Application of NO generating agents as radiosensitizer and their modes of action.

我们从p53功能的角度研究了一氧化氮生成剂硝酸异山梨酯（ISDN）对肿瘤细胞放疗和热疗在体内和体外的影响，ISDN是一种非常流行的心绞痛药物。用携带野生型、突变型p53基因或单独携带新霉素耐药基因（neo）的载体转染可移植的p53缺陷人非小细胞肺癌（NSCLC） H1299细胞作为对照。ISDN （0.3 mM）对44℃下的辐射敏感性和热敏性均有显著提高，且与p53无关，而ISDN在37℃下无细胞毒性。Western blot分析表明，热诱导的Hsp72的衰变刺激了热敏感性的增加。无论p53基因是否存在，ISDN （0.3 mM）均可增强这些移植肿瘤在10 Gy或43℃的体内加热后的生长延迟，而lSDN对肿瘤生长没有影响。免疫组织化学分析（TUNEL）表明，两例患者肿瘤生长延迟的增强部分是由于诱导p53非依赖性细胞凋亡。这些发现表明，通过放射或热疗和ISDN联合治疗，p53非依赖性凋亡诱导了有效的细胞杀伤和肿瘤生长延迟。

We examined effects of a nitric oxide-generating agent, isosorbide dinitrate(ISDN), which is a quite popular drug for angina pectoris, on radiotherapy and hyperthermia to cancer cells in vifro and in vivo from an aspect of p53 functions.Transplantable p53-deficient human non-small cell lung cancer(NSCLC) H1299 cells were transfected with a vector carrying wild-type, mutant p53 gene or a neomycin-resistant gene(neo)alone as a control.Radiosensitivity and thermosensitivity at 44℃ of these transfectants in vitro was increased with ISDN (0.3 mM) in a p53-independent manner, although ISDN revealed no cytotoxicity at 37℃ in vitro. Western blot analysis indicated that the increase of thermosensitivity was partially due to a stimulation of decay of heat-induced Hsp72.Growth delay of these transplanted tumors after irradiation at 10 Gy or heating at 43℃ in vivo was enhanced with ISDN (0.3 mM) regardless of their p53 gene status, although lSDN revealed no effect on tumor growth.Immunohistochemical analysis(TUNEL method) indicated that the enhancement of tumor growth delay was partially due to induction of p53-independent apoptosisin both cases.These findings suggested that a p53-independent apoptosis induced an efficient cell killing and tumor growth delay by combined treatment with radiation or hyperthermia and ISDN.