[An anti-P-gp/anti-CD3 bispecific antibody cytotoxic to human multidrug resistant KB cells].

Objective To study the specific cytotoxicity mediated by anti-P-gp/anti-CD_3 diabodies in multidrug resistant solid tumor using P-gp as target.Methods The anti-P-gp/anti-CD_3 diabodies were secreted from E.coli strain 16C9 containing the expression plasmid PAYZDCP,grown at 30℃ in a shaker flask;the diabodies were purified by affinity chromatography and identified by SDS-PAGE;the effect of the anti-P-gp/anti-CD_3 diabody mediated lysis of P-gp-expressing tumor cells was assayed by ~(51)Cr release assay in vitro,and by human KB nude mouse xenograft models in vivo.Results The diabodies were generated by bacteria as a soluble functional form and purified by one-step affinity chromatography with a yield(4 mg/L) culture medium.In()~(51)Cr release assay,the diabodies targeted human activated T cellls to lyse P-gp~+-KB/MDR cells in a dose-dependent manner.It suggested that the diabody was able to induce an efficient lysis of the target cells by human T cells in vitro.When combined with activated human T cells,the diabody significantly inhibited the growth of KB/MDR,but had no effect on KB xenografts.Conclusion The anti-P-gp/anti-CD_3 bispecific antibody is a potent agent for targeting human T lymphocytes to lyse solid tumor cells overexpressing P-gp in vitro and in vivo.