EVALUATION OF CHEMOPREVENTIVE AGENTS USING A TRANSGENIC MOUSE MELANOMA MODEL

我们已经开发出对这种病毒敏感的转基因小鼠品系 黑色素瘤的发展。这些小鼠提供了一个模型系统来评估 化学预防药物，因为它们表现出必要的特征： 肿瘤发展的高发生率，中等潜伏期和 肿瘤发展的进行性阶段。我们已经证明了 化学致癌物7，12-二甲基苯并[a]菲与环境 致癌物紫外线照射(280-340 nm)会导致TPras中的黑色素瘤 转基因小鼠。DMBA处理的小鼠的黑色素瘤表现出遗传和 染色体改变类似于人类黑色素瘤的描述。 使用TPras转基因小鼠作为我们的模型，我们建议测试 假设某些化学预防药物将预防DMBA-和/或 紫外线通过保护DNA损伤或调节ras诱导黑色素瘤 信号通路。激活RAS中的上行和下行事件 已经证明了细胞增殖所必需的途径 黑素细胞。此外，在大约25%的患者中观察到ras基因突变。 在暴露在阳光下的部位形成的黑色素瘤。其具体目标是 将致力于解决我们的假设是：1)评估效果 维甲酸(维甲酸、泛维甲酸)、紫苏醇(PA)、 表没食子儿茶素没食子酸酯(EGCG)和α-二氟甲基鸟氨酸(DFMO) Tpras转基因小鼠模型中黑色素瘤发生的研究。我们会 评价预防性药物对癌前病变发生的影响 病变、肿瘤、潜伏期、肿瘤大小和数量以及转移 传播；2)研究哪些化学预防药物可以预防或阻断紫外线- 诱导黑素细胞DNA损伤。特别是，我们将研究 上述试剂对嘧啶二聚体形成的影响及对生物活性的影响 活性氧物种的产生；以及3)研究其影响 视黄酸、PA和DFMO在紫外线诱导的小鼠表观遗传效应中的作用 黑素细胞，特别是ras途径的激活。我们会监控 G蛋白的活化/法尼化，以及AP-1的活性。生物学 黑素细胞中与ras通路激活相关的活性 包括增殖和诱导细胞凋亡。这些临床前研究 研究旨在引导开发新的化学预防措施 人类黑色素瘤皮肤癌的治疗策略。

We have developed transgenic mouse lines that are susceptible to the development of melanoma. These mice provide a model system for evaluating chemopreventive agents because they exhibit the necessary characteristics: a high incidence of tumor development, a moderate latency period and progressive stages of tumor development. We have demonstrated that the chemical carcinogen, 7, 12-dimethylbenz[a]anthracene and the environmental carcinogen, UV irradiation (280-340 nm), will cause melanoma in the TPras transgenic mice. The melanoma from DMBA-treated mice exhibit genetic and chromosomal alterations similar to those described for human melanomas. Using TPras transgenic mouse lines as our models, we propose to test the hypothesis that certain chemopreventive agents will prevent DMBA- and/or UV-induced melanoma by protecting against DNA damage or modulating the ras signaling pathway. Activation of upstream and downstream events in the ras pathways have been demonstrated as necessary for proliferation of melanocytes. In addition ras mutations have been observed in about 25% of the melanoma that developed in sun-exposed sites. The specific aims that will be pursued to address our hypothesis are: 1) to evaluate the effects of retinoids (tretinoin, panretinin), perillyl alcohol (PA), epigallocatechin gallate (EGCG), and alpha-difluoromethylornithine (DFMO) on melanoma development in the Tpras transgenic mouse models. We will asses the effect of preventive agents on development of premalignant lesions, tumors, latency period, size and number of tumors, and metastatic spread; 2) To study which chemopreventive agents may prevent or block UV- induced DNA damage in melanocytes. In particular, we will examine the effects of the above agents on formation of pyrimidine dimers and the generation of reactive oxygen species; and 3) To investigate the effects of retinoids, PA, and DFMO in UV-induced epigenetic effects in melanocytes, specifically activation of the ras pathway. We will monitor activation/farnesylation of G-proteins, and AP-1 activity. Biological activities in melanocytes associated with activation of the ras pathway include proliferation as well as induction of apoptosis. These preclinical studies are designed to lead to the development of new chemopreventive strategies for human melanoma skin cancers.