Inhibition of skin cancer by caffeine: Effects on late stages of carcinogenesis

描述（由申请人提供）：阳光诱导的皮肤癌是美国最常见的癌症。在早期的研究中，我们用UVB每周两次治疗SKH-1小鼠，持续20周。这些启动的小鼠没有肿瘤，但它们在接下来的几个月内有很高的发展肿瘤的风险（高风险小鼠）。每周5天对这些高危小鼠局部应用咖啡因抑制了肿瘤的发生，并选择性地增加了肿瘤中的细胞凋亡，但在远离肿瘤的表皮区域中没有。我们的主要假设是咖啡因通过抑制ATR/Chk 1依赖的G2/M细胞周期检查点导致过早的有丝分裂和细胞死亡来诱导细胞凋亡。在准备对咖啡因对人类的影响进行转化研究时，我们评估了公众常用的四种商业保湿霜的致瘤性。所有四个有致瘤活性时，局部应用于高风险小鼠几个月。为了克服这一障碍，我们开发了一种新的自定义混合霜，它缺乏致瘤活性，可用于人类的转化研究。我们计划实现以下具体目标：1.确定在我们新开发的非致瘤性Custom Blend乳膏中局部应用咖啡因对UVB预处理的高风险SKH-1小鼠的致癌作用的影响，并研究治疗对表皮和肿瘤局部增生区域中的细胞凋亡、增殖和ATR/Chk 1信号转导通路的影响。还将研究口服咖啡因的效果。2.通过研究短期治疗（例如，局部应用咖啡因3小时、6小时、24小时、48小时、7天或14天）后，在表皮局灶性增生区域和肿瘤中基于Aim 1的关键分子标志物上的作用，确定咖啡因作用的主要靶点或早期事件。3.启动一项转化研究，以确定局部应用咖啡因对人类皮肤光化性角化病细胞凋亡、增殖和ATR/Chk 1通路的影响。通过目标1中的研究确定的关键分子标志物将在局部应用咖啡因或安慰剂两周之前和之后的大角化病活检中确定。公共卫生相关性：我们提出的关于咖啡因对紫外线诱导的癌症形成的影响的机制研究是开发预防日光诱导的皮肤癌的新方法的重要步骤。我们对咖啡因影响的研究也可能对摄入含咖啡因饮料和巧克力的人有重要意义。

DESCRIPTION (provided by applicant): Sunlight-induced skin cancer is the most prevalent cancer in the United States. In earlier studies we treated SKH-1 mice with UVB twice a week for 20 weeks. These initiated mice have no tumors, but they have a high risk of developing tumors during the next several months (high risk mice). Topical applications of caffeine 5 days a week to these high risk mice inhibited carcinogenesis and selectively increased apoptosis in the tumors but not in areas of the epidermis away from the tumors. Our leading hypothesis is that caffeine induces apoptosis by inhibition of the ATR/Chk1-dependent G2/M cell cycle checkpoint leading to premature mitosis and cell death. In preparation for translational studies on the effects of caffeine in humans, we evaluated the tumorigenicity of four commercial moisturizing creams that are commonly used by the public. All four had tumorigenic activity when applied topically for several months to high risk mice. To overcome this obstacle, we developed a novel Custom Blend cream that lacks tumorigenic activity and can be used for translational studies in humans. We plan to pursue the following specific aims: 1. Determine the effects of topical applications of caffeine in our newly developed non-tumorigenic Custom Blend cream on carcinogenesis in UVB-pretreated high risk SKH-1 mice and study the effects of the treatment on apoptosis, proliferation and the ATR/Chk1 signal transduction pathway in focal hyperplastic areas of the epidermis and in tumors. The effects of oral administration of caffeine will also be studied. 2. Determine the primary targets or early events for the action of caffeine by studying its effect on key molecular markers based on Aim 1 in epidermal focal hyperplastic areas and tumors after short term treatment (e.g. with topically applied caffeine for 3 hr, 6 hr, 24 hr, 48 hr, 7 days, or 14 days). 3. Initiate a translational study to determine the effects of topical applications of caffeine on apoptosis, proliferation and the ATR/Chk1 pathway in actinic keratoses in human skin. Key molecular markers identified by research in Aim 1 will be determined in biopsies of large keratoses before and after two weeks of topical applications of caffeine or placebo. PUBLIC HEALTH RELEVANCE:Our proposed mechanistic studies on the effects of caffeine on ultraviolet light-induced cancer formation are important steps on the road to the development of a novel approach for the prevention of sunlight-induced skin cancer. Our studies on the effects of caffeine may also have importance for individuals ingesting caffeine-containing beverages and chocolate.