CircRNA XPO4作为ceRNA调控三阴乳腺癌顺铂耐药的作用和机制研究

Chemotherapy is one of the main treatments for triple negative breast cancer（TNBC） at present, and the therapeutic effects are significantly attenuated by the reduction of cellular sensitivity to chemotherapy. Circular RNA (circRNA) is a new kind of non-coding RNA, which plays a key role in regulating the occurrence and development of some human diseases, especially in cancer. In the present study, we had applied circRNA arrays for analyzing expression profiles of circRNAs in 3 cases of responsive and nonresponsive TNBC tissues, respectively. Our results showed that expression of circXPO4 was significantly up-regulated in the nonresponsive tumor tissues of TNBC, which was consistent with the large-scale clinical validation. Moreover, effects of cisplatin on cell growth, apoptosis and colony formation were obviously weakened by overexpression of circXPO4 in TNBC cells, while knockdown of circXPO4 had the opposite roles. Furthermore, circXPO4, mainly localized in the cytoplasm fractions, was integrated with miR-200c-5p. These results suggest that circXPO4 likely decreases the chemosensitivity of cisplatin via miR-200c in TNBC. Here, we will further investigate the roles and mechanisms of circXPO4 as a ceRNA in the chemotherapy resistance of cisplatin via using TNBC cells, animal model and human clinical samples. This study will help to provide a novel research direction and experimental evidence for improving the clinical treatments of TNBC.

目前化疗是三阴乳腺癌的主要治疗方式之一，而肿瘤细胞化疗敏感性降低严重影响其治疗效果。环状RNA（circRNA）是一类新发现的非编码RNA，参与调控了许多疾病包括肿瘤的发生发展过程。本项目前期通过对顺铂敏感和不敏感的三阴乳腺癌病人的肿瘤组织进行环状RNA芯片筛选分析，发现circXPO4在顺铂不敏感的肿瘤组织中显著上调，并且与较大样本的验证相一致。在三阴乳腺癌细胞中过表达circXPO4能减弱顺铂对肿瘤细胞生长、凋亡和克隆形成的作用，而敲减其表达有相反效果。而且该circRNA主要定位在胞浆中且能与miR-200c-5p相结合。这些结果初步表明circXPO4可能通过miR-200c减弱三阴乳腺癌对顺铂的化疗敏感性。本研究拟从细胞水平、动物模型和临床样本三个方面探索circXPO4作为ceRNA调控三阴乳腺癌顺铂耐药的作用及其分子机制，从而为三阴乳腺癌的临床治疗提供新的研究方向和实验依据。

三阴性乳腺癌(TNBC)是一种致死性恶性肿瘤，其特征是缺乏雌激素及孕激素受体，且HER2过表达。基于TNBC的特点，目前尚无有效的靶向治疗方法。因此，找到参与调节TNBC进展的关键因子，探寻三阴乳腺癌化疗或放疗等治疗抵抗的可能原因并探究其分子作用机制至关重要。本项目在研究过程中发现了多个可能参与三阴乳腺癌治疗抵抗后导致肿瘤进展的关键调节因子和信号通路，包括研究证实SHP-2介导ZEB1表达上调在三阴性乳腺癌PDGF-B诱导细胞增殖和转移表型中发挥重要作用，PDGF-B对ZEB1表达的促进作用是通过下调miR-200表达来完成的，LINC00152在乳腺癌中表达显著上调可作为生存预后不良的指标，LINC00152敲低在体内和体外均能抑制细胞增殖和致癌性，并且LINC00152可直接与KLF5蛋白结合，提高KLF5的稳定性，蛋白DEPDC1还可以作为诊断TNBC的标记物；同时项目组成员还研究发现ZEB1蛋白高表达在乳腺癌行顺铂新辅助治疗患者以及激素受体阳性和HER2过表达亚组中，是病理完全缓解和患者无病生存的负性相关预测指标，并对调控ZEB1参与顺铂耐药过程的可能机制进行深入研究，发现ZEB1参与TNBC顺铂耐药上游受到circXPO4和miR-200的调控，该circRNA主要定位在胞浆中且能与miR-200c-5p相结合，并可能通过miR-200c减弱三阴乳腺癌对顺铂的化疗敏感性，PDL1的SNP基因型可以预测乳腺癌顺铂参与的新辅助化疗疗效预测；在研究过程中我们还发现肝素结合生长因子(HDGF)在辐射抵抗的乳腺癌细胞中表达上调，而敲低其表达在体内外均可抑制乳腺癌细胞的辐射抵抗，RXRα与HDGF启动子结合可阻断HDGF的转录活性，从而抑制乳腺癌的辐射抵抗，TKT和STAT3可以诱导HDGF增强肿瘤细胞的辐射抵抗，影响STAT3-tyr705和STAT3-ser727磷酸化及STAT3转录活性。总之，本项目完善了多个非编码RNA通过下游作用靶点调控三阴乳腺癌治疗抵抗导致肿瘤进展的作用和分子机制，为今后三阴乳腺癌的临床治疗提高患者生存率提供了新的调控靶点和实验依据。