骨肉瘤是青少年骨骼系统最常见恶性肿瘤。近来研究发现肿瘤干细胞(TSCs)是恶性肿瘤发生、进展的根源。我们前期通过iTRAQ筛选、验证，发现eEF1A2在高转移、耐药及成球富集细胞中显著高表达；而敲低eEF1A2，肿瘤细胞干性下调，且出现成骨向分化。eEF1A2是翻译水平重要调控因子，最新发现在肿瘤发病中举足轻重。目前eEF1A2在骨肉瘤TSCs成骨分化中作用及翻译水平调控机制尚未阐明。现拟在前期基础上利用CD117/Stro-1分选骨肉瘤TSCs；通过功能实验，明确eEF1A2与骨肉瘤TSCs关系；运用细胞、动物模型验证eEF1A2在骨肉瘤TSCs成骨分化中作用；应用RIP-Seq、RIP等筛选并验证靶基因；结合功能实验、临床病例，分析eEF1A2及其靶基因功能和临床意义。本项目旨在研究eEF1A2在骨肉瘤TSCs成骨向分化中的作用及翻译水平调控机制，探索骨肉瘤新的分子靶标和治疗策略。

Osteosarcoma is the most common malignant bone tumor in adolescent. Recently, tumor stem cells are proved to be the radical cause of metastasis and drug resistance. In our preparatory studies, up-regulation of eEF1A2 was found in the high metastatic, drug resis tant and spheroid enriched osteosarcoma cells by iTRAQ screen and validation. Then, we knocked down eEF1A2 in chemo-resistant osteosarcoma cells. It could induce the osteoblastic differentiation and reduced the tumorigenic capacity of the cells.eEF1A2 is an well-known regulator on the protein translation. Recently the role of eEF1A2 in the tumorigenesis and development was also been reported. However, it is still unclear about the role of eEF1A2 in trans-differentiation of osteosarcoma tumor stem cells to osteoblasts and the concerning mechanism of regulation on protein translational level. We propose to enrich osteosarcoma tumor stem cells by the CD117/Stro-1 screening; identify relationship between eEF1A2 and osteosarcoma tumor stem cell by function test; validate role of eEF1A2 on osteoblast differentiation of osteosarcoma tumor stem cells in vitro and in vivo; screen the eEF1A2 downstream target genes by RIP-Seq and RIP; analyze eEF1A2 and function of those target genes via combination of functional tests and clinical research. Together, this project aim to investigate the role of eEF1A2 in the transdifferentiation of osteosarcoma tumor stem cells to osteoblasts and mechanism of regulation on protein translational level, and explore new strategies and bio markers for osteosarcoma treatment.