cokinetic properties in vivo compared to native enzyme, as is the case for ricin A chain (11, 12)? What concentration of glucose oxidase can be attained within lymphoma implants in vivo?

We report here that cultured human lymphoma cells in the absence of sonicated eosinophils are sensitive to killing by glucose oxldase (@3-Dglucose:oxygen..oxido reductase; EC 1.1.3.4) at concentrations as low as 0.025pg/mI,a levelthat canberapidlyattainedin s.c.tumor implantsin mice that receive a single nonlethal injection of enzyme. Multiple clono genie assays were used to measure the survival of human lymphoma cell lines (H9 and ARH-77) cultured for 14 days in complete RPMI 1640 supplemented with exogenous glucose oxidase (0.025—23@igJnil) or an Immunoconjugate containing glucose oxidase (0.25—25pg/mI) in the pres ence or absence of catalase (10 @igJml) or an equal number of sonicated human eosinophils with or without supplemental 100 pas Br, 1, or SCN. In addition, we used an immunoassay to measure the concentration of glucose oxidase in s.c. implants of the Sp 2/0 myeloma tumor at 0—30mm after an l.v. Injection of 50 @ag of enzyme into 21 BALB/c mice. Doses of glucose oxidase as small as 0.025 @aaJml killed more than 3 logs of tumor cells. Catalase completely inhibited, and sonicated human eosinophfls partially inhibited, the killing by glucose oxidase or immunoconjugate, whereas supplemental halides had no effect. Glucose oxldase i.v. produced levels >0.04 pg/g of tumor for 30 mm after injection with a peak concen tratlon of 0.079 pg/g of tumor within 5 mEnofinjection. These results are important because certain human lymphomas contain extensive extracel lular deposits of eoslnophll peroxidase, thereby making these tumors potentially less susceptible to killing by otherwise therapeutic doses of