骨肉瘤是最常见的原发恶性骨肿瘤，预后差且发病机制不清。研究显示在骨肉瘤进展中，肿瘤相关成纤维细胞（TAF）扮演重要角色，因而深入探索TAF与骨肉瘤细胞间相互沟通机制显得非常必要。课题组前期通过10对骨肉瘤患者与健康人血浆外泌体miRNA测序及实验发现：TAF分泌的miR-3164通过外泌体进入骨肉瘤细胞，增强其恶性潜能。进一步实验显示miR-3164直接调控RAB5C，而后者可能参与E-cadherin胞内循环转运。据此提出假说：TAF来源外泌体中miR-3164通过靶向RAB5C，干预E-cadherin循环转运而促进骨肉瘤恶性进展。本研究拟使用CRISPR/cas9技术、PDX模型、条件性基因敲除小鼠等进行多层面验证，阐明TAF通过外泌体中miR-3164促进骨肉瘤恶性进展的功能与机制；明确血浆外泌体miR-3164可否作为监测进展的液体活检指标，为改善骨肉瘤患者预后提供新的临床策略。

Osteosarcoma is the most common primary malignant bone tumor with poor prognosis and unclear pathogenesis. It has been shown that tumor associated fibroblast (TAF), key component of tumor microenvironment, plays a crucial role in the progression of osteosarcoma. Therefore, it’s of great importance to identify the exact communication mechanisms between TAFs and osteosarcoma cells. Based on our previous experiments and by comparing miRNA sequencing results of plasma exosome between 10 pairs of osteosarcoma patients and age-matched healthy donors, we found that TAF-derived exosomal miR-3164 can promote osteosarcoma progression. Further research reveals that miR-3164 elicits its pro-oncogenic function by targeting RAB5C, which is involved in the endocytosis, trafficking and recycling of E-cadherin. Hence, we suppose that exosomal transfer of TAF-derived miR-3164 promotes progression of osteosarcoma by targeting RAB5C. In this present study, we aim to clarify the exact mechanisms of TAF-derived exosomal miR-3164 in the development and progression of osteosarcoma, with CRISPR/cas9 techniques, conditional knockout mice, PDX models etc. In addition, we will determined whether plasma exosomal miR-3164 could serve as a feasible biomarker for the evaluation of therapeutic efficiency and monitoring of progression. The accomplishment of this study would provide a new strategy for the management of osteosarcoma.