CANCER PROCOAGULANT AND TISSUE FACTOR ARE DIFFERENTLY MODULATED BY ALL-TRANS-RETINOIC ACID IN ACUTE PROMYELOCYTIC LEUKEMIA-CELLS

All-trans-retinoic acid (ATRA) downregulates the expression of two cel lular procoagulants, tissue factor (TF) and cancer procoagulant (CP), in human promyelocytic leukemia cells. To evaluate whether or not chan ges of the procoagulant activities (PCAs) may share mechanisms with th e ATRA-induced cyto-differentiation process, we have characterized the effect of ATRA on the TF and CP expression by NB4 cells, an ATRA matu ration-inducible cell line, and two NB4-derived cell lines resistant t o ATRA-induced maturation, the NB4.306 and NB4.007/6 cells. Next, we e valuated the effect on the PCAs of the NB4 parental cells of three syn thetic retinoid analogues, ie: AM580 (selective for the retinoic acid receptor [RAR] alpha), capable to induce the granulocytic differentiat ion of NB4 cells; and CD2019 (selective for RAR beta) and CD437 (selec tive for RAR gamma), both lacking this capability. Cells were treated with either ATRA or the analogues (10(-6) to 10(-8) mol/L) for 96 hour s. The effect on cell differentiation was evaluated by morphologic cha nges, cell proliferation, nitro blue tetrazolium reduction assay, and flow cytometry analysis of the CD33 and CD11b surface-antigen expressi on. PCA was first measured in 20 mmol/L Veronal Buffer cell extracts b y the one-stage clotting assay of normal and FVII-deficient plasmas. F urther TF and CP have been characterized and quantified in cell-sample preparations by chromogenic and immunological assays. In the first se ries of experiments, ATRA downregulates both TF and CP in NB4 parental cells, as expected. However, in the differentiation-resistant cell li nes, it induced a significant loss of TF but had little or no effect o n CP. In a second series of experiments, in the NB4 parental cells, th e RAR alpha agonist (AM580) induced cell maturation and reduced 91% CP expression, whereas CD437 and CD2019 had no cyto-differentiating effe cts and did not affect CP levels. On the other hand, in the same cells the TF expression was reduced by ATRA and AM580, but also by the RAR beta agonist CD2019, which did not induce cell maturation. These data indicate that in NB4 cells, ATRA modulation of CP occurs in parallel w ith signs of cell differentiation, while the regulation of TF appears to be at least in part independent from these processes, and involves both alpha and beta nuclear retinoid receptors. (C) 1998 by The Americ an Society of Hematology.