Regulation of tumor promotion by RasGRP1

肿瘤促进是一个可逆的和非遗传毒性阶段的致癌作用，因此，各种！ 这一过程的组成部分是发展基于机制的抗癌药物的中心目标， 化学预防药物在化学诱导的致癌作用的小鼠皮肤模型中，肿瘤促进是通过以下方式实现的： 将致癌物处理的表皮暴露于佛波醇酯，其诱导那些角质形成细胞的克隆扩增 携带致癌物诱导的H-Ras基因激活突变。佛波醇与苯并三氮唑 酯和Ras信号在肿瘤促进中的作用尚未确定。虽然蛋白激酶C（PKC）在历史上 被认为是负责所有佛波醇酯的行动，非PKC受体的发现投下了怀疑， 假设一个排他性的PKC介导的作用。我们最近将新的Ras激活剂RasGRP 1表征为 佛波酯的高亲和力受体，我们的初步数据表明，RasGRP 1在表皮表达 角质形成细胞是化学致癌作用的靶细胞。这些数据表明，RasGRP 1可能代表了一种新的， Ras和佛波酯信号在表皮中的直接联系。本提案将处理这一可能性。 我们假设佛波醇酯可以调节角质形成细胞中RasGRP 1的活性，并且这种调节 有助于在癌症形成期间通过肿瘤促进激活的机制。测试的具体目标是 假设：（1）确定RasGRP 1在佛波醇酯诱导的反应中的功能作用， 角质形成细胞，包括生长停滞，分化和凋亡;（2）确定RasGRP 1信号传导是否改变 在启动的（H-Ras突变的）角质形成细胞中，通过RasGRP 1表达水平的变化， 底物亲和性或两者兼而有之;以及（3）建立体内模型以研究RasGRP 1在皮肤癌发生中的作用 和肿瘤促进（RasGRP 1的敲除和转基因动物）。总的来说，这项研究的结果 潜在的解开一个新的分子靶点的佛波酯信号的传输参与致癌作用。 这一信息可能会导致未来的方法，开发新的化学预防化合物靶向肿瘤 _romotion事件。

Tumor promotion is a reversible and non-genotoxic stage in carcinogenesis and, as a consequence, the various ! components of this process are central targets for the development of mechanism-based anticancer and[ chemopreventive drugs. In the mouse skin model of chemical-induced carcinogenesis, tumor promotion is achieved by] exposure of carcinogen-treated epidermis to phorbol esters, which induce the clonal expansion of those keratinocytes carrying the carcinogen-induced activating mutation in the H-Ras gene. The nature of the interaction between phorbol esters and Ras signaling in tumor promotion has not been defined yet. Although protein kinase C (PKC) has historically been considered responsible for all phorbol ester actions, the discovery of non-PKC receptors casts doubts on the assumption of an exclusive PKC-mediated effect. We have recently characterized the novel Ras activator RasGRP1 as a high affinity receptor for phorbol esters, and our preliminary data indicate that RasGRP1 is expressed in the epidermal keratinocyte, the target cell in chemical carcinogenesis. These data suggest that RasGRP1 may represent a novel and direct link between Ras and phorbol ester signaling in the epidermis. The present proposal will address this possibility. We hypothesize that phorbol esters can modulate RasGRP1 activity in keratinocytes, and that this modulation contributes to the mechanisms activated by tumor promotion during cancer formation. The specific aims to test the hypothesis are: (1) to define the functional role of RasGRP1 on the responses induced by phorbol esters in keratinocytes, including growth arrest, differentiation, and apoptosis; (2) to determine if RasGRP1 signaling is altered in initiated (H-Ras-mutated) keratinocytes, either by changes in the level of expression of RasGRP1, changes in substrate affinity, or both; and (3) to establish in vivo models to investigate the role of RasGRP1 in skin carcinogenesis and tumor promotion (knockout and transgenic animals for RasGRP1). Taken together, the results of this study have the potential to unravel a new molecular target for the transmission of phorbol ester-signals involved in carcinogenesis. This information could lead to future approaches for developing novel chemopreventive compounds targeted to tumor _romotion events.