FOLYL- AND ANTIFOLYLPOLYGLUTAMATES IN COMBINATION CHEMOTHERAPY

这项研究的长期目标是改进化疗 使用新型抗叶酸或新型还原叶酸类似物治疗癌症 生化调节，以产生增加的治疗指数。这个 所使用的方法也可以定义抗叶基-和 叶基多谷氨酸代谢物的细胞毒性和选择性。这个 抗叶酸甲氨蝶呤(MTX)联合用药临床有效 化疗方案，但其疗效往往受到耐药性的限制 在更高的剂量下无法克服，因为达到了毒性， 也就是说，它不够有选择性。MTX的多个谷氨酸盐参与了 其细胞毒性为单一毒剂，但其对细胞毒性的贡献 并且(特别是)使用该试剂的组合中的选择性是 未知。外源还原型叶酸(如亚叶酸(LV)；5-甲酰四氢叶酸 氢叶酸)被用来从MTX的细胞毒性效应中解救出来 增强其他药物(如5-氟尿嘧啶[FU])的细胞毒性。这个 叶基多谷氨酸合成在实现这些效应中的作用以及 在寄主中的毒性和选择性尚不清楚。这项提议将 确定MTX和MTX的非多谷氨酰化类似物的替代是否 LV在联合化疗中产生任何治疗优势。这个 MTX和LV的类似物将含有4-氟谷氨酸而不是谷氨酸， 足以阻断类似物的多谷氨酰化的改变。这个 拟议的药物组合研究将比较生物化学、 LV或MTX方案的细胞毒作用和治疗效果 包含这些非多谷氨酰化“模拟物”的治疗方案。细胞毒性 将通过体外生长和/或克隆试验使用人类 白血病细胞系CCRF-CEM和合适的小鼠模型(用于扩展 体内治疗研究)；时间和剂量依赖于 详细调查了。在可行的情况下，生物化学决定因素 我们将探讨其细胞毒性。将进行调查的方案包括： 序贯MTX/5FU、LV/5-FU和LV抢救MTX 细胞毒性。MTX和LV以及它们各自的氟化“模拟物”将被 比较以确定它们是否在生化上等价，除了 多聚谷氨酰化。如果类比是真的“模仿，结果来自 细胞毒性和疗效研究将产生关于 多聚谷氨酸在这些组合中的作用。希望这一天 在这些研究中获得的知识将为更多 完善的治疗方案，提高了疗效。

The long term objective of this research is to improve chemotherapy of cancer by using novel antifolates or novel reduced-folate analogs for biochemical modulation to yield an increased therapeutic index. The approach to be used may also define the role of antifolyl- and folylpolyglutamate metabolites in cytotoxicity and selectivity. The antifolate methotrexate (MTX) is clinically effective in combination chemotherapy regimens, but its efficacy is often limited by resistance which cannot be overcome at higher doses because toxicity is reached, i.e., it is not selective enough. Polyglutamates of MTX are implicated in its cytotoxicity as a single agent, but their contribution to cytotoxicity and (particularly) selectivity in combinations using this agent are unknown. Exogenous reduced folates (as leucovorin (LV); 5-formyltetra- hydrofolate) are used to "rescue" from the cytotoxic effects of MTX and to augment the cytotoxicity of other drugs (e.g., 5-fluorouracil [FU]). The role of folylpolyglutamate synthesis in achieving these effects as well as in host toxicity and selectivity are unknown. This proposal will determine whether substitution of nonpolyglutamylatable analogs of MTX and LV in combination chemotherapy yields any therapeutic advantage. The analogs of MTX and LV will contain 4-fluoroglutamate instead of glutamate, a change sufficient to block polyglutamylation of the analog. The proposed studies of drug combinations will compare the biochemical, cytotoxic, and therapeutic effects of LV or MTX in a regimen with the same regimen containing these nonpolyglutamylatable "mimics". Cytotoxicity will be assessed by out-growth and/or clonogenic assays using the human leukemia cell line CCRF-CEM and an appropriate murine model (for extension to in vivo therapeutic studies); time and dose dependence will be investigated in detail. Where feasible the biochemical determinants of cytotoxicity will be explored. The regimens to be investigated are: sequential MTX/5FU, simultaneous LV/5-FU, and LV rescue of MTX cytotoxicity. MTX and LV and their respective fluorinated "mimics" will be compared to determine if they are biochemically equivalent, except for polyglutamylation. If the analogs are true "mimics, the results from the cytotoxicity and efficacy studies would yield basic knowledge about the role of polyglutamates in these combinations. It is hoped that the knowledge gained in these studies will provide a basis for more sophisticated therapy protocols with improved efficacy.