外泌体介导的肾癌肺转移前微环境改变调控肿瘤细胞间质上皮转化的机制研究

With only 12% of 5-year survival rate, metastatic renal cell carcinoma（RCC）is a hot issue which is needed to be solved in clinic, however, its mechanism is not fully understood. Recent studies have shown that tumor exosomes can initiate pre-metastatic niche formation in distant organs, and promote tumor metastasis. Previously, we had found that exosomes from resistant cells could endow recipient RCC cells with drug resistance (Cancer Cell，2016), but its role in metastasis of RCC is unclear. Our preliminary experimental results showed that protein concentrations of exosomes from RCC cells with high metastatic potential were significantly higher than those from low metastatic subline. After injecting tumor exosomes into the tail veins of mice, we found that lung tissue from the mice showed characteristic changes of pre-metastatic niche, including the recruitment of bone marrow-derived cells (BMDCs). Furthermore, we found that BMDCs were able to induce mesenchymal to epithelial transition (MET) and colony forming in RCC cells under co-culture conditions in vitro. Accordingly, we hypothesize that exosomes may initiate the formation of pre-metastatic niche in lung, which then induces MET in tumor cells, thereby promoting the distant colonization of tumor cells.We propose to further explore the role of exosomes in the pre-metastatic niche, as well as the regulation of pre-metastatic niche on the tumor cell MET. It could be helpful to expand our understanding on mechanism of RCC metastasis and identify new predictive biomarkers and therapeutic targets.

肾癌患者一旦出现远处转移，5年生存率仅为12%，目前肾癌转移机制尚不完全清楚。近来研究表明，外泌体能够通过诱导转移靶器官微环境改变，促进肿瘤转移。我们既往研究发现，外泌体具有传播并诱导肾癌耐药的作用（Cancer Cell，2016），但其在肾癌转移中的作用尚不明确。通过对比高转移能力和低转移能力肾癌细胞来源外泌体，我们发现前者蛋白浓度明显高于后者。而将高转移能力肾癌细胞来源外泌体注入小鼠体内后发现，小鼠肺组织出现了大量骨髓源细胞募集等典型的转移前微环境改变。将募集的骨髓源细胞和肾癌细胞进行体外共培养时发现，肾癌细胞上皮样表型标记物表达上调，且克隆形成能力明显增强。据此，我们推测外泌体介导肾癌肺转移前微环境的形成，继而诱导肿瘤细胞发生间质上皮转化（MET），促进肿瘤定植。本项目拟进一步探究肾癌转移前微环境形成的始动因素，及其对肿瘤细胞MET的调控作用，从而寻找肾癌转移预警标记和干预靶点。

我国已成为世界上肾癌发病和死亡人数最多的国家，肾癌致死原因主要是转移，其中肺转移最为常见。外泌体是由细胞释放出的直径为50-150nm的膜性囊泡。肿瘤细胞来源的外泌体能介导转移前微环境形成从而影响肿瘤的定植转移过程，但是肾癌细胞外泌体在肾癌发生肺转移过程中的作用及机制仍不清楚。本课题采用高通量测序技术、细胞和分子生物学技术以及动物实验，以循环中外泌体为切入点，发现了肾癌细胞源性外泌体中的miR-6826-5p可以激活肺成纤维细胞，促进肾癌转移前微环境的形成，诱导肾癌细胞发生MET过程，最终促进肾癌的转移。本课题从临床实践出发，通过探讨外泌体介导转移前微环境形成的作用机理，阐明了转移前微环境形成对促进肿瘤定植的作用及机制，为预测肾癌肿瘤转移、寻找治疗靶点提供了有力的证据。