title: Sensitivity of human acute myeloid leukaemia to diphtheria toxin-GM-CSF fusion protein.
abstract: The potential to selectively eliminate acute myeloid leukaemia (AML) cells with the GM-CSF-diphtheria toxin fusion protein (DT-GM-CSF) was studied under conditions of autonomous proliferation in vitro with no growth factors (GFs) added and after growth stimulation with a mixture of human (hu)G-CSF, huIL-3 and huSCF. DNA synthesis was maximally inhibited after 48 h exposure to DT-GM-CSF. Cell viability and AML colony forming ability in vitro were reduced. 18/22 samples were found to be sensitive to DT-GM-CSF, with 50% inhibition of DNA synthesis (ID50) at concentrations ranging from 0.1 to 16 ng/ml, and four samples were minimally or not sensitive to DT-GM-CSF (ID50 > or = 99 ng/ml). From the 15 samples which showed autonomous proliferation, 13 were sensitive to inhibition of proliferation by DT-GM-CSF. The level of GM-CSF receptor (GM-CSFR) expression was determined by flow cytometry after labelling with specific antibodies for the alpha and beta subunits. Although the toxicity to DT-GM-CSF was specifically mediated by the GM-CSFR, no correlation was found between the level of expression of the GM-CSFR alpha or beta subunit and the sensitivity for DT-GM-CSF. These in vitro studies show that the DT-GM-CSF fusion protein can be used for specifically targeting and eliminating leukaemic cells in the majority of AML cases.
authors.affiliation: Institute of Haematology, Erasmus University, Rotterdam, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Rozemuller
authors.forename: E J
authors.initials: EJ
authors.lastname: Rombouts
authors.forename: I P
authors.initials: IP
authors.lastname: Touw
authors.forename: D J
authors.initials: DJ
authors.lastname: FitzGerald
authors.forename: R J
authors.initials: RJ
authors.lastname: Kreitman
authors.forename: I
authors.initials: I
authors.lastname: Pastan
authors.forename: A
authors.initials: A
authors.lastname: Hagenbeek
authors.forename: A C
authors.initials: AC
authors.lastname: Martens
mesh_terms: D000208:Acute Disease; D002455:Cell Division; D004167:Diphtheria Toxin / Q000627:therapeutic use*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000627:therapeutic use*; D006801:Humans; D007951:Leukemia, Myeloid / Q000473:pathology / Q000628:therapy*; D014407:Tumor Cells, Cultured
chemical_list: D004167:Diphtheria Toxin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor