CDX2 homeoprotein regulates ST6GalNAc-I in intestinal metaplasia

This study, performed by a group of investigators at IPATIMUP and published in Laboratory Investigation, identified the marker of intestinal differentiation CDX2 as a modulator of the glycoproteome in intestinal metaplasia, a precursor lesion of gastric cancer characterized by a transdifferentiation of the gastric mucosa into intestinal mucosa. The study showed that CDX2 transcription factor directly regulates ST6GalNAc-I gene in intestinal metaplasia lesions. This gene codes for the sialyltransferase responsible for the biosynthesis of sialyl-Tn antigen, which is aberrantly expressed in intestinal metaplasia and in gastric cancer and which contributes for tumor aggressiveness and worse prognosis. Therefore, these findings contributed to a better understanding of how cancer-associated glycosylation is regulated, which is indispensable to understand the mechanisms of tumor progression.

Authors and Affiliations:

Rita Pinto^1,2,3, Rita Barros^1,2, Isabel Pereira-Castro^2,8, Patricia Mesquita⁴, Luis Teixeira da Costa⁵, Eric Paul Bennett⁶, Raquel Almeida^1,2,3,7 and Leonor David^1,2,3

¹Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal;

²Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal;

³Faculty of Medicine, University of Porto, Porto, Portugal;

⁴Instituto Nacional de Investigação Agrária e Veterinária, Quinta da Fonte Boa, Vale de Santarém, Portugal;

⁵ICAAM, Universidade de Évora, Évora, Portugal;

6Copenhagen Center for Glycomics, Departments of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark and

7Department of Biology, Faculty of Sciences, University of Porto, Porto, Portugal; ⁸Current address: Gene Regulation Group, IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.

Abstract:

De novo expression of Sialyl-Tn (STn) antigen is one of the most common features of intestinal metaplasia (IM) and gastric carcinomas, and its biosynthesis has been mostly attributed to ST6GalNAc-I activity. However, the regulation of this glycosyltransferase expression is not elucidated. In IM lesions and in the intestine, CDX2 homeobox transcription factor is co-expressed with STn and ST6GalNAc-I. We therefore hypothesized that CDX2 might induce STn expression by positive regulation of ST6GalNAc-I. We showed that ST6GalNAc-I transcript levels and CDX2 have a coordinated expression upon Caco-2 in vitro differentiation, and overexpression of CDX2 in MKN45 gastric cells increases ST6GalNAc-I transcript levels. Nine putative CDX-binding sites in the ST6GalNAc-I-regulatory sequence were identified and analyzed by chromatin immunoprecipitation in Caco-2 cells and in IM. The results showed that CDX2 protein is recruited to all regions, being the most proximal sites preferentially occupied in vivo. Luciferase assays demonstrated that CDX2 is able to transactivate ST6GalNac-I-regulatory region. The induction was stronger for the regions mapped in the neighbourhood of ATG start codon and site-directed mutagenesis of these sites confirmed their importance. In conclusion, we show that CDX2 transcriptionally regulates ST6GalNAc-I gene expression, specifically in the preneoplastic IM lesion.

Journal: Laboratory Investigation

Link: http://www.nature.com/labinvest/journal/vaop/ncurrent/full/labinvest201552a.html