Department of Cancer Studies and Molecular Medicine and MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom.
Clin Cancer Res. 2013 Jun 15;19(12):3212-23. doi: 10.1158/1078-0432.CCR-12-2185. Epub 2013 Apr 30.
The lymph node microenvironment promotes resistance to chemotherapy in chronic lymphocytic leukemia (CLL), partly through induction of BCL2 family prosurvival proteins. Currently available inhibitors do not target all BCL2 family prosurvival proteins and their effectiveness is also modified by proapoptotic BCL2 homology domain 3 (BH3) only protein expression. The goal of this study was to evaluate synergy between the eIF4E/eIF4G interaction inhibitor, 4EGI-1, and the BH3 mimetic, ABT-737.
CLL cells were cultured in conditions to mimic the lymph node microenvironment. Protein synthesis and cap-complex formation were determined. Polysome association of mRNAs from BCL2 family survival genes was analyzed by translational profiling. The effects of 4EGI-1 and the BCL2/BCL2L1 antagonist, ABT-737, on CLL cell apoptosis were determined.
Protein synthesis was increased approximately 6-fold by stromal cell/CD154 culture in a phosphoinositide 3-kinase α (PI3Kα)-specific manner and was reduced by 4EGI-1. PI3K inhibitors and 4EGI-1 also reduced cap-complex formation but only 4EGI-1 consistently reduced BCL2L1 and BCL2A1 protein levels. 4EGI-1, but not PI3K inhibitors or rapamycin, induced an endoplasmic reticulum stress response including proapoptotic NOXA and the translation inhibitor phosphorylated eIF2α. 4EGI-1 and ABT-737 synergized to cause apoptosis, independent of levels of prosurvival protein expression in individual patients.
Overall protein synthesis and cap-complex formation are induced by microenvironment stimuli in CLL. Inhibition of the cap-complex was not sufficient to repress BCL2 family prosurvival expression, but 4EGI-1 inhibited BCL2A1 and BCL2L1 while inducing NOXA through cap-dependent and -independent mechanisms. 4EGI-1 and ABT-737 synergized to produce apoptosis, and these agents may be the basis for a therapeutically useful combination.
淋巴结微环境促进慢性淋巴细胞白血病（CLL）对化疗的耐药性，部分原因是诱导 BCL2 家族生存蛋白。目前可用的抑制剂不能靶向所有 BCL2 家族生存蛋白，其有效性也受到促凋亡 BCL2 同源结构域 3（BH3）仅蛋白表达的修饰。本研究的目的是评估 eIF4E/eIF4G 相互作用抑制剂 4EGI-1 与 BH3 模拟物 ABT-737 的协同作用。
CLL 细胞在模拟淋巴结微环境的条件下培养。测定蛋白质合成和帽复合物形成。通过翻译谱分析 BCL2 家族生存基因的 mRNA 多核糖体结合。测定 4EGI-1 和 BCL2/BCL2L1 拮抗剂 ABT-737 对 CLL 细胞凋亡的影响。
在 PI3Kα 特异性方式下，基质细胞/CD154 培养使蛋白质合成增加约 6 倍，4EGI-1 降低了蛋白质合成。PI3K 抑制剂和 4EGI-1 也降低了帽复合物的形成，但只有 4EGI-1 始终降低 BCL2L1 和 BCL2A1 蛋白水平。4EGI-1，但不是 PI3K 抑制剂或雷帕霉素，诱导内质网应激反应，包括促凋亡的 NOXA 和翻译抑制剂磷酸化 eIF2α。4EGI-1 和 ABT-737 协同作用导致凋亡，与个体患者中生存蛋白表达水平无关。
总体而言，蛋白质合成和帽复合物的形成在 CLL 中受到微环境刺激的诱导。帽复合物的抑制不足以抑制 BCL2 家族生存蛋白的表达，但 4EGI-1 通过帽依赖性和非依赖性机制抑制 BCL2A1 和 BCL2L1，同时诱导 NOXA。4EGI-1 和 ABT-737 协同作用产生凋亡，这些药物可能是一种具有治疗意义的联合用药的基础。
