GENETIC AND GENOMIC RESPONSES TO DNA DAMAGE

随着对某些癌症更成功的治疗方法的发展，继发性恶性肿瘤已经成为一个越来越重要的问题。此外，最近对接受大剂量化疗、使用造血生长因子或造血系统细胞支持的患者的支持性护理的进展，导致接受长时间和大剂量DNA损伤治疗的患者数量急剧增加。已经设计了一种研究这种治疗的分子效应的方法，使用的是通过过表达凋亡抑制因子Bclxl而使细胞抵抗程序性细胞死亡的细胞。基因差异显示已经被用来比较化疗药物存在和不存在的情况下具有不同作用机制的基因表达。这项技术导致了一些转录本的识别，这些转录本因长期接触破坏DNA的化疗而特别上调。在鉴定的转录本中，有一个逆转座子家族的成员。通过这项技术确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。细胞程序性死亡是抵御遭受重大DNA损伤或染色体异常的细胞持续增殖的关键防御机制。主要的基因组重排和非整倍体是癌症中常见的事件，这表明从DNA损伤到细胞程序性死亡的信号通路在大多数癌细胞中存在缺陷。这一反应途径的缺陷可能是导致致癌转化中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，正在使用逆转录病毒cDNA库对参与这一凋亡信号通路的因素进行遗传筛选。在化疗敏感的肿瘤中，暴露于DNA损伤的化疗与诱导程序性细胞死亡或凋亡有关。暴露于这些制剂也与继发性恶性肿瘤特有的染色体重排有关。这项提议试图更好地定义这两种分子途径，从DNA损伤到细胞程序性死亡，以及从DNA损伤到染色体异常。了解细胞对DNA损伤的各种反应的分子基础对于设计化学预防和治疗抗癌策略都是相关的。

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.