PN-1调控肿瘤干细胞特性和EMT在肺癌放疗抵抗中的作用机制研究

Radiotherapy is one of the important treatment methods for lung cancer, about 40% - 50% of patients after radiotherapy will appear uncontrolled or recurrence in the case of local tumor. Radioresistance is the main reason for the failure of clinical radiotherapy in lung cancer. Therefore, screening and identification of the molecular markers for radioresistance have become one of the hot topics. In the previous study, we have found that the gene of PN-1 is highly expressed in non-small cell lung cancer (NSCLC) radiation-resistant cells (A549R and PC9R), and it may affect radiotherapy resistance by regulating the characteristics of cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT). In addition, for the patients with radiation therapy alone in one course of treatment, their blood samples are collected before the treatment. We found that the concentrations of PN-1 in serum are significantly higher in progressive disease (PD) patients compared with stable disease (SD) and partial response (PR). The results suggest that PN-1 may be one of the potential molecular markers in the radioresistance of lung cancer. Based on vitro cells, vivo mice, and clinical humans, we will further demonstrate the functions of PN-1 in radioresistance of NSCLC, and explore its molecular mechanism on regulating the characteristics of CSCs and the effect of EMT on radiotherapy. Then, we will prospectively verify the clinical significance of PN-1 in radiotherapy. Our study will lay the foundation for the implementation of individualized treatment and the rational application of comprehensive treatment.

放射治疗是肺癌的重要治疗手段之一，约40%-50%的患者在放疗后会出现局部肿瘤未控或复发，放疗抵抗是局部治疗失败的主要原因。因此，放疗抵抗相关分子标志物的筛选鉴定是目前研究热点之一。前期研究中，我们发现PN-1基因在非小细胞肺癌放疗耐受细胞（A549R和PC9R）中高表达，且有可能通过调控肿瘤干细胞特性和上皮间质转化（EMT）影响放疗抵抗；另外，针对单一病程仅接受放疗的肺癌患者，发现PD患者放疗前血清中的PN-1含量明显高于SD和PR患者，这表明PN-1基因可能是肺癌放疗抵抗的潜在分子标志物之一。基于此，本项目将从体外细胞、体内小鼠、临床人体三个水平，明确PN-1基因在非小细胞肺癌放疗抵抗中的功能，探讨其调控肿瘤干细胞特性和EMT相关的放疗抵抗分子机制，并前瞻性验证血清中PN-1表达对放疗疗效的预测意义，为肺癌放射治疗的个体化、精准化实施及综合治疗的合理应用奠定基础。

虽然DNA损伤应答(DNA damage response，DDR)与肺癌细胞的放射抗性特征有关，但DDR的具体调节因子和潜在机制尚不清楚。本研究中，我们发现人源丝氨酸蛋白酶抑制剂SERPINE2是肺癌放射敏感性和DDR的调节因子。SERPINE2在经电离辐射后表现出放射抗性的细胞中表达上调，并且SERPINE2敲低后提高了体外和体内肿瘤细胞的放射敏感性。从功能上讲，SERPINE2缺失会导致同源重组修复降低、细胞周期检查点的快速恢复以及抑制肿瘤细胞的迁移和侵袭；从机制上讲，SERPINE2敲低可以抑制DNA损伤修复过程中p-ATM和下游修复蛋白RAD51的累积，RAD51的过表达还可以挽救肺癌细胞的DNA损伤和放射抗性表型。进一步，SERPINE2可以直接与MRE11和ATM蛋白相互作用，以促进ATM在同源重组介导的DNA双链断裂修复中的磷酸化。此外，SERPINE2的高表达与临床肺腺癌患者的不良预后相关，血清中SERPINE2的高浓度预示着非小细胞肺癌患者对放疗的反应不佳。总之，本研究不仅揭示了 SERPINE2 在调节DNA损伤修复中的新功能，提供了一种经过深思熟虑的方法来解释SERPINE2与肺癌之间关系的分子机制，而且还为SERPINE2作为克服肺癌放射抗性的有希望的临床靶点提供了证据。本项目已经发表SCI论文5篇（其中IF>5论文4篇，核心成果发表在国际期刊《CANCER LETTERS》上），获国家发明专利授权一项；同时，项目研究期限内协助培养研究生2人，项目组成员有2人晋升职称（中级和副高级各一人）；项目经费使用合理规范，无超支透支违规使用情况。