Investigation of molecular mechanism of radiosensitivity of the tumor cell and its clinical application

1.检测了两种不同放射敏感性细胞株的DNA-PK活性。其中一例为HK-1（恶性淋巴瘤），另一例为Suzuki（甲状腺癌）。Suzuki比HK-1更敏感。2.以人骨肉瘤细胞系MG-63为材料，制备直径为100 μ m的小球体，观察其DNA-PK活性在单层培养和球体培养中是否存在差异。球形培养的MG-63细胞比单层培养的MG-63细胞更耐辐射。我们用单层培养的对数期和汇合期MG-63细胞作为对照。3. X射线照射后潜在致死性损伤的修复有两个过程，一个是快速的修复过程，大约在1小时内完成，高渗盐水处理可以打断这个过程;另一个是缓慢的修复过程，需要几个小时才能完成，条件培养基的应用可以促进这个过程。高渗盐水处理可能通过抑制DNA-PK活性来阻断DNA双链断裂的修复，这可能是高渗盐水处理抑制快速修复过程的一种机制。G-361细胞（D_0= 145 cGy，Dq= 249 cGy）比P39细胞（D_0= 74 cGy，Dq= 85 cGy）具有更强的耐辐射性和更快的PLD修复能力。然而，在两种细胞系中，高渗盐水处理组与未处理组之间的DNA-PK活性无显著差异。

1.We measured the activity of DNA-PK (DNA-dependent protein kinase) of two established cell lines that have the different radiosensitivity. One of them was HK-1 (malignant lymphoma) and the other was Suzuki(thyroid cancer). Suzuki is more radiosensitive than HK-1. However, there was no significant difference of the activity of DNA-PK between them.2.We made samll multicellular spheroids 100 mum in diameter with human osteosarcoma cell line (MG-63) to examine whether there was the difference of the activity of DNA-PK between monolayr and spheroid culture. MG-63 cells in spheroid culture become more radioresistant than monolayr culture. We used MG-63 cells of log phase and confluent phase of growth in monolayr culture as a control. However, there was no significant difference of the activity of DNA-PK in monolayr culture and spheroid culture.3.There are two processes of repair of potentially lethal damage following X irradiaiton ; a rapid repair process, which is completed in about 1 hour, is interrupted by hypertonic saline treatment, and a slower process, which requires several hours to be completed, is facilitated by the application of condititioned medium. As a medhanism of inhibition of a rapid repair process by hypertonic saline treatment, there was the possibility that hypertonic saline treatment might block the repair of DNA double strand break by inhibiting the activity of DNA-PK.Then, we used two types of malignant melanoma cell lines to check such possibility. G-361 cells (D_0=145cGy, Dq=249cGy) are more radioresistant and have the higher ability of a rapid repair process of PLD than P39 (D_0=74cGy, Dq=85cGy). However, in both cel lines, there was no significant difference of the activity of DNA-PK between groups with hypertonic saline treatment and those without treatment.