Antifolate Resistance in Osteosarcoma

描述（由申请人提供）：骨肉瘤患者有效化疗和手术的确定导致了结局的显着改善。骨肉瘤预后的确定仍然是基于临床分期系统。其他预后因素的识别可能允许治疗分层。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。对甲氨蝶呤（一种常规用于骨肉瘤治疗的高剂量药物）耐药性的分子基础的了解取得了进展，这将有助于确定体外评估，从而预测对该药物的反应。最近发现的与甲氨蝶呤摄取有关的还原叶酸载体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。这些生物因素的研究可能会允许优先考虑的治疗策略作为新的代理，避免抗叶酸耐药性已经开发出来。本研究的目的是探讨与甲氨蝶呤耐药相关的生物学因素作为骨肉瘤患者预后的预测因子。从作为儿童肿瘤组治疗研究的一部分接受治疗的患者中获得的骨肉瘤肿瘤样本将测定还原叶酸载体、二氢叶酸还原酶、叶酰聚谷氨酸合成酶和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。这些测定的结果将与肿瘤对术前化疗的组织学反应和新诊断的局部骨肉瘤患者的大型统一治疗队列中的患者存活率相关，以潜在地将这些测定确定为预后因素。将对骨肉瘤肿瘤样本和患者的正常细胞进行筛选，以确定还原叶酸载体序列的改变。还原叶酸载体宿主多态性的存在将与高剂量甲氨蝶呤给药后观察到的毒性和清除甲氨蝶呤所需的时间相关，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价。希望通过本提案获得的信息能够开发骨肉瘤的风险分层治疗，其中考虑到患者出现治疗相关毒性的可能性和对新药的反应可能性。

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.