EXPERIMENTAL RADIOTHERAPY--CARCINOGENESIS, AND PROTECTOR

虽然本研究的最终目标仍然是表征化学预防策略，以减少在治疗潜在可治愈的肿瘤疾病期间通过电离辐射对正常组织的遗传毒性损伤，但本应用的重点是研究硫醇对自发转移发展过程的抑制作用。本研究将利用能够在C3H小鼠中生长的SA-NH肉瘤作为自发转移形成的模型。SA-NH细胞系也可在体外条件下生长。选择氨磷汀、n -乙酰半胱氨酸（NAC）和卡托普利作为研究的硫醇，因为它们目前都在临床使用，并且在啮齿动物肿瘤模型中都被观察到对转移发展有抑制作用。如果这些硫醇中的任何一种或全部被发现能有效地抑制小鼠体内的转移形成，那么它们作为抗转移剂的使用将迅速转化为癌症治疗的临床方案。这项研究将只关注硫醇相关的性质，这些性质可以影响转移过程中某些很好表征的步骤。将测试三个假设。首先，因为硫醇是巯基供体，它们可以刺激细胞内血管抑制素的产生，血管抑制素是一种来自纤溶酶原的血管生成抑制剂。其次，凭借其螯合锌的能力，硫醇可以抑制锌与需要锌的基质金属蛋白酶（MMPs）的结合。通过这种方式抑制肿瘤细胞侵入正常组织所需的MMP活性。第三，硫醇可以增强肿瘤细胞中MnSOD的基因表达和酶活性，从而降低转移表型。使用的技术包括Northern blot分析评估MnSOD基因表达；Western blot分析评估血管抑制素的产生；酶谱分析测定MMP活性；自发性转移试验，评估原发肿瘤手术切除后形成的肺转移；还有一项人工转移试验，包括评估在体外条件下处理过的活的肿瘤细胞注射到受体动物的侧尾静脉后形成的肺肿瘤。

While the ultimate goal of this investigation continues to be the characterization of chemopreventive strategies to reduce the genotoxic damage to normal tissues by ionizing radiation during the treatment of potentially curable neoplastic disease, the focus of this application is directed to the investigation of the inhibitory effects of thiols on the process of spontaneous metastasis development. This study will utilize the SA-NH sarcoma that is capable of being grown in C3H mice as a model of spontaneous metastasis formation. SA-NH cell lines are also available for growth under in vitro conditions. The thiols chosen for study are amifostine, N-acetylcysteine (NAC), and captopril because each is currently in clinical use and each has been observed to have an inhibitory effect on metastases development in rodent tumor models. It is anticipated that if any or all of these thiols are found effective in inhibiting metastases formation in mice, their use as anti-metastatic agents could rapidly be translated to clinical protocols for cancer treatment. This study will focus only on thiol related properties that can affect certain well characterized steps in the metastatic process. Three hypotheses will be tested. First, because thiols are sulfhydryl doners they can stimulate the intracellular production of angiostatin, an inhibitor of angiogenesis, from plasminogen. Second, by virtue of their ability to chelate zinc, thiols can inhibit zinc binding to the zinc requiring matrix metalloproteinases (MMPs). In this manner MMP activities required for tumor cell invasion into normal tissues are inhibited. And third, thiols can enhance gene expression and enzyme activity of MnSOD in tumor cells which in turn leads to a reduced metastatic phenotype. Techniques to be used include Northern blot analysis to assess MnSOD gene expression; Western blot analysis to assess angiostatin production; zymogram analysis to measure MMP activities; a spontaneous metastases assay involving the assessment of pulmonary metastases formed following the surgical removal of the primary tumor; and an artificial metastasis assay involving the assessment of pulmonary tumors formed following the injection of viable tumor cells treated under in vitro conditions and then injected into the lateral tail veins of recipient animals.