微泡（MV）是新近发现的细胞间通讯的重要介质，是不同表型细胞间互通有无的关键途径。基于近期胶质母细胞瘤（GBM）来源微泡横向传递EGFRvIII的重大发现，本课题组围绕EGFRvIII-MV对受体细胞放射敏感性的影响展开了研究。我们前期研究发现，电离辐射诱导MV的分泌、释放；外源性EGFRvIII-MV通过膜融合途径使GBM受体细胞获得性表达EGFRvIII，促进电离辐射后DNA双链断裂(DSB)修复，下调其放射敏感性，是异质性细胞间协同抵抗电离辐射的潜在机制。本项目拟在上述基础上，从临床角度探明外周血中EGFRvIII-MV浓度与GBM患者放疗疗效和预后之间的联系；深入研究离体和在体条件下微泡源性EGFRvIII对受体细胞PI3K/Akt、DNA-PKcs、DNA DSB修复及放射敏感性的影响。开展本课题有助于进一步认识微泡在GBM放射抵抗中的作用，为肿瘤放射增敏提供新思路。

Microvesicles are plasma-membrane-derived particles that released from cells by the outward budding and fission of the plasma membrane. As a novel mediator of intercellular communication, microvesicle transfer bioactive lipids and proteins, including oncogene products and receptors, from the cell of origin to recipient cells. Recently, microvesicle derived from tumor cells transfer the oncogenic receptor EGFRvIII from more aggressive to indolent glioma cells, which shed light on a flexible interoperability mechanism among different tumor-cell subsets. EGFRvIII, a truncated and oncogenic form of the epidermal growth factor receptor variant, has been implicated to confer radiation resistance of glioblastoma multiforme (GBM). However, the effect of EGFRvIII-MV on radiosensitivity of GBM remains to be elucidated. Using scanning electron microscopy, we have discovered that IR triggers the generation and secretion of microvesicles. Interestingly, we demonstrated that incubation for 24 hours prior to irradiation with microvesicles resulted in a significant decrease of radiosensitivity in U87 human glioblastoma cell. Based on these discoveries, we hypothesize that membrance microvesicles containing EGFRvIII may represent a critical survival mechanism for glioblastoma cells against IR by horizontal propagation of oncogenes and phenotype transformation among subsets of cancer cells. In this proposal, we will thus focus on EGFRvIII-MV merge with the plasma membranes of the cancer cells lacking EGFRvIII, and whether this event leads to the transfer of the oncogenic activity, including activation of PI3K/Akt/DNA-PK signalling pathway, acceleration of DNA DSB repair and promotion of GBM radioresistance or not. Findings are expected to advance our understanding of the molecular mechanisms that radiation-induced microvesicles modulate radiosensitivity in glioblastoma and provide a promising strategy for radiosensitization of glioblastoma.

多形性胶质母细胞瘤(GBM) 是一类由不同表型和生物学行为的细胞亚群构成的、高度异质性的中枢神经系统病变，微环境和肿瘤细胞之间是密不可分的功能整体。然而，既往研究多以单一细胞为研究对象，忽视了微环境下异质性细胞间的通讯和对话，难以实现临床转化。本项目首次以微泡这一新型胞间通讯载体为对象，以“EGFRvIII阳性微泡促进受体细胞DNA DSB修复，下调其放射敏感性”这一现象为切入点，通过为期4年的实验研究，创新性发现：1）EGFRvIII-MV通过膜融合途径使受体细胞获得EGFRvIII表型，选择性激活PI3K/Akt信号途径，并通过“Akt-DNA-PKcs正反馈环”活化DNA-PK，促进DSB修复，进而下调GBM细胞的放射敏感性；2）靶向干预EGFRvIII-MV的释放和膜融合过程能有效提高GBM放射敏感性；3）GBM患者外周血中EGFRvIII-MV浓度与GBM患者放疗疗效和预后呈负相关。本项目证实了“异质性肿瘤细胞通过微泡横向传递EGFRvIII协同抵抗电离辐射”这一假说，为肿瘤放射增敏提供新视角和新靶点，同时也为临床上放疗增敏药物的开发、遴选提供新途径。