Ricin fusion toxin targeted to the human granulocyte-macrophage colony stimulating factor receptor is selectively toxic to acute myeloid leukemia cells

Chris Burbage, Edward P. Tagge, Billie Harris, Philip Hall, Tao Fu, Mark C. Willingham, Arthur E. Frankel

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Treatment failure of patients with acute myelogenous leukemia (AML) is frequently due to the development of multidrug resistance phenotype blasts. We have expressed a fusion protein consisting of human granulocyte-macrophage colony stimulating factor (GMCSF) fused to the N-terminus of a lectin-deficient ricin toxin B chain (RTB) in Spodoptera frugiperda insect cells. The fusion protein was purified by immunoaffinity chromatography and reassociated with chemically deglycosylated ricin toxin A chain (RTA). The resulting fusion toxin was found to react with antibodies to GMCSF, RTB and RTA and had the predicted molecular mass of 80 kDa. GMCSF-ricin bound poorly to asialofetuin (K(d) = 106 M-1) and receptor negative cells indicating loss of lectin activity, but bound strongly to GMCSF receptor positive HL60 cells. Ligand displacement assays showed fusion toxin affinity 2.6-fold less than native GMCSF. Selective inhibition of protein synthesis was observed on receptor positive cells. Induction of apoptosis was also observed on receptor positive cells. Cells expressing multidrug resistance gene products (P-gp, Bcl2 and BclX(L)) were also sensitive to fusion toxin. These results suggest that GMCSF-ricin deserves further preclinical development.

Original languageEnglish (US)
Pages (from-to)681-690
Number of pages10
JournalLeukemia Research
Volume21
Issue number7
DOIs
StatePublished - Jul 1 1997

Keywords

  • GMCSF receptor
  • Myeloid leukemia cells
  • Ricin

ASJC Scopus subject areas

  • Hematology
  • Oncology
  • Cancer Research

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