骨转移是肺癌的主要并发症之一，是降低患者生活质量和导致死亡的重要因素，目前对肺癌骨转移发生的机制认识有限，尚缺乏快速有效的无创性早期诊断方法及治疗策略。液态活检是近期肿瘤生物学研究的焦点，特别是存在于外周血中的外泌体被认为对肿瘤发生发展具有潜在的调控作用，但目前对外泌体在肺癌骨转移中的功能机制还知之甚少。在前期研究中，我们成功构建了非小细胞肺癌骨转移小鼠模型，筛选出具有定向骨转移能力的肺癌细胞亚株A549-BM，并发现肺癌骨转移患者外周血中的外泌体具有促进破骨细胞分化作用，其中的miR-17及其靶基因PTEN可能参与肺癌骨转移。在本申请项目中，我们将深入研究外泌体miR-17介导肺癌细胞和破骨细胞间信息交流的机制，解析miR-17/PTEN通路在调控骨微环境及肺癌骨转移中的功能及分子机制。项目研究结果将揭示调控肺癌骨转移发生的新机制，为肺癌骨转移的预防和临床诊治提供分子靶和新策略。

Bone metastasis of lung cancer is one of the main factors that impair the prognosis in lung cancer patients and contribute to cancer-related death. Thus, effective therapeutic interventions, as well as early noninvasive diagnosis index, to stop lung cancer bone metastasis are urgently needed. However, our ability to design effective diagnostic methods and therapeutic interventions aiming to stop lung cancer bone metastasis is limited because of our poor understanding of the molecular mechanisms underlying the bone metastasis of lung cancer. Liquid biopsy is one of the frontier topics in cancer biology, while exosomes, as well as exosomal molecules, are proposed as excellent candidate biomarkers in both diagnostic and therapeutic application for anticancer metastasis. However, the roles and molecular mechanisms of exosomes in regulating lung cancer bone metastasis remain largely unclear. In our previous study, we constructed a mouse model of bone metastasis of lung cancer and established a bone metastatic lung cancer cell line A549-BM, and found that exosomes from bone metastatic lung cancer patients significantly promoted osteoclast differentiation. Importantly, we found that exsomal miR-17 and its target gene PTEN were significantly correlated with bone metastasis. In this research plan, we will further identify the roles and mechanisms of exosomal miR-17 in lung cancer cell-osteoclast communication , and examine the function of miR-17/PTEN pathway in regulating bone microenvironment and bone metastasis of lung cancer. The obtained results will advance our understanding of the molecular mechanisms underlying lung cancer bone metastasis, and provide useful information for the strategies of effective lung cancer bone metastasis prevention, diagnosis and therapeutics.