To define which myeloid cells provide the bulk of IL-1β to fuel tumor cell NF-κΒ activity, we isolated BM cells from C57BL/6 mice and drove them toward monocyte and neutrophil differentiation by macrophage colony-stimulating factor (M-CSF) and granulocyte-colony-stimulating factor (G-CSF culture, respectively. This evidence concerns the gene CSF1 and neoplasm.