ATM介导的自噬在分化型甲状腺癌碘-131内照射敏感性中的作用及调控机制

The radiosensitivity of iodine-131 internal radiation is low in some differentiated thyroid carcinoma (DTC), which mainly results in the resistance to iodine-131 treatment. However, the relative mechanism remains to be further discussed. Our previous study indicated that inhibition of autophagy decreased the iodine-131-induced cell death；our bioinformatic analysis showed the high expression of ATM in thyroid cancer, and that T263 site of MAPK14 was its potential target; the research during PhD period verified that inhibition of ATM reduced the expression and activation of MAPK14 and further decreased the autophagy induced by external ionizing radiation. Thus we raise our hypothesis that ATM regulated autophagy by phosphorylating MAPK14 on T263 site, which is the potential target for increasing the radiosensitivity of iodine-131 internal radiation in DTC. In this project, inhibitors, gene silencing and gene rescuing techniques will be used to explore the effects of autophagy and ATM on the radiosensitivity of iodine-131 internal radiation. Furthermore, in order to study the mechanisms by which the phosphorylation of MAPK14 on T263 site by ATM plays an important role on both autophagy and radiosensitivity induced by iodine-131, in vitro kinase assay and the site-directed mutagenesis related tests will be conducted. Finally, the aim of our project is to illustrate the functions and molecular mechanisms by which ATM-mediated autophagy regulates iodine-131 radiosensitivity, providing theoretical basis for clinical prediction and reversal of iodine-131 resistance in DTC.

分化型甲状腺癌碘-131内照射敏感性低是碘-131治疗抵抗的重要原因，相关机制有待进一步论证。我们前期研究表明抑制自噬可降低碘-131内照射诱导的细胞死亡；生物信息学结果显示ATM在甲状腺癌中高表达，MAPK14 T263位点为其潜在磷酸化靶点；申请人博士研究工作证实抑制ATM可下调MAPK14并降低外照射诱导的自噬水平。因此提出假设：ATM通过磷酸化MAPK14 T263位点介导的自噬是提高碘-131内照射敏感性的潜在靶标。本项目将在体内、外实验中利用抑制剂、基因沉默和基因挽救技术等探讨自噬和ATM对碘-131内照射敏感性的影响；联合体外激酶实验和定点突变等方法，探索ATM通过MAPK14 T263位点的磷酸化调控自噬和内照射敏感性的分子机制。本研究旨在阐明ATM介导的自噬在碘-131治疗抵抗中的作用及机制，为临床上预判和逆转分化型甲状腺癌患者碘-131治疗抵抗提供理论依据。

分化型甲状腺癌碘-131内照射敏感性低是碘-131治疗抵抗的重要原因，相关机制有待进一步论证。本研究旨在阐明ATM介导的自噬在碘-131治疗抵抗中的作用及机制，为临床上预判和逆转分化型甲状腺癌患者碘-131治疗抵抗提供理论依据。首先，我们综述了细胞质中ATM在各种类型自噬中的主要功能。在非选择性自噬中，我们重点阐述了其在电离辐射（IR）诱导自噬中的作用机制，主要涉及MAPK14信号通路，mTOR信号通路和Beclin1/PI3KIII复合物。在选择性自噬中，例如线粒体自噬，过氧化物酶体自噬和脂质体自噬，相关信号通路主要包括ATM-PEX5，ATM-AMPK-TSC2-mTORC1-ULK1，PPM1D-ATM-MTOR，PINKI/Parkin和NAD+/SIRT1。其次，我们揭示了ATM可能是IR诱导的自噬和G2/M细胞周期阻滞crosstalk的潜在机制。我们的研究结果表明，Beclin 1敲低可以减少IR诱导的自噬，IR增强Beclin1/PIK3CIII复合物活性。进一步评估自噬和G2 / M细胞周期阻滞之间的可能关系，与自噬抑制剂3MA类似，Beclin 1敲低延迟IR诱导的G2 / M阻滞。IR使Beclin 1与G2 / M细胞周期检查点相关蛋白（即PLK1和CDC25C）之间的相互作用增加。另外，3MA和Beclin 1敲低都抑制了IR诱导的细胞凋亡。机制方面，IR诱导了Beclin 1和Tip60之间的相互作用，且引起二者在细胞内的重新分布。体外激酶结果显示，Beclin 1 T57可能是ATM的靶向磷酸化位点。最后，我们还通过一项大规模病例对照研究证实了肥胖可能是DTC潜在的危险因素，肥胖干预、治疗可能使甲状腺癌防治获益，并可能进一步减轻肥胖相关癌症负担。综上所述，我们的研究表明，ATM介导的自噬在放疗抵抗中的作用及机制，以期为临床上改善分化型甲状腺癌的诊断和治疗提供理论依据。