Department of Biochemistry, Pusan National University School of Medicine, Yangsan, South Korea.
Mol Cancer. 2010 Jul 28;9:199. doi: 10.1186/1476-4598-9-199.
The development of new modulator possessing high efficacy, low toxicity and high selectivity is a pivotal approach to overcome P-glycoprotein (P-gp) mediated multidrug resistance (MDR) in cancer treatment. In this study, we suggest a new molecular mechanism that TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) down-regulates P-glycoprotein (P-gp) through inhibition of DNA-PKcs/Akt/GSK-3beta pathway and activation of caspases and thereby sensitize MDR cells to MDR-related drugs.
MDR variants, CEM/VLB10-2, CEM/VLB55-8 and CEM/VLB100 cells, with gradually increased levels of P-gp derived from human lymphoblastic leukemia CEM cells, were gradually more susceptible to TRAIL-induced apoptosis and cytotoxicity than parental CEM cells. The P-gp level of MDR variants was positively correlated with the levels of DNA-PKcs, pAkt, pGSK-3beta and c-Myc as well as DR5 and negatively correlated with the level of c-FLIPs. Hypersensitivity of CEM/VLB100 cells to TRAIL was accompanied by the activation of mitochondrial apoptotic pathway as well as the activation of initiator caspases. In addition, TRAIL-induced down-regulation of DNA-PKcs/Akt/GSK-3beta pathway and c-FLIP and up-regulation of cell surface expression of death receptors were associated with the increased susceptibility to TRAIL of MDR cells. Moreover, TRAIL inhibited P-gp efflux function via caspase-3-dependent degradation of P-gp as well as DNA-PKcs and subsequently sensitized MDR cells to MDR-related drugs such as vinblastine and doxorubicin. We also found that suppression of DNA-PKcs by siRNA enhanced the susceptibility of MDR cells to vincristine as well as TRAIL via down-regulation of c-FLIP and P-gp expression and up-regulation of DR5.
This study showed for the first time that the MDR variant of CEM cells was hypersensitive to TRAIL due to up-regulation of DR5 and concomitant down-regulation of c-FLIP, and degradation of P-gp and DNA-PKcs by activation of caspase-3 might be important determinants of TRAIL-induced sensitization of MDR cells to MDR-related drugs. Therefore, combination of TRAIL and chemotherapeutic drugs may be a good strategy for treatment of cancer with multidrug resistance.
开发具有高效、低毒和高选择性的新型调节剂是克服癌症治疗中 P-糖蛋白（P-gp）介导的多药耐药（MDR）的关键方法。在这项研究中，我们提出了一种新的分子机制，即 TRAIL（肿瘤坏死因子相关凋亡诱导配体）通过抑制 DNA-PKcs/Akt/GSK-3β 途径和激活半胱天冬酶来下调 P-糖蛋白（P-gp），从而使 MDR 细胞对 MDR 相关药物敏感。
源自人白血病 CEM 细胞的 MDR 变体 CEM/VLB10-2、CEM/VLB55-8 和 CEM/VLB100 细胞，其 P-gp 水平逐渐升高，对 TRAIL 诱导的凋亡和细胞毒性的敏感性逐渐高于亲本 CEM 细胞。MDR 变体的 P-gp 水平与 DNA-PKcs、pAkt、pGSK-3β 和 c-Myc 以及 DR5 的水平呈正相关，与 c-FLIPs 的水平呈负相关。CEM/VLB100 细胞对 TRAIL 的超敏性伴随着线粒体凋亡途径的激活以及起始半胱天冬酶的激活。此外，TRAIL 诱导的 DNA-PKcs/Akt/GSK-3β 途径和 c-FLIP 的下调以及细胞表面死亡受体的上调与 MDR 细胞对 TRAIL 的敏感性增加有关。此外，TRAIL 通过 caspase-3 依赖性 P-gp 降解抑制 P-gp 外排功能，随后使 MDR 细胞对长春碱和阿霉素等 MDR 相关药物敏感。我们还发现，siRNA 抑制 DNA-PKcs 通过下调 c-FLIP 和 P-gp 表达以及上调 DR5，增强了 MDR 细胞对长春新碱和 TRAIL 的敏感性。
本研究首次表明，CEM 细胞的 MDR 变体对 TRAIL 敏感，这是由于 DR5 的上调和同时 c-FLIP 的下调，以及 caspase-3 的激活导致 P-gp 和 DNA-PKcs 的降解，这可能是 TRAIL 诱导 MDR 细胞对 MDR 相关药物敏感的重要决定因素。因此，TRAIL 与化疗药物的联合应用可能是治疗多药耐药癌症的一种很好的策略。
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