EVALUATION OF CHEMOPREVENTIVE AGENTS USING A TRANSGENIC MOUSE MELANOMA MODEL

我们已经开发出转基因小鼠品系， 黑色素瘤的发展这些小鼠提供了一个模型系统， 化学预防剂，因为它们表现出必要的特性： 肿瘤发生率高，潜伏期中等， 肿瘤发展的渐进阶段。我们已经证明， 化学致癌物7，12-二甲基苯并[a]蒽与环境 致癌物质紫外线照射（280-340 nm）将导致TPras中的黑色素瘤 转基因小鼠DMBA处理小鼠的黑色素瘤表现出遗传和 与人类黑色素瘤相似的染色体改变。 使用TPras转基因小鼠系作为我们的模型，我们建议测试 假设某些化学预防剂将防止DMBA-和/或 紫外线诱导的黑色素瘤通过保护免受DNA损伤或调节ras 信号通路ras上游和下游事件的激活 已经证明，这些途径是细胞增殖所必需的。 黑素细胞此外，在约25%的人中观察到ras突变。 暴露在阳光下的皮肤上长出的黑色素瘤具体目标是， 将追求解决我们的假设是：1）评估的影响， 类维生素A（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） 在Tpras转基因小鼠模型中黑色素瘤的发展。我们将 评估预防药物对癌前病变发展的影响 病变、肿瘤、潜伏期、肿瘤大小和数量以及转移 2）研究哪些化学预防剂可以预防或阻断紫外线- 导致黑素细胞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以及 活性氧的产生;和3）研究影响 类维生素A、PA和DFMO在紫外线诱导的表观遗传效应中的作用 黑素细胞，特别是ras通路的激活。我们会监察 G蛋白的活化/法尼基化和AP-1活性。生物 与ras通路激活相关的黑素细胞活性 包括增殖以及诱导凋亡。这些临床前 研究旨在开发新的化学预防药物， 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.