CCL2 and breast cancer: MCP-1 has been widely implicated in the metastasis of breast cancer to the lung—Qian et al. (2011) showed that MCP-1 promoted breast cancer lung metastasis by recruiting inflammatory monocytes, and Bonapace et al. (2014) showed an acceleration of breast cancer lung metastasis subsequent to the cessation of MCP-1 inhibition [3, 68].