The effects of dexamethasone and tetradecanoyl phorbol acetate on plasminogen activator release by human acute myeloid leukemia cells

This investigation was undertaken to examine the extent to which leukemic cell functions are susceptible to regulation in vitro and to investigate their heterogeneity in this regard. Since plasminogen activator release is known to be a modulatable cellular function that can be influenced by antiinflammatory steroids and tetradecanoyl phorbol acetate (TPA), the effect of these two compounds on the secretion of urokinase- or tissue-type enzymes by leukemic cells was studied. The release of both enzyme species could be stimulated or suppressed by these substances by mechanisms that were inhibitable by actinomycin-D and hence required transcription of new mRNA. Plasminogen activator release by cells from 41/45 patients with AML was either stimulated or inhibited by 10(-7) M dexamethasone, implying that most AML cells possess glucocorticoid receptors. In 26/45 cases, the enzyme was inhibited by this steroid to less than 25% of control values. Pronounced inhibition of this degree was not encountered with normal polymorphonuclear leukocytes. Plasminogen activator secretion by AML cells was profoundly inhibited in 20/41 cases by 1 ng/ml TPA and stimulated in 8/41 cases. Leukemic blasts varied considerably in their response to dexamethasone and TPA. Plasminogen activator release should prove a sensitive means of monitoring the responses of AML cells to biologically active compounds.