Constitutive expression of the granulocyte-macrophage colony-stimulating factor gene in human solid tumors

We detected constitutive expression of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene in 3 human solid tumors by Northern blot analysis. Two of them were also found to secrete the GM-CSF protein by colony forming unit-culture assay. Southern blot analysis of each tumor DNA showed no gross rearrangement of the GM-CSF gene. This is the first report that demonstrates expression of the GM-CSF gene in solid tumors at the mRNA level.