DIVERSE EXPRESSION OF CYTOSOLIC PHOSPHOLIPASE-A(2), 5-LIPOXYGENASE AND PROSTAGLANDIN-H SYNTHASE-2 IN ACUTE PRE-B-LYMPHOCYTIC LEUKEMIA-CELLS

Several lines of evidence suggest that phospholipases A(2), leukotrienes and prostaglandins play a role in the proliferation of haemopoietic cells, The expression of genes involved in the biosynthesis of leukotrienes and prostaglandins was investigated in peripheral B lymphoblasts, isolated from eight patients with acute pre-B-lymphocytic leukaemia (pre B-ALL). RT-PCR analysis demonstrated that four of the investigated pre-B-ALL clones expressed the gene coding for cytosolic phospholipase A(2) (cPLA(2)), but not the gene coding for 5-lipoxygenase. In contrast, the remaining four pre-B-ALL clones expressed 5-lipoxygenase but not cPLA(2), suggesting that the transcriptional regulation of these two genes are different and that their cellular functions are not linked to each other. The capacity of pre B-ALL cells to produce LTB(4) and to express the 5-lipoxygenase protein, correlated with the expression of 5-lipoxygenase mRNA. All pre-B-ALL clones expressed genes coding for 5-lipoxygenase activating protein (FLAP), leukotriene A(4) hydrolase and prostaglandin (PG)H synthase 1, Seven of the eight pre B-ALL clones expressed PGH synthase 2, In comparison, normal tonsillar B cells did not express cPLA(2) or PGH synthase 2.