Allen John D, Jackson Sonja C, Schinkel Alfred H
Division of Experimental Therapy, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
Cancer Res. 2002 Apr 15;62(8):2294-9.
The recent identification of mutations at arginine 482 (R482) in human Breast Cancer Resistance Protein (BCRP) in two drug-selected cell lines largely explains some discrepancies observed in the cross-resistance profiles of human cell lines overexpressing this multidrug transporter. We find that each of three mouse cell lines independently selected for resistance to the anthracycline doxorubicin also acquired mutations in the cognate mouse transporter Bcrp1 exclusively at R482. Although the mouse Bcrp1 amino acid substitutions (M or S) are distinct from those seen in the human cell lines (G or T), they all have similar consequences: (a) greater resistance to anthracyclines (and bisantrene); (b) relatively lower resistance to topotecan; (c) greatly enhanced efflux of the dye rhodamine 123. The ready selection of R482X mutations seen in vitro might also occur in tumors treated with anthracyclines. Thus, it is noteworthy that the efficacy of Bcrp1 inhibitors applicable in vivo was not markedly affected by the presence of the mutations. We found that the Bcrp1 mutations all occurred after previous amplification and overexpression of the wild-type gene under doxorubicin selection; wild-type Bcrp1 is evidently able to mediate substantial resistance to anthracyclines, and this was confirmed in Bcrp1-transduced cell lines. These observations emphasize the general importance of the arginine at amino acid 482 for substrate specificity of the transporter, while reminding us that unmutated Bcrp1 remains a potential source of resistance to anthracyclines and a potential factor in anthracycline pharmacokinetics. The same is most likely true of human BCRP, given its profound similarities to mouse Bcrp1.
最近在两种药物筛选的细胞系中发现人乳腺癌耐药蛋白（BCRP）的精氨酸482（R482）位点发生突变，这在很大程度上解释了在过表达这种多药转运蛋白的人细胞系交叉耐药谱中观察到的一些差异。我们发现，三个独立筛选出对蒽环类药物阿霉素耐药的小鼠细胞系，其同源小鼠转运蛋白Bcrp1也仅在R482位点发生了突变。尽管小鼠Bcrp1的氨基酸替代（M或S）与在人细胞系中看到的不同（G或T），但它们都有相似的结果：（a）对蒽环类药物（和双苯丙胺）有更高的耐药性；（b）对拓扑替康的耐药性相对较低；（c）罗丹明123染料的外排大大增强。在体外容易筛选到的R482X突变也可能发生在用蒽环类药物治疗的肿瘤中。因此，值得注意的是，体内适用的Bcrp1抑制剂的疗效并未受到这些突变存在的明显影响。我们发现，Bcrp1突变均发生在阿霉素选择下野生型基因先前扩增和过表达之后；野生型Bcrp1显然能够介导对蒽环类药物的实质性耐药，这在转导了Bcrp1的细胞系中得到了证实。这些观察结果强调了482位氨基酸处的精氨酸对转运蛋白底物特异性的普遍重要性，同时提醒我们未突变的Bcrp1仍然是对蒽环类药物耐药的潜在来源以及蒽环类药物药代动力学的潜在因素。鉴于人BCRP与小鼠Bcrp1有很大的相似性，人BCRP很可能也是如此。
