Unit of Translational Research, Catalan Institute of Oncology-Girona, Avenida de Francia S/N, E-17007 Girona, Catalonia, Spain.
Biochem Biophys Res Commun. 2011 Apr 8;407(2):412-9. doi: 10.1016/j.bbrc.2011.03.039. Epub 2011 Mar 21.
Primary resistance of HER2 gene-amplified breast carcinomas (BC) to HER-targeted therapies can be explained in terms of overactive HER2-independent downstream pro-survival pathways. We here confirm that constitutive overexpression of Inhibitor of Apoptosis (IAP) survivin is indispensable for survival of HER2-positive BC cells with intrinsic cross-resistance to multiple HER1/2 inhibitors. The IC₅₀ values for the HER1/2 Tyrosine Kinase Inhibitors (TKIs) gefitinib, erlotinib and lapatinib were up to 40-fold higher in trastuzumab-unresponsive JIMT-1 cells than in trastuzumab-naïve SKBR3 cells. ELISA-based and immunoblotting assays demonstrated that trastuzumab-refractory JIMT-1 cells constitutively expressed ~ 4 times more survivin protein than trastuzumab-responsive SKBR3 cells. In response to trastuzumab, JIMT-1 cells accumulated ~10 times more survivin than SKBR3 cells. HER1/2 TKIs failed to down-regulate survivin expression in JIMT-1 cells whereas equimolar doses of HER1/HER2 TKIs drastically depleted survivin protein in SKBR3 cells. ELISA-based detection of histone-associated DNA fragments confirmed that trastuzumab-refractory JIMT-1 cells were intrinsically protected against the apoptotic effects of HER1/2 TKIs. Of note, when we knocked-down survivin expression using siRNA and then added trastuzumab, cell proliferation and colony formation were completely suppressed in JIMT-1 cells. Our current findings may be extremely helpful to design successful combinatorial strategies aimed to circumvent the occurrence of de novo resistance to HER2-directed drugs using survivin antagonists.
HER2 基因扩增型乳腺癌（BC）对 HER 靶向治疗的原发性耐药可以用 HER2 非依赖性下游生存促进途径过度激活来解释。我们在此证实，凋亡抑制剂（IAP）survivin 的组成性过表达对于具有内在的对多种 HER1/2 抑制剂交叉耐药的 HER2 阳性 BC 细胞的生存是必不可少的。与曲妥珠单抗-naive SKBR3 细胞相比，曲妥珠单抗无应答的 JIMT-1 细胞中 HER1/2 酪氨酸激酶抑制剂（TKI）吉非替尼、厄洛替尼和拉帕替尼的 IC₅₀ 值高 40 倍。ELISA 测定和免疫印迹分析表明，与曲妥珠单抗敏感的 SKBR3 细胞相比，曲妥珠单抗耐药的 JIMT-1 细胞中 survivin 蛋白表达水平持续升高约 4 倍。在曲妥珠单抗的作用下，JIMT-1 细胞中 survivin 的积累量比 SKBR3 细胞多 10 倍。HER1/2 TKIs 未能下调 JIMT-1 细胞中的 survivin 表达，而等摩尔剂量的 HER1/HER2 TKIs 则使 SKBR3 细胞中的 survivin 蛋白大量耗竭。ELISA 检测组蛋白相关的 DNA 片段证实，曲妥珠单抗耐药的 JIMT-1 细胞对 HER1/2 TKIs 的凋亡作用具有内在的保护作用。值得注意的是，当我们使用 siRNA 敲低 survivin 表达，然后加入曲妥珠单抗时，JIMT-1 细胞的增殖和集落形成完全受到抑制。我们目前的研究结果可能对设计成功的联合策略非常有帮助，旨在通过使用 survivin 拮抗剂来规避对 HER2 靶向药物的新出现的耐药性。
