Abstract B230: Neutralizing CCL2 inhibits breast tumor growth and metastasis

Abstract

Abstract CCL2, (CC-chemokine ligand 2 or monocyte chemoattractant protein-1 (MCP-1)), is overexpressed in many human tumors. CCL2 is believed to exert direct effects on tumor cells (via increased proliferation/survival and migration) and the tumor stroma (via recruitment of tumor associated macrophages and promotion of angiogenesis at the tumor site). CCL2 expression levels in primary breast tumors have been correlated with macrophage infiltration and blood vessel density, which in turn correlate with disease stage and worse prognosis. These correlations suggest that CCL2 could be a key player in breast tumor growth/metastasis. To study the effect of neutralizing CCL2 in vivo, the human breast tumor cell lines MDA-MB-231 and MAXF857, both ER−, PR−, Her2lo, were implanted orthotopically in the mammary fat pad in immunocompromised mice. When tumors reached 70–100 mm3, a cocktail of neutralizing antibodies to human CCL2 (CNTO 888) and to the mouse orthologs, MCP-1 and MCP-5 (collectively termed CCL2 blockade) was administered i.p twice a week at 10 mg/Kg each for the study duration. In both models, CCL2 blockade significantly inhibited the growth of primary tumors (P<0.01). In addition, CCL2 blockade significantly reduced the number of visible lung metastases in the MDA-MB-231 model (P<0.008), suggesting that CCL2 promotes metastasis as well as primary tumor growth. To further study the role of CCL2 in tumor growth and metastasis, in vitro studies were conducted to mimic the in vivo interactions between tumor and stroma. MDA-MB-231 cells migrated toward CCL2 in a dose-dependent manner (P<0.05), which was significantly inhibited by CNTO 888 (P<0.01). When MDA-MB-231 cells were incubated with normal human lung fibroblasts (NHLF) to model the tumor-lung interaction, the tumor cells induced a 3-fold increase in CCL2 expression by NHLF (P<0.001), through both direct and indirect co-culture. These results suggest that tumor-stroma crosstalk results in increased expression of CCL2 by lung fibroblasts, which could help drive the migration/growth of tumors in the lung. Taken together with the in vivo data, the results indicate that CCL2 plays a role in the migration, seeding and/or growth of tumor cells in distant sites. To determine if neutralizing CCL2 could increase efficacy if combined with other agents, CCL2 blockade was dosed as described above, either alone or in combination with bevacizumab (i.p. once a week 10 mg/Kg) or docetaxel (i.p q7dx3 30 mg/Kg) in the MDA-MB-231 orthotopic model (tumors were 70–100 mm3 at treatment initiation). The combination therapies showed significantly greater inhibition of primary tumor growth (P<0.018) and increased survival (P<0.028) as compared to treatment with CCL2 blockade, bevacizumab or docetaxel alone. In addition, only treatments that included CCL2 blockade significantly reduced visible lung metastases (P<0.008). These results indicate that neutralizing CCL2 in combination with a taxane or an anti-angiogenesis agent may lead to increased efficacy in the treatment of patients with breast cancer. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B230.