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

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。据估计，美国每年报告的皮肤癌新病例约为100万例。通过暴露在紫外线(UV)辐射或环境化学物质中启动皮肤肿瘤发生涉及到DNA损伤的获得。癌前或“启动”细胞随后的克隆性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。这项建议的主要目的是确定caspase-2是否在消除皮肤癌小鼠模型中具有遗传损伤的细胞方面发挥作用。这项研究的基本原理是基于令人振奋的新证据，这些证据表明，DNA损伤诱导的转化或肿瘤来源的人类细胞系在很大程度上依赖于caspase-2的激活。特别是，申请人的发现表明，caspase-2的激活发生在线粒体细胞色素c释放的上游，并形成apaf-1凋亡体，以响应DNA破坏的抗肿瘤药物依托泊苷。这些观察，再加上caspase-2基因敲除小鼠缺乏戏剧性表型的知识，表明虽然caspase-2对于正常的发育细胞杀伤是必不可少的，但它可能在病理细胞杀伤中发挥基础作用。需要检验的假设是，caspase-2对于处理DNA受损的细胞至关重要，以防止突变积累和/或癌前细胞的克隆性扩张。Caspase-2基因敲除小鼠和野生型小鼠将用于这些研究，并将在组织病理学和分子水平上分析它们对致癌物质的反应，包括化学和物理上的。为了验证这一假说，提出了以下具体目标：1)确定caspase-2的缺失是否改变了体内角质形成细胞在紫外线辐射或引发剂7，12-二甲基苯(A)菲(DMBA)照射后发生凋亡的敏感性；2)确定紫外线或DMBA(肿瘤促进剂12-十八烷酰佛波醇-13-乙酸酯(TPA)治疗是否导致肿瘤形成，这是否与caspase-2基因敲除小鼠与野生型小鼠相比，促进细胞增殖和/或抑制表皮细胞凋亡相一致；3)检测野生型或caspase-2基因缺陷小鼠培养的新生角质形成细胞对DNA损伤诱导的细胞凋亡的敏感性。总之，这些研究将为Caspase-2、S通过促进诱变剂暴露后角质形成细胞的凋亡来调节体内肿瘤发展的能力提供重要的新信息。

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.