CircRNA_100227/miR-217/PTEN构成ceRNA网络调控直肠癌放射敏感性的机制研究

Preoperative radiochemotherapy has already been a standard therapeutic regimen of locally advanced rectal cancer. However, there are significant individual differences in the efficacy of preoperative radiotherapy for rectal cancer in clinical practice. Therefore, it is necessary to screen biomarkers and radiosensitizers that are related to radiotherapy of rectal cancer. The applicant previously found that circRNA_100227 was lowly expressed in rectal cancer patients with radioresistance, and up-regulation of circRNA_100227 could increase the radiosensitivity of rectal cancer cells. It was confirmed via luciferase assay that circRNA_100227 and miR-217 could directly bind to each other. Therefore, it is speculated that circRNA_100227 regulates the PTEN/PI3K/AKT signaling pathway via competitive binding to miR-217, thus increasing the radiosensitivity of rectal cancer cells..To test this hypothesis, we examined the relationship between circRNA_100227, miR-217 and PTEN at three levels, namely, in vivo, cells and molecules, using rectal cancer tissues, cell lines and tumor-bearing mice, respectively. The findings showed that circRNA_100227 increased the molecular mechanism of radiosensitivity of rectal cancer by competitively binding miR-217 to regulate the PTEN / PI3K / AKT signaling pathway.

术前同步放化疗后行根治性手术是局部进展期直肠癌的标准治疗方案。但是在临床实践中直肠癌术前放疗效果具有显著的个体差异，因此，迫切需要筛选与直肠癌放疗敏感相关的生物学标志物及放射增敏剂。申请人前期发现：在直肠癌放疗抵抗患者中circRNA_100227低表达，且上调circRNA_100227可以增加直肠癌细胞的放射敏感性。免疫荧光素酶证实circRNA_100227与miR-217可直接结合。因此，我们推测circRNA_100227通过竞争性结合miR-217调控直肠癌细胞的放射敏感性。. 为验证这一假说，以直肠癌组织，细胞及小鼠为研究对象，在体内、细胞及分子三个水平，探索circRNA_100227，miR-217和PTEN三者之间的关系，并阐明circRNA_100227通过竞争性结合miR-217调控PTEN/PI3K/AKT信号通路增加直肠癌放射敏感性的分子机制。

术前同步放化疗后行根治性手术是局部进展期直肠癌的标准治疗方案。但是在临床实践中直肠癌术前放疗效果具有显著的个体差异，因此，迫切需要筛选与直肠癌放疗敏感相关的生物学标志物及放射增敏剂。通过对直肠癌放射敏感及不敏感组织标本（放化疗前活检组织）进行基因测序，发现100个具有明显的差异表达的circRNAs。后选取10个差异circRNAs，经qRT-PCR验证，发现circATL2在直肠癌放射敏感组织中高表达。在体内及体外实验中证实，上调circATL2表达，能显著提高肠癌的放射敏感性。随后继续通过分析在直肠癌放射敏感组织中低表达的8个miRNA，通过RIP和免疫荧光素酶实验，验证了miR-205与circATL2是直接结合的关系。通过生物信息学方法预测PTEN可能是miR-205潜在的靶基因，且通过免疫荧光素酶实验证实PTEN是miR-205的直接作用靶基因。进一步的挽救实验，证实了直肠癌中circATL2、miR-205和PTEN三者的ceRNA机制，进而影响PI3K/AKT通路的活化，调控直肠癌的放射敏感性。本研究从体内、细胞及分子三个水平，验证了circATL2通过竞争性结合miR-205,调控PTEN/PI3K/AKT信号通路，影响直肠癌放射敏感性的分子机理，从而为circATL2作为直肠癌术前同步放化疗的增敏剂提供理论依据。