CCL2 and neoplasm: At the same time, GRP78 silencing in tumor cells, particularly in the murine breast cancer cell line 4T1B, leads to increased secretion of MCP-1, which recruits macrophages into the tumor microenvironment, and a reduction in CD47, a “self” signal that makes the tumor more vulnerable to macrophage-mediated phagocytosis [321,322].