ANTICANCER DRUG EFFLUX TRANSPORTERS IN DEVELOPMENT

肿瘤细胞对多种化疗药物(MDR)的耐药性是大多数人类癌症治疗的主要障碍。多药耐药现象赋予肿瘤细胞承受许多结构上无关的抗肿瘤药物的致命剂量的能力。多药耐药的特征是膜相关糖蛋白的过度表达；在这些与药物外排有关的ATP结合盒(ABC)转运体中，研究最多的两种是P-糖蛋白(P-Gly)和多药耐药相关蛋白(MRP1)。关于ABC转运蛋白在个体发育过程中的表达以及它们的发育如何影响宿主对治疗药物的反应，在子宫和出生后的早期生活中，人们知之甚少。同样，关于它们在癌症化疗药物对正常组织的毒性中的作用以及它们对儿童时期恶性疾病治疗的重要性的信息很少。因此，我们计划通过研究P-Gly(mdr1a/1b)和多药耐药蛋白家族(MRPs 1-7)在出生前和出生后1、3和10-12周龄时的组织分布，确定小鼠的发育模式，大致对应于胎儿、新生儿、儿童和成年发育期。作为模型系统，我们将使用野生型和遗传缺陷的mrp1(-/-)；mdr1a/1b(-/-)；以及mrp1(-/-)、mdr1a/1b(-/-)小鼠和从其衍生的胚胎成纤维细胞系：(A)评估这些ABC转运蛋白在几种抗癌药物保护正常组织中的作用，特别是强调它们与长春新碱和甲氨蝶呤的关系，包括它们对这些药物新陈代谢和药代动力学的影响；(B)确定缺少一个或多个ABC转运蛋白的影响，以及确定可能的补偿机制的存在；以及(C)确定P-Gly和MRP转运蛋白家族(MRP 1-6)在预测儿童癌症对抗肿瘤药物的反应中的作用。因此，我们将获得关于在儿童癌症中测量ABC转运蛋白在选择最具诱导反应潜力的治疗药物方面的作用，以及使用基因敲除小鼠和细胞系作为模型系统来评估ABC转运蛋白在正常组织中对抗癌药物的毒性和处置的作用。

Resistance of tumor cells to multiple chemotherapeutic agents (MDR) is a major obstacle to the treatment of most human cancers. The phenomenon of MDR confers upon malignant cells the ability to withstand exposure to lethal doses of many structurally unrelated antineoplastic agents. Multidrug resistance has been characterized by the overexpression of membrane-associated glycoproteins; the two most studied of these ATP-binding cassette (ABC) transporters which have a role in drug efflux are the P-glycoprotein (P-gly) and the multidrug resistance (-associated) protein (MRP1). Little is known about the expression of the ABC transporters during ontogeny and how their development impacts the host response to therapeutic agents in utero and in early postnatal life. Similarly, little information is available on their role in the toxicity of cancer chemotherapeutic agents to normal tissues and their importance to the treatment of malignant diseases during childhood. Accordingly, we plan to determine the murine development patterns of the P-gly (mdr1a/1b) and the multidrug resistance protein family (mrps 1-7) by examining the tissue distribution of these ABC transporters prenatally and postnatally at 1, 3, and 10-12 weeks of age, corresponding approximately to the fetal, newborn, childhood and adulthood developmental periods. As model systems we will employ wild-type and genetically deficient mrp1 (-/-); mdr1a/1b(-/-); and mrp1 (- /-), mdr1a/1b(-/-) mice and embryonic fibroblast cell lines derived therefrom (a) to evaluate the role of these ABC transporters in protecting normal tissue from several anticancer agents, particularly stressing their relationships to vincristine and methotrexate, including their impact on the metabolism and pharmacokinetic disposition of these drugs; (b) to determine the impact of the absence of one or more of the ABC transporters, as well as determine the presence of possible compensatory mechanisms; and (c) to ascertain the involvement of the P-gly and the MRP family of transporters (MRPs 1-6) in the prediction of response of childhood cancers to antineoplastic agents. Thus, we will obtain information on the utility of measurements of the ABC transporters in childhood cancers in selecting therapeutic agents with the greatest potential to induce response and on the use of knockout mice and cell lines as model systems to estimate the role of the ABC transporters on the toxicity to and disposition of anticancer agents in normal tissues.