CDX1 is a transcription factor that plays a key role in intestinal development and differentiation. However, the downstream targets of CDX1 are less well defined than those of its close homologue, CDX2. We report here the identification of downstream targets of CDX1 using microarray gene-expression analysis and other approaches. Keratin 20 (KRT20), a member of the intermediate filament and a well-known marker of intestinal differentiation, was initially identified as one of the genes likely to be directly regulated by CDX1. CDX1 and KRT20 mRNA expression were significantly correlated in a panel of 38 colorectal cancer cell lines. Deletion and mutation analysis of the KRT20 promoter showed that the minimum regulatory region for the control of KRT20 expression by CDX1 is within 246 bp upstream of the KRT20 transcription start site. ChIP analysis confirmed that CDX1 binds to the predicted CDX elements in this region of the KRT20 promoter in vivo. In addition, immunohistochemistry showed expression of CDX1 parallels that of KRT20 in the normal crypt, which further supports their close relationship. In summary, our observations strongly imply that KRT20 is directly regulated by CDX1, and therefore suggest a role for CDX1 in maintaining differentiation in intestinal epithelial cells. Because a key feature of the development of a cancer is an unbalanced program of proliferation and differentiation, dysregulation of CDX1 may be an advantage for the development of a colorectal carcinoma. This could, therefore, explain the relatively frequent down regulation of CDX1 in colorectal carcinomas by hypermethylation.colorectal cancer ͉ epithelial ͉ cell lines ͉ methylation ͉ cancer stem cells M embers of the keratin family provide structural support for the cell. They are also involved in apoptosis and protect cells from stress (1). Mutations of some keratins lead to genetic diseases, for example, of the skin and the liver (2-4). Keratin 20 (KRT20), a member of the keratin family, has been cloned and classified as a type-I keratin with a highly conserved amino acid sequence (5). It is mainly expressed in the cytoplasm of epithelial cells in the small and large intestine and in Merkel cells of the skin (5). As KRT20 is expressed in the epithelial cells of the crypt, it has been widely studied as a marker of differentiation in normal epithelium and colorectal cancer (CRC) samples (6-9). Previous studies have suggested that KRT20 is phosphorylated in association with mucin secretion and filament organization (10, 11). Transgenic mice with mutations at a conserved Arg to His site (R80H) show collapse of intermediate filaments.Despite its clearly important functions in the intestine, little is known about the regulation of KRT20.CDX1 is a homeobox transcription factor that is important for intestinal development and is specifically expressed in the small and large intestine in both mice and humans (12-15). CDX1 plays a role in intestinal epithelial cell differentiation (16) and is down-regulated in a number of CRC-derived cell lines...

The molecular pathogenesis of Barrett's metaplasia (BM) of the esophagus is poorly understood. The change to an intestinal phenotype occurs on a background of esophagitis due to refluxing acid and bile. CDX1, an important regulator of normal intestinal development, was studied as a potential key molecule in the pathogenesis of BM. CDX1 mRNA and protein were universally expressed in all samples of BM tested but not in normal esophageal squamous or gastric body epithelia. This tissue-specific expression was attributable to the methylation status of the CDX1 promoter. Conjugated bile salts and the inflammatory cytokines ⌻NF-␣ and IL-1␤ were all found to increase CDX1 mRNA expression in vitro. These effects were primarily mediated by NF-B signaling but only occurred when the CDX1 promoter was unmethylated or partially methylated. The data suggest that CDX1 is a key molecule linking etiological agents of BM to the development of an intestinal phenotype. Although the initial trigger for CDX1 promoter demethylation is not yet identified, it seems likely that demethylation of its promoter may be the key to the induction and maintenance of CDX1 expression and so of the BM phenotype.colorectal carcinoma ͉ deoxycytidine ͉ gastroesophageal reflux disease ͉ intestinal metaplasia ͉ promoter methylation

BackgroundSoft tissue sarcomas (STS) are rare tumours arising in mesenchymal tissues. Gastrointestinal stromal tumour (GIST) is the commonest STS and arises within the wall of the gastrointestinal (GI) tract. While most GISTs occur in the stomach they do occur in all parts of the GI tract. As with other STS, it is important that GISTs are managed by expert teams, to ensure consistent and optimal treatment, as well as recruitment to clinical trials, and the ongoing accumulation of further knowledge of the disease. The development of appropriate guidance, by an experienced panel referring to the evidence available, is therefore a useful foundation on which to build progress in the field.MethodologyBritish Sarcoma Group guidelines for the management of GIST were initially developed by a panel of physicians experienced in the management of GIST. This current version has been updated and amended with reference to other European and US guidance. We have received input from representatives of all diagnostic and treatment disciplines as well as patient representatives. Levels of evidence and strength of recommendation gradings are those used by ESMO adapted from those published by the Infectious Disease Society of America.ConclusionsThe guidelines cover aetiology, genetics and underlying molecular mechanisms, diagnosis and initial investigations, staging and risk stratification, surgery, neoadjuvant and adjuvant therapy, the management of advanced disease and follow-up. The importance of mutational analysis in guiding treatment is highlighted, since this can indicate the most effective treatment and avoid administration of ineffective drugs, emphasising the need for management in specialist centres.