Phospho-MEK1/2 and uPAR Expression Determine Sensitivity of AML Blasts to a Urokinase-Activated Anthrax Lethal Toxin (PrAgU2/LF).
In this study, we attempt to target both the urokinase plasminogen activator and the mitogen-activated protein kinase pathway in acute myeloid leukemia (AML) cell lines and primary AML blasts using PrAgU2/LF, a urokinase-activated anthrax lethal toxin. PrAgU2/LF was cytotoxic to five out of nine AML cell lines. Cytotoxicity of PrAgU2/LF appeared to be nonapoptotic and was associated with MAPK activation and urokinase activity because all the PrAgU2/LF-sensitive cell lines showed both uPAR expression and high levels of MEK1/2 phosphorylation. Inhibition of uPAR or desensitization of cells to MEK1/2 inhibition blocked toxicity of PrAgU2/LF, indicating requirement for both uPAR expression and MAPK activation for activity. PrAgU2/LF was also cytotoxic to primary blasts from AML patients, with blasts from four out of five patients showing a cytotoxic response to PrAgU2/LF. Cytotoxicity of primary AML blasts was also dependent on uPAR expression and phos-MEK1/2 levels. CD34(+) bone marrow blasts and peripheral blood mononuclear cells lacked uPAR expression and were resistant to PrAgU2/LF, demonstrating the lack of toxicity to normal hematological cells and, therefore, the tumor selectivity of this approach. Dose escalation in mice revealed that the maximal tolerated dose of PrAgU2/LF is at least 5.7-fold higher than that of the wild-type anthrax lethal toxin, PrAg/LF, further demonstrating the increased safety of this molecule. We have shown, in this study, that PrAgU2/LF is a novel, dual-specific molecule for the selective targeting of AML.
Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Beirut 1102 2801, Lebanon.
Amira
A
Bekdash
Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Beirut 1102 2801, Lebanon.
Manal
M
Darwish
School of Molecular & Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK.
Zahra
Z
Timsah
Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Beirut 1102 2801, Lebanon.
Elias
E
Kassab
Department of Internal Medicine, School of Medicine, Lebanese American University, Beirut 1102-2801, Lebanon.
Hadi
H
Ghanem
Department of Pathology, School of Medicine, Lebanese American University, Beirut 1102-2801, Lebanon.
Vicky
V
Najjar
Department of Pathology, School of Medicine, Lebanese American University, Beirut 1102-2801, Lebanon.
Marwan
M
Ghosn
Department of Pathology, School of Medicine, Lebanese American University, Beirut 1102-2801, Lebanon.
Selim
S
Nasser
Department of Internal Medicine and Experimental Pathology, School of Medicine, American University of Beirut, Lebanon; Department of Immunology and Microbiology, School of Medicine, American University of Beirut, Lebanon.
Hiba
H
El-Hajj
Department of Internal Medicine, School of Medicine, American University of Beirut, Lebanon; Department of Anatomy, School of Medicine, American University of Beirut, Lebanon; Department of Cell Biology and Physiological Sciences, School of Medicine, American University of Beirut, Lebanon.
Ali
A
Bazerbachi
Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Shihui
S
Liu
Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Stephen H
SH
Leppla
Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, Dallas, Texas 75390.
Arthur E
AE
Frankel
Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Beirut 1102 2801, Lebanon. Electronic address: ralph.abihabib@lau.edu.lb.
Ralph J
RJ
Abi-Habib