OPA1促进ER阳性乳腺癌Tamoxifen耐药的机制研究

Tamoxifen is preferred for endocrine adjuvant therapy in patients with ER positive breast cancer. However, the emergence of drug resistance in long-term treatment patients brings challenges to clinical therapy. OPA1 is a nuclear-encoded protein located in inner mitochondrial membrane. It promotes mitochondrial fusion in inner membrane, meanwhile, it is involved in cell apoptosis procedure. In our previous work, we found that OPA1 was expressed more in tamoxifen resistant (TR) cells than parental cells (P). Clinical database analysis showed that high expression of OPA1 was associated with poor prognosis in breast cancer. However, it is still unclear whether OPA1 participates in the process of Tamoxifen resistance. Based on the results we have got, we propose the following experimental objectives: (1) Determine the effects of OPA1 on tamoxifen tolerance in breast cancer cells; (2) Search potential miRNA which targets OPA1 to reveal the reason of the higher expression of OPA1 in TR cells, and verify the regulatory efficiency of miRNA on OPA1; (3) Clarify the biological function and regulatory effect of miRNA-OPA1 signal axis in TR breast cancer cells; Through our research, we hope to illuminate the role and function of OPA1 in the process of tamoxifen resistant, determine the mechanism of OPA1 in promoting drug resistance in ER positive breast cancer, and we also hope to find and provide new target, new strategy and new important basis for breast cancer individualized treatment and prevention in the future.

他莫昔芬（Tamoxifen）是ER阳性乳腺癌患者内分泌治疗的首选药物，然而在长期治疗过程中出现的耐药，给临床治疗带来挑战。OPA1是线粒体内膜蛋白，具有促线粒体融合，调控凋亡等功能。在我们前期工作中，发现OPA1在Tamoxifen耐药细胞中高表达，且与乳腺癌临床预后不良相关。但OPA1是否参与乳腺癌Tamoxifen耐药以及可能存在的机制，目前尚不清楚。本课题旨在前期研究基础上：①明确OPA1对细胞Tamoxifen耐药性的影响；②筛选靶向OPA1的miRNA，验证目标miRNA对OPA1的调控功能；③揭示miRNA-OPA1信号轴对乳腺癌Tamoxifen耐药性能的调控。期望通过研究，明确OPA1在Tamoxifen耐药过程中作用，阐明OPA1参与Tamoxifen耐药的可能的上游机制，为今后个体化治疗与预防提供新靶点、新思路以及新的重要依据。

ER阳性乳腺癌发生tamoxifen耐药，给临床治疗带来巨大挑战，新的有效靶点成为临床治疗迫切需求。OPA1在线粒体融合、细胞凋亡调控中发挥重要作用，与肿瘤关系密切，但是其是否参与乳腺癌tamoxifen耐药及其相关机制研究，目前尚无明确报道。本项目分别从体外分子和细胞水平、临床病例分析和整体动物实验三个层研究OPA1促进ER阳性乳腺癌Tamoxifen耐药的机制。我们的研究有以下几个重要发现：1，OPA1在乳腺癌组织和tamoxifen耐药（TR）细胞中表达增加，且其高表达与乳腺癌临床预后不良显著相关，提示靶向OPA1的治疗方案具有重要临床意义。2. P和TR细胞在能量代谢中具有显著差异，OPA1通过一系列代谢重编程，如改变线粒体形态，提高线粒体膜电位，降低ROS含量等方式促进细胞tamoxifen耐药。下调OPA1表达，细胞对tamoxifen敏感性增加。3. miR-495-3p/OPA1信号轴参与乳腺癌tamoxifen耐药功能调控。miR-495-3p在耐药细胞和乳腺癌组织中低表达，其可通过靶向抑制OPA1从而发挥肿瘤抑制子的作用。利用小分子抑制剂MYLS22抑制OPA1，细胞对tamoxifen耐受性显著降低。4，P65-OPA1信号通路活化，促进OPA1表达，进一步促进乳腺癌tamoxifen耐药。5、病理石蜡切片组化结果显示，OPA1和磷酸化P65在经tamoxifen治疗后的乳腺癌复发患者中表达升高，OPA1表达和P65磷酸化水平显示出较好一致性。动物实验证实初步证实抑制OPA1可有效抑制肿瘤细胞生长。我们的研究丰富了我们对乳腺癌tamoxifen耐药机制的认知水平，同时也必将对未来临床乳腺癌tamoxifen耐药的治疗具有重要的实际指导意义。