INTRACELLULAR SIGNAL-TRANSDUCING ELEMENTS INVOLVED IN TRANSENDOTHELIAL MIGRATION OF LYMPHOMA-CELLS

To investigate the molecular mechanisms underlying transendothelial mi gration of turner cells, an essential process for their hematogenous d issemination, we developed an in vitro model system that allows the se parate monitoring of cell adhesion and transmigration processes. This system uses a human pre-B lymphoma cell line, Nalm-6, and a cultured m ouse endothelial cell line, KOP2.16, Nalm-6 cells rapidly adhered to K OP2.16 and subsequently transmigrated underneath them. Using this mode l, we examined the effects on transendothelial migration, of various r eagents which specifically interfere with the function of intracellula r signal transduction molecules. Treatment of Nalm-6 cells with wortma nnin (WMN), herbimycin A, pertussis toxin, or C3 exoenzyme of Clostrid ium botulinum, which specifically inhibit PI3 kinase and/or myosin lig ht chain kinase, herbimycin-sensitive tyrosine kinases, heterotrimeric G proteins, and the small G proteins rho/rac, respectively, reduced t ransmigration in a dose-dependent manner. Pretreatment of KOP2.16 endo thelial cells with WMN also reduced transmigration in a dose-dependent manner. Binding of Nalm-6 to KOP2.16 was not affected, even when Nalm -6 or KOP2.16 cells were pretreated with these inhibitors, indicating that the reduction of transmigration was not due to a reduction of Nal m-6 binding to KOP2.16, These results also indicate that the signal tr ansduction pathway(s) involved in transmigration can be dissociated fr om that of adhesion. Our results support the notion that endothelial c ells are not a passive barrier in lymphoma extravasation, but that the y assist lymphoma cell extravasation.