DIFFERENTIATION OF GRANULOCYTES AND MACROPHAGES

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The objectives of this project are to characterize the molecular control of myeloid leukemia cells by first establishing the nature of the specific glycoproteins (colony-stimulating factors, CSFs) controlling cell division and differentiation of normal granulocytes and macrophages, then determining the actions of the CSFs on leukemia cells. We have established that four glycoproteins interact to control normal mouse granulocytes and macrophages: GM-CSF, M-CSF, G-CSF, and MultiCSF (IL-3). All four have been purified to homogeneity in small amounts. cDNAs have been cloned for GM-CSF and Multi-CSF with bacterial expression and the recombinant material has similar in vitro and in vivo properties to the native molecules. We have established that G-CSF can suppress myeloid leukemic cells by enforcing terminal differentiation. Using 125I-labeled G-CSF, we have shown that receptor numbers on leukemia cells are similar to those on normal GM precursor cells. Differentiation-unresponsive leukemia cells have been shown to lack membrane receptors for G-CSF. These studies will be extended using radiolabeled GM-CSF, and the genetic elements controlling GM-CSF will be sequenced and analyzed. Amino acid sequence data has been obtained from purified G-CSF and attempts are in progress to clone a cDNA for G-CSF, a first step towards the mass production of G-CSF. (M)