EXPERIMENTAL RADIOTHERAPY--CARCINOGENESIS, AND PROTECTOR

虽然这项研究的最终目标仍然是确定化学预防策略的特征，以减少在潜在可治愈的肿瘤疾病治疗期间电离辐射对正常组织的遗传毒性损害，但这项研究的重点是研究硫醇对自发转移发展的抑制作用。这项研究将利用能够在C3H小鼠体内生长的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。选择用于研究的硫醇是氨磷汀、N-乙酰半胱氨酸(NAC)和卡托普利，因为它们目前都在临床上使用，而且都被观察到对啮齿动物肿瘤模型中的转移发展具有抑制作用。预计如果这些硫醇中的任何一个或全部被发现有效地抑制小鼠的转移形成，它们作为抗转移药物的使用可能很快被转化为癌症治疗的临床方案。这项研究将只集中在硫醇相关的性质上，这些性质可以影响转移过程中某些特征明确的步骤。三个假说将被检验。首先，由于硫醇是巯基供体，它们可以刺激纤溶酶原在细胞内产生血管生成抑制物血管抑素。其次，由于硫醇具有螯合锌的能力，因此可以抑制锌与需要基质金属蛋白酶(MMPs)的锌的结合。通过这种方式，肿瘤细胞侵袭正常组织所需的基质金属蛋白酶活性被抑制。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。将使用的技术包括：Northern印迹分析以评估MnSOD基因的表达；Western印迹分析以评估血管抑素的产生；酶谱分析以测量基质金属蛋白酶的活性；自发转移分析，涉及评估手术切除原发肿瘤后形成的肺转移；以及人工转移测试，涉及评估在体外条件下处理的活肿瘤细胞注射后形成的肺肿瘤，然后注入受体动物的尾侧静脉。

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.