Antifolate Resistance in Osteosarcoma

描述（由申请人提供）：骨肉瘤患者的有效化疗和手术的确定已经导致了结果的显着改善。骨肉瘤的预后仍以临床分期系统为基础。其他预后因素的识别可能允许分层治疗。研究与化疗耐药或反应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，随着对甲氨蝶呤耐药分子基础的了解的进展，将允许进行体外评估，以预测对该药物的反应。最近发现的与甲氨蝶呤摄取有关的叶酸载体减少的突变和多态性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。对这些生物因素的研究可能会使治疗策略优先，因为可以避免抗叶酸耐药的新药物已经开发出来。本研究的目的是探讨与甲氨蝶呤耐药性相关的生物学因素作为骨肉瘤患者预后的预测因素。作为儿童肿瘤组治疗研究的一部分，从接受治疗的患者中获得的骨肉瘤肿瘤样本将被检测叶酸载体减少、二氢叶酸还原酶、叶酸聚谷氨酸合成酶和γ -谷氨酰水解酶表达的变化，以及甲氨蝶呤摄取和聚谷氨酰化的功能测定。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规模统一治疗队列中的患者生存率相关联，以潜在地确定这些检测作为预后因素。骨肉瘤肿瘤样本和患者的正常细胞将筛选减少叶酸载体序列的改变。叶酸载体宿主多态性减少的存在与高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，以确定其在预测患者毒性方面的效用。肿瘤特异性突变将作为预后因素进行评估。希望通过本提案获得的信息将允许骨肉瘤风险分层治疗的发展，考虑到患者治疗相关毒性的可能性和对新药反应的可能性。

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.