受体酪氨酸激酶EphB4通过调控KRAS信号通路介导乳腺癌HER2靶向治疗耐药的作用与机制研究

HER2-positive breast cancer is highly malignant and resistance to HER2-targeted therapy remains a big challenge for the treatment of this disease. EphB4, a member of the Eph family of receptor tyrosine kinases, is frequently overexpressed and plays an oncogenic role in a number of cancer types. We recently found that high levels of EphB4 are associated with HER2-positive breast cancer and correlated with poor prognosis. We further showed that ectopic expression of EphB4 promoted the growth of HER2-positive breast cancer cells and confers resistance to lapatinib, a small molecule inhibitor of HER2 kinase. Conversely, EphB4 knockdown sensitizes cells to lapatinib. Our recent transcriptome profiling analysis revealed a strong association between EphB4 overexpression and KRAS pathway activation. Built upon these findings, we hypothesize that EphB4 may activate KRAS signaling through phosphorylation of its tyrosine protein substrates and thus results in resistance to lapatinib. Herein, using integrated analyses of phosphotyrosine proteomics and transcriptome profiling by RNA-seq, we propose to investigate molecular mechanisms by which EphB4 confers resistance to HER2-targeted inhibition. Meanwhile, using patient-derived breast cancer tissues and mouse xenograft models, we will evaluate if targeting EphB4 may enhance the efficacy of lapatinib in HER2 positive breast cancer. The current project aims to identify effective therapeutic strategies that overcome resistance to HER2-directed treatment.

HER2阳性乳腺癌恶性程度高，预后差，抗HER2治疗耐药是此类疾病治疗的难题。EphB4是受体酪氨酸激酶Eph家族成员，在多种肿瘤中呈高表达且有致癌作用。申请人前期研究发现：EphB4在HER2阳性乳腺癌中呈显著高表达且与不良预后相关，过表达EphB4可促进HER2阳性乳腺癌细胞生长并导致HER2激酶抑制剂拉帕替尼耐药；反之，敲低EphB4使细胞对拉帕替尼敏感。进一步通过转录组学分析发现，过表达EphB4与KRAS通路激活呈显著正相关。由此我们假设：EphB4可能通过磷酸化其酪氨酸蛋白底物激活KRAS通路从而导致HER2靶向治疗耐药。本项目拟通过酪氨酸磷酸化蛋白质组学、转录组学分析等手段，深入研究EphB4介导HER2靶向治疗耐药的分子机制，并结合临床乳腺癌组织芯片与小鼠移植瘤模型验证抑制EphB4增强拉帕替尼抗HER2治疗作用的有效性。本研究将为攻克乳腺癌HER2靶向治疗耐药提供新思路。

TCGA数据库分析结果显示，在HER2阳性乳腺癌中，受体酪氨酸激酶EphB4的呈显著高表达，且EphB4高表达提示患者预后较差。因此，本研究主要探索EphB4高表达对HER2阳性乳腺癌细胞的影响以及EphB4作为HER2阳性乳腺癌治疗靶点的潜力。在本项目中，我们发现EphB4过表达能够促进HER2阳性乳腺癌细胞增殖、迁移和侵袭，并使其对HER2/EGFR抑制剂Lapatinib产生耐药性。此外，通过结合转录组学分析和酪氨酸磷酸化蛋白质组学分析，我们阐明了：EphB4通过活化SHP2/GAB1-MEK信号级联及其下游c-MYC，从而使得HER2阳性乳腺癌细胞对Lapatinib耐药。最后，我们还证明，在HER2阳性乳腺肿瘤中，联合应用EphB4小分子抑制剂与Lapatinib比单药治疗使用更有效。本项目研究结果为决定临床上克服HER2靶向治疗耐药提供了新思路，也为在HER2阳性乳腺癌中联合靶向EphB4提供了理论依据。