The System of Response to DNA Damage Suppresses Environmental Melanomagenesis

该计划将使用系统生物学方法来研究人类黑素细胞经历肿瘤性转化、克隆性扩张和恶性进展为皮肤黑色素瘤的机制(S)。拟议的研究是基于这样一个前提，即环境致癌物质太阳辐射通过诱导增殖中的黑素细胞染色体损伤而促进黑色素瘤的发展。恶性黑色素瘤是一个重大的公共卫生问题，因为其发病率正在上升，而且没有有效的医疗干预措施来降低发病率和死亡率。该计划的指导性假设是，对DNA损伤防御系统的崩溃是微核细胞获得突变子表型的基础，这种突变子表型减少了诱导癌症多阶段发展的每个后续步骤所需的太阳辐射的有效剂量。DNA修复和细胞周期检查点的功能缺陷单独或共同导致基因组不稳定，从而增加黑色素瘤发展所需基因改变在单个克隆中积累的可能性。三个研究项目和三个服务核心将广泛互动，以定量和定性地监测紫外线损伤的人和鼠黑素细胞对DNA损伤的反应系统。两个研究项目将确定核苷酸切除修复、复制后修复、双链断裂修复和细胞周期检查点对紫外线诱导的DNA损伤的反应如何协作，以抑制黑色素瘤肿瘤抑制基因CDKN2A/INK4a中的染色体异常和等位基因缺失。功能分析将黑色素瘤细胞系和黑素细胞中的染色体不稳定和缺陷DNA损伤反应与黑色素瘤基因的变化联系起来。第三个研究项目使用小鼠和人类黑色素瘤的体内模型来监测黑色素瘤发展阶段的染色体不稳定。项目调查将确定黑色素瘤癌基因的激活突变和黑色素瘤抑制基因的失活突变如何导致染色体不稳定和恶性进展。新的发现将导致发现对特定类型的黑色素瘤和黑色素瘤进展的不同阶段具有潜在治疗和预后价值的生物标记物。将建立计算模型来预测DNA修复和检查点功能如何抑制紫外线诱导的染色体损伤。这些研究将确定与黑色素瘤相关的基因改变单独和组合在一起对紫外线染色体变种表型的贡献程度，并增强环境致癌作用。从这个项目中学到的经验教训也将影响风险评估的方法，因为它表明致癌物质的有效剂量在癌症的多步骤发展过程中下降。

This program will use a systems biology approach to investigate the mechanism(s) whereby human melanocytes undergo neoplastic transformation, clonal expansion, and malignant progression to cutaneous melanomas. The proposed studies are based on the premise that an environmental carcinogen, solar radiation, contributes to development of melanoma by inducing chromosomal damage in proliferating melanocytes. Malignant melanomas are of significant public health concern because their incidence is rising and no effective medical intervention is available for reducing morbidity and mortality. The guiding hypothesis of this program is that breakdowns in the systems of defense against DNA damage underlie the acquisition by meianocytes of a mutator phenotype, which reduces the effective dose of solar radiation needed to induce each subsequent step in the multi-stage development of cancer. Functional defects in DNA repair and cell cycle checkpoints, individually and in concert, contribute to genome destabilization, and thus increase the probability of accumulation in a single clone of the genetic alterations required for development of melanoma. Three research projects and three service cores will interact extensively to monitor quantitatively and qualitatively the system of response to DNA damage in UV-damaged human and murine melanocytes. Two research projects will determine how nucleotide excision repair, post-replication repair, double-strand break repair, and cell cycle checkpoint responses to UV-induced DNA damage cooperate to suppress chromosomal aberrations and allelic deletions in the melanoma tumor suppressor locus CDKN2A/INK4A. Functional assays will associate chromosomal instability and defective DNA damage responses in melanoma cell lines and melanocytes with alterations in melanomagenic genes. A third research project uses in vivo models of melanoma in mice and humans to monitor chromosomal destabilization during stages of development of melanoma. Program investigations will determine how activating mutations in melanoma oncogenes and inactivating mutations in melanoma suppressor genes contribute to chromsomal instability and malignant progression. New findings will lead to the discovery of biomarkers with potential therapeutic and prognostic value for specific types of melanomas and different stages of melanoma progression. Computational models will be created to predict how DNA repair and checkpoint functions suppress UV-induced chromsomal damage. These studies will establish the degree to which melanoma-associated genetic alterations alone and in combinations contribute to a UV-chromosomalmutator phenotype and enhance environmental carcinogenesis. Lessons learned in this program will also impact on methods of risk assessment by showing that the effective dose of a carcinogen falls during the multi-step development of cancer.