INBRE: KUMC: ROLE OF CASPASE-2 IN SKIN CANCER PREVENTION

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。据估计，美国每年约有100万皮肤癌新病例。暴露于紫外线（UV）辐射或环境化学物质引发的皮肤肿瘤发生涉及DNA损伤的获得。肿瘤前或“起始”细胞的克隆扩增不仅取决于细胞增殖的增加，还取决于细胞凋亡率的降低。这项提议的主要目的是确定caspase-2是否在消除皮肤癌变小鼠模型中具有遗传病变的细胞中发挥作用。这条研究路线的基本原理是基于令人兴奋的新证据，表明DNA损伤诱导的转化或肿瘤衍生的人类细胞系的凋亡在很大程度上取决于caspase-2的激活。特别是，申请人的研究结果表明，caspase-2激活发生在线粒体细胞色素c释放和Apaf-1凋亡体形成的上游，以响应dna损伤的抗肿瘤药物依托oposide。这些观察结果，结合caspase-2敲除小鼠缺乏戏剧性表型的知识，表明尽管caspase-2在正常发育细胞杀伤中是必不可少的，但它可能在病理细胞杀伤中发挥基本作用。待验证的假设是，caspase-2对于处理DNA受损的细胞至关重要，以防止突变的积累和/或肿瘤前细胞的克隆扩增。Caspase-2敲除小鼠和野生型小鼠将用于这些研究，它们对化学和物理致癌物质的反应将在组织病理学和分子水平上进行分析。为了验证这一假设，我们提出了以下具体目标：1)确定caspase-2的缺乏是否会改变体内角质形成细胞在暴露于紫外线辐射或引发剂7,12-二甲基苯(a)蒽（DMBA）后发生凋亡的易感性；2)确定UV或DMBA -肿瘤启动子12- Otetradecanoylphorbol- 13-acetate （TPA）处理是否导致肿瘤形成，以及这是否与caspase-2敲除小鼠表皮细胞增殖增加和/或细胞凋亡抑制相一致；3)测定野生型或caspase-2缺陷小鼠培养的新生角质形成细胞对DNA损伤诱导的凋亡的敏感性。综合起来，这些研究将提供关于caspase-2？在诱变原暴露后，通过促进角质形成细胞的凋亡来调节体内肿瘤发展的能力。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Estimates indicate that about one million new cases of skin cancer are reported in the United States annually. Initiation of skin tumorigenesis by exposure to ultraviolet (UV) radiation or environmental chemicals involves the acquisition of DNA lesions. Subsequent clonal expansion of preneoplastic or "initiated" cells depends not only on increased cell proliferation but also on a decreased rate of cells undergoing apoptosis. The broad objective of this proposal is to determine whether caspase-2 plays a role in the elimination of cells with genetic lesions in a mouse model of skin carcinogenesis. The rationale for this line of investigation is based on exciting new evidence indicating that DNA damage-induced apoptosis of transformed or tumor-derived human cell lines depends to a large extent upon caspase-2 activation. In particular, the applicant's findings demonstrated that caspase-2 activation occurs upstream of mitochondrial cytochrome c release and formation of the Apaf-1 apoptosome in response to the DNA-damaging antineoplastic drug etoposide. These observations, combined with the knowledge that caspase-2 knockout mice lack a dramatic phenotype, suggest that while caspase-2 is dispensable for normal developmental cell killing, it may play a fundamental role in pathological cell killing. The hypothesis to be tested is that caspase-2 is critical for the disposal of cells with damaged DNA to prevent the accumulation of mutations and/or the clonal expansion of preneoplastic cells. Caspase-2 knockout and wild-type mice will be used for these studies and their response to carcinogenic agents, both chemical and physical, will be analyzed at the histopathological and molecular levels. The following specific aims are proposed to test the hypothesis: 1) Determine whether a deficiency of caspase-2 alters the susceptibility of keratinocytes in vivo to undergo apoptosis following exposure to either UV radiation or the initiating agent 7,12- dimethylbenz(a)anthracene (DMBA); 2) Determine whether UV or DMBA ¿ the tumor promoter 12- Otetradecanoylphorbol- 13-acetate (TPA) treatment results in tumor formation and whether this coincides with increased cell proliferation and/or a suppression of apoptosis in the epidermis of caspase-2 knockout versus wild-type mice; and 3) Determine the susceptibility of cultured neonatal keratinocytes from wild-type or caspase-2-deficient mice to DNA damage-induced apoptosis. Combined, these studies will provide critical new information about caspase-2?s ability to modulate tumor development in vivo by promoting apoptosis of keratinocytes after mutagen exposure.