title: FTY720 produces caspase-independent cell death of acute lymphoblastic leukemia cells.
abstract: Acute lymphoblastic leukemia (ALL), the most common form of childhood cancer, usually responds to chemotherapy but patients who develop disease relapse have a poor prognosis. New agents to treat ALL are urgently required. FTY720 is an immunosuppressive drug that has promising in vitro activity in a number of malignancies, with the proposed mechanism being the reactivation of the protein serine/threonine phosphatase, PP2A. FTY720 reduced the proliferation and viability of Ph(+) and Ph(-) ALL cell lines and patient samples with IC 50 values for viability between 5.3 to 7.9 μM. Cell death was caspase-independent with negligible activation of caspase-3 and no inhibition of FTY720-induced cell death by the caspase inhibitor Z-VAD-FMK. The cytotoxic effects of FTY720 were independent of PP2A reactivation as determined by the lack of effect of the PP2A inhibitor okadaic acid. Features of autophagy, including autophagosomes, LC3II expression and increased autophagic flux, were induced by FTY720. However the phosphorylated form of FTY720 (FTY720-P) similarly induced autophagy but not cell death. This suggests that autophagy is prosurvival in this setting, a finding supported by protection from cell death induced by the cytotoxic agent vincristine. FTY720 also induced reactive oxygen species (ROS) and the antioxidant N-acetyl-cysteine (NAC) partially reversed the cytotoxic effects, demonstrating a role for ROS generation in the cell death mechanism. FTY720 is an active drug in vitro in ALL cell lines and patient samples. Evidence supports a caspase-independent mechanism of cell death with the occurrence of autophagy and necrosis.
authors: Westmead Institute for Cancer Research, Westmead Millennium Institute, The University of Sydney, Sydney, Australia.
authors: Craig T
authors: CT
authors: Wallington-Beddoe
authors: John
authors: J
authors: Hewson
authors: Kenneth F
authors: KF
authors: Bradstock
authors: Linda J
authors: LJ
authors: Bendall
mesh_terms: D000293:Adolescent; D000368:Aged; D001343:Autophagy / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002648:Child; D002675:Child, Preschool; D019610:Cytoprotection / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D000068876:Fingolimod Hydrochloride; D006801:Humans; D008297:Male; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000201:enzymology / Q000473:pathology*; D011409:Propylene Glycols / Q000494:pharmacology*; D054648:Protein Phosphatase 2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D049349:Receptors, Lysosphingolipid / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D055815:Young Adult
chemical_list: D011409:Propylene Glycols; D017382:Reactive Oxygen Species; D049349:Receptors, Lysosphingolipid; D054648:Protein Phosphatase 2; D020169:Caspases; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine