– Monocyte chemoattractant protein 1 (MCP-1), also called CCL2, is a member of the beta (C-C) subfamily of chemokines that is a chemoattractant for monocytes and basophils but not eosinophils or neutrophils. CCL2 binds the cognate receptor CCR2, and together this signaling pair has been shown to have multiple pro-tumorigenic roles, from mediating tumor growth and angiogenesis to recruiting and usurping host stromal cells to support tumor progression. CCL2 is found in the circulation, where it has been suggested as a diagnostic biomarker of breast cancer and prostate cancer. CCL2 can also induce arachidonic acid release in human monocytes, which has been shown to be involved in adhesion and induction of the chemotactic response, in a pertussis-toxinsensitive manner.