Sphingosine kinase-1 is a downstream regulator of imatinib-induced apoptosis in chronic myeloid leukemia cells.
We examined the involvement of sphingosine kinase-1 (SphK1), which governs the ceramide/sphingosine-1-phosphate balance, in susceptibility to imatinib of either sensitive or resistant chronic myeloid leukemia cells. Imatinib-sensitive LAMA84-s displayed marked SphK1 inhibition coupled with increased content of ceramide and decreased pro-survival sphingosine-1-phosphate. Conversely, no changes in the sphingolipid metabolism were observed in LAMA84-r treated with imatinib. Overcoming imatinib resistance in LAMA84-r with farnesyltransferase or MEK/ERK inhibitors as well as with cytosine arabinoside led to SphK1 inhibition. Overexpression of SphK1 in LAMA84-s cells impaired apoptosis and inhibited the effects of imatinib on caspase-3 activation, cytochrome c and Smac release from mitochondria through modulation of Bim, Bcl-xL and Mcl-1 expression. Pharmacological inhibition of SphK1 with F-12509a or its silencing by siRNA induced apoptosis of both imatinib-sensitive and -resistant cells, suggesting that SphK1 inhibition was critical for apoptosis signaling. We also show that imatinib-sensitive and -resistant primary cells from chronic myeloid leukemia patients can be successfully killed in vitro by the F-12509a inhibitor. These results uncover the involvement of SphK1 in regulating imatinib-induced apoptosis and establish that SphK1 is a downstream effector of the Bcr-Abl/Ras/ERK pathway inhibited by imatinib but upstream regulator of Bcl-2 family members.
Bonhoure
E
E
CNRS, Institut de Pharmacologie et de Biologie Structurale, UMR5089, Toulouse, France.
Lauret
A
A
Barnes
D J
DJ
Martin
C
C
Malavaud
B
B
Kohama
T
T
Melo
J V
JV
Cuvillier
O
O
D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D001549:Benzamides; D016227:Benzoquinones / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D016044:Fusion Proteins, bcr-abl / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D015398:Signal Transduction; D000099157:Sphingosine Kinase
D051017:Apoptosis Regulatory Proteins; D001549:Benzamides; D016227:Benzoquinones; D016044:Fusion Proteins, bcr-abl; D000068877:Imatinib Mesylate; D017853:Phosphotransferases (Alcohol Group Acceptor); D010879:Piperazines; D019253:Proto-Oncogene Proteins c-bcl-2; D011743:Pyrimidines; D000099157:Sphingosine Kinase; C411675:F 12509A