STUDIES OF MULTIDRUG RESISTANCE IN MAMMALIAN CELLS

对化疗剂的耐药性的发展是在化疗中观察到的。 临床，并已在组织培养细胞中进行了广泛研究。 一 不寻常的表型是多药耐药，其中细胞是 用任何一种细胞毒性药物攻击产生耐药性 不仅对选择性试剂而且对其它试剂也具有交叉抗性， 看似无关的化合物 这种多药耐药（MDR）表型 与膜糖蛋白的过度产生有关，包括 P-糖蛋白，并在某些情况下与胞质的过度生产 蛋白质也是。 因此，表型是复杂的，遗传 耐药性和交叉耐药性的基础被以下事实所掩盖： 多个基因的差异扩增（我们称之为MMPs基因） 介导的糖蛋白的过度生产，而其他共扩增 基因介导至少一种胞质蛋白的表达， 其他蛋白质也是。 虽然多重耐药的最终原因 是降低的细胞内药物浓度， 抗性或交互抗性机制中的扩增基因产物 在模拟组织培养系统中以及在对 化疗仍然是个谜 随着重组DNA技术的应用， DNA转染技术和核径流转录测定，我们 建议确定MMP 3基因产品在建立 的MDR表型，并确定其产物也可能 参与其表达。 此外，当放大时， MMP 3基因的表达可以远远超过它们的基因拷贝数，这表明 这种过度表达并不是由扩增单独介导的。 我们会的 因此，确定这种增强表达的分子基础， 它可能表明在缺乏蛋白质的情况下过度表达的机制， 放大 最后，我们建议测量表达水平， 人肿瘤细胞系和正常细胞中的MMP 3基因 线，肿瘤和正常组织，以确定其程度 这些基因在人类细胞中表达的水平，以及它们是否 过表达可以被证明与许多耐药相关， 患者表现出多种化疗剂。

The development of resistance to chemotherapeutic agents is observed in the clinic, and has been studied extensively in tissue culture cells. One unusual phenotype is that of multidrug resistance, in which cells that are challenged with any one of a variety of cytotoxic drugs develop resistance not only to the selective agent but also cross-resistance to other, seemingly unrelated, compounds. This multidrug-resistant (mdr) phenotype is associated with the overproduction of membrane glycoproteins, including p-glycoprotein, and in some cases with the overproduction of cytosolic proteins as well. The phenotype is complex, therefore, and the genetic basis for resistance and cross-resistance is obscured by the fact that the differential amplification of multiple genes (which we call MDRA genes) mediates the overproduction of the glycoproteins, whereas other coamplified genes mediate the expression of at least one cytosolic protein and probably other proteins as well. While the ultimate cause of multidrug resistance is the lowered intracellular concentration of drug, the role of any of the amplified gene products in the mechanism of resistance or cross-resistance in model tissue culture systems and in human tumors refractory to chemotherapy, remains obscure. With the use of recombinant DNA technology, DNA transfection techniques, and nuclear runoff transcription assays, we propose to define the role of the MDRA gene products in the establishment of the mdr phenotype, and to identify other genes whose products may also be involved in its expression. Additionally, when amplified, the expression of MDRA genes can far exceed their gene copy number, suggesting that overexpression is not mediated by amplification alone. We will, therefore, determine the molecular basis for this enhanced expression for it may indicate a mechanism for overexpression in the absence of amplification. Finally, we propose to measure the levels of expression of MDRA genes in a large number of human tumor cell lines and normal cell lines, and tumors and normal tissues in an effort to determine the extent to which these genes are expressed in human cells and whether their overexpression can be shown to be associated with the resistance that many patients display to a wide variety of chemotherapeutic agents.