CSF2 and neoplasm: MDSCs are considered aberrantly activated immature cells of the myeloid compartment, whose expansion is mediated primarily by granulocyte-macrophage colony stimulation factor (GM-CSF), macrophage CSF (M-CSF) and granulocyte CSF (G-CSF), amongst other tumor-secreted growth factors 4, and likely activated by many different pro-inflammatory stimuli, such as interleukin 6 (IL-6), IL-1β, tumor necrosis factor (TNF) or interferon γ (IFN-γ) 5.