University of Colorado Denver, School of Medicine, Department of Dermatology , Aurora, CO 80045, USA.
Biol Open. 2012 Feb 15;1(2):92-100. doi: 10.1242/bio.2011035. Epub 2011 Nov 16.
The BH3 mimetic ABT-737 is a potent inhibitor of the anti-apoptotic proteins Bcl-2, Bcl-X(L), and Bcl-w. The Bcl-2 family modulates sensitivity to anticancer drugs in many cancers, including melanomas. In this study, we examined whether ABT-737 is effective in killing melanoma cells either alone or in combination with a proteasome inhibitor already in clinical use (Bortezomib) in vitro and in vivo, and further evaluated the mechanisms of action. Results showed that ABT-737 alone induced modest cytotoxicity in melanoma cells, but only at higher doses. Knock-down of the anti-apoptotic proteins Bcl-2, Bcl-X(L), or Mcl-1 with siRNAs demonstrated that Mcl-1 is the critical mediator of melanoma's resistance to ABT-737 treatment. However, ABT-737 displayed strong synergistic lethality when combined with Bortezomib. Immunoblot analyses demonstrated that Bortezomib increased expression of Noxa, a pro-apoptotic Bcl-2 member that antagonizes Mcl-1. Additionally, siRNA-mediated inhibition of Noxa expression protected melanoma cells from cytotoxicity induced by the combination treatment. These results demonstrate that Bortezomib synergizes with ABT-737 by neutralizing Mcl-1's function via increased levels of Noxa. In a xenograft mouse model, although drug doses were limited due to toxicity, ABT-737 or Bortezomib slowed melanoma tumor growth compared to the control, and the drug combination significantly decreased growth compared to either drug alone. These data imply that less toxic drugs fulfilling a function similar to Bortezomib to neutralize Mcl-1 are promising candidates for combination with ABT-737 for treating melanomas.
BH3 模拟物 ABT-737 是一种有效的抗凋亡蛋白 Bcl-2、Bcl-X(L) 和 Bcl-w 的抑制剂。Bcl-2 家族在许多癌症中调节对癌症药物的敏感性，包括黑色素瘤。在这项研究中，我们研究了 ABT-737 单独或与已在临床使用的蛋白酶体抑制剂（硼替佐米）联合应用于体外和体内黑色素瘤细胞的有效性，进一步评估了其作用机制。结果表明，ABT-737 单独作用于黑色素瘤细胞时仅在较高剂量时诱导适度的细胞毒性，但 Bcl-2、Bcl-X(L) 或 Mcl-1 的 siRNA 敲低表明 Mcl-1 是黑色素瘤细胞对 ABT-737 治疗耐药的关键介质。然而，ABT-737 与硼替佐米联合使用时显示出强烈的协同致死作用。免疫印迹分析表明，硼替佐米增加了促凋亡 Bcl-2 成员 Noxa 的表达，Noxa 拮抗 Mcl-1。此外，Noxa 的 siRNA 介导的抑制表达可保护黑色素瘤细胞免受联合治疗诱导的细胞毒性。这些结果表明，硼替佐米通过增加 Noxa 的水平来中和 Mcl-1 的功能，与 ABT-737 协同作用。在异种移植小鼠模型中，尽管由于毒性限制了药物剂量，但与对照组相比，ABT-737 或硼替佐米均减缓了黑色素瘤肿瘤的生长，并且药物联合治疗与单独使用任一药物相比，显著降低了肿瘤生长。这些数据表明，具有类似于硼替佐米的中和 Mcl-1 功能的毒性较小的药物与 ABT-737 联合治疗黑色素瘤具有很大的应用前景。
