PROTRACTED TREATMENT WITH PHORBOL ESTER MODULATES J-7 HUMAN HEPATOMA-CELL-INDUCED AGGREGATION AND COAGULATION OF HUMAN PLATELET-RICH PLASMA

In heparinized human platelet-rich plasma (PRP), J-7 human hepatoma ce lls initially induced platelet aggregation; then a clot formed. ADP-sc avenger systems, apyrase and creatine phosphate/creatine phosphokinase did not inhibit this tumor-cell-induced platelet aggregation (TCIPA), whereas hirudin and concanavalin A completely blocked it. J-7 cells a lso shortened the recalcification time of normal and of Factor-VIII- a nd -IX-deficient human plasma, although it was inactive in shortening the recalcification time of Factor-VII-deficient plasma. After treatme nt with phorbol 12,13-dibutyrate (PDBu) for 5 to 90 min, the aggregati on and coagulation abilities of J-7 cells were unaffected. Prolonged t reatment of J-7 cells with PDBu but not with alpha-PDBu for 24 and 72 hr resulted in gradual loss of aggregation and coagulation. Staurospor ine antagonized the effect of PDBu and restored aggregation and coagul ation in J-7 cells. Protracted treatment with PDBu (24 or 72 hr) did n ot affect adherence of J-7 cells to the extracellular-matrix proteins (i.e., fibrinogen, fibronectin, laminin, vitronectin and collagen type s I and IV) or to the surface of plastic culture dishes. The treatment also did not affect J-7 cell detachment from plastic culture dishes. These in vitro results demonstrate that protracted phorbol ester treat ment diminishes TCIPA and blood coagulation of tumor cells. (C) 1994 W iley-Liss, Inc.