RELATIONSHIP OF ACIVICIN-INDUCED MONOCYTOID DIFFERENTIATION OF HUMAN MYELOID-LEUKEMIA CELLS TO ACIVICIN-INDUCED MODULATION OF GROWTH-FACTOR, CYTOKINE, AND PROTOONCOGENE MESSENGER-RNA EXPRESSION

We have previously noted that the glutamine antagonist acivicin (alpha-S,5S-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid) induces monocytoid differentiation of freshly isolated human myeloid leukemia cells and HL-60 cells. This study was designed to determine the effects of acivicin on the levels of HL-60 cell mRNA transcripts of several cytokines, growth factors, and protooncogenes implicated in the control of hematopoietic cell proliferation and differentiation. Control HL-60 cells did not express mRNA for granulocyte-colony-stimulating factor, granulocyte-macrophage-colony-stimulating factor, interleukin 3, or interleukin 6, and acivicin or phorbol myristate acetate did not induce their expression. Phorbol myristate acetate reduced expression of c-myc, c-myb, and heat shock protein 70 and enhanced those of macrophage-colony-stimulating factor and c-fms. Acivicin caused a decreased expression of c-myc, and an increased expression of mRNA for interleukin 1-beta and tumor necrosis factor alpha (TNF-alpha). The drug also caused an initial increase in c-myb, followed by a subsequent decrease below baseline levels. Supernatants and lysates of acivicin-treated HL-60 cells contained increased levels of interleukin 1-beta. Both TNF-alpha and interleukin 1-beta have been shown previously to influence hematopoietic cell differentiation. In our experiments, exogenous interleukin 1 added to HL-60 cells did not induce differentiation, but the combination of interleukin 1 and TNF synergistically enhanced the process. Pretreatment of the cells with TNF enhanced their responsiveness to subsequent treatment with interleukin 1. Our results demonstrate that the glutamine antagonist acivicin modulates HL-60 cell expression of TNF-alpha, interleukin 1-beta, c-myc, and c-myb and suggest that interleukin 1-beta and TNF-alpha might (in an autocrine manner) cause the differentiation.