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转化、克隆扩增和恶性进展为皮肤黑素瘤的机制。提出的研究是基于一个前提，即环境致癌物，太阳辐射，通过诱导增殖黑色素细胞的染色体损伤，促进黑色素瘤的发展。恶性黑色素瘤的发病率正在上升，而且没有有效的医疗干预措施来降低发病率和死亡率，因此引起了重大的公共卫生关注。该计划的指导假设是，防御DNA损伤系统的故障是减数细胞获得突变表型的基础，这减少了在多阶段癌症发展中诱导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，无论是单独的还是共同的，都会导致基因组不稳定，从而增加了黑色素瘤发展所需的遗传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地相互作用，定量和定性地监测紫外线损伤的人类和小鼠黑色素细胞对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损伤的反应如何协同抑制黑色素瘤肿瘤抑制位点CDKN2A/INK4A的染色体畸变和等位基因缺失。功能分析将黑色素瘤细胞系和黑色素细胞的染色体不稳定性和有缺陷的DNA损伤反应与黑色素瘤基因的改变联系起来。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志物。将创建计算模型来预测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多大程度上有助于紫外线染色体突变表型和增强环境致癌作用。通过表明致癌物质的有效剂量在癌症发展的多个阶段中下降，从这个项目中吸取的经验教训也将影响风险评估的方法。

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.