote or inhibit tumorigenesis depending of the inflammatory context.

AIMS: The phosphatase and tensin homolog (PTEN), a negative regulator of the phosphatidylinositol 3-kinase/ AKT pathway, is one of the most frequently mutated/deleted gene in various human cancers. PTEN has also been shown to regulate numerous cellular processes such as genomic stability, stem cell renewal, senescence and cell differentiation. However, the potential effects of Pten on gastric organogenesis and homeostasis have not yet been explored. The aim of our study is to investigate the role of epithelial Pten signaling in the maintenance and specification of gastric epithelium. METHODS: Using the Cre/loxP system, we have generated a mouse model with a deletion of Pten exclusively in the foregut endoderm (PtenαGEC). Glandular architecture was assessed with H&E staining. Analysis of cell proliferation was performed by immunofluorescence with a PCNA antibody. Gastric cell type patterns from control and mutant mice were analyzed by antibody- specific immunostaining, alcian blue and Periodic Acid Schiff stainings. RESULTS: PtenαGEC mice are viable and have no severe abnormality in gastric organogenesis. Loss of Pten in the stomach epithelium was confirmed by IHC and, as expected, leads to an increase of p-Akt in the mutant gastric glands. Histological analysis by H&E staining demonstrates a disorganized glandular architecture associated with cystic regions in the corpus from 4 months of age. The PtenαGEC mice display a delocalization and upregulation in epithelial proliferation associated to an increase of the glands length. Analysis of the different cell lineages shows an increase in the mucus cell population. Furthermore, chromogranin A immunostaining shows an increase in the number of enteroendocrine cells in Pten mutant mice. Analysis of parietal cells reveals a significant decrease in this cell population in PtenαGEC mice. Surprisingly, zymogenic cells are absent from the glandular epithelium in mutant mice, whereas GSII positive cells, specific for neck cells, are increased and delocalized to the basal region. The latter observations suggest a possible induction of SPEM (spasmolytic polypeptide-expressing metaplasia) in these mice. Furthermore with aging, loss of PTEN leads to an increasing inflammatory process demonstrated by the expression of myeloperoxidase positive cells in the cystic regions and the mesenchyme. CONCLUSION: Altogether, our results indicate that PTEN in the gastric epithelium impacts on gastric gland architecture, negatively regulates the proliferation and plays an important role in the regulation of the cytodifferentiation and maturation of gastric cells. Finally loss epithelial Pten is sufficient for SPEM development and presence of inflammatory markers with age. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2251. doi:1538-7445.AM2012-2251

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