Macrophages are, for example, recruited by the chemokine ligand 2 (CCL2) secreted by cancer cells and, once at the tumour site, they are reprogrammed from an M1 anti-tumour phenotype to an M2 pro-tumorigenic phenotype, which promotes the secretion of pro-angiogenic, pro-invasive and immunosuppressive factors.83–85 TAMs can also induce early dissemination from the primary tumour by producing Wnt186 and play a critical role in guiding the intravasation of invasive cancer cells into the bloodstream87 (Fig. 2). Here, CCL2 is linked to cancer.