甲状腺癌是最常见的内分泌恶性肿瘤，放射性碘(131I)治疗分化型甲状腺癌(DTC)疗效确切，但随着疗程延长部分肿瘤会产生放射性碘抵抗。放射性碘抵抗的分化型甲状腺癌(RR-DTC)恶性程度较高，预后较差。电离辐射能通过诱导细胞DNA双链断裂(DSB)杀死肿瘤细胞，抑制DSB修复可提高细胞对电离辐射的敏感性。去泛素化酶BRCC36既参与了DSB的同源重组修复，也能协助细胞有丝分裂纺锤体正常组装。我们推测抑制BRCC36不仅能抑制DNA损伤修复，提高DTC对131I的敏感性，还能使细胞有丝分裂失败而凋亡，从而提高131I的疗效，降低放射性碘抵抗发生的可能性。本项目从细胞水平首先验证131I对DTC细胞DNA的损伤作用，随后研究抑制BRCC36对DTC细胞的131I敏感性和细胞周期和分裂的影响，为深入研究BRCC36的临床应用打下基础。

Thyroid cancer is the most common endocrine malignancy. The effect of radioactive iodine (131I) treatment in differentiated thyroid cancer (DTC) is positive, however, the radioactive iodine uptake in some of tumors reduce or disappear in the treatment process. The radioactive iodine-refractory differentiated thyroid cancer (RR-DTC) is almost poorly differentiated, and not sensitive to the traditional treatment methods, which is a difficult problem in the treatment of thyroid cancer. Ionizing radiation (IR) can injure cells by induce DNA double-strand break (DSB), so we can enhance the sensitivity to IR by suppressing the DSB repair. The deubiquitinating enzyme BRCC36 not only participates in the homologous recombination repair (HR) of DSB, but also contributes to the proper mitotic spindle assembly in mammalian cells. Here, we hypothesize that the suppression of BRCC36 can inhibit the DSB repair, enhance the sensitivity of DTC cells to 131I treatment, make cell mitosis failure and induce apoptosis, thus to improve the therapeutic effect of 131I treatment, decrease the times and dose of 131I treatment, and reduce the possibility of radioactive iodine resistance occurs. First, we will validate the DNA damage of DTC cells by 131I treatment. Then, we will investigate the change of sensitivity of DTC cells to 131I treatment and the success rate of mitosis when the expression of BRCC36 is suppressed. In general, the aim of the project is lay a basis for further research on the clinical application of BRCC36.

甲状腺癌是最常见的内分泌恶性肿瘤，放射性碘(131I)治疗分化型甲状腺癌(DTC)疗效确切，但随着疗程延长部分肿瘤会产生放射性碘抵抗。放射性碘抵抗的分化型甲状腺癌(RR-DTC)恶性程度较高，预后较差。电离辐射能通过诱导细胞DNA双链断裂(DSB)杀死肿瘤细胞，抑制DSB修复可提高细胞对电离辐射的敏感性。去泛素化酶BRCC36既参与了DSB的同源重组修复，也能协助细胞有丝分裂纺锤体正常组装。本项目初步研究了BRCC36在131I诱导的DTC细胞株BCPAP和TPC-1的DSB的修复中发挥的作用。首先我们通过γH2AX免疫荧光和Western Blotting证明，放射性浓度梯度和时间梯度的131I均能诱导BCPAP和TPC-1细胞发生DSB。随后我们设计合成了BRCC36干扰siRNA并构建shRNA质粒，流式细胞术结果表明BRCC36干扰后的BCPAP和TPC-1细胞发生S期阻滞和凋亡，提示BRCC36与细胞DNA合成与细胞增殖有关。放射性浓度梯度和时间梯度的131I处理BRCC36干扰的BCPAP和TPC-1细胞，与未干扰组相比，γH2AX foci水平明显上升，G2期比例和凋亡率明显增多，表明BRCC36在DSB修复中发挥着重要作用。此外，MEK 1/2靶向抑制剂能抑制BRCC36的表达，提示BRCC36可能受MEK/ERK通路的调控。这些结果提示BRCC36不仅能抑制DNA损伤修复，提高DTC对131I的敏感性，还能使细胞周期阻滞和凋亡，从而提高131I的疗效，降低放射性碘抵抗发生的可能性。