Obatoclax is a direct and potent antagonist of membrane-restricted Mcl-1 and is synthetic lethal with treatment that induces Bim.
Obatoclax is a direct and potent antagonist of membrane-restricted Mcl-1 and is synthetic lethal with treatment that induces Bim.
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DOI：
10.1186/s12885-015-1582-5
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发表时间：
2015-08-01
期刊：
影响因子：
3.8
通讯作者：
Shore GC
中科院分区：
文献类型：
--
作者：
Nguyen M;Cencic R;Ertel F;Bernier C;Pelletier J;Roulston A;Silvius JR;Shore GC
Obatoclax是一种临床阶段候选药物，已被提出靶向和抑制Bcl-2家族的促生存成员，从而有助于癌细胞致死。然而，这种化合物的不溶性已经排除了许多经典的药物-靶标相互作用测定法用于其研究。因此，提出的作用机制的直接证明，以及对单个Bcl-2家族成员的偏好，仍有待建立。采用修饰的蛋白质和脂质，我们概括了线粒体外膜Mcl-1和巴克在合成的大单层脂质体的组成关联和拓扑结构，并测量bak依赖性双层渗透性。此外，采用依赖于Mcl-1存活的细胞和肿瘤模型。我们发现tBid - Mcl-1 -巴克轴对双层透化的调节与tBid - Bcl-XL - Bax模型密切相关。Obatoclax快速并完全分配到脂质体脂质中，但也在脂质体颗粒之间快速交换。在该系统中，发现obatoclax是脂质体结合的Mcl-1的直接且有效的拮抗剂，但不是脂质体结合的Bcl-XL的拮抗剂，并且不直接影响巴克。相对于Mcl-1过量2.5摩尔的obatoclax克服了Mcl-1介导的对tBid-Bak活化的抑制。Bim诱导巴克低聚物也发现了类似的结果。Obatoclax在依赖于Mcl-1的细胞模型中表现出有效的致死性，但在依赖于Bcl-XL的细胞中没有。分子建模预测obatoclax的3-甲氧基部分渗透到Mcl-1的BH 3结合位点的P2口袋中。奥巴克拉的去甲氧基衍生物未能抑制蛋白脂质体中的Mcl-1，并且不能杀死其存活依赖于Mcl-1的细胞。与单独的媒介物相比，用obatoclax全身性治疗携带Tsc 2 +/- Em-myc淋巴瘤（其细胞依赖于Mcl-1存活）的小鼠赋予了存活优势（分别为中值31天对22天; p=0.003）。在Akt-淋巴瘤小鼠模型中，obatoclax的抗肿瘤作用与多柔比星协同。最后，用地塞米松处理多发性骨髓瘤KMS 11细胞模型（依赖于Mcl-1存活）诱导Bim和Bim依赖性致死。如Mcl-1拮抗剂所预测的，奥巴克拉和地塞米松在该模型中具有协同作用。总之，这些发现表明obatoclax是膜限制性Mcl-1的有效拮抗剂。Obatoclax代表了产生第二代Mcl-1抑制剂的有吸引力的化学系列。
Obatoclax is a clinical stage drug candidate that has been proposed to target and inhibit prosurvival members of the Bcl-2 family, and thereby contribute to cancer cell lethality. The insolubility of this compound, however, has precluded the use of many classical drug-target interaction assays for its study. Thus, a direct demonstration of the proposed mechanism of action, and preferences for individual Bcl-2 family members, remain to be established. Employing modified proteins and lipids, we recapitulated the constitutive association and topology of mitochondrial outer membrane Mcl-1 and Bak in synthetic large unilamellar liposomes, and measured bakdependent bilayer permeability. Additionally, cellular and tumor models, dependent on Mcl-1 for survival, were employed. We show that regulation of bilayer permeabilization by the tBid – Mcl-1 - Bak axis closely resemblesthe tBid - Bcl-XL - Bax model. Obatoclax rapidly and completely partitioned into liposomal lipid but also rapidly exchanged between liposome particles. In this system, obatoclax was found to be a direct and potent antagonist of liposome-bound Mcl-1 but not of liposome-bound Bcl-XL, and did not directly influence Bak. A 2.5 molar excess of obatoclax relative to Mcl-1 overcame Mcl-1-mediated inhibition of tBid-Bak activation. Similar results were found for induction of Bak oligomers by Bim. Obatoclax exhibited potent lethality in a cellmodel dependent on Mcl-1 for viability but not in cells dependent on Bcl-XL. Molecular modeling predicts that the 3-methoxy moiety of obatoclax penetrates into the P2 pocket of the BH3 binding site of Mcl-1. A desmethoxy derivative of obatoclax failed to inhibit Mcl-1 in proteoliposomes and did not kill cells whose survival depends on Mcl-1. Systemic treatment of mice bearing Tsc2+/- Em-myc lymphomas (whose cells depend on Mcl-1 for survival) with obatoclax conferred a survival advantage compared to vehicle alone (median 31 days vs 22 days, respectively; p=0.003). In an Akt-lymphoma mouse model, the anti-tumor effects of obatoclax synergized with doxorubicin. Finally, treatment of the multiple myeloma KMS11 cell model (dependent on Mcl-1 for survival) with dexamethasone induced Bim and Bim-dependent lethality. As predicted for an Mcl-1 antagonist, obatoclax and dexamethasone were synergistic in this model. Taken together, these findings indicate that obatoclax is a potent antagonist of membranerestricted Mcl-1. Obatoclax represents an attractive chemical series to generate second generation Mcl-1 inhibitors.