title: A specific and potent immunotoxin composed of antibody ZME-018 and the plant toxin gelonin.
abstract: Murine monoclonal antibody ZME-018 recognizes a 240 Kda glycoprotein present on the surface of most human melanoma cells and on over 80% of human biopsy specimens tested. Gelonin is a ribosome-inactivating plant toxin similar in nature and rivaling the activity of ricin A chain. ZME-018 was coupled to purified gelonin using the reagents SPDP and 2-iminothiolane. The ZME-gelonin conjugate was purified by S-300 Sephacryl and Blue Sepharose chromatography, removing unreacted gelonin and antibody, respectively. PAGE analysis showed that ZME was coupled to 1, 2, or 3 gelonin molecules. The ZME-gelonin conjugate was 10(6)-fold more active than gelonin itself in inhibiting the growth of log-phase human melanoma cells in culture. The immunoconjugate was not cytotoxic to antigen negative T-24 (human bladder carcinoma) cells. Treatment of melanoma cells with recombinant IFN-alpha or TNF substantially augmented the cytotoxicity of the immunoconjugate while treatment with IFN-gamma had a minor effect. Using the human tumor colony assay of melanoma cells obtained from fresh biopsy specimens, greater than 90% growth suppression was observed in 2 of 4 samples tested at a concentration of 250 ng/ml. In addition, 25% growth suppression was observed with a third sample tested, and no growth suppression was observed in 1 sample. Thus, clonogenic melanoma cells are sensitive in vitro to the cytotoxic activity of this immunotoxin at concentrations which we presume are pharmacologically relevant.
authors.affiliation: Department of Clinical Immunology and Biological Therapy, M.D. Anderson Cancer Center, Houston, TX 77030.
authors.forename: M G
authors.initials: MG
authors.lastname: Rosenblum
authors.forename: J L
authors.initials: JL
authors.lastname: Murray
authors.forename: L
authors.initials: L
authors.lastname: Cheung
authors.forename: R
authors.initials: R
authors.lastname: Rifkin
authors.forename: S
authors.initials: S
authors.lastname: Salmon
authors.forename: R
authors.initials: R
authors.lastname: Bartholomew
mesh_terms: D000912:Antibodies, Neoplasm; D003602:Cytotoxicity, Immunologic; D006801:Humans; D000922:Immunotoxins / Q000302:isolation & purification* / Q000494:pharmacology; D007370:Interferon Type I / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D008545:Melanoma / Q000276:immunology; D010940:Plant Proteins / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D054789:Ribosome Inactivating Proteins, Type 1; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014410:Tumor Stem Cell Assay
chemical_list: D000912:Antibodies, Neoplasm; D000922:Immunotoxins; D007370:Interferon Type I; D010940:Plant Proteins; D011500:Protein Synthesis Inhibitors; D054789:Ribosome Inactivating Proteins, Type 1; D014409:Tumor Necrosis Factor-alpha; C025674:GEL protein, Gelonium multiflorum; D007371:Interferon-gamma