Ebp1与Anxa2相互作用促进乳腺癌细胞他莫昔芬耐药的分子机制研究

Tamoxifen is the most commonly used agent in endocrine therapy of breast cancer. TAM resistance is the main cause of treatment failure in hormone receptor positive breast cancer, however, the accurate mechanism remains unclear. Activation of EGFR signaling pathway has been regarded as the leading cause of TAM resistance; recently, it has been reported that epithelial-mesenchymal transition (EMT) was involved in TAM resistance. We previously showed that Anxa2 is the key factor to mediate EMT of hormone receptor-positive breast cancer cells through the EGFR signaling pathway. The proteomic results showed that Ebp1 is the core protein of the Anxa2-interacting network, which also affects the activation of Anxa2. In addition, Ebp1 is also a binding protein of EGFR family members and was reported as a regulatory protein of TAM sensitivity. Therefore, we hypothesize that: Ebp1 interacts with Anxa2 and regulates TAM resistance in hormone receptor positive breast cancer cell through the mediation of activation of EGFR signaling pathway. In this study, we plan to employ a series of molecular biology, cell biology experiments and in vivo SCID animal models to elucidate the details of how Epb1 interacts with Anxa2, and to investigate the potential effect of Ebp1 and Anxa2 knockdown on EMT, TAM sensitivity, and activation of EGFR signaling pathway in hormone receptor positive breast cancer cells. Our study will provide new knowledge to better understand the molecular mechanism of TAM resistance, and provide clues for finding new molecular targets for the treatment of patients with TAM resistance.

他莫昔芬（TAM）耐药是激素受体阳性乳腺癌治疗失败的重要原因，具体机制尚不明确。目前研究表明EGFR信号通路激活是导致TAM耐药的主要原因，近年来有报道上皮间质转化（EMT）和TAM耐药具有相关性。我们前期研究发现，Anxa2通过EGFR信号通路介导激素受体阳性乳腺癌细胞的EMT；随后的蛋白组学发现Ebp1是Anxa2相互作用网络的核心蛋白，其表达影响Anxa2的激活，而Ebp1也是EGFR家族成员的结合蛋白并调控细胞对TAM的敏感性。因此我们推测：Ebp1通过与Anxa2相互作用介导EGFR信号通路的激活从而调控TAM耐药。本研究将通过一系列分子和细胞生物学实验及动物模型，阐明Ebp1对Anxa2的调控模式，明确Anxa2和Ebp1的表达变化对激素受体阳性乳腺癌细胞EMT、TAM敏感性以及EGFR信号通路活化的影响。其研究成果将丰富TAM耐药的机理，为耐药乳腺癌治疗提供新的靶点和思路。

选择性雌激素受体调节剂他莫昔芬（Tamoxifen，TAM）是应用最为广泛的内分泌治疗药物，TAM耐药是激素受体阳性乳腺癌治疗失败的重要原因，是亟待解决的临床挑战，具体分子机制尚不明确。本次研究通过构建稳定的TAM耐药的ERα阳性乳腺癌细胞系，发现TAM耐药乳腺癌细胞出现上皮间质转化（epithelial-mesenchymal transition，EMT）现象，细胞获得间质细胞的形态学改变，EMT相关标志物也在mRNA和蛋白水平发生表达改变，并且细胞增殖能力提高。前期研究我们发现Anxa2可以介导乳腺癌的EMT，本次研究中我们发现外源性刺激和稳定的耐药乳腺癌细胞中，Anxa2表达上调，并且伴随其23位Tyr的磷酸化激活及下游分子ERK1/2的磷酸化激活。将Anxa2降表达后，ERα阳性乳腺癌细胞和TAM耐药的乳腺癌细胞出现类MET转换，同时对TAM敏感性增强，同时，体外功能学实验证实，Anxa2降表达后，降低了TAM耐药的乳腺癌细胞的增殖、迁移和侵袭能力。综上，本研究初步证实Anxa2可能通过其23Tyr磷酸化激活介导EMT，在乳腺癌ERα阳性乳腺癌细胞TAM耐药中发挥重要作用，从而促进乳腺癌的增殖和转移能力。因此，Anxa2可能成为新的治疗靶点，帮助逆转乳腺癌TAM耐药。

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