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Article Dans Une Revue Journal of Biological Chemistry Année : 2003

Human MUC2 Mucin Gene Is Transcriptionally Regulated by Cdx Homeodomain Proteins in Gastrointestinal Carcinoma Cell Lines

Patrícia Mesquita
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Jacinta Serpa
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Elisabete Silva
Pascal Pigny
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Filipe Santos Silva
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Celso Reis
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Debra Silberg
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Isabelle van Seuningen
Leonor David

Résumé

In intestinal metaplasia and 30% of gastric carcino-mas, MUC2 intestinal mucin and the intestine-specific transcription factors Cdx-1 and Cdx-2 are aberrantly expressed. The involvement of Cdx-1 and Cdx-2 in the intestinal development and their role in transcription of several intestinal genes support the hypothesis that Cdx-1 and/or Cdx-2 play important roles in the aberrant intestinal differentiation program of intestinal metapla-sia and gastric carcinoma. To clarify the mechanisms of transcriptional regulation of the MUC2 mucin gene in gastric cells, pGL3 deletion constructs covering 2.6 kb of the human MUC2 promoter were used in transient transfection assays, enabling us to identify a relevant region for MUC2 transcription in all gastric cell lines. To evaluate the role of Cdx-1 and Cdx-2 in MUC2 transcription we performed co-transfection experiments with expression vectors encoding Cdx-1 and Cdx-2. In two of the four gastric carcinoma cell lines and in all colon carci-noma cell lines we observed transactivation of the MUC2 promoter by Cdx-2. Using gel shift assays we identified two Cdx-2 binding sites at ؊177/؊171 and ؊191/؊187. Only simultaneous mutation of the two sites resulted in inhibition of Cdx-2-mediated transactivation of MUC2 promoter, implying that both Cdx-2 sites are active. Finally , stable expression of Cdx-2 in a gastric cell line initially not expressing Cdx-2, led to induction of MUC2 expression. In conclusion, this work demonstrates that Cdx-2 activates the expression of MUC2 mucin gene in gastric cells, inducing an intestinal transdifferentiation phenotype that parallels what is observed both in intestinal metaplasia and some gastric carcinomas. There is consistent data indicating that in human stomach as well as in other organs mucin genes are expressed in a regulated cell-and tissue-specific manner and that altered mucin gene expression occurs in cancer and precancerous le-sions (1). In normal gastric mucosa most studies show little or no expression of the intestinal mucin MUC2 (2-9). In intestinal metaplasia, a preneoplastic lesion of the stomach characterized by the transdifferentiation of the gastric mucosa to an intestinal phenotype, there are alterations in the mucin expression pattern including de novo expression of MUC2, mostly in goblet cells (10). Thirty percent of gastric carcinomas, including all carcinomas of the mucinous type, also aberrantly express MUC2 intestinal mucin (11, 12). The molecular mechanisms responsible for the regulation of MUC2 transcription and expression are beginning to be elucidated. The structure of MUC2 promoter was characterized (13, 14) and MUC2 expression was reported to be regulated by methylation of the promoter (15-17) and by the Sp1 family of transcription factors (13, 18, 19). It has also been described that MUC2 is transcriptionally activated by p53 (20) and, in tracheobronchial epithelial cells, by lipopolysaccharide from Pseudomonas aeruginosa (21, 22) and epidermal growth factor (19). However, information on MUC2 transcriptional regulation in gastric cells, in relation with the overexpression of MUC2 in intestinal metaplasia and gastric carcinoma, is essentially unknown. The intestine-specific homeobox genes Cdx-1 1 and Cdx-2 were also recently shown to be aberrantly expressed in intestinal metaplasia and in a subset of gastric carcinomas. Both in intestinal metaplasia and in gastric carcinoma, expression of Cdx-1 and Cdx-2 is closely associated with the expression of mucin MUC2 (23). Altogether, these observations suggest that Cdx-1 and/or Cdx-2 play important roles in the aberrant intestinal differentiation program of intestinal metaplasia and some gastric carcinomas, partly due to MUC2 regulation at the tran-scriptional level (23). This hypothesis is further supported by the direct involvement of Cdx-1 and Cdx-2 in the differentiation of intestinal epithelial cells (24), namely in transgenic models (25) and by the evidence showing that they act as transcription factors for several intestinal genes such as su-crase-isomaltase (24, 26, 27), lactase-phlorizin hydrolase (27-30), intestine phospholipaseA/lysophospholipase (31), clau-din-2 (32), and more recently ␤-1,3-galactosyltransferase T5 (33). Since the promoter of MUC2 contains some Cdx putative binding sites, we hypothesized that Cdx-1 or Cdx-2 might func-* This work was supported by Fundaçã o para a Ciência e a Tecnologia and Programa Operacional Ciência, Tecnologia, Inovaçã o do Quadro Comunitá rio de Apoio III (
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hal-02905842 , version 1 (23-07-2020)

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Patrícia Mesquita, Nicolas Jonckheere, Raquel Almeida, Marie-Paule Ducourouble, Jacinta Serpa, et al.. Human MUC2 Mucin Gene Is Transcriptionally Regulated by Cdx Homeodomain Proteins in Gastrointestinal Carcinoma Cell Lines. Journal of Biological Chemistry, 2003, ⟨10.1074/jbc.M309019200⟩. ⟨hal-02905842⟩

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