The chemokine receptors XCR1, CXCR1 and CXCR2 regulate oral epithelial cell behaviour.

Abstract

Chemokines are chemoattractant cytokines which act on specific receptors and play an important role in tumour biology. The aim of this project was to determine whether the chemokine receptors XCRl, CXCRl and CXCR2 and their respective ligands lymphotactin, IL-8 (CXCRl&2) and GRO-a regulate the behaviour of normal and malignant oral epithelial cells. XCRl, CXCRl and CXCR2 mRNA and surface protein expression was detected in normal and oral cancer cell lines. Lymphotactin, IL-8 and GRO-a facilitated intracellular activation of ERK1/2 signaling pathway and stimulated migration, invasion and proliferation of all cells. These effects were mediated through XCRl for lymphotactin, CXCRl and CXCR2 for IL-8 and CXCR2 for GRO-a. The cancer cells showed a greater response than normal cells and a direct relationship between receptor expression and migration, invasion and proliferation was observed. XCRl but not lymphotactin was expressed by epithelial cells in normal oral mucosa in vivo and both were expressed and upregulated in inflammation and cancer. Constitutive expression of both XCRl and lymphotactin was found in regional lymph nodes and on metastatic tumours. Lymphotactin mRNA al}d constitutive intracellular protein was detected in normal and cancerous oral cells. Exposure of normal cells to lymphotactin resulted in increased adhesion to fibronectin but not collagen and stimulated MMP-2 and -9 release whereas exposure of cancer cells resulted in increased adhesion to both collagen and fibronectin and stimulated MMP-2, 9 and MMP-7 release. These findings show for the first time that XCRl and its ligand lymphotactin are expressed by epithelial cells in a range of oral conditions and strongly suggest that they play an important role in regulating the behaviour of normal and malignant epithelial cells. Similarly CXCRl and CXCR2 are upregulated on malignant oral cells in vitro and may be important in the biology of oral cancer