Molecular Determinants of Methotrexate in ALL

甲氨蝶呤治疗 ALL 的分子决定因素

• 批准号: 6885795
• 负责人: JULIO C BARREDO
• 金额: $ 29.93万
• 依托单位: MEDICAL UNIVERSITY OF SOUTH CAROLINA
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-05-01 至 2009-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6885795
• 关键词: acute lymphocytic leukemia; adolescence (12-20); child (0-11); clinical research; drug metabolism; drug resistance; gene expression; human subject; human therapy evaluation; methotrexate; neoplasm /cancer chemotherapy; patient oriented research; pediatric neoplasm /cancer; pediatric pharmacology; pharmacokinetics; polymerase chain reaction; posttranslational modifications; relapse /recurrence; single nucleotide polymorphism; site directed mutagenesis; tetrahydrofolylpolyglutamate synthase; western blottings

DESCRIPTION (provided by applicant): This research project aims to increase our understanding of the mechanisms of action and resistance to methotrexate (MTX), a universal component of therapies for children with acute lymphoblastic leukemia (ALL). The long-term objectives are to incorporate this knowledge in the design of ALL trials based on novel molecular targets and to improve event-free survival (EFS) for patients with resistant phenotypes. Even though the antifolate MTX is widely used in ALL therapies, important unanswered questions remain with respect to molecular determinants of drug resistance, heterogeneity of clinical response, optimal dose(s) and schedule(s). It has been demonstrated that lymphoblast accumulation of MTX polyglutamates (MTX-PGs) correlates with clinical outcome. Metabolism to MTX-PGs depends on serum MTX concentration, transport across the cell membrane, and more important the cell lineage-specific expression of Folyl-gamma-polyglutamate Synthetase (FPGS). Non-random translocations that characterize ALL clones are important predictors of clinical outcome and characterize ALL subtypes that exhibit significant heterogeneity of FPGS expression. Due to their effects on gene transcription and cell cycle control, non-random translocations may alter drug metabolism and resistance. We hypothesize that molecular mechanisms associated with non-random translocations lead to differences in metabolism to MTX-PGs by altering lymphoblast FPGS expression. We propose these translocations represent molecular "pathways" present in leukemic clones that result in the heterogeneity of FPGS expression, patterns of MTX metabolism, and clinical response to MTX seen in childhood ALL subtypes. In addition, single nucleotide polymorphisms (SNPs) of FPGS have been recently identified in an ethnically diverse panel of individuals. We propose these SNPs also contribute to the heterogeneity of PFGS expression in ALL, and their prevalence and physiologic impact will be investigated. In addition, drug-induced mutations leading to in vitro resistance to anti-folates have been described. Consequently, we also hypothesize that drug-induced mutations of FPGS can be detected at the time of relapse from ALL and may represent a novel mechanism of resistance after relapse. More important, because these genetic abnormalities are not present in normal hematopoietic cells, they offer selective targets for gene therapy or other molecular approaches in ALL.

描述（由申请人提供）：该研究项目旨在加深我们对甲氨蝶呤 (MTX) 的作用机制和耐药性的了解，甲氨蝶呤 (MTX) 是儿童急性淋巴细胞白血病 (ALL) 治疗的通用组成部分。长期目标是将这些知识纳入基于新分子靶点的 ALL 试验设计中，并提高耐药表型患者的无事件生存期 (EFS)。尽管抗叶酸剂 MTX 广泛用于 ALL 治疗，但在耐药性的分子决定因素、临床反应的异质性、最佳剂量和时间表方面仍然存在重要的未解答问题。已证明淋巴母细胞中 MTX 聚谷氨酸盐 (MTX-PG) 的积累与临床结果相关。 MTX-PG 的代谢取决于血清 MTX 浓度、跨细胞膜的转运，更重要的是叶酰-γ-聚谷氨酸合成酶 (FPGS) 的细胞谱系特异性表达。表征 ALL 克隆的非随机易位是临床结果的重要预测因子，并且表征表现出 FPGS 表达显着异质性的 ALL 亚型。由于它们对基因转录和细胞周期控制的影响，非随机易位可能会改变药物代谢和耐药性。我们假设与非随机易位相关的分子机制通过改变淋巴母细胞 FPGS 表达而导致 MTX-PG 代谢差异。我们认为这些易位代表了白血病克隆中存在的分子“途径”，导致儿童 ALL 亚型中 FPGS 表达、MTX 代谢模式以及对 MTX 的临床反应的异质性。此外，最近在不同种族的个体中发现了 FPGS 的单核苷酸多态性 (SNP)。我们认为这些 SNP 也导致 ALL 中 PFGS 表达的异质性，并且将研究它们的患病率和生理影响。此外，已经描述了导致体外对抗叶酸剂耐药的药物诱导突变。因此，我们还假设药物诱导的 FPGS 突变可以在 ALL 复发时检测到，并且可能代表复发后的一种新的耐药机制。更重要的是，由于正常造血细胞中不存在这些遗传异常，因此它们为 ALL 的基因治疗或其他分子方法提供了选择性靶点。