MODULATION OF ACUTE MYELOBLASTIC-LEUKEMIA (AML) CELL-PROLIFERATION AND BLAST COLONY FORMATION BY ANTISENSE OLIGOMER FOR IL-1-BETA CONVERTING-ENZYME (ICE) AND IL-1 RECEPTOR ANTAGONIST (IL-1RA)

In the present study we investigated the effects of IL-1 antagonism on the autonomous growth of cells in acute myeloblastic leukemia (AML). To examine the role of pro-IL-1 processing, antisense technology was e mployed with 16-mer phosphorothioate oligodeoxynucleotide directed aga inst human IL-1 beta converting enzyme (ICR) in 7 randomly selected AM L cases. The addition of 10-75 mu M of antisense oligonucleotide (but not of control oligonucleotide) significantly inhibited spontaneous pr oliferation of bone marrow- (BM) and peripheral blood- (PB) derived lo w density leukemic cells in a dose-dependent way. Similarly, spontaneo us as well as induced CFU-AML colony formation was inhibited by human ICE antisense oligonucleotide with sample-to-sample variability. In se parate experiments, in order to examine the effects of blockade of end ogenously produced IL-1 to IL-1 receptors, the functional activity of human recombinant IL-1 receptor antagonist (IL-1ra) was tested. Contin uous exposure to high concentrations of IL-1ra (up to 100 mu g/ml) pro duced dose-dependent inhibition of spontaneous proliferatioin of the B M-derived blast cells from 9 of the 14 patients and of the PB-derived cells from 10 of the 14 patients. However, in some of these patients, the lower IL-1ra doses (down to 100 ng/ml) induced potentiation of spo ntaneous proliferation, suggesting a novel regulatory pathway for IL-1 receptor engagement. Similar results were obtained on CFU-AML colony formation, showing inhibition at higher IL-1ra doses, but in a few AML cases stimulatory effect at lower IL-1ra doses. Since the growth of A ML cells, as presented here by spontaneous proliferation and AML proge nitors, could be inhibited more efficiently by antisense oligonucleoti de to ICE in comparison to IL-1ra, these experiments provide evidence that pro-IL-1 processing mediated by ICE is an essential step in the a utonomous growth of AML cells.