CCL2 and neoplasm: Primary tumour hypoxia, for example, provides cytokines and growth factors capable of establishing a PMN through the recruitment of CD11b+Ly6CmedLy6G+ myeloid cells (driven partly by hypoxic tumour cell-derived monocyte chemotactic protein-1 (MCP-1), also known as CCL2) and a reduction in the cytotoxic effector functions of NK cell populations (attributed to the concomitant increase of CD11b+Ly6CmedLy6G+ myeloid cells) [43].