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

本研究从p53功能的角度探讨了一氧化氮产生剂硝酸异山梨酯（isosorbiddinitrate，ISDN）对体外和体内肿瘤细胞放疗和热疗的影响。ISDN（0.3mM）能不依赖于p53的方式提高这些转染子的体外辐射敏感性和44℃下的热敏感性，而ISDN在37℃下无细胞毒性。Western blot分析表明，热敏感性的增加部分是由于热诱导的Hsp 72衰变的刺激所致。ISDN可增强10戈伊照射或43℃加热后移植瘤的生长延迟（0.3mM），而不管它们的p53基因状态如何，尽管lSDN显示对肿瘤生长没有影响。TUNEL法显示，两例肿瘤生长延迟的增强部分是由于p53非依赖性凋亡的诱导，这些结果表明，p53-通过放射或热疗与ISDN的联合治疗，独立的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.