Secreted Trefoil Factor 2 Activates the CXCR4 Receptor in Epithelial and Lymphocytic Cancer Cell Lines

Zinaida Dubeykovskaya,Alexander Dubeykovskiy,Joel Solal-Cohen,Timothy C Wang

doi:10.1074/jbc.m804935200

Abstract

The secreted trefoil factor family 2 (TFF2) protein contributes to the protection of the gastrointestinal mucosa from injury by strengthening and stabilizing mucin gels, stimulating epithelial restitution, and restraining the associated inflammation. Although trefoil factors have been shown to activate signaling pathways, no cell surface receptor has been directly linked to trefoil peptide signaling. Here we demonstrate the ability of TFF2 peptide to activate signaling via the CXCR4 chemokine receptor in cancer cell lines. We found that both mouse and human TFF2 proteins (at approximately 0.5 microm) activate Ca2+ signaling in lymphoblastic Jurkat cells that could be abrogated by receptor desensitization (with SDF-1alpha) or pretreatment with the specific antagonist AMD3100 or an anti-CXCR4 antibody. TFF2 pretreatment of Jurkat cells decreased Ca2+ rise and chemotactic response to SDF-1alpha. In addition, the CXCR4-negative gastric epithelial cell line AGS became highly responsive to TFF2 treatment upon expression of the CXCR4 receptor. TFF2-induced activation of mitogen-activated protein kinases in gastric and pancreatic cancer cells, KATO III and AsPC-1, respectively, was also dependent on the presence of the CXCR4 receptor. Finally we demonstrate a distinct proliferative effect of TFF2 protein on an AGS gastric cancer cell line that expresses CXCR4. Overall these data identify CXCR4 as a bona fide signaling receptor for TFF2 and suggest a mechanism through which TFF2 may modulate immune and tumorigenic responses in vivo.

Highlights

trefoil factor family 2 (TFF2) Attenuates stromal cell-derived factor (SDF)-1␣/CXCR4-mediated Chemotaxis and Ca2ϩ Signaling in Jurkat Cells—We and others have previously demonstrated TFF2 mRNA expression in the secondary mouse lymphoid organs, namely the spleen and thymus [25,26,27]
TFF2 gene expression has been shown in a number of malignancies [33], but the absence of TFF2 expression in Jurkat cells provided us with an opportunity to study TFF2 function through stable overexpression
green fluorescent protein (GFP) expression was strictly localized to the cytoplasm, the majority of TFF2 protein was found in the culture medium

Summary

Introduction

A significant (up to 30%) inhibition of SDF-1␣-dependent Jurkat cell migration was observed when recombinant murine TFF2 was applied at a concentration 500 – 600 nM (Fig. 1, bottom). We found that both proteins were able to induce a calcium mobilization in Jurkat cells with the same optimal effective concentration (ϳ500 – 600 nM) as recombinant mouse TFF2 (Fig. 3, bottom, and data not shown).

Results

Conclusion