G蛋白偶联受体APLNR在乳腺癌上皮间质转化中的作用及机制研究

Breast cancer is the most common cancer in women. Metastasis is the major cause of death in breast cancer. Previous studies suggested epithelial-mesenchymal transition (EMT) be a key step in cancer metastasis, but the specific molecular mechanisms of EMT and breast cancer metastasis remained largely unknown. Based on bioinformatics analyses using breast cancer data in TCGA and GEO databases, we found APLNR was inversely correlated to distant recurrence free survival and overall survival. Our pilot experiments showed that when APLNR was down-regulated, the ability of cell proliferation, migration and invasion in breast cancer was significantly inhibited, along with reduced expression of mesenchymal markers but increased expression of epithelial markers. It was known that EMT can be directly induced through expression and activation of EMT-inducing transcription factors (EMT-TFs), which was consistent with our results from correlation analysis that the expression of APLNR showed a high correlativity with several EMT-TFs. This research project aims to reveal the molecular mechanisms of APLNR in inducing EMT to promote breast cancer metastasis by regulating expression of specific EMT-TFs. It is hoped that the findings from this work will help to prevent metastasis of breast cancer and provide novel targets for cancer therapy.

乳腺癌是女性最常见的恶性肿瘤，远处转移是其主要死因。研究表明上皮细胞-间质转化（EMT）是肿瘤转移的重要环节，但调控乳腺癌细胞EMT的具体机制尚不明确。课题组前期通过数据库大样本数据挖掘及生物信息学分析发现G蛋白偶联受体APLNR与乳腺癌远处转移和愈后密切相关；体外实验显示下调乳腺癌细胞中APLNR的表达可抑制细胞的增殖和侵袭能力，且能抑制肿瘤间质表型分子表达，并促进上皮表型分子表达，说明APLNR可能是通过促进乳腺癌细胞的EMT过程来促进其侵袭和远处转移。文献报道EMT诱导转录因子（EMT-TFs）的激活是启动EMT的关键。本项目拟从乳腺癌细胞系、小鼠模型及临床组织标本三个层面，验证APLNR通过诱导癌细胞EMT作用促进乳腺癌侵袭转移，并筛选出受APLNR调控的EMT-TF，阐明具体分子机制。本课题研究可为阻断乳腺癌转移途径提供研究基础，为靶向药物开发提供新的作用位点和策略。

乳腺癌已跃居为发病率第一位的恶性肿瘤，每4位初诊癌症患者中即有一位乳腺癌患者。近年来，我国乳腺癌的发病率及死亡率呈逐年上升趋势。远处转移是乳腺癌致死的主要原因，而抑制乳腺癌侵袭转移是当前乳腺癌临床治疗和基础研究的热点及难点。本项目研究发现G蛋白偶联受体APLNR高表达与乳腺癌患者较差的无病生存及总生存相关，并且APLNR高表达的乳腺癌患者对新辅助化疗的反应较差。体外实验证实APLNR参与调控乳腺癌细胞增殖、克隆形成、迁移侵袭等过程，其主要分子机制为调控乳腺癌细胞上皮间质转化（EMT）过程。因此，APLNR为乳腺癌治疗的潜在靶点。此外，约80%的乳腺癌患者雌激素受体（estrogen receptor, ER）表达阳性。约20%的ER+早期乳腺癌患者最终发生肿瘤的复发及转移，因而攻克内分泌治疗耐药是改善该类患者预后的重中之重。已有研究报道内分泌耐药的ER+乳腺癌细胞EMT水平显著升高，本项目研究发现ER+乳腺癌细胞经选择性激素受体调节剂（SERM）他莫昔芬及下调剂（SERD）氟维司群短期及长期诱导后，变得对GPX4抑制剂RSL3敏感并在其作用下发生脂质过氧化所致的细胞铁死亡。SAT1或为其分子机制中关键因子，SAT1敲除可逆转他莫昔芬及氟维司群诱导的RSL3敏感性。因而诱导乳腺癌细胞铁死亡是攻克内分泌耐药的新思路。