Mechanism of Action of TOP2-Directed Anticancer Drugs

TOP2靶向抗癌药物的作用机制

• 批准号: 7526710
• 负责人: LEROY F LIU
• 金额: $ 28.11万
• 依托单位: UNIV OF MED/DENT NJ-R W JOHNSON MED SCH
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-03-10 至 2013-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7526710
• 关键词: Acute Myelocytic Leukemia; Adverse effects; Animal Model; Antineoplastic Agents; Apoptotic; Binding; Bortezomib; Caspase Inhibitor; Cell Cycle; Cells; Chimeric Proteins; Chromosomal translocation; Chromosome Condensation; Clinic; Complex; Cultured Cells; DNA; DNA Double Strand Break; DNA Sequence Rearrangement; DNA biosynthesis; DNA-Directed RNA Polymerase; Development; Down-Regulation; Doxorubicin; Drug Delivery Systems; Equilibrium; Etoposide; Event; Exhibits; Foundations; Gene Expression; Gene Fusion; Genes; Genetic Transcription; Goals; Hematopoietic; Human; Isoenzymes; Knockout Mice; Lead; Link; MLL gene; Mediating; Mitoxantrone; Molecular; Mus; Myeloid Progenitor Cells; Nonhomologous DNA End Joining; Pathway interactions; Pharmaceutical Preparations; Play; Proliferating; Proteasome Inhibition; Protein Overexpression; Proteins; Public Health; Role; Skin; Skin Carcinogenesis; Stem cells; Testing; Therapy-Related Acute Myeloid Leukemia; Topoisomerase II; Ubiquitin; base; cancer therapy; improved; molecular modeling; mouse model; multicatalytic endopeptidase complex; neoplastic cell; novel; nuclease; promoter; segregation; small hairpin RNA; stem

DESCRIPTION (provided by applicant): The long-term goal of this application is to understand the mechanism of action of topoisomerase II (Top2)-targeting drugs. Top2-targeting drugs such as etoposide (VP-16), doxorubicin and mitoxantrone are among the most effective and widely used anticancer drugs in the clinic. Despite their impressive antitumor activities, Top2-targeting drugs are known to cause serious side effects such as t-AML (therapy-related acute myeloid leukemia). Etoposide-induced t-AML is frequently associated with balanced translocations of the mixed lineage leukemia gene (MLL) and many MLL partner genes, resulting in the expression of MLL fusion proteins. There has been substantial evidence that these translocations are primarily the consequence of etoposide-induced DNA cleavage(s) within the breakpoint cluster region (BCR) of the human MLL gene. Both Top2 and CAD (an apoptotic nuclease) have been shown to be involved in etoposide-induced DNA cleavage(s) within the MLL BCR. Our recent studies have suggested that the two Top2 isozymes, Top21 and Top22 may play different roles in the antitumor activity and side effects of Top2-targeting drugs. Top21 targeting has been suggested to contribute to the antitumor activity of etoposide while the role of Top22 targeting by etoposide is unclear. Our preliminary studies have demonstrated that Top22 targeting by etoposide triggers transcription-dependent, proteasome-mediated degradation of Top22 (Top22 down-regulation), resulting in the exposure of Top22-concealed DNA double-strand breaks. In addition, Top22 is primarily responsible for etoposide-induced DNA sequence rearrangements and skin carcinogenesis. In the current proposal, we plan to test the hypothesis that the Top22 isozyme is primarily responsible for etoposide-induced MLL translocations and t-AML. In addition, we plan to elucidate the molecular mechanism for etoposide-induced MLL translocations by determining the roles of Top22 isozyme, proteasome and CAD using both cell culture and animal models. The specific aims are (1) to determine the role of the Top22 isozyme in etoposide-induced MLL translocations and t-AML, (2) to determine whether proteasome and the apoptotic nuclease CAD are involved in etoposide-induced MLL translocations and t-AML, and (3) to elucidate the molecular mechanism for etoposide-induced Top22 down-regulation. Successful completion of the proposed studies will not only advance our understanding of the molecular basis for Top2 drug-induced t-AML but also provide a theoretical foundation for developing Top2 isozyme-specific anticancer drugs, as well as new strategies, for more efficacious Top2-based cancer therapy. PUBLIC HEALTH RELEVANCE: The successful demonstration of the role of Top22 in MLL translocations will provide the necessary theoretical foundation for developing Top21 isozyme-specific anticancer drugs which are expected to exhibit reduced toxic side effects (e.g. t-AML). In addition, elucidation of the molecular basis for etoposide-induced MLL translocations can also lead to development of new strategies for improving current Top2-based therapy. For example, ICRF-187 (for specific down-regulation of Top22), bortezomib (for inhibition of proteasome) or caspase inhibitors (for blocking CAD activation) could be employed to reduce the toxic side effects associated with current Top2-based therapy.

描述（申请人提供）：本申请的长期目标是了解拓扑异构酶II（Top2）靶向药物的作用机制。依托泊苷（VP-16）、阿霉素和米托蒽醌等Top2靶向药物是临床上最有效、最广泛使用的抗癌药物。尽管 Top2 靶向药物具有令人印象深刻的抗肿瘤活性，但已知会引起严重的副作用，例如 t-AML（治疗相关的急性髓系白血病）。依托泊苷诱导的 t-AML 通常与混合谱系白血病基因 (MLL) 和许多 MLL 伴侣基因的平衡易位相关，从而导致 MLL 融合蛋白的表达。有大量证据表明，这些易位主要是人类 MLL 基因断点簇区域 (BCR) 内依托泊苷诱导的 DNA 裂解的结果。 Top2 和 CAD（一种凋亡核酸酶）均已被证明参与 MLL BCR 内依托泊苷诱导的 DNA 切割。我们最近的研究表明，两种Top2同工酶Top21和Top22可能在Top2靶向药物的抗肿瘤活性和副作用中发挥不同的作用。 Top21 靶向被认为有助于依托泊苷的抗肿瘤活性，而依托泊苷靶向 Top22 的作用尚不清楚。我们的初步研究表明，依托泊苷靶向 Top22 会触发转录依赖性、蛋白酶体介导的 Top22 降解（Top22 下调），从而导致 Top22 隐藏的 DNA 双链断裂暴露。此外，Top22 主要负责依托泊苷诱导的 DNA 序列重排和皮肤癌发生。在当前的提案中，我们计划检验 Top22 同工酶主要负责依托泊苷诱导的 MLL 易位和 t-AML 的假设。此外，我们计划通过细胞培养和动物模型确定 Top22 同工酶、蛋白酶体和 CAD 的作用，阐明依托泊苷诱导的 MLL 易位的分子机制。具体目标是 (1) 确定 Top22 同工酶在依托泊苷诱导的 MLL 易位和 t-AML 中的作用，(2) 确定蛋白酶体和凋亡核酸酶 CAD 是否参与依托泊苷诱导的 MLL 易位和 t-AML，以及 (3) 阐明依托泊苷诱导的 Top22 下调的分子机制。拟议研究的成功完成不仅将增进我们对Top2药物诱导的t-AML分子基础的理解，而且为开发Top2同工酶特异性抗癌药物以及更有效的基于Top2的癌症治疗提供新策略提供理论基础。公共健康相关性：Top22 在 MLL 易位中的作用的成功证明将为开发 Top21 同工酶特异性抗癌药物提供必要的理论基础，这些药物有望减少毒副作用（例如 t-AML）。此外，阐明依托泊苷诱导的 MLL 易位的分子基础也可以导致开发新策略来改进当前基于 Top2 的治疗。例如，ICRF-187（用于特定下调 Top22）、硼替佐米（用于抑制蛋白酶体）或半胱天冬酶抑制剂（用于阻断 CAD 激活）可用于减少与当前基于 Top2 的疗法相关的毒副作用。