Role of p53 homologs in DNA repair in human keratinocytes

描述(由申请人提供)： 项目摘要/摘要非黑色素瘤皮肤癌是美国普通人群中最常见的恶性肿瘤，在退伍军人中非常常见。虽然这些皮肤癌通常不是致命的，但它们可能是发病率的主要来源，损害生活质量，并利用大量的卫生保健资源。表皮角质形成细胞的DNA累积损伤，尤其是太阳紫外线辐射，是非黑色素瘤皮肤癌发生的重要因素。此外，其他皮肤病的某些治疗方法使用的DNA损伤剂会增加皮肤癌的风险。大而扭曲的DNA损伤可以通过核苷酸切除修复的过程移除，但对角质形成细胞中DNA修复的调节知之甚少。临床观察和最近的体外研究，包括PI实验室的研究，表明人类角质形成细胞具有调节核苷酸切除修复的独特机制。在非角质形成细胞类型中，肿瘤抑制基因P53的缺失通常会导致最丰富的UVR诱导的光产物的修复丧失。然而，目前获奖期间的工作证明，角质形成细胞需要同时失去P53和家族的另一成员P63，然后修复才会受到影响。此外，PI实验室最近的工作表明，P53和P63的双重缺陷与鳞癌的核苷酸切除修复受损有关，这可能被利用来优先杀死这些癌症。目前的建议试图了解P53和P63在正常生理过程中调节人类角质形成细胞DNA修复的机制，并确定它们在非黑色素瘤皮肤癌的发生和行为中的作用。我们假设P53和P63在未分化和终末分化的角质形成细胞中协调调节UVR诱导的主要DNA光产物的修复，这一过程的失调发生在鳞状细胞癌中，并为突变和肿瘤进展提供了一种可能用于治疗的机制。这些假说将通过以下特定目的进行检验：1)确定P53和P63调节角质形成细胞修复蛋白水平的机制；2)确定P63在角质形成细胞分化过程中核苷酸切除修复中的作用；3)评估核苷酸切除修复对角质形成细胞中p63过度表达的反应；以及4)建立、表征和纠正鳞癌中p63介导的修复失调。最后，本项目将阐明表皮皮肤细胞独特的光保护机制的分子基础，使我们能够了解这些机制在皮肤癌发生过程中是如何发挥作用的，并提出预防和治疗皮肤癌的新策略。

DESCRIPTION (provided by applicant): Project Summary/Abstract Non-melanoma skin cancers are the most common malignancies in the general population of the United States and are highly prevalent in the veteran population. While not usually fatal, these skin cancers can be a major source of morbidity, impair quality of life, and utilize significant health care resources. Cumulative DNA damage in epidermal keratinocytes, particularly from solar ultraviolet radiation, is an important factor in the development of non-melanoma skin cancers. In addition, certain therapies for other skin diseases utilize DNA damaging agents that increase the risk of skin cancer. Bulky, distorting DNA lesions are removed by the process of nucleotide excision repair, but little is known about the regulation of DNA repair in keratinocytes. Clinical observations and recent in vitro studies, including those from the PI's laboratory, indicate that human keratinocytes possess unique mechanisms for regulating nucleotide excision repair. Loss of the tumor suppressor, p53, in non-keratinocyte cell types typically results in a loss of repair of the most abundant UVR- induced photoproduct. However, work during the current award period has documented that keratinocytes require loss of both p53 and another member of the family-p63-before repair is compromised. Furthermore, recent work in the PI's laboratory suggests that a dual deficiency in p53 and p63 is associated with impaired nucleotide excision repair in squamous cell carcinomas that could be exploited to preferentially kill these cancers. The current proposal seeks to understand the mechanisms by which p53 and p63 regulate DNA repair in human keratinocytes during normal physiology, and to determine their role in the genesis and behavior of non-melanoma skin cancers. We hypothesize that p53 and p63 coordinately regulate repair of the major UVR-induced DNA photoproducts in both undifferentiated and terminally differentiating keratinocytes, and that dysregulation of this process occurs in squamous cell carcinomas and provides a mechanism for mutagenesis and tumor progression that may be therapeutically exploitable. The hypotheses will be tested by the following Specific Aims: 1) To determine the mechanisms by which p53 and p63 regulate repair protein levels in keratinocytes; 2) To determine the role of p63 in nucleotide excision repair during keratinocyte differentiation; 3) To assess the response of nucleotide excision repair to p63 over-expression in keratinocytes; and 4) To model, characterize and correct p63-mediated repair dysregulation in squamous cell carcinomas. At its conclusion, this project will elucidate the molecular basis of the unique photoprotective mechanisms of epidermal skin cells, allow us to understand how these mechanisms are dysfunctional during skin carcinogenesis, and suggest new strategies for preventing and treating skin cancers.