Ado-trastuzumab emtansine (Kadcyla®; T-DM1) is an antibody-drug conjugate developed to treat trastuzumab-resistant disease. Despite initial favorable outcomes, most patients eventually cease to respond due to developing acquired resistance to T-DM1. Currently, there is no targeted therapy to treat T-DM1-resistant disease. To explore novel therapeutic targets to improve therapeutic efficacy of T-DM1, we generated T-DM1-resistant cells using trastuzumab-resistant JIMT1 cells. We found that the loss of human epidermal growth factor receptor 2 confers T-DM1 resistance, which in turn activates a compensatory mechanism that increases epidermal growth factor receptor (EGFR) expression. Upregulation of EGFR increases the protein levels of α5β1 and αVβ3 integrins, resulting in enhanced motility and invasion of T-DM1-resistant cells. This study delineates previously unappreciated relationships between α5β1 and αVβ3 and suggests that specific integrins should be carefully selected as therapeutic targets to treat T-DM1-resistant disease. Specifically, silencing β1 integrin expression by siRNA in T-DM1-resistant cells destabilizes α5, but increases expression of αV, a critical integrin mediating the invasion and metastases in many different cancers. As a consequence, T-DM1-resistant cells gain metastatic potential and become more invasive. This finding is underscored by the fact that β1 integrin blockage induced by an inhibitory antibody, MAB 13, significantly increases invasion of T-DM1-resistant cells. However, the increased cell invasion induced by β1 integrin blockage can be significantly reduced by either EGFR inhibitor or specific siRNA against αV integrin. The discovery of functional cooperation between EGFR and αV integrin in regulating cell growth and invasion provides an opportunity to develop novel therapeutic strategy by dual-targeting EGFR and specific integrin to overcome T-DM1 resistance.

Ado-曲妥珠单抗Emtansine（Kadcyla®; T-DM1）是开发用于治疗曲妥珠单抗耐药性的抗体-药物偶联物。尽管最初取得了良好的结果，但大多数患者由于对T-DM1产生后天抵抗力而最终停止反应。当前，没有靶向疗法可治疗T-DM1耐药性疾病。为了探索提高T-DM1疗效的新型治疗靶标，我们使用抗曲妥珠单抗的JIMT1细胞生成了T-DM1耐药细胞。我们发现，人类表皮生长因子受体2的丧失赋予T-DM1抗性，进而激活了一种补偿机制，该机制增加了表皮生长因子受体（EGFR）的表达。EGFR的上调增加了α5β1和αVβ3整联蛋白的蛋白水平，导致运动性增强和T-DM1耐药细胞的侵袭。这项研究描述了先前未认识到的α5β1和αVβ3之间的关系，并建议应谨慎选择特定的整联蛋白作为治疗T-DM1耐药性疾病的治疗靶标。具体而言，在T-DM1耐药细胞中通过siRNA沉默β1整联蛋白表达会破坏α5的稳定性，但会增加αV的表达，αV是在许多不同癌症中介导侵袭和转移的关键整联蛋白。结果，T-DM1耐药细胞获得转移的潜力，并更具侵入性。抑制性抗体MAB 13诱导的β1整联蛋白阻断显着增加了对T-DM1耐药细胞的侵袭，这一事实凸显了这一发现。但是，EGFR抑制剂或针对αV整合素的特异性siRNA可以显着降低β1整合素阻滞诱导的细胞侵袭增加。