title: Variable cytotoxicity of diphtheria toxin 388-granulocyte-macrophage colony-stimulating factor fusion protein for acute myelogenous leukemia stem cells.
abstract: In this study, the utility of DT388-granulocyte-macrophage colony-stimulating factor (GM-CSF) for the ex vivo purging and direct administration to patients with acute myeloid leukemia (AML) is tested using clonogenic assays, long-term cultures (LTC), and NOD/SCID mice as assays for leukemic progenitors. We compare the ability of 24-hour exposure to 0.3 microg/mL (4 nM) DT388-GM-CSF to kill AML colony forming cells (CFC) and the more primitive AML progenitors detected after 6 weeks in stromal cocultures (AML LTC-initiating cells or AML LTC-IC) and after 8 weeks in NOD/SCID mice.AML samples (n = 10), expressing a mean of 35 to 1466 GM-CSF receptors/blast, showed mean (range) percent kills of AML CFC and LTC-IC of 61 (17-98) and 46 (0-94) respectively with a direct correlation (r = 0.69) between the % kills detected in the in vitro assays. Among 5 evaluable samples the percent reduction in AML cell engraftment in NOD/SCID marrow following ex vivo DT388-GM-CSF treatment varied from 38% to 100%. 40% to 56% of normal bone marrow CFC and 31% to 48% of normal LTC-IC survived the same ex vivo treatment (n = 3). In subsequent experiments, NOD/SCID mice received AML blast cell injections intravenously followed in 24 hours by 1.5 microg DT388-GM-CSF daily intraperitoneally for 5 days. A reduction of marrow blast cells was seen with 7 of 9 samples tested 4 to 12 weeks post one course of toxin. Repeating the 5-day course of toxin 2 or 3 times at 4-week intervals did not improve the response, while delaying administration until 4 to 8 weeks post AML cell injection reduced the toxin's effectiveness (n = 5).This fusion toxin may prove useful for in vitro purging of stem cell harvests from selected AML patients and for direct administration to such patients.
authors.affiliation: Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Feuring-Buske
authors.forename: A
authors.initials: A
authors.lastname: Frankel
authors.forename: B
authors.initials: B
authors.lastname: Gerhard
authors.forename: D
authors.initials: D
authors.lastname: Hogge
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000187:drug effects / Q000473:pathology; D016465:Bone Marrow Purging; D016923:Cell Death; D020732:Cytogenetic Analysis; D004167:Diphtheria Toxin / Q000235:genetics / Q000494:pharmacology / Q000627:therapeutic use*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000494:pharmacology / Q000627:therapeutic use*; D006412:Hematopoietic Stem Cells / Q000473:pathology*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000032:analysis; D011993:Recombinant Fusion Proteins / Q000494:pharmacology / Q000627:therapeutic use*; D013154:Spleen / Q000473:pathology; D014407:Tumor Cells, Cultured
chemical_list: D004167:Diphtheria Toxin; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D011993:Recombinant Fusion Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor