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

1.我们测量了DNA-PK （dna依赖性蛋白激酶）的活性，建立了两个细胞系具有不同的放射敏感性。1例为HK-1（恶性淋巴瘤），1例为铃木（甲状腺癌）。铃木比HK-1对辐射更敏感。DNA-PK活性差异无统计学意义(2)。我们用人骨肉瘤细胞系MG-63制备直径为100 μ m的多细胞小球体，观察单层培养与球体培养之间DNA-PK活性的差异。球形培养的MG-63细胞比单层培养的抗辐射能力强。我们以MG-63细胞的对数期和融合期为对照进行单层培养。而在单层培养和球形培养中，DNA-PK活性无显著差异。X射线照射后的潜在致命损伤有两个修复过程；一个快速的修复过程，大约在1小时内完成，被高渗盐水治疗打断，而一个较慢的过程，需要几个小时才能完成，通过应用条件培养基促进。作为高渗盐水处理抑制快速修复过程的一种机制，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。然后，我们用两种恶性黑色素瘤细胞系来检验这种可能性。G-361细胞（D_0=145cGy, Dq=249cGy）比P39细胞（D_0=74cGy, Dq=85cGy）具有更强的抗辐射能力和更强的PLD快速修复能力。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.