Department of Sarcoma Medical Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd Houston, TX 77030, United States.
Mol Oncol. 2011 Feb;5(1):93-104. doi: 10.1016/j.molonc.2010.10.003. Epub 2010 Oct 16.
Although imatinib mesylate has revolutionized the management of patients with gastrointestinal stromal tumor (GIST), resistance and progression almost inevitably develop with long-term monotherapy. To enhance imatinib-induced cytotoxicity and overcome imatinib-resistance in GIST cells, we examined the antitumor effects of the pro-apoptotic Bcl-2/Bcl-x(L) inhibitor ABT-737, alone and in combination with imatinib.
We treated imatinib-sensitive, GIST-T1 and GIST882, and imatinib-resistant cells with ABT-737 alone and with imatinib. We determined the anti-proliferative and apoptotic effects by cell viability assay, flow cytometric apoptosis and cell cycle analysis, immunoblotting, and nuclear morphology. Synergism was determined by isobologram analysis.
The IC(50) of single-agent ABT-737 at 72 h was 10 μM in imatinib-sensitive GIST-T1 and GIST882 cells, and 1 μM in imatinib-resistant GIST48IM cells. ABT-737 and imatinib combined synergistically in a time- and dose-dependent manner to inhibit the proliferation and induce apoptosis of all GIST cells, as evidenced by cell viability and apoptosis assays, caspase activation, PARP cleavage, and morphologic changes. Isobologram analyses revealed strongly synergistic drug interactions, with combination indices <0.5 for most ABT-737/imatinib combinations. Thus, clinically relevant in vitro concentrations of ABT-737 have single-agent antitumor activity and are synergistic in combination with imatinib.
We provide the first preclinical evidence that Bcl-2/Bcl-x(L) inhibition with ABT-737 synergistically enhances imatinib-induced cytotoxicity via apoptosis, and that direct engagement of apoptotic cell death may be an effective approach to circumvent imatinib-resistance in GIST.
甲磺酸伊马替尼已彻底改变了胃肠道间质瘤（GIST）患者的治疗方法，但长期单药治疗几乎不可避免地会导致耐药和进展。为了增强伊马替尼诱导的细胞毒性并克服 GIST 细胞中的伊马替尼耐药性，我们研究了促凋亡 Bcl-2/Bcl-x(L)抑制剂 ABT-737 单独使用和与伊马替尼联合使用的抗肿瘤作用。
我们用 ABT-737 单独和与伊马替尼联合处理伊马替尼敏感的 GIST-T1 和 GIST882 以及伊马替尼耐药细胞，通过细胞活力测定、流式细胞术凋亡和细胞周期分析、免疫印迹和核形态学来确定抗增殖和凋亡作用。通过等对分析确定协同作用。
72 小时时，单药 ABT-737 的 IC50 在伊马替尼敏感的 GIST-T1 和 GIST882 细胞中为 10 μM，在伊马替尼耐药的 GIST48IM 细胞中为 1 μM。ABT-737 和伊马替尼在时间和剂量依赖性方式上联合协同抑制所有 GIST 细胞的增殖并诱导其凋亡，这通过细胞活力和凋亡测定、半胱天冬酶激活、PARP 切割和形态变化得到证实。等对分析显示药物相互作用具有强烈的协同作用，大多数 ABT-737/伊马替尼组合的组合指数<0.5。因此，ABT-737 的临床相关体外浓度具有单药抗肿瘤活性，并与伊马替尼联合具有协同作用。
我们提供了第一个临床前证据，即通过凋亡，Bcl-2/Bcl-x(L) 抑制与 ABT-737 协同增强伊马替尼诱导的细胞毒性，并且直接参与细胞凋亡可能是规避 GIST 中伊马替尼耐药的有效方法。
