The Role of C/EBPa in Genome Stability and Tumor Progression

描述(申请人提供)：癌症是一种由体细胞基因组改变引起的疾病，是基因改变的积累推动了肿瘤的发生。此外，发育中的肿瘤细胞获得这些基因改变的速度最终决定了癌症的发生。人类皮肤经常受到太阳辐射引起的DNA损伤，角质形成细胞已经发展出复杂的途径来响应UVB诱导的DNA损伤。最近，我们首次提供了CCAAT/增强子结合蛋白1(C/EBP1)的遗传学证据，它是碱性亮氨酸拉链转录因子家族的成员，通过利用小鼠表皮靶向切除C/EBP1发挥上皮肿瘤抑制作用。这些小鼠对UVB和致癌物诱导的鳞状乳头状瘤发展高度敏感，这些良性皮肤肿瘤表现出高度加速的恶性进展为鳞状细胞癌。人皮肤鳞状细胞癌和基底细胞癌以及小鼠皮肤鳞状细胞癌表现为弱表达或消融的C/EBP1表达。综上所述，这些发现表明C/EBP1在皮肤癌中通过维持基因组发挥肿瘤抑制功能。我们假设，C/EBP1表达的减少或去除会导致DNA损伤诱导的G1检查点受损，从而导致体细胞突变的积累，促进皮肤癌的进展。这项建议的总体目标是了解C/EBP1缺失如何导致恶性肿瘤进展速度的增加，重点是C/EBP1在DNA损伤诱导的G1检查点中的作用。为了达到这一目的，我们的目标是1)描述C/EBP1在DNA损伤诱导的G1检查点中发挥作用的分子机制，2)为C/EBP1消融后基因组不稳定/突变子表型增加提供分子证据。。 公共卫生相关性：了解C/EBP1如何影响癌症进展速度和突变的获得，将为进一步深入了解致癌物和UVB诱导的皮肤癌以及许多C/EBP1表达降低的癌症的机制提供帮助。最近对人类癌症基因组的分析发现，特定癌症相关基因的突变在特定的肿瘤类型中可能会有很大差异，并表明识别基因组点突变的来源可能是一种比针对特定癌症基因更有效的治疗策略，因为其他基本基因的突变将被突变子表型增强和选择。针对点突变遗传不稳定性的药物可能会延迟突变的积累，从而防止癌症的发生。

DESCRIPTION (provided by applicant): Cancer is a disease that arises from genomic alterations in somatic cells and it is the accumulation of genetic alterations that drives tumorigenesis. Moreover, it is the rate at which a developing tumor cell acquires these genetic alterations that ultimately determines the onset of cancer. Human skin is routinely subjected to DNA damage induced by solar radiation and keratinocytes have developed intricate pathways to response to UVB-induced DNA damage. Recently, we provided the first genetic evidence CCAAT/enhancer binding protein 1 (C/EBP1), a member of the basic leucine zipper family of transcription factors, functions as an epithelial tumor suppressor through utilization of mice with an epidermal-targeted ablation of C/EBP1. These mice are highly susceptible to UVB- and carcinogen-induced squamous papilloma development and these benign skin tumors display a highly accelerated rate of malignant progression to squamous cell carcinomas. Human skin squamous cell carcinomas and basal cell carcinomas as well as mouse skin squamous carcinomas display weak or ablated expression of C/EBP1. Together these findings suggest a tumor suppressor function of C/EBP1 in skin cancer through maintenance of the genome. We hypothesize that reduced or ablated expression of C/EBP1 results in an impaired DNA damage-induced G1 checkpoint, resulting in the accumulation of somatic mutations and promoting skin cancer progression. The overall objective of this proposal is to understand how the loss of C/EBP1 contributes to an increased rate of malignant tumor progression focusing on the role of C/EBP1 in the DNA damage- induced G1 checkpoint. To address this objective we aim to 1) delineate the molecular mechanism through which C/EBP1 functions in the DNA damaged-induced G1 checkpoint and 2) provide molecular evidence for increased genome instability/mutator phenotype in response to C/EBP1 ablation. . PUBLIC HEALTH RELEVANCE: Understanding how C/EBP1 influences the rate of cancer progression and the acquisition of mutations will provide further insights to the mechanisms of carcinogen- and UVB-induced skin cancer as well as numerous cancers where C/EBP1 expression is diminished. Recent analysis of the genomes from human cancers discovered that mutations in specific cancer associated genes can vary dramatically within a give tumor type and suggest the identification of the origin of genomic point mutations may be a more effective strategy for cancer treatment than targeting a specific cancer gene as mutations in other essential genes will be enhanced and selected by the mutator phenotype. Drugs that target point mutation genetic instability may delay the accumulation of mutations and subsequently prevent cancer onset.