GENETIC AND GENOMIC RESPONSES TO DNA DAMAGE

随着对某些癌症的治疗越来越成功，继发性恶性肿瘤已成为越来越重要的问题。此外，最近对接受高剂量化疗的患者的支持性护理的进展，包括造血生长因子或造血系统细胞支持，导致接受长时间和高剂量dna损伤治疗的患者数量急剧增加。通过过度表达凋亡抑制剂Bcl-xL使细胞抵抗程序性细胞死亡，设计了一种研究这种治疗的分子效应的方法。差异mRNA显示已被用于比较存在和不存在具有不同作用机制的化疗药物时的基因表达。这项技术已经鉴定出了一些转录本，这些转录本通过长期暴露于dna损伤化疗而特异性上调。在鉴定的转录本中，有一个家族的反转录因子的成员。通过这种技术鉴定的移动元件和其他转录本在细胞对DNA损伤的反应中的作用将被探索。程序性细胞死亡是一种关键的防御机制，防止遭受重大DNA损伤或染色体异常的细胞继续增殖。主要的基因组重排和非整倍体是癌症中常见的事件，这表明在大多数癌细胞中，从DNA损伤到程序性细胞死亡的信号通路是有缺陷的。这种反应途径的缺陷可能是允许致癌转化中涉及的基因组改变的关键。在暴露于dna损伤剂的哺乳动物细胞中，利用逆转录病毒cDNA文库对参与这一凋亡信号通路的因子进行遗传筛选。在化疗敏感肿瘤中，暴露于dna损伤化疗与诱导程序性细胞死亡或细胞凋亡有关。暴露于这些药物也与继发性恶性肿瘤的特征性染色体重排有关。这一建议试图更好地定义这两种分子途径，从DNA损伤到程序性细胞死亡，从DNA损伤到染色体异常。了解各种细胞对DNA损伤反应的分子基础与化学预防和治疗抗癌策略的设计有关。

As more successful therapy for certain cancers has evolved, secondary malignancy has become an increasingly important concern. In addition, recent progress in supportive care for patients undergoing high dose chemotherapy, with hematopoietic growth factors or hematopoietic system cell support, has led to a dramatic increase in the number of patients treated with prolonged and high dose DNA-damaging therapy. A method for studying the molecular effects of such therapy has been designed using cells made resistant to programmed cell death by overexpression of the apoptotic inhibitor Bcl-xL. Differential mRNA display has been used to compare gene expression in the presence and absence of chemotherapeutic agents with various mechanisms of action. This technique has resulted in the identification of a number of transcripts specifically upregulated by prolonged exposure to DNA-damaging chemotherapy. Among the transcripts identified are members of a family of retrotransposable elements. The role of mobile elements and of other transcripts identified by this technique in the cellular response to DNA damage will be explored. Programmed cell death is a critical defense mechanism against the continued proliferation of cells suffering major DNA damage or chromosomal aberrancy. Major genomic rearrangements and aneuploidy are frequent events in cancer, suggesting that the signaling pathway from DNA damage to programmed cell death is defective in the majority of cancer cells. Defects in this response pathway may be critical in permitting the genomic alterations involved in carcinogenic transformation. A genetic screen for factors involved in this apoptotic signaling pathway is being performed using a retroviral cDNA library in mammalian cells exposed to DNA-damaging agents. Exposure to DNA-damaging chemotherapy is associated with induction of programmed cell death, or apoptosis, in chemosensitive tumors. Exposure to these agents has also been associated with characteristic chromosomal rearrangements of secondary malignancies. This proposal seeks to better define both of these molecular pathways, from DNA damage to programmed cell death, and from DNA damage to chromosomal aberrancy. Understanding the molecular basis of the various cellular responses to DNA damage is relevant to the design of both chemopreventative and therapeutic anticancer strategies.