促125I粒子放疗肝癌敏感性的机制研究：NER通路扮演的角色？

Resistance to radiotherapy is a fundamental problem that limits the effectiveness of much radiotherapy currently used to treat cancer, specially in liver cancer radiotherapy. However, the mechanism of liver cancer radiotherapy resistance is not well documented. In our preliminary studies, we illustrated that iodine-125 combine with transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma treatment lead to a good short-term result; we further investigated the effectiveness of iodine-125 treating hepatocellular carcinoma was not as well as we willing to, and found iodine-125 radiotherapy resistance. Recently, reports indicated that nucleotide excision repair (NER) pathway gene lead to the platinum chemotherapy resistance, and both platinum drugs and iodine-125 treatment principle were to lead to the tumor's DNA damage. We hypothesis that liver cancer iodine-125 radiotherapy resistance is mediated by nucleotide excision repair pathway. in the proposal, p53-deficient, p53-mutation and wild-type p53 gene liver cancer cell lines will be used to demonstrate the relationship between NER gene and PTEN/PI3K/AKT pathway underwent iodine-125 radiation, RT-PCR will be applied for gene expression, immunoblotting analysis, ELISA and gene cloning techniques will be utilized to demonstrate cell signaling pathway. We tried to illustrate the major mechanism of iodine-125 radiology resistance and discuss how new molecularly-targeted therapies are being increasingly used to overcome these resistance mechanisms.

放疗及铂类药物化疗均是使肿瘤DNA损伤而致细胞凋亡。既往对铂类药物的研究中，发现肿瘤细胞的DNA修复主要是通过增强NER (Nucleotide Excision Repair)基因的表达而降低化疗敏感性。近来发现125I粒子近距离、持续放疗可增强肝癌放疗效果，但125I仅能导致与其结合的肝癌细胞凋亡，而残存的肝癌细胞可能通过增强NER通路的基因表达来加快肿瘤DNA修复，从而抑制肝癌细胞对125I的放射线损伤。本研究目的是探寻抑制125I放疗肝癌敏感性的靶点。我们选用NER通路的XPC和ERCC1为目标基因，使用PCR、免疫印迹分析及基因重组、克隆等技术对P53缺失、P53变异和有野生性P53的肝癌细胞受125I放射前、后的XPC、ERCC1及PTEN/PI3K/AKT的表达水平进行研究，探索NER通路基因在125I放射治疗肝癌的中所扮演的角色，为增强125I放射治疗肝癌敏感性提供新思路。

近来发现125I粒子近距离、持续放疗可增强肝癌放疗效果，但125I仅能导致与其结合的肝癌细胞凋亡，既往对铂类药物的研究中，发现肿瘤细胞的DNA修复主要是通过增强NER (Nucleotide Excision Repair)基因的表达而降低化疗敏感性。残存的肝癌细胞可能通过增强NER通路的基因表达来加快肿瘤DNA修复，从而抑制肝癌细胞对125I的放射线损伤。本研究目的是探寻抑制125I放疗肝癌敏感性的靶点。我们选用NER通路的XPC和ERCC1为目标基因，使用PCR、免疫印迹分析及基因重组、克隆等技术对P53缺失、P53变异和有野生性P53的肝癌细胞受125I放射前、后的XPC、ERCC1的表达水平进行研究，结果显示，p53野生型肝癌细胞对125I的放疗敏感程度最高，其次是p53突变型，再次是p53敲除型；NER通路的XPC在125I的放疗后的肝癌细胞中表达量明显降低，表明125I抗肿瘤作用可能是通过抑制NER通路XPC和ERCC1基因，抑制细胞DNA修复，诱导凋亡。本研究通过探索NER通路基因在125I放射治疗肝癌的中所扮演的角色，为增强125I放射治疗肝癌敏感性提供新思路，为提高肝癌患者的生存期提供了一定的帮助。