ATF3基因对恶性胶质瘤放疗敏感性的作用及其机制

Radiation therapy is one of the important therapeutic treatments against malignant glioma. However, the two major issues that need to be resolved for radiation therapy of malignant glioma are the radiation induced normal brain tissue damage and resistance of glioma cells to radiation. Previously，we found that the transcriptional factor ATF3 could effectively protect neuronal cells from apoptosis induced by deprivation of neuronal growth factor via long non-coding RNA LAT. The role and underlying mechanism of ATF3 on radiosensitivity of glioma need to be further investigated. Our pilot experiment indicates that inhibition of ATF3 can decrease radio-sensitivity of glioma cells. Further investigation showed that the protein expression level of ATF3 and LGP2 was negatively correlated in glioma cells that treated by ionizing radiation. Bioinformatics analysis shows that there is an ATF3 binding sequence within LGP2 promoter. Thus, we propose a hypothesis that ATF3 enhances the radio-sensitivity of malignant glioma via direct inhibition of LGP2 transcription. The current project is: planning to test the effect of ATF3 on radio-sensitivity of glioma cells on cellular and animal levels, respectively. We will further use Crispr, CHIP and Dual-Luciferase Reporter Assay to fully clarify the underlying mechanism of ATF3 induced radio-sensitization of gliomas. This will eventually provide a new theoretical support and target for the development of a novel glioma radio-sensitizer that targets ATF3 signal pathway.

放疗是治疗恶性胶质瘤的重要手段之一。但面临射线对胶质瘤周围正常脑组织的损伤和胶质瘤细胞对射线的抵抗两大难题。我们前期研究发现,转录因子ATF3通过调控长链非编码RNA LAT对抗去神经生长因子诱导的神经元凋亡能有效保护神经元。ATF3对胶质瘤放疗敏感性的作用及其机制则有待进一步阐明。预实验发现：抑制ATF3表达能降低胶质瘤细胞的放疗敏感性；胶质瘤细胞经照射后ATF3与LGP2蛋白表达水平呈负相关；生物信息学预测显示LGP2启动子存在ATF3结合序列。由此我们提出假说：ATF3通过直接负性转录调控LGP2来增强胶质瘤的放疗敏感性。本项目拟在细胞和动物水平检测ATF3对胶质瘤放疗敏感性的作用，运用CRISPR、CHIP和双荧光素酶报告基因等方法阐明ATF3调控胶质瘤放疗敏感性的分子机制，最终为以ATF3信号通路为靶点的恶性胶质瘤新型放疗增敏剂的研发提供理论依据和靶标。

胶质瘤放疗抵抗一直是临床难题。我们研究发现,放射线或其化学模拟剂zeocin能上调胶质瘤细胞中转录因子ATF3表达。过表达ATF3基因在细胞水平能抑制胶质瘤生长。机制研究发现：zeocin能显著抑制胶质瘤细胞总m6A水平，上调RNA m6A去甲基化酶FTO和ALKBH5，激活长链dsRNA，同时能显著上调磷酸化PKR以及下游磷酸化eIF-2a水平。生物信息学预测显示免疫检查点分子PDL1基因启动子存在 ATF3结合序列。进一步发现，过表达ATF3能显著上调PDL1 mRNA和蛋白水平，抑制ATF3能下调PDL1 mRNA和蛋白水平。本研究结果提示，放射线诱导的ATF3/PDL1信号轴的激活是放疗诱导的胶质瘤免疫逃逸和抵抗的潜在分子机制。在此基础上，我们提出：放疗联合PDL1抑制剂的组合疗法是一种潜在的对抗胶质瘤放疗耐受的新策略。