骨肉瘤起始细胞(OTICs)的存在是骨肉瘤辐射抵抗并制约其疗效的主要因素之一，但目前对参与调控OTICs辐射抵抗的分子机制尚不清楚。我们前期研究发现，miR-214与骨肉瘤放疗疗效负相关，抑制其表达能显著增加X射线诱导的骨肉瘤细胞凋亡；OTICs高表达miR-214，预测显示PHLDA2基因是其直接作用靶点。文献报道，OTICs中PHLDA2表达降低，并可能通过PH结构域影响PI3K/AKT通路的活性。本项目拟首先确认PHLDA2与miR-214的直接作用关系；体外分离培养OTICs，结合X射线干扰等试验因素，利用细胞增殖、凋亡和迁移、裸鼠成瘤、临床大样本表型与功能验证以及转录组学分析等实验方法，研究miR-214是如何通过抑制PHLDA2的表达，从而激活PI3K/AKT信号通络，并最终影响OTICs辐射抵抗的功能与分子机制，以期为提高OTICs的放疗敏感性及骨肉瘤的治疗效果提供新的靶点。

Osteosarcoma tumor-initiating cells(OTICs) may be one of the main factors of radioresistance, and also restrict the improvement of therapeutic effect in osteosarcoma. However, the molecular mechanism of OTICs’ radioresistance has not been fully understood. Our previous study has shown that the expression of miR-214 was negatively associated with the response to radiation, and knockdown miR-214 significantly enhanced the apoptosis induced by X-ray in osteosarcoma cells. Furthermore, we confirmed that the expression of miR-214 was upregulated in OTICs. and predicted that PHLDA2 may be the direct target of miR-214 by bioinformatic softwares. Meanwhile, it has been reported that PHLDA2 was downregulated in OTICs, which could modulate the activation of PI3K/AKT pathway by PH domain .In this research, the direct relationship between miR-214 and PHLDA2 was confirmed firstly. Then OTICs, isolated and cultured in vitro, were combined with X-ray interference. Some experimental methods were used, such as proliferation, apoptosis, migration, model of nude mice, clinical verification experiments between phenotype and function, and transcriptome analysis, to clarify the mechanism how miR-214 inhibited PHLDA2 expression, activated PI3K/AKT pathway, and ultimately affected the radioresistance of OTICs. The aim of this study was to overcome the radioresistance of OTICs and offer a new target to improve the therapeutic effect of osteosarcoma.