A potent and specific immunotoxin for tumor cells expressing disialoganglioside GD2 |
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Authors: | Kalpana Mujoo Ralph A. Reisfeld Lawrence Cheung Michael G. Rosenblum |
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Affiliation: | (1) Immunopharmacology Section, Department of Clinical Immunology and Biological Therapy, M. D. Anderson Cancer Center, 1515 Holcombe, 77 030 Houston, Texas, USA;(2) Scripps Clinic and Research Foundation, 92 037 La Jolla, CA, USA |
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Abstract: | Summary Monoclonal antibody 14G2a (anti-GD2) reacts with cell lines and tumor tissues of neuroectodermal origin that express disialoganglioside GD2. mAb 14G2a was coupled to the ribosome-inactivating plant toxin gelonin with the heterobifunctional cross-linking reagentN-succinimidyl-3(2-pyridyldithio)propionate. The activity of the immunotoxin was assessed by a cell-free translation assay that confirmed the presence of active gelonin coupled to 14G2a. Data from an enzyme-linked immunosorbent assay demonstrated the specificity and immunoreactivity of the 14G2a-gelonin immunotoxin, which was identical to that of native 14G2a. Assays for complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) revealed that these functional properties of the native 14G2a antibody were also preserved in the 14G2a-gelonin immunotoxin. The gelonin-14G2a immunotoxin was directly cytotoxic to human melanoma (A375-M and AAB-527) cells and was 1000-fold more active than native gelonin in inhibiting the growth of human melanoma cells in vitro. The augmentation of tumor cell killing of 14G2a-gelonin immunotoxin was examined with several lysosomotropic compounds. Chloroquine and monensin, when combined with 14G2a-gelonin immunotoxin, augmented its cytotoxicity more than 10-fold. Biological response modifiers such as tumor necrosis factor and interferon and chemotherapeutic agents such as cisplatinum andN,N -bis(2-chloroethyl)-N-nitrosourea (carmustine) augmented the cytotoxicity of 14G2a-gelonin 4- to 5-fold. The results of these studies suggest that 14G2a-gelonin may operate directly by both cytotoxic efforts and indirectly by mediating both ADCC and CDC activity against tumor cells; thus it may prove useful in the future for therapy of human neuroectodermal tumors.Research conducted, in part, by the Clayton Foundation for Research |
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Keywords: | Monoclonal antibodies Toxins Immunotoxins Cytotoxicity |
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