Cxcl10 Chemokine Induces Migration of ING4-Deficient Breast Cancer Cells via a Novel Cross Talk Mechanism between the Cxcr3 and Egfr Receptors

Abstract

The chemokine Cxcl10 has been associated with poor prognosis in breast cancer, but the mechanism is not well understood. Our previous study has shown that <i>CXCL10</i> was repressed by the ING4 tumor suppressor, suggesting a potential inverse functional relationship. We thus investigated a role for Cxcl10 in the context of ING4 deficiencies in breast cancer. We first analyzed public gene expression data sets and found that patients with <i>CXCL10</i>-high/<i>ING4</i>-low expressing tumors had significantly reduced disease-free survival in breast cancer. <i>In vitro</i>, Cxcl10 induced migration of <i>ING4</i>-deleted breast cancer cells but not of <i>ING4</i>-intact cells. Using inhibitors, we found that Cxcl10-induced migration of <i>ING4</i>-deleted cells required Cxcr3, Egfr, and the Gβγ subunits downstream of Cxcr3 but not Gαi. Immunofluorescent imaging showed that Cxcl10 induced early transient colocalization between Cxcr3 and Egfr in both <i>ING4</i>-intact and <i>ING4</i>-deleted cells, which recurred only in <i>ING4</i>-deleted cells. A peptide agent that binds to the internal juxtamembrane domain of Egfr inhibited Cxcr3/Egfr colocalization and cell migration. Taken together, these results presented a novel mechanism of Cxcl10 that elicits migration of <i>ING4</i>-deleted cells, in part by inducing a physical or proximal association between Cxcr3 and Egfr and signaling downstream via Gβγ. These results further indicated that ING4 plays a critical role in the regulation of Cxcl10 signaling that enables breast cancer progression.