METABOLIC AND MOLECULAR CONTROL OF MYELOPOIESIS

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Continuous presence of a glycoprotein termed colony stimulating factor (CSF) is necessary for the in vitro clonal growth of the committed granulocyte-macrophage progenitor cell (CFU-GM). CSF stimulates the release of arachidonic acid from membrane phospholipids, and arachidonic acid is then transformed to products of cyclooxygenation and lipoxygenation. Inhibition of lipoxygenase and specifically of the synthesis of leukotrienes C and D (LTC and LTD) blocks CSF-induced colony growth, and the block can be partially reversed by addition of LTC or LTD. CFU-GM from a subset of patients with acute non-lymphoblastic leukemia (ANLL) exhibit resistance to the inhibitory effects of high concentrations of lipoxygenase inhibitors. This may reflect a release from a normal regulatory mechanism related to oncogenesis. The metabolism of lipoxygenase intermediates to LTC and LTD depends on glutathione reductase, glutathione S-transferase and gamma-glutamyl transpeptidase. The genes for two of these enzymes have been localized to chromosomes that are frequently involved in cytogenetic abnormalities associated with ANLL. The overall objective of the proposed research is to further elucidate the role of arachidonic acid and glutathione metabolism in normal CSF stimulated CFU-GM growth and in leukemia by 1) determining the role of specific critical enzymes of leukotriene and glutathione metabolism in normal and leukemic myeloid cell; and 2) examining changes in the activity of those specific enzymes as leukemic cell lines are induced to differentiate. To accomplish this, recombinant human CSF, semi-purified bone marrow progenitor cells from normal and leukemic individuals, and well- characterized human leukemic cell lines will be used. Enzymes in the lipoxygenase pathway will be inhibited selectively. Patterns of inhibition of the leukemic cell lines will be compared with normal and leukemic bone marrow cells. The content and activity of enzymes which are found to impact on normal and leukemic colony formation will be quantitated and related to growth patterns. The results of these studies will enhance our knowledge of normal and neoplastic regulation and will serve to focus future studies on the molecular genetics of altered regulation in leukemic cells.