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. cDNAs for both mouse and human GM-CSF encode precursor proteins with a 17 amino acid (aa) signal peptide that is cleaved toform mature proteins with 124 and 127 aa residues, respectively. 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. GM-CSF is manufactured using recombinant DNA technology and is marketed as a protein therapeutic called molgramostim or, when the protein is expressed in yeast cells, sargramostim. It is used as a medication to stimulate the production of white blood cells and thus prevent neutropenia following chemotherapy. GM-CSF has also recently been evaluated in clinical trials for its potential as a vaccine adjuvant in HIV-infected patients. The preliminary results have been promising, but GM-CSF is not presently FDA-approved for this purpose.
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.