Tumor cells aberrantly express
chemokines and/or
chemokine receptors, and some may promote
tumor growth and
metastasis. We examined the expression and function of
chemokine receptor CXCR3 in a syngeneic murine model of metastatic
breast cancer. By flow cytometry, CXCR3 was detected in all murine mammary tumor cell lines examined. All human
breast cancer cell lines examined also expressed CXCR3, as did the immortalized but nontumorigenic MCF-10A cell line. Interaction of CXCR3
ligands, CXCL9, CXCL10, and CXCL11, with CXCR3 on the highly malignant murine mammary tumor cell line 66.1 resulted in intracellular
calcium mobilization and chemotaxis in vitro. To test the hypothesis that
tumor metastasis is facilitated by CXCR3 expressed by
tumor cells, we employed a small molecular weight antagonist of CXCR3,
AMG487. 66.1
tumor cells were pretreated with
AMG487 prior to i.v. injection into immune-competent female mice. Antagonism of CXCR3 on 66.1
tumor cells inhibited experimental lung
metastasis, and this antimetastatic activity was compromised in mice depleted of natural killer cells. Systemic administration of
AMG487 also inhibited experimental lung
metastasis. In contrast to the antimetastatic effect of
AMG487, local growth of 66.1 mammary
tumors was not affected by receptor antagonism. These studies indicate that murine mammary
tumor cells express CXCR3 which facilitates the development of lung
metastases. These studies also indicate for the first time that a small molecular weight antagonist of CXCR3 has the potential to inhibit
tumor metastasis.