Relationship between thyroid tumor radiosensitivity and nuclear localization of DNA-dependent protein kinase catalytic subunit
Relationship between thyroid tumor radiosensitivity and nuclear localization of DNA-dependent protein kinase catalytic subunit
复制标题
甲状腺肿瘤放射敏感性与DNA依赖性蛋白激酶催化亚基核定位的关系
作者：
Ihara M;Shichijo K;Ashizawa K;Matsuda K;Otsubo R;Horie I;Nakashima M;Kudo T
甲状腺肿瘤是最常见的内分泌恶性肿瘤类型，通常用放射性碘（RAI）治疗，以破坏手术干预后残留的癌细胞。我们先前报道了在非同源末端连接中起关键作用的双链DNA依赖性蛋白激酶催化亚基（DNA-PKcs）的表达水平与癌细胞的放射敏感性相关。具体而言，细胞表达高水平的DNA-PKcs表现出辐射抗性，而细胞表达低水平的辐射处理敏感。在这项研究中，我们观察到全长天然DNA-PKcs（460 kDa）的抗辐射的FRO和KTC-2细胞通过蛋白质印迹分析使用的抗体对DNA-PKcs的C-末端。相反，在辐射敏感的TPC-1和KTC-1细胞中观察到裂解的DNA-PKcs（175 kDa）。在中度辐射敏感的WRO细胞中观察到几乎等量的DNA-PKcs。我们还描述了一种简单的方法，用于预测放射治疗的疗效在个别情况下的甲状腺癌的基础上染色的DNA-PKcs在人类癌细胞系。免疫荧光染色显示，本地DNA-PKcs主要定位在细胞质中，只有很少定位在辐射抗性甲状腺癌细胞的细胞核，而在辐射敏感的癌细胞的175 kDa裂解的DNA-PKcs的C-末端片段主要定位在细胞核内。因此，DNA-PKcs在γ射线照射后向细胞核移动。我们的研究结果提出了一种新的方法来分类人类甲状腺肿瘤的基础上，其细胞分布模式的DNA-PKcs结合其放射敏感性。
Thyroid tumors are the most common types of endocrine malignancies and are commonly treated with radioactive iodine (RAI) to destroy remaining cancer cells following surgical intervention. We previously reported that the expression levels of double-stranded DNA-dependent protein kinase catalytic subunit (DNA-PKcs), which plays a key role in non-homologous end joining, are correlated with the radiosensitivity of cancer cells. Specifically, cells expressing high levels of DNA-PKcs exhibited radiation resistance, whereas cells expressing low levels were sensitive to radiation treatment. In this study, we observed full-length native DNA-PKcs (460 kDa) in radiation-resistant FRO and KTC-2 cells through western blot analysis using an antibody against the C-terminus of DNA-PKcs. In contrast, cleaved DNA-PKcs (175 kDa) were observed in radiation-sensitive TPC-1 and KTC-1 cells. Almost equal amounts of DNA-PKcs were observed in moderately radiation-sensitive WRO cells. We also describe a simple method for the prediction of radiation therapy efficacy in individual cases of thyroid cancers based on staining for DNA-PKcs in human cancer cell lines. Immunofluorescent staining showed that native DNA-PKcs was localized largely in the cytoplasm and only rarely localized in the nuclei of radiation-resistant thyroid cancer cells, whereas in radiation-sensitive cancer cells a 175-kDa cleaved C-terminal fragment of DNA-PKcs was localized mainly inside the nuclei. Therefore, DNA-PKcs moved to the nucleus after γ-ray irradiation. Our results suggest a new method for classifying human thyroid tumors based on their cellular distribution patterns of DNA-PKcs in combination with their radiosensitivity.