深入研究乳腺癌细胞的耐药分子机制，增加乳腺癌耐药细胞对靶向药物的敏感性成为乳腺癌治疗的研究热点。本课题前期研究显示，化疗耐受患者的乳腺癌组织以及乳腺癌耐药细胞株中叶酸受体（FR-a）表达均显著降低，与之相反，Hrd1表达显著增加。进一步研究显示，干扰乳腺癌耐药细胞中Hrd1的表达增加FR-a的表达，免疫共沉淀结果提示Hrd1与FR-a存在直接作用。本研究将从蛋白酶体降解机制和内质网应激诱导耐药角度，研究Hrd1通过调节FR-a的表达进而影响乳腺癌耐药细胞对叶酸的摄取和内化。在此基础上，构建同位素标记的包裹干扰Hrd1 (si-Hrd1)和紫杉醇的靶向给药纳米胶束用于耐药乳腺癌治疗。本项目的意义在于不仅揭示E3泛素连接酶Hrd1在乳腺癌耐药中的机制，并为叶酸受体介导的靶向药物治疗乳腺癌耐药提供依据。

It is important to explore the molecular mechanism of drug resistance in breast cancer and enhance sensitivity of targeted drug to drug-resistant breast cancer cells. Our preliminary results showed that levels of folate receptor (FR-a) were significantly decreased in tumor tissues of drug-resistant breast cancer patients and in drug-resistant breast cancer cells, while Hrd1 expression was significantly increased. Further studies showed that silencing of Hrd1 expression significantly increased the expression of FR-a in drug-resistant breast cancer cells. The result from co-immunoprecipitation showed that Hrd1 could interact with FR-a. This study will focus on the proteasomal degradation mechanism and drug resistance induced by endoplasmic reticulum stress (ER stress). We will also explore the role of Hrd1 regulating FR-a expression on folate intake and internalization in drug-resistant breast cancer cells. Meanwhile, we have prepared the isotopically labeled delivery of siRNA of Hrd1 and paclitaxel drug with nanoparticles for drug-resistant breast cancer therapy. Therefore, the significance of this study is to reveal the role and mechanism of Hrd1 on drug resistance in breast cancer. This strategy also provides evidence for designing targeted drug delivery system mediated by folate receptor for drug-resistant breast cancer treatment.

ER阳性的乳腺癌是女性最常见的恶性肿瘤之一，经常应用他莫昔芬这种ER受体拮抗剂进行治疗。但在治疗过程中ER阳性的乳腺癌细胞常对其产生耐药致使治疗失败。 本研究中，我们在MCF7细胞中应用免疫共沉淀联合质谱分析检测发现，S100A8是HRD1的下游直接结合蛋白。我进一步的研究表明，S100A8与HRD1在亚细胞器上共定位于胞浆之中。同时，HRD1过表达可以降低S100A8的表达，而HRD1的敲低则可直接引起S100A8的升高。在乳腺癌他莫昔芬耐药细胞中，HRD1的高表达可增加其药物敏感性。在体内实验中，我们亦发现了同样的结果。本项目的意义在于，进一步揭示了乳腺癌他莫昔芬耐药的分子机制，同时，还为今后乳腺癌他莫昔芬耐药的治疗提供了新的靶点以及依据。