Antifolate Resistance in Osteosarcoma

描述(由申请人提供)：对骨肉瘤患者有效的化疗和手术的确定导致了结果的显著改善。骨肉瘤预后的判断仍然基于临床分期系统。确定更多的预后因素可能允许分层治疗。研究与化疗耐药或疗效相关的生物学特征可以确定预后因素。甲氨蝶呤是一种常规用于骨肉瘤治疗的大剂量药物，对其耐药的分子基础的了解取得的进展，将使我们能够识别可能预测该药物疗效的体外评估。最近发现的参与甲氨蝶呤摄取的还原叶酸载体的突变和多态也可能是肿瘤化疗反应和患者治疗相关毒性的重要决定因素。随着避免抗叶酸耐药性的新药物的开发，对这些生物因素的研究可能会使治疗策略优先考虑。本研究的目的是探讨与甲氨蝶呤耐药相关的生物学因素对骨肉瘤患者预后的预测作用。作为儿童肿瘤组治疗研究的一部分，从患者身上获得的骨肉瘤样本将被检测还原叶酸载体、二氢叶酸还原酶、叶基多谷氨酸合成酶和伽马-谷氨酰水解酶表达的变化，以及甲氨蝶呤摄取和多谷氨酸化的功能分析。这些检测的结果将与肿瘤对术前化疗的组织学反应和新诊断的局限性骨肉瘤患者的大量统一治疗队列中的患者生存期相关联，以潜在地将这些检测确定为预后因素。将对骨肉瘤肿瘤样本和患者正常细胞进行叶酸还原携带者序列改变的筛查。减少的叶酸载体宿主多态的存在将与大剂量甲氨蝶呤给药后观察到的毒性以及清除甲氨蝶呤所需的时间有关，以确定它们在预测患者毒性方面的有效性。肿瘤特异性突变将被评估为预后因素。希望通过这项建议获得的信息将有助于骨肉瘤风险分层治疗的发展，该治疗考虑到患者治疗相关毒性的可能性和对新药物的反应概率。

DESCRIPTION (provided by applicant): The identification of effective chemotherapy and surgery for patients with osteosarcoma has led to significant improvements in outcome. The determination of prognosis in osteosarcoma continues to be based on clinical staging systems. The identification of additional prognostic factors may allow stratification of therapy. Investigation of biological features related to chemotherapy resistance or response may identify prognostic factors. Advances in the understanding of the molecular basis of resistance to methotrexate, an agent routinely used in high doses for osteosarcoma treatment, will allow the identification of in vitro assessments which may predict response to this drug. Recently identified mutations and polymorphisms in the reduced folate carrier which is involved in methotrexate uptake may also be important determinants of tumor chemotherapy response and patient treatment related toxicity. Studies of these biological factors may allow prioritization of therapeutic strategies as newer agents which avoid antifolate resistance have been developed. The aim of this study is to investigate biological factors related to methotrexate resistance as predictors of prognosis in patients with osteosarcoma. Osteosarcoma tumor samples obtained from patients treated as part of Children's Oncology Group therapeutic studies will be assayed for changes in reduced folate carrier, dihydrofolate reductase, folylpolyglutamate synthetase and gamma-glutamyl hydrolase expression as well as functional assays for methotrexate uptake and polyglutamylation. The results of these assays will be correlated with the histologic response of the tumors to preoperative chemotherapy and patient survival in a large uniformly treated cohort of patients with newly diagnosed localized osteosarcoma to potentially identify these assays as prognostic factors. Osteosarcoma tumor samples and patient's normal cells will be screened for alterations in reduced folate carrier sequence. The presence of the reduced folate carrier host polymorphisms will be related to the toxicity observed following high-dose methotrexate administration and the time required to clear the methotrexate to determine their utility at predicting patient toxicity. The tumor specific mutations will be evaluated as prognostic factors. It is hoped that the information obtained through this proposal will allow the development of risk stratified therapy for osteosarcoma that takes into account patients' likelihood of therapy related toxicity and probability of response to new agents.