GENETIC ANALYSIS OF THE MULTIDRUG RESISTANCE PHENOTYPE IN TUMOR CELLS

对多种药物的耐药性是成功治疗的主要障碍 人类癌症的化疗。多药耐药的一个机制是 17万道尔顿能量依赖性药物外排泵的表达 (P-糖蛋白或多药转运蛋白，人多药耐药基因的产物 该基因对秋水仙碱、阿霉素、长春新碱、 长春花碱、腐霉素D和放线菌素D的几条研究路线 关于多药转运者：1)证据 P-糖蛋白在囊泡和跨泡中的转运活性依赖于ATP 获得了上皮单层；2)新型表达载体， 利用全长mdr1基因作为显性可选择标记 在培养细胞和多药耐药基因中引入和扩增非选择基因 逆转录病毒载体已经被开发出来；3)许多人类肿瘤表达mdr1 RNA，这种表达可能预测某些癌症的耐药性，以及 与其他细菌耐药的发展相关；4)转基因 已经构建了人mdr1基因在小鼠体内的表达 骨髓的水平与人类肿瘤中发现的水平相当。这一级别 Mdr1的表达足以抵抗白细胞减少症 通过多药耐药药物；5)mdr1RNA的表达增加在 染毒后培养的啮齿动物细胞中再生大鼠肝脏 化疗药物，以及热休克后的肾癌细胞；6) 人多药耐药基因的内含子-外显子结构已经确定 支持两部分独立进化的模型 多药运送者。同样，mdr1基因的缺失分析是 与氨基和氨基都贡献的重要功能一致 分子的羧基末端的一半是一项研究证明 疏水剂对P-糖蛋白两半的光亲和标记 药物~3H-叠氮多宾；以及7)P-糖蛋白通过泵起作用的证据 得到了脂类双层外的疏水药物。

Resistance to multiple drugs is major impediment to the successful chemotherapy of human cancers. One mechanism of multidrug-resistance is the expression of a 170,000 dalton energy-dependent drug efflux pump (P-glycoprotein or the multidrug transporter, the product of the human MDR1 gene) which confers resistance to colchicine, adriamycin, vincristine, vinblastine, puromycin, and actinomycin D. Several lines of investigation concerning the multidrug transporter have been pursued: 1) Evidence for ATP-dependent transport activity of P-glycoprotein in vesicles and across epithelial monolayers has been obtained; 2) Novel expression vectors which utilize a full-length MDR1 cDNA as a dominant selectable marker are used to introduce and amplify non-selectable genes in cultured cells and MDR1 retroviral vectors have been developed; 3) Many human tumors express MDR1 RNA, and this expression may predict drug-resistance in some cancers, and correlate with the development of drug-resistance in others; 4) Transgenic mice have been constructed in which the human MDR1 mRNA is expressed in the bone marrow at levels comparable to those found in human tumors. This level of MDR1 expression is sufficient to confer resistance to leukopenia induced by MDR drugs; 5) Increased expression of MDR1 RNA has been demonstrated in regenerating rat liver, in cultured rodent cells after exposure to chemotherapeutic agents, and in kidney cancer cells after heat shock; 6) The intron-exon structure of the human MDR1 gene has been determined and supports a model of independent evolution of the two halves of the multidrug transporter. Similarly, a deletion analysis of the MDR1 cDNA is consistent with important functions being contributed by both the amino and carboxy-terminal halves of the molecule as is a study demonstrating photoaffinity labeling of both halves of P-glycoprotein by the hydrophobic drug 3H-azidopine; and 7) Evidence that P-glycoprotein acts by pumping hydrophobic drugs out of the lipid bilayer has been obtained.