Bilardi Rebecca A, Anstee Natasha S, Glaser Stefan P, Robati Mikara, Vandenberg Cassandra J, Cory Suzanne
Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria 3052, Australia.
Department of Medical Biology, University of Melbourne, Victoria 3010, Australia.
Cell Death Dis. 2016 Sep 1;7(9):e2351. doi: 10.1038/cddis.2016.258.
Inhibition of the apoptosis pathway controlled by opposing members of the Bcl-2 protein family plays a central role in cancer development and resistance to therapy. To investigate how pro-apoptotic Bcl-2 homology domain 3 (BH3)-only proteins impact on acute myeloid leukemia (AML), we generated mixed lineage leukemia (MLL)-AF9 and MLL-ENL AMLs from BH3-only gene knockout mice. Disease development was not accelerated by loss of Bim, Puma, Noxa, Bmf, or combinations thereof; hence these BH3-only proteins are apparently ineffectual as tumor suppressors in this model. We tested the sensitivity of MLL-AF9 AMLs of each genotype in vitro to standard chemotherapeutic drugs and to the proteasome inhibitor bortezomib, with or without the BH3 mimetic ABT-737. Loss of Puma and/or Noxa increased resistance to cytarabine, daunorubicin and etoposide, while loss of Bim protected against cytarabine and loss of Bmf had no impact. ABT-737 increased sensitivity to the genotoxic drugs but was not dependent on any BH3-only protein tested. The AML lines were very sensitive to bortezomib and loss of Noxa conveyed significant resistance. In vivo, several MLL-AF9 AMLs responded well to daunorubicin and this response was highly dependent on Puma and Noxa but not Bim. Combination therapy with ABT-737 provided little added benefit at the daunorubicin dose trialed. Bortezomib also extended survival of AML-bearing mice, albeit less than daunorubicin. In summary, our genetic studies reveal the importance of Puma and Noxa for the action of genotoxics currently used to treat MLL-driven AML and suggest that, while addition of ABT-737-like BH3 mimetics might enhance their efficacy, new Noxa-like BH3 mimetics targeting Mcl-1 might have greater potential.
由Bcl-2蛋白家族中功能相反的成员所控制的凋亡途径的抑制在癌症发展和对治疗的抗性中起着核心作用。为了研究仅含促凋亡Bcl-2同源结构域3（BH3）的蛋白如何影响急性髓系白血病（AML），我们从仅含BH3基因敲除小鼠中生成了混合谱系白血病（MLL）-AF9和MLL-ENL AML。Bim、Puma、Noxa、Bmf或它们的组合缺失并未加速疾病发展；因此，在该模型中，这些仅含BH3的蛋白显然作为肿瘤抑制因子无效。我们在体外测试了每种基因型的MLL-AF9 AML对标准化疗药物和蛋白酶体抑制剂硼替佐米的敏感性，有无BH3模拟物ABT-737。Puma和/或Noxa缺失增加了对阿糖胞苷、柔红霉素和依托泊苷的抗性，而Bim缺失对阿糖胞苷有保护作用，Bmf缺失则无影响。ABT-737增加了对基因毒性药物的敏感性，但不依赖于所测试的任何仅含BH3的蛋白。AML细胞系对硼替佐米非常敏感，Noxa缺失传递出显著抗性。在体内，几种MLL-AF9 AML对柔红霉素反应良好，这种反应高度依赖于Puma和Noxa而非Bim。在试验的柔红霉素剂量下，与ABT-737联合治疗几乎没有额外益处。硼替佐米也延长了荷AML小鼠的生存期，尽管不如柔红霉素。总之，我们的遗传学研究揭示了Puma和Noxa对于目前用于治疗MLL驱动的AML的基因毒性药物作用的重要性，并表明，虽然添加ABT-737样的BH3模拟物可能增强其疗效，但靶向Mcl-1的新的Noxa样BH3模拟物可能具有更大潜力。
