Park Soo-Jung, Kim Mi-Ju, Kim Hak-Bong, Kang Chi-Dug, Kim Sun-Hee
Department of Biochemistry, Pusan National University School of Medicine, Yangsan 622-770, South Korea.
Biochem J. 2009 Apr 28;420(1):73-81. doi: 10.1042/BJ20082131.
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.
对伊马替尼的耐药通常与Bcr-Abl信号的重新激活有关。然而，在一些慢性粒细胞白血病（CML）患者中，不依赖Bcr-Abl的信号通路可能被激活并导致伊马替尼耐药。我们从K562细胞中分离出三种对伊马替尼耐药的K562/R1、R2和R3变体，其Bcr-Abl逐渐缺失，以开发针对伊马替尼耐药CML的有效治疗策略。有趣的是，我们发现与对TRAIL（肿瘤坏死因子相关凋亡诱导因子）高度耐药的K562细胞相比，这些细胞对TRAIL变得高度敏感。用TRAIL处理K562/R3细胞导致TRAIL受体途径激活，包括半胱天冬酶8激活、Bid裂解、细胞色素c释放和半胱天冬酶3激活。与K562细胞相比，这些结果伴随着伊马替尼耐药的K562变体中c-FLIP（细胞FLICE [Fas相关死亡结构域样白细胞介素1β转换酶]抑制蛋白）的下调。在K562/R3细胞中过表达c-FLIP获得了对TRAIL的耐药性，相反，c-FLIP沉默的K562细胞对TRAIL变得敏感。此外，Bcr-Abl沉默的K562细胞显示c-FLIP下调，并随后克服了对TRAIL的耐药性。综上所述，我们的结果首次证明，伊马替尼耐药细胞中Bcr-Abl的缺失导致c-FLIP下调，随后增加了对TRAIL的敏感性，表明TRAIL可能是治疗Bcr-Abl缺失的伊马替尼耐药CML的有效策略。
