Role of interleukin-4 in the negative regulation of proliferation of chronic myelomonocytic leukemia cells.

We studied the effects of interleukin-4 (IL-4) on the spontaneous proliferation of chronic myelomonocytic leukemia (CMMoL) cells in vitro to clarify whether IL-4 can act as a negative regulator of hematopoiesis. The results clearly show that IL-4 suppressed spontaneous DNA synthesis and colony formation by CMMoL cells in vitro. Colony formation by CMMoL cells was substantially suppressed by adding either an anti-IL-6 or anti-GM-CSF antibody to the colony assay system. This suppression was abrogated by the treatment of IL-4 with an anti-IL-4 antibody. Furthermore, the production of IL-6 or GM-CSF was markedly inhibited by adding IL-4 to the culture system. These observations indicate that IL-4 can act as a negative regulator for the autocrine growth of CMMoL cells by inhibiting their production of IL-6 and/or GM-CSF.