Cytotoxicity of an internalizing 7E11-C5 Mab-Se immunoconjugate against DU145 prostate tumor cells

J. Chen, M. Boylan, T. W. Reid, J. E. Spallholz

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Abstract

A prostate specific membrane (PSM) antigen monoclonal antibody Mab 7E11-C5 has been covalently labeled with a superoxide generating selenium (Se) compound, selenocystamine, forming a 7E11-C5 Mab-Se immunoconjugate Mab-Se. The Mab-Se immunoconjugate generated superoxide in vitro by the oxidation of glutathione (GSH). The binding of the Mab-Se to DU-145 prostate tumor cells was enhanced by the conjugation of Se to the Mab as indicated by an ELISA assay. A [3H]-thymidine cell incorporation assay indicated that the in vitro cytotoxichy of the Mab-Se towards DU-145 prostate tumor cells was similar to the that of selenocystamine alone. SDS-PAGE electrophoresis showed that the molecular weight of the Mab-Se immunoconjugate was not altered by the conjugation of selenocystamine. A 20 nm gold (Au) colloid was electrostatically attached to both native 7E11-C5 Mab and the Mab-Se immunoconjugate to form a native Mab-Au and Se-Mab-Au immunoconjugates. Both Au labeled native Mab and a non-toxic level of Mab-Se immunoconjugate were incubated with DU-145 prostate tumor cells. After 24 hr the gold particles were found totally accumulated inside the lysosome of the tumor cells following capping as demonstrated by electron micrographs. It is suggested that the Mab-Se antibody is internalized by the phagolysosome which carries conjugated selenocystamine into the tumor cells. EM observation also showed that the damage to the DU-145 tumor cells induced by atoxic amount of the Mab-Se immunoconjugate was to the cell membrane, the endoplasmic reticula and mitochondria.

Original languageEnglish
Pages (from-to)A403
JournalFASEB Journal
Volume11
Issue number3
StatePublished - Dec 1 1997

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