The cytokines C−C motif chemokine ligand (CCL) 2 and CCL5, which promote the recruitment of tumor-associated macrophages (TAMs)27,28, as well as interleukin (IL)-8, which is a ligand for C−X−C motif chemokine receptor (CXCR) 1 and CXCR2, are highly expressed on the surface of M2 macrophages, and TAMs have an M2-like phenotype29. Here, CXCR1 is linked to neoplasm.