Van der Bliek A M, Van der Velde-Koerts T, Ling V, Borst P
Mol Cell Biol. 1986 May;6(5):1671-8. doi: 10.1128/mcb.6.5.1671-1678.1986.
Multidrug-resistant cells are cross-resistant to a wide range of unrelated drugs, many of which are used in cancer chemotherapy. We constructed a cDNA library from RNA of the multidrug-resistant Chinese hamster ovary cell line CHRC5. By differential screening we isolated cDNAs derived from mRNAs that are overexpressed in this cell line. The cDNAs could be grouped in five classes on the basis of transcript lengths detected in RNA blots. We infer that each class codes for a separate protein. The corresponding genes are amplified 10 or 30 times in CHRC5 DNA, providing an explanation for the constitutive overexpression found in this cell line. Despite differential amplification, the genes may be linked in one large amplicon as indicated by the hybridization analysis of large fragments of CHRC5 DNA separated by pulsed field gradient gel electrophoresis. Therefore, some of these genes might be fortuitously coamplified and not contribute functionally to the resistant phenotype. It is also possible, however, that genes involved in drug resistance are clustered. One of our clones cross-hybridized with the recently described cDNA pCHP1 (J. R. Riordan, K. Deuchars, N. Kartner, N. Alon, J. Trent, and V. Ling, Nature [London] 316:817-819, 1985) encoding part of the 170-kilodalton P-glycoprotein, a protein which is frequently overproduced in multidrug-resistant cells. The nature of the four other genes is still unknown. Sequences of four of the five classes of cDNAs are conserved in mouse and human DNA.
多药耐药细胞对多种不相关药物具有交叉耐药性，其中许多药物用于癌症化疗。我们从多药耐药的中国仓鼠卵巢细胞系CHRC5的RNA构建了一个cDNA文库。通过差异筛选，我们分离出了在该细胞系中过表达的mRNA衍生的cDNA。根据RNA印迹中检测到的转录本长度，这些cDNA可分为五类。我们推断每一类编码一种单独的蛋白质。相应的基因在CHRC5 DNA中扩增了10倍或30倍，这为该细胞系中组成型过表达提供了解释。尽管存在差异扩增，但如通过脉冲场梯度凝胶电泳分离的CHRC5 DNA大片段的杂交分析所示，这些基因可能在一个大的扩增子中相连。因此，其中一些基因可能是偶然共扩增的，对耐药表型没有功能贡献。然而，也有可能参与耐药的基因是成簇的。我们的一个克隆与最近描述的编码170千道尔顿P-糖蛋白部分的cDNA pCHP1（J. R. Riordan、K. Deuchars、N. Kartner、N. Alon、J. Trent和V. Ling，《自然》[伦敦]316:817 - 819，1985）交叉杂交，P-糖蛋白是一种在多药耐药细胞中经常过度产生的蛋白质。其他四个基因的性质仍然未知。五类cDNA中的四类序列在小鼠和人类DNA中是保守的。
