CCL2 and breast cancer: Similar results are documented by Bussard and colleagues showing an increased presence of osteoblast-derived cytokines including IL-6, IL-8, MCP-1, macrophage-inflammatory protein 2 (MIP-2), and vascular endothelial growth factor (VEGF) in the presence of MDA-MB-231 breast cancer cells in ex vivo cultures of tumor bearing bones from athymic mice, or even in the presence of conditioned medium in vitro (34).