In summary, the TME recruits monocytes and macrophages through the CSF1-CSF1R, CCL2-CCR2, CCL4-CCR5, IL-33-ST2, CXCL12-CXCR4, IL-8-CXCR2 and PGE2-EP4/EP2 pathways; thus, these pathways are major targets for potential interventions in tumor treatment. Here, PTGER4 is linked to neoplasm.