Granulocyte-macrophage colony stimulating factor (GM-CSF) is a cytokine that functions as a white blood cell growth factor. GM-CSF stimulates stem cells to produce granulocytes (neutrophils, eosinophils and basophils) and monocytes. GM-CSF signals via signal transducer and activator of transcription, STAT5. In macrophages, it has also been shown to signal via STAT3. Although GM-CSF was initially characterized by its ability to stimulate neutrophil, monocyte/macrophage and eosinophil colony formation, it has since been shown that it has additional activities on hematopoietic, as well as non-hematopoietic lineage cells.
Increased levels of GM-CSF have been reported in the serum of some cancer patients, including patients with lung cancer and patients with acute myelogenous leukemia. GM-CSF has also been reported to be increased in the peripheral blood of bronchial asthma patients and in extracts of psoriatic scales.