NUTRITIONAL REGULATION OF RAS PROTO-ONCOGENE ACTIVITY

Ras介导的正常调节逃逸似乎是一个常见的事件 癌症的多步骤发生。 许多体外研究表明， 证明了ras和其他原癌基因产物之间的相互作用， 尤其是myc和肿瘤抑制因子p53。 一个有用的研究模型 这些相互作用中的一种是市售的p53 "敲除"小鼠， 一种转基因小鼠，其中无效p53生殖系突变阻止了 p53的一个或两个等位基因的表达。 这种p53缺陷 动物发育正常，但容易发生早期肿瘤;事实上，75%的 的纯合子在6月龄时发生自发性肿瘤。 这些 小鼠可用于研究p53基因剂量和不同饮食的影响 或者它们可以被用来作为一种加速的 不需要暴露于化学物质的致癌作用， 和/或促进肿瘤发生。 此外，从胚胎培养的成纤维细胞 与各种遗传背景的结合提供了一个强大的体外系统， 解决一些相同的问题。 我们将使用ras、myc 和p53来评估这些原癌基因mRNAs在各种 转基因小鼠的组织。 正在与S博士进行研究。赫斯特因 研究热量限制的影响（一种有效但效果不佳的 了解饮食方案，显着抑制肿瘤的发展， 啮齿动物）;这些研究将确定这种饮食操纵如何 结合p53基因剂量影响原癌基因表达。 另一个感兴趣的领域是单萜的饮食效应， 柠檬烯是橙子油的主要成分， 在动物模型中的肿瘤发生。 柠檬烯的部分作用可能是 通过其对ras蛋白的法尼基化的抑制， 翻译脂质修饰是ras定位于 质膜和因此的Ras活性。 使用敏感的半- 我们以前开发的ras定量分析，我们将能够 检测柠檬烯对p53缺陷小鼠体内ras的影响， 体外

Ras-mediated escape from normal regulation appears to be a frequent event in the multi-step genesis of cancer. A number of in vitro studies have demonstrated interactions between ras and other proto-oncogene products, especially myc and the tumor suppressor p53. A useful model for the study of these interactions is the commercially available p53 "knockout" mouse, a transgenic mouse in which null p53 germ line mutations prevent the expression of either one or both alleles for p53. Such p53-deficient animals develop normally but are prone to early tumorigenesis; indeed, 75% of homozygotes develop spontaneous neoplasms by 6 months of age. These mice can be used to study the effects of p53 gene dosage and various diets on carcinogenesis, or they can be used as a model of accelerated carcinogenesis that does not require exposure to chemicals that initiate and/or promote tumorigenesis. Moreover, fibroblasts cultured from embryos with the various genetic backgrounds afford a powerful in vitro system for addressing some of the same issues. We will use cDNA probes for ras, myc and p53 to assess the expression of these proto-oncogene mRNAs in various tissues from transgenic mice. Studies in progress with Dr. S. Hursting are investigating the effect of caloric restriction (a potent but poorly understood dietary regimen that dramatically inhibits tumor development in rodents); these studies will determine how this dietary manipulation combines with the gene dosage of p53 to affect proto-oncogene expression. Another area of interest is the dietary effect of the monoterpene, limonene, a major component of orange oil that has been shown to inhibit tumorigenesis in animal models. Part of the action of limonene may be through its inhibition of the farnesylation of ras proteins; this post- translational lipid modification is required for location of ras to the plasma membrane and hence ras activity. Using the sensitive semi- quantitative assay for ras we previously developed, we will be able to examine the effects of limonene on ras in p53-deficient mice in vivo and in vitro.