We have previously shown a fraction of stromal fibroblasts/myofibroblasts (Fibs) from leukemic bone marrow cells expresses leukemia-specific transcripts along with hematopoietic and Fib-related markers. Normal bone marrow-derived Fibs (nFibs) do not express CD34 or CD45; however, nFibs may express hematopoietic markers with some specific stimulations. CD34 expression was detected in nFib cultures following the addition of a culture supernatant of blood mononuclear cells stimulated with phytohemagglutinin (PHA)-P. To identify the molecules responsible for inducing CD34 expression in nFibs, cDNA clones were isolated using functional expression cloning with a library constructed from PHA-P stimulated human blood mononuclear cells. Positive clones inducing CD34 transcription in nFibs were selected. We confirmed that an isolated positive cDNA clone encoded human interleukin (IL)-1 beta (beta). CD34 expression was observed in the nFib cultures with recombinant human (rh) IL-1 beta protein. And CD34 transcription was suppressed when a rhIL-1 beta neutralizing antibody was added to the IL-1 beta-stimulated nFib cultures. nFibs expressed gp130 and IL-6 receptors, and CD45 expression was detected in nFibs cultured with rhIL-1 beta and rhIL-6. Chronic myelogenous leukemia (CML) cells reportedly respond well to IL-1 beta. When CML-derived Fibs were cultured with rhIL-1 beta and rhIL-6, CD45-positive cells increased in number. Cell fate may be influenced by an external specific stimulation without gene introduction. (C) 2020 Elsevier Inc. All rights reserved.