Sensitization of imatinib-resistant CML cells to TRAIL-induced apoptosis is mediated through down-regulation of Bcr-Abl as well as c-FLIP.
Resistance to imatinib is commonly associated with reactivation of Bcr-Abl signalling. However, Bcr-Abl-independent signalling pathways may be activated and contributed to imatinib resistance in some CML (chronic myelogenous leukaemia) patients. We had isolated three imatinib-resistant K562/R1, R2 and R3 variants with gradual loss of Bcr-Abl from K562 cells to develop effective therapeutic strategies for imatinib-resistant CML. Interestingly, we found that these cells became highly sensitive to TRAIL (tumour necrosis factor-related apoptosis-inducing factor) in comparison with K562 cells showing high resistance to TRAIL. Treatment of K562/R3 cells with TRAIL resulted in activation of TRAIL receptor pathway by including caspase 8 activation, Bid cleavage, cytochrome c release and caspase 3 activation. These results were accompanied by down-regulation of c-FLIP {cellular FLICE [FADD (Fas-associated death domain)-like interleukin 1beta-converting enzyme]-inhibitory protein} in imatinib-resistant K562 variants compared with K562 cells. Overexpression of c-FLIP in K562/R3 cells acquired TRAIL resistance and conversely, c-FLIP-silenced K562 cells became sensitive to TRAIL. Moreover, Bcr-Abl-silenced K562 cells showed down-regulation of c-FLIP and the subsequent overcome of TRAIL resistance. Taken together, our results demonstrated for the first time that the loss of Bcr-Abl in imatinib-resistant cells led to the down-regulation of c-FLIP and subsequent increase of TRAIL sensitivity, suggesting that TRAIL could be an effective strategy for the treatment of imatinib-resistant CML with loss of Bcr-Abl.
Park
Soo-Jung
SJ
Department of Biochemistry, Pusan National University School of Medicine, Yangsan 622-770, South Korea.
Kim
Mi-Ju
MJ
Kim
Hak-Bong
HB
Kang
Chi-Dug
CD
Kim
Sun-Hee
SH
D017209:Apoptosis; D001549:Benzamides; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics*; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D020868:Gene Silencing; D006801:Humans; D000068877:Imatinib Mesylate; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology; D010879:Piperazines / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology
D001549:Benzamides; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D010879:Piperazines; D011743:Pyrimidines; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl