EXTRACHROMOSOMAL DNA--A NEW TARGET FOR ANTITUMOR DRUGS

染色体外DNA（附加体）可以是异常敏感的， 拓扑异构酶II等DNA相互作用抗肿瘤药物的作用 目标代理人。 此外，与基因相关的附加体元件 已经发现在肿瘤细胞和肿瘤中的扩增是 双小染色体的前体和均匀染色区域。 这样的DNA通常含有与肿瘤发生相关的基因（例如c-myc）， 耐药性（如P-糖蛋白）。 该计划的目标是 开发基于附加体作为新靶点的化疗策略， DNA反应性药物的评价。 小鼠成纤维细胞组织培养细胞 系（935.11）由附加体元件肿瘤性转化，用于 评价药物介导的损伤及其在确定的染色体外的修复 体外DNA靶标。 这些相同的细胞也可以作为皮下生长， （s.c.）允许在体内评价药物诱导的小鼠肿瘤 对附加体的损害。 对935.11细胞游离体的损伤程度 体内测定中的序列与治疗功效相关。 基于 在理解DNA反应性药物对 附加体成分 我们将探讨 优先药物诱导的对附加体的损伤。 具体目标： 1)描述游离型元件上药物诱导的病变，并评价 靶向染色体外DNA作为改善 药物治疗策略。 抗肿瘤药物与游离体的相互作用将 使用935.1体外模型系统进行研究。 本研究包括 基于拓扑形式的游离体中DNA损伤的定量 环状DNA的转化以及因子的阐明 导致染色体外DNA相对于基因组DNA的优先损伤。 将在对游离体的损伤和细胞毒性活性之间进行比较。 2)评估治疗效果和选择性 靶向赋予肿瘤表型的附加体DNA。 药物性 附加体的损伤和相应的治疗效果将是 在携带935.1细胞的小鼠中表征为固体s.c.肿瘤 对游离体的定量和定性损伤将是 选择和调度具有改善治疗价值的药物。 3)作为治疗策略的基础，评估增强靶向 抗肿瘤药物对自发发生的附加体， 耐药性和致癌因素。 抗肿瘤药物将是 研究了它们破坏双拷贝的附加型前体的能力， 分钟和含有扩增序列的均质染色区域 耐药性和致癌因素。 将寻求关系 药物对这些DNA的作用和生物反应之间的联系 细胞死亡或表型变化。

Extrachromosomal DNA (episomes) can be extraordinally sensitive to the actions of DNA inter-active antitumor drugs including topoisomerase II targeted agents. Furthermore, episomal elements associated with gene amplification in neoplastic cells and tumors have been found to be precursors of double minute chromosomes and homogeneously staining regions. Such DNAs often contain genes associated with oncogenesis (e.g. c-myc) and drug resistance (e.g. p-glycoprotein). The goal of this program is to develop chemotherapeutic strategies based upon episomes as new targets for evaluation of DNA reactive drugs. A mouse fibroblast tissue culture cell line (935.11) neoplastically transformed by an episomal element is used to evaluate drug mediated damage and its repair on a define extrachromosomal DNA target in vitro. These same cells can also be grown as a sub-cutaneous (s.c.) tumor in mice which allows for in vivo evaluation of drug-induced damage to the episome. The extent of damage to 935.11 cell episomal sequences in the in vivo assay correlates with therapeutic efficacy. Based upon an understanding of the mechanisms of action of DNA reactive drugs on episomal elements. We shall explore the biological consequences of preferential drug induced damage to episomes. SPECIFIC AIMS: 1) To characterize drug-induced lesions on episomal elements and evaluate the potential for targeting extrachromosomal DNA as a means for improving drug treatment strategies. Antitumor drug interaction with episomes will be investigated using the 935.1 in vitro model system. This study includes quantitation of DNA lesions in episomes based on topological forms conversion of the circular DNA as well as elucidation of factors contributing to preferential damage of extrachromosomal versus genomic DNA. Comparisons will be made between damage to episomes and cytotoxic activity. 2) To assess relationships between therapeutic efficacy and selective targeting of episomal DNA that confer neoplastic phenotypes. Drug-induced damage of episomes and corresponding therapeutic efficacy will be characterized in mice bearing the 935.1 cells as a solid s.c. tumor. Quantitative and qualitative damage to the episomes will be the basis for selecting and scheduling drugs with improved therapeutic value. 3) To evaluate as a basis for therapeutic strategies, enhanced targeting of antitumor drugs toward spontaneously occurring episomes which harbor drug resistance and oncogenic factors. Anti-tumor drug will be investigated for their abilities to damage episomal precursors of double minutes and homogenous staining regions containing amplified sequences of drug resistance and oncogenic factors. Relationships will be sought between drug effects on these DNAs and biological responses that lead to cell death or phenotypic changes.