The extremely important immunosuppressive mechanism in tumor microenvironment is the activity of tumor-associated macrophages (TAMs), which are initially attracted into tumors by macrophage chemoattractants (e.g., CCL2, monocyte chemoattractant protein 1 -MCP-1 or by colony-stimulating factor 1 (CSF-1). Here, CCL2 is linked to neoplasm.