MEG-O1S CELLS HAVE RECEPTORS FOR AND RESPOND TO IL-3, IL-6, AND SCF

An established megakaryoblastic cell line, MEG-Ols, was used to study receptor expression and receptor-mediated responses to factors known t o affect megakaryocytopoiesis. In addition, the antigenic characterist ics of this cell line were further defined. MEG-01s cells were CD34(+) CD33(+)CD38+/-HLA-DR(-) and expressed erythroid and granulocytic diffe rentiation antigens as well as many megakaryocytic lineage-restricted antigens. These cells also expressed receptors for interleukin-3 (IL-3 ), IL-6, and stem cell factor (SCF), as measured by flow cytometry and /or RNA expression. MEG-01s cell proliferation or survival was only ma rginally influenced by these factors and their combinations. c-kit, th e receptor for SCF, was downmodulated by its ligand. This modulation w as time-dependent, appeared to involve receptor conformational changes , and became concentration-dependent by day 3. Northern blot analysis indicated that amounts of c-kit RNA increased as downmodulation procee ded. IL-3 induced IL-6 secretion in these cells, which was augmented b y a protein kinase-C (PKC) inhibitor, H7, and reduced by a tyrosine ki nase inhibitor, genistein. Evidence for autocrine regulation of this c ell line by IL-6 was demonstrated by the inhibitory effects of an anti sense oligonucleotide on H-3-thymidine (H-3-TdR) incorporation. These cells should prove useful for studies of the early signal transduction mechanisms involved in cytokine function.