Diphtheria toxin fused to granulocyte-macrophage colony-stimulating factor eliminates acute myeloid leukemia cells with the potential to initiate leukemia in immunodeficient mice, but spares normal hemopoietic stem cells.
We studied the cell kill induced by granulocyte-macrophage colony-stimulating factor (GM-CSF ) fused to Diphtheria Toxin (DT-GM-CSF ) in acute myeloid leukemia (AML) samples and in populations of normal primitive hemopoietic progenitor cells. AML samples from three patients were incubated in vitro with 100 ng/mL DT-GM-CSF for 48 hours, and AML cell kill was determined in a proliferation assay, a clonogenic assay colony-forming unit-AML (CFU-AML) and a quantitative long-term bone marrow (BM) culture ie, the leukemic-cobblestone area forming cell assay (L-CAFC). To measure an effect on cells with in vivo leukemia initiating potential DT-GM-CSF exposed AML cells were transplanted into immunodeficient mice. In two out of three samples it was shown that all AML subsets, including those with long-term abilities in vivo (severe combined immunodeficient mice) and in vitro (L-CAFC assay) were reduced in number by DT-GM-CSF. Cell kill induced by DT-GM-CSF could be prevented by coincubation with an excess of GM-CSF, demonstrating that sensitivity to DT-GM-CSF is specifically mediated by the GM-CSF receptor. Therefore, binding and internalization of GM-CSF probably occur in immature AML precursors of these two cases of AML. The third AML sample was not responsive to either GM-CSF or DT-GM-CSF. The number of committed progenitors of normal bone marrow (burst-forming unit-erythroid, colony-forming unit granulocyte- macrophage, and cobble stone area forming cell [CAFC] week 2) and also the number of cells with long-term repopulating ability, assayed as week 6 CAFC, were unchanged after exposure to DT-GM-CSF (100 ng/mL, 48 hours). These studies show that DT-GM-CSF may be used to eliminate myeloid leukemic cells with long-term potential in vitro and in immunodeficient mice, whereas normal hemopoietic stem cells are spared.
Terpstra
W
W
Institute of Hematology, Erasmus University, Rotterdam, The Netherlands.
Rozemuller
H
H
Breems
D A
DA
Rombouts
E J
EJ
Prins
A
A
FitzGerald
D J
DJ
Kreitman
R J
RJ
Wielenga
J J
JJ
Ploemacher
R E
RE
Löwenberg
B
B
Hagenbeek
A
A
Martens
A C
AC
D000208:Acute Disease; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D004167:Diphtheria Toxin / Q000235:genetics / Q000627:therapeutic use*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000627:therapeutic use*; D006412:Hematopoietic Stem Cells / Q000187:drug effects* / Q000473:pathology; D006801:Humans; D007942:Leukemia, Experimental / Q000188:drug therapy* / Q000473:pathology; D007951:Leukemia, Myeloid / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000627:therapeutic use*
D004167:Diphtheria Toxin; D011993:Recombinant Fusion Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor