基于ERα分子靶点的TM601抗Luminal型乳腺癌转移的机制研究

Relapse and metastasis are main causes of death for breast cancer patients. The abnormal activation of ERα(estrogen receptor α)-related signal pathways plays a key role in luminal breast cancer’s development and progression, it is also a capital element responsible for the failure of endocrine therapy. Our previous study showed TM601, a peptide found in the venom of the deathstalker scorpion, can not only inhibit the luminal breast cancer cell’s migration in vitro and vivo effectively, but also suppress the protein level of ERα in situ. And the combination between TM601 and ERα was showed by binding assay. In this study, we would like to analyze the antitumor effect of TM601, binding to the ligand binding domain of ERα, from the perspective of protein structure and biology: the combination of TM601 and ERα promote an ubiquitin modification of ERα mediated by CHIP (carboxyl terminus of Hsc70-interacting protein), leading a ligand-independent degradation of ERα via ubiquitin-proteasome pathway. Furthermore, the combination also suppress the protein expression level of VASP (vasodilator-stimulated phosphoprotein), a cytoskeleton regulatory protein, through the decline of transcription activated of ERα, subsequently reducing cell movement ability, inhibiting the invasion of luminal breast cancer. Taking together, the work will reveal the antitumor effect of TM601 and may provide a brand-new strategy for the therapy purpose.

乳腺癌的转移复发是导致患者死亡的主要原因。ERα通路的异常活化在Luminal型乳腺癌的发生发展中发挥关键作用，也是导致内分泌治疗失败的关键环节。本课题组前期实验发现以ERα为靶点，以色列金蝎蝎毒多肽TM601在细胞及动物水平有效抑制Luminal型乳腺癌细胞迁移并下调瘤体中ERα的蛋白水平。此外，体外结合实验提示TM601可以和ERα蛋白结合。因此，本项目拟从蛋白质结构和功能的角度，着重阐释TM601通过与ERα的LBD区中Helix12结构域结合，一方面促进CHIP介导的ERα的泛素化修饰，导致其经由配体非依赖的泛素化-蛋白酶体途径降解；另一方面抑制ERα AF-2转录激活域对细胞骨架相关蛋白VASP的转录激活作用，从而降低细胞运动能力，抑制Luminal型乳腺癌的迁移。本项目的开展将揭示TM601靶向ERα抑制Luminal型乳腺癌转移的分子机制，为开拓乳腺癌治疗新策略奠定理论基础。

乳腺癌是全世界女性中最常见的恶性肿瘤之一。大约70％至75％的原发性乳腺癌属于雌激素受体（ER）阳性乳腺癌。在ER阳性乳腺癌的发展中，ERα途径的异常激活起重要作用，也是导致临床内分泌治疗失败的关键。本项目发现小分子肽氯毒素（CTX）可以显著抑制乳腺癌细胞的增殖，迁移和侵袭。体外研究结果表明CTX抑制乳腺癌细胞中ERα的表达。在本项目中我们深入研究了CTX调控ERα的机制，发现CTX可以直接与ERα结合并改变其LBD结构域的蛋白质二级结构，从而抑制ERα信号通路。此外，本项目发现VASP是ERα信号通路的靶基因，而CTX可以通过ERα/ VASP信号通路抑制乳腺癌细胞的增殖，迁移和侵袭。体内研究CTX显著抑制过表达ERα的乳腺肿瘤，更重要的是，基于CTX与ERα相互作用的机制，CTX可以在体内靶向过表达ERα的乳腺肿瘤。本项目揭示了CTX抗ERα阳性乳腺癌的新机制，也为研究CTX抗ERα相关肿瘤提供了重要参考。

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