耐药是骨肉瘤预后不良的重要原因之一。研究表明肿瘤干细胞可能是导致耐药的重要因素，而骨肉瘤干细胞活化及耐药的作用机制还不明确。本项目通过芯片分析结合PDX模型检测发现对化疗不敏感的骨肉瘤JAK/STAT3信号通路异常活化，且其上游OSMR表达显著上调，已知OSMR是造血干细胞活化的重要细胞因子受体，我们发现在OSMR信号激活的骨肉瘤中细胞干性及耐药性增强。据此我们推测OSMR及其激活的JAK/STAT3信号通路对骨肉瘤干细胞活化及耐药有重要调控作用。本课题拟通过对骨肉瘤临床样本和细胞系的检测，利用PDX模型、CRISPR-Cas9基因组修饰技术以及经典分子生物学等方法，阐释OSMR异常表达及其调控骨肉瘤细胞干性和导致耐药的作用及分子机制；系统分析OSMR异常表达与骨肉瘤耐药、预后等临床特征之间的关系，进一步明确OSMR在骨肉瘤个体化治疗中的应用价值。本研究结果有望为研究骨肉瘤耐药提供新思路。

Drug resistance is a key factor of poor prognosis in Osteosarcoma (OS). Accumulative evidences have showed that cancer stem cells may be a major cause of drug resistance. Effects and mechanisms of osteosarcoma stem cell activation and leading to drug resistance remains unclear. Our group performed the network chip database analysis and validated by the osteosarcoma patient derived xenograft (PDX) Models. We found abnormal activation of JAK/STAT3 signaling pathway and significant increasing in its upstream OSMR expression in chemotherapy resistance osteosarcoma. It’s know that OSMR is an important cytokine receptor to activate hematopoietic stem cell, we found that OSMR activated osteosarcoma cell has enhanced stemness and drug resistance. So we speculate OSMR and activated JAK / STAT3 signaling pathway in osteosarcoma plays an important role in stem cell activation and drug resistance regulation. In this project, we plan to systematically analyze its biological functions in cancer stem cell and drug resistance by using CRISPR-Cas9 systems to knockdown OSMR in OS cell lines, PDC and PDX model. To identify the specific molecules involved in the deregulation of OSMR mediated drug resistance of OS, classical molecule biological methods such as genetic modification, molecular pathway inhibition and so on will be adopted. We will further demonstrate our findings in clinical samples to evaluate the OSMR as a potential target for OS treatment as well as a prognosis marker for drug resistant OS patients. The results will provide a new conception on researching OS drug resistance.