CXCL12 and neoplasm: Additionally, MDSC can be produced in the bone marrow in response to tumor derived factors i.e. Granulocyte Colony Stimulating Factor (G-CSF), IL-6, Granulocyte Monocyte Colony Stimulating Factor (GM-CSF), IL-1β, Prostaglandin E2 (PGE2) and Tumor Necrosis Factor A (TNFα) and are recruited to the tumor site by CXCL12 and CXCL5 [15].