A specific and potent immunotoxin composed of antibody ZME-018 and the plant toxin gelonin

Mol Biother. 1991 Mar;3(1):6-13.


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.

MeSH terms

  • Antibodies, Neoplasm
  • Cytotoxicity, Immunologic
  • Humans
  • Immunotoxins / isolation & purification*
  • Immunotoxins / pharmacology
  • Interferon Type I / pharmacology
  • Interferon-gamma / pharmacology
  • Melanoma / immunology
  • Plant Proteins* / pharmacology
  • Protein Synthesis Inhibitors / pharmacology
  • Ribosome Inactivating Proteins, Type 1
  • Tumor Necrosis Factor-alpha / pharmacology
  • Tumor Stem Cell Assay


  • Antibodies, Neoplasm
  • Immunotoxins
  • Interferon Type I
  • Plant Proteins
  • Protein Synthesis Inhibitors
  • Ribosome Inactivating Proteins, Type 1
  • Tumor Necrosis Factor-alpha
  • GEL protein, Gelonium multiflorum
  • Interferon-gamma