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 employed with 16-mer phosphorothioate oligodeoxynucleotide directed against human IL-1 beta converting enzyme (ICR) in 7 randomly selected AML cases. The addition of 10-75 microM of antisense oligonucleotide (but not of control oligonucleotide) significantly inhibited spontaneous proliferation of bone marrow- (BM) and peripheral blood- (PB) derived low density leukemic cells in a dose-dependent way. Similarly, spontaneous as well as induced CFU-AML colony formation was inhibited by human ICE antisense oligonucleotide with sample-to-sample variability. In separate experiments, in order to examine the effects of blockade of endogenously produced IL-1 to IL-1 receptors, the functional activity of human recombinant IL-1 receptor antagonist (IL-1ra) was tested. Continuous exposure to high concentrations of IL-1ra (up to 100 micrograms/ml) produced dose-dependent inhibition of spontaneous proliferation of the BM-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 spontaneous 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.(ABSTRACT TRUNCATED AT 250 WORDS)