Molecular Determinants of Methotrexate in ALL

甲氨蝶呤治疗 ALL 的分子决定因素

• 批准号: 7333720
• 负责人: JULIO C BARREDO
• 金额: $ 23.18万
• 依托单位: UNIVERSITY OF MIAMI SCHOOL OF MEDICINE
• 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/7333720
• 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(申请人提供)：这项研究项目旨在增加我们对甲氨蝶呤(MTX)的作用机制和耐药性的了解，MTX是治疗儿童急性淋巴细胞白血病(ALL)的通用成分。长期目标是将这一知识纳入基于新分子靶点的所有试验的设计中，并提高耐药表型患者的无事件生存率(EFS)。尽管抗叶酸甲氨蝶呤被广泛用于所有疗法，但关于耐药性的分子决定因素、临床反应的异质性、最佳剂量(S)和方案(S)，仍有一些重要的未回答的问题。已有研究表明，淋巴母细胞中MTX聚谷氨酸酯(MTX-PGs)的蓄积与临床结局相关。对MTX-PGs的代谢依赖于血清MTX浓度，跨细胞膜的转运，更重要的是细胞系特异性的叶基-γ-聚谷氨酸合成酶(Folyl-Gamma-PolyGlamate Synthetase，FPGS)的表达。以所有克隆为特征的非随机易位是临床结果的重要预测指标，也是表现出显着的FPGS表达异质性的所有亚型的特征。由于其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的代谢和耐药性。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的表达而导致对MTX-PGs的代谢差异。我们认为，这些易位代表了白血病克隆中存在的导致FPGS表达、MTX代谢模式和临床反应的异质性的白血病克隆，在儿童所有亚型中都可以看到。此外，最近在一个不同种族的个体中发现了FPGS的单核苷酸多态(SNPs)。我们认为这些SNP也导致了急性淋巴细胞白血病中PFGS表达的异质性，并将对其患病率和生理影响进行调查。此外，还描述了药物诱导的突变导致体外抗叶酸耐药性的情况。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，并可能代表复发后耐药的一种新机制。更重要的是，由于这些基因异常不存在于正常的造血细胞中，它们为基因治疗或其他分子方法提供了选择性靶点。