Granulocyte-colony stimulating factor (G-CSF) is a glycoprotein growth factor, cytokine, and hormone that stimulates bone marrow to produce granulocytes and stem cells and release them into the bloodstream. Also functions in the differentiation, proliferation, and survival of neutrophils via the JAK/STAT, Ras/MAPK, and PI3K/Akt signal transduction pathways.