ABT-737 overcomes resistance to immunotoxin-mediated apoptosis and enhances the delivery of pseudomonas exotoxin-based proteins to the cell cytosol.
ABT-737 overcomes resistance to immunotoxin-mediated apoptosis and enhances the delivery of pseudomonas exotoxin-based proteins to the cell cytosol.
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DOI：
10.1158/1535-7163.mct-10-0257
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发表时间：
2010-07
影响因子：
5.7
通讯作者：
Fitzgerald DJ
中科院分区：
文献类型：
--
作者：
Traini R;Ben-Josef G;Pastrana DV;Moskatel E;Sharma AK;Antignani A;Fitzgerald DJ
以假单胞菌外毒素(PE)为基础的免疫毒素(抗体-毒素融合蛋白)在毛细胞白血病患者中实现了频繁的完全缓解，但在其他癌症中的客观反应要少得多。为了解决可能的耐药机制，我们使用结肠癌细胞系DLD1在一个模型系统中研究了免疫毒素的活性。尽管会导致蛋白质合成的完全抑制，但没有证据表明针对转铁蛋白受体的免疫毒素会导致这些细胞的凋亡。为了说明存活的Bcl2蛋白可能起到的保护作用，仅BH3的模拟物ABT-737被单独测试或与免疫毒素联合测试。免疫毒素和ABT-737单独都没有激活caspase3，而联合使用则表现出很大的激活作用。在其他上皮细胞系中，ABT-737将PE相关免疫毒素的细胞毒性提高了20倍，但不增强白喉毒素或放线菌亚胺。由于PE通过内质网(ER)转运到胞浆，而其他毒素不能，因此我们研究了ABT-737对ER的影响。ABT-737可刺激内质网应激反应因子ATF4水平升高。由于其在内质网中的活性，ABT-737可能特别适合于增强免疫毒素的活性，这些免疫毒素从内质网转移到细胞胞浆。
Pseudomonas exotoxin (PE)-based immunotoxins (antibody-toxin fusion proteins) have achieved frequent complete remissions in patients with hairy cell leukemia but far fewer objective responses in other cancers. To address possible mechanisms of resistance, we investigated immunotoxin activity in a model system using the colon cancer cell line, DLD1. Despite causing complete inhibition of protein synthesis, there was no evidence that an immunotoxin targeted to the transferrin receptor caused apoptosis in these cells. To address a possible protective role of prosurvival Bcl-2 proteins, the BH3-only mimetic, ABT-737, was tested alone or in combination with immunotoxins. Neither the immunotoxin nor ABT-737 alone activated caspase 3, while the combination exhibited substantial activation. In other epithelial cell lines, ABT-737 enhanced the cytoxicity of PE-related immunotoxins by as much as 20-fold, but did not enhance diphtheria toxin or cycloheximide. Because PE translocates to the cytosol via the endoplasmic reticulum (ER) and the other toxins do not, ABT-737-mediated effects on the ER were investigated. ABT-737 treatment stimulated increased levels of ER stress response factor, ATF4. Because of its activity in the ER, ABT-737 may be particularly well suited for enhancing the activity of immunotoxins that translocate from the ER to the cell cytosol.