Abstract A53: CXCR4 drives the metastatic phenotype in breast cancer through induction of CXCR2, transactivation of HER2/EGFR, and activation of MEK and PI3K pathways

Abstract

Abstract Introduction: Aberrant expression of CXCR4 in human breast cancer correlates with metastasis and poor prognosis. Expression of a carboxyl-truncated CXCR4 (CXCR4ΔCTD) is associated with constitutive CXCR4 activity in MCF-7 breast cancer cells, increased motility, loss of E-cadherin, enhanced estrogen independent growth and lung metastasis in vivo. Here, we characterize the mechanism by which CXCR4 induces a mesenchymal phenotype with metastatic properties. Methods: MCF-7 cells expressing wild-type CXCR4 (CXCR4WT) or CXCR4ΔCTD were evaluated in two-dimensional (2D) and three-dimensional reconstituted basement membrane (3D rBM) cultures for cell morphology and expression of factors that regulate the epithelial to mesenchymal transition (EMT) and cell migration. Effects of inhibition of key cytokine/chemokine signaling pathways activated by CXCR4 were examined. Tumor cell migration within the tumor microenvironment was followed using intravital imaging. Results: In 2D culture, MCF-7 CXCR4ΔCTD but not CXCR4WT cells, exhibited EMT characterized by up-regulation of ZEB-1 and cadherin 11, loss of E-cadherin, p120 isoform switching, and activation of ERK1/2, and MMP-2. The up-regulation of ZEB-1 was coincident with down-regulation of miR-200b and miR200c. In contrast to the 2D environment, 3D rBM MCF-7 CXCR4WT cultures exhibited the same stellate morphology of CXCR4ΔCTD cells, while MCF-7 control cells formed round acinar clusters. Expression of CXCR4 resulted in induction of expression of CXCR2, CXCR7, CXCL1, CXCL8, CCL2, IL-6 and GM-CSF by MCF-7 cells in 3DrBM, but not 2D culture. CXCR4 expression also induced transactivation of HER2 and EGFR. CXCL1, CXCL8 and CXCR2 appear to signal through a CXCR2 autocrine loop. In 3D rBM culture combined inhibition of CXCR4 and MEK1, or PI3K and MEK1/2 resulted in a change in morphology of CXCR4 expressing cells from stellate to round acinar clusters resembling controls. Combined inhibition of CXCR2 with MEK1, PI3K, or CXCR4 inhibitors also resulted in reversion of the stellate phenotype in 3D rBM. In vivo studies revealed that MCF-7 CXCR4WT and MCF-7CXCR4ΔCTD tumor cells migrate in a collective manner capable of lymphatic spread in athymic nude mice. Conclusions: Elevated expression or constitutive activation of CXCR4 results in EMT that is accompanied by up-regulation of receptors and cytokines important in collective cell migration leading to lymphatic invasion and tumor metastasis. Citation Format: Tammy Sobolik, Yingjun Su, Sam Wells, Ann Richmond. CXCR4 drives the metastatic phenotype in breast cancer through induction of CXCR2, transactivation of HER2/EGFR, and activation of MEK and PI3K pathways. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A53.