Trastuzumab emtansine (T-DM1) is an antibody–drug conjugate (ADC) that has demonstrated clinical benefit for patients with HER2+ metastatic breast cancer; however, its clinical activity is limited by inherent or acquired drug resistance. The molecular mechanisms that drive clinical resistance to T-DM1, especially in HER2+ tumors, are not well understood. We used HER2+ cell lines to develop models of T-DM1 resistance using a cyclical dosing schema in which cells received T-DM1 in an “on-off” routine until a T-DM1–resistant population was generated. T-DM1–resistant N87 cells (N87-TM) were cross-resistant to a panel of trastuzumab-ADCs (T-ADCs) with non–cleavable-linked auristatins. N87-TM cells do not have a decrease in HER2 protein levels or an increase in drug transporter protein (e.g., MDR1) expression compared with parental N87 cells. Intriguingly, T-ADCs using auristatin payloads attached via an enzymatically cleavable linker overcome T-DM1 resistance in N87-TM cells. Importantly, N87-TM cells implanted into athymic mice formed T-DM1 refractory tumors that remain sensitive to T-ADCs with cleavable-linked auristatin payloads. Comparative proteomic profiling suggested enrichment in proteins that mediate caveolae formation and endocytosis in the N87-TM cells. Indeed, N87-TM cells internalize T-ADCs into intracellular caveolin-1 (CAV1)–positive puncta and alter their trafficking to the lysosome compared with N87 cells. T-DM1 colocalization into intracellular CAV1-positive puncta correlated with reduced response to T-DM1 in a panel of HER2+ cell lines. Together, these data suggest that caveolae-mediated endocytosis of T-DM1 may serve as a novel predictive biomarker for patient response to T-DM1. Mol Cancer Ther; 17(1); 243–53. ©2017 AACR.

中文翻译：

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Caveolae 介导的内吞作用作为对曲妥珠单抗 emtansine (T-DM1) 耐药的新机制

Trastuzumab emtansine (T-DM1) 是一种抗体药物偶联物 (ADC)，已证明对 HER2+ 转移性乳腺癌患者具有临床益处；然而，其临床活性受到固有或获得性耐药性的限制。驱动 T-DM1 临床耐药的分子机制，尤其是在 HER2+ 肿瘤中，尚不清楚。我们使用 HER2+ 细胞系来开发 T-DM1 抗性模型，使用循环给药方案，其中细胞以“开-关”程序接受 T-DM1，直到产生 T-DM1 抗性群体。T-DM1 抗性 N87 细胞 (N87-TM) 对一组曲妥珠单抗-ADCs (T-ADCs) 与不可裂解连接的auristatins 具有交叉抗性。与亲本 N87 细胞相比，N87-TM 细胞没有降低 HER2 蛋白水平或增加药物转运蛋白（例如，MDR1）表达。有趣的是，使用 auristatin 有效载荷的 T-ADC 通过酶促裂解接头连接，克服了 N87-TM 细胞中的 T-DM1 抗性。重要的是，植入无胸腺小鼠的 N87-TM 细胞形成了 T-DM1 难治性肿瘤，这些肿瘤对具有可切割连接的 auristatin 有效载荷的 T-ADC 保持敏感。比较蛋白质组学分析表明，在 N87-TM 细胞中介导小窝形成和内吞作用的蛋白质富集。事实上，与 N87 细胞相比，N87-TM 细胞将 T-ADC 内化为细胞内小窝蛋白 1 (CAV1) 阳性斑点并改变它们向溶酶体的运输。T-DM1 共定位到细胞内 CAV1 阳性斑点与一组 HER2+ 细胞系中对 T-DM1 的反应降低相关。一起，这些数据表明，细胞膜穴样内陷介导的 T-DM1 内吞作用可作为患者对 T-DM1 反应的新型预测生物标志物。摩尔癌症治疗; 17(1); 243-53。©2017 AACR。