Cytotoxic effect of immunoconjugate composed of glucose-oxidase coupled to an anti-ganglioside (GD2) antibody on spheroids.

As a new treatment protocol for neuroblastoma, the chimeric (human/mouse) antiganglioside GD2 antibody chl4.18 is being clinically tested. To improve the therapeutic effect of the antibody alone, we are currently investigating the cytotoxicity of glucose-oxidase coupled to the antibody chl4.18 on spheroids of the neuroblastoma cell line SK-N-LO. The cytotoxic effect of glucose-oxidase is achieved by the production of hydrogenperoxide (H2O2) and probably by the following reaction of H2O2 with iron to form hydrogen radicals (OH.). The cytotoxicity of glucose-oxidase was measured by two viability tests (MTT and WST 1). After a 4 hour treatment of the spheroids with the immunoconjugate, a reduction of viability to 50% (MTT-test) and 25% (WST 1-test), respectively, was obtained. The difference between the results of these two tests, might be explained by the different measurement protocols.