Basic research for the gene therapy to the radioresistant tumors

背景：DNA双链断裂（DSB）是电离辐射所致的主要致死性损伤。DNA DSB修复能力对于肿瘤和正常细胞的固有辐射敏感性至关重要。DNA-PKcs、Ku 70、Ku 85、XRRCC 4和NBS 1在DNA双链断裂修复中起重要作用。方法：作为放射抗性肿瘤基因治疗的基础研究，我们采用免疫组化方法检测了134例不同放射敏感性的正常组织和肿瘤组织中DNA-PKcs、Ku 70、Ku 85、XRRCC 4和NBS 1的表达。Ku 70、Ku 85、DNA-PKcs、XRCC 4和NBS 1在所有检查的肿瘤组织中均呈免疫阳性。Ku 70、Ku 85、DNA-PKcs的染色为胞核染色，XRCC 4和NBS 1的染色为胞核和胞浆染色。这5种蛋白在癌组织和相应正常组织中的表达无明显差异。在不同放射敏感性的肿瘤组织中，这5种蛋白的核染色强度无明显差异，但在非霍奇金淋巴瘤（B或T细胞）中的表达较低。间质细胞普遍表达这五种蛋白质的频率远低于肿瘤或上皮细胞在肿瘤和正常tissues.Discussion：我们没有观察到辐射敏感性和表达的五种蛋白质参与修复的DNA DSB的NHEJ之间的关系。那么问题就来了，为什么这五种蛋白表达相似的肿瘤具有不同的内在放射敏感性？一种可能性是这些蛋白质的表达并不一定反映其功能。具有这些蛋白质的相似表达的细胞在其功能中可能具有不同的功效。为了阐明这个问题，有必要使用反映这五种蛋白质功能的抗体。我们正计划寻找这些底物的特定位点的底物。

BACKGROUND: DNA double-strand breaks (DSB) are the major lethal lesions induced by ionizing radiation. The capability for DNA DSB repair is crucial for inherent radiosensitivity of tumor and normal cells. DNA-PKcs, Ku70, Ku85, XRCC4, and NBS1 play a critical role in DNA DSB repair.METHODS: As a basic research for the gene therapy to the radioresistant tumors, we immunohistochemically investigated the expression of DNA-PKcs, Ku70, Ku85, XRRCC4, and NBS1 in 134 specimens from various normal and tumor tissues with different radiosensitivity.RESULTS: Immunopositivity to Ku70, Ku85, DNA-PKcs, XRCC4 and NBS1 was found in all tumor tissues examined. The staining for Ku70, Ku85, DNA-PKcs was nuclear, but for XRCC4 and NBS1 it was nuclear and cytoplasmic. There were no apparent differences in the expression of these five proteins among cancerous tissues and the corresponding normal tissues. No apparent differences in nuclear staining intensity were detected in the expression of these five proteins among tumor tissues with different radiosensitivity, although non-Hodgkin's lymphoma (B or T cell) tended to show a lower expression than he others. The stromal cells generally expressed these five proteins at much lower frequency than either tumor or epithelial cells in both tumor and normal tissues.DISCUSSION: We did not observe the relationship between radiosensitivity and expression of the five proteins involved in repair of DNA DSB by NHEJ. The questions then arises as to why tumors with similar expressions of the five proteins have different intrinsic radiosensitivity? One possibility is that expression of those proteins does not necessarily reflect their function. Cells which have a similar expression of these proteins could have different efficacies in their function. To elucidate this problem, it is necessary to use antibodies which reflect the function of these five proteins. We are planning to find the substrates of specific sites of these substrates.