Hypoxia-inducible factor-1-dependent regulation of the multidrug resistance (MDR1) gene.
Hypoxia-inducible factor-1-dependent regulation of the multidrug resistance (MDR1) gene.
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发表时间：
2002-06
期刊：
影响因子：
11.2
通讯作者：
K. Comerford;T. Wallace;Jörn Karhausen;N. Louis;M. Montalto;S. Colgan
中科院分区：
文献类型：
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作者：
K. Comerford;T. Wallace;Jörn Karhausen;N. Louis;M. Montalto;S. Colgan
快速生长的肿瘤的微环境与能量需求的增加和血管供应的减少有关，导致局灶性缺氧。许多低氧反应基因与肿瘤的生长有关，在这里我们证明了多药耐药(MDR1)基因产物P-糖蛋白，一个与肿瘤对化疗药物耐药相关的约17万个跨膜蛋白，是由环境低氧诱导的。使用RNA定量微阵列分析的初步研究显示，暴露于低氧(Po(2)20torr，18h)的上皮细胞的MDR大约增加了7倍。这些发现在mRNA和蛋白质水平上得到了进一步证实。通过分析维拉帕米可抑制地高辛和罗丹明123在完整的T84细胞中的外流，研究了P-糖蛋白的功能，发现低氧使P-糖蛋白的功能增强了7+/-0.4倍。随后的研究证实，在未转化的原代培养的人微血管内皮细胞中，低氧诱导了mdr1基因的表达并增加了P-糖蛋白的表达，而对多细胞球体在低氧条件下的分析显示，对阿霉素的耐药性增加。对mdr1基因的检测发现了低氧诱导因子-1(HIF-1)的结合部位，反义寡核苷酸抑制HIF-1的表达导致低氧诱导的mdr1表达显著抑制，基本mdr1表达几乎完全丧失。使用荧光素酶启动子的研究表明，在低氧条件下，细胞的活性显著增加，这种低氧诱导性在缺乏HIF-1位点的截短结构和HIF-1结合位点突变体中丧失。这些研究的延伸也确定了Sp1在这种缺氧反应中的作用。综上所述，这些数据表明mdr1基因对低氧有反应，这些结果可能表明低氧诱导的P-糖蛋白表达是某些肿瘤对化疗药物耐药的一种途径。
The microenvironment of rapidly growing tumors is associated with increased energy demand and diminished vascular supply, resulting in focal areas of prominent hypoxia. A number of hypoxia-responsive genes have been associated with growing tumors, and here we demonstrate that the multidrug resistance (MDR1) gene product P-glycoprotein, a Mr approximately 170,000 transmembrane protein associated with tumor resistance to chemotherapeutics, is induced by ambient hypoxia. Initial studies using quantitative microarray analysis of RNA revealed an approximately 7-fold increase in MDR in epithelial cells exposed to hypoxia (pO(2) 20 torr, 18 h). These findings were further confirmed at the mRNA and protein level. P-Glycoprotein function was studied by analysis of verapamil-inhibitable efflux of digoxin and rhodamine 123 in intact T84 cells and revealed that hypoxia enhances P-glycoprotein function by as much as 7 +/- 0.4-fold over normoxia. Subsequent studies confirmed hypoxia-elicited MDR1 gene induction and increased P-glycoprotein expression in nontransformed, primary cultures of human microvascular endothelial cells, and analysis of multicellular spheroids subjected to hypoxia revealed increased resistance to doxorubicin. Examination of the MDR1 gene identified a binding site for hypoxia inducible factor-1 (HIF-1), and inhibition of HIF-1 expression by antisense oligonucleotides resulted in significant inhibition of hypoxia-inducible MDR1 expression and a nearly complete loss of basal MDR1 expression. Studies using luciferase promoter constructs revealed a significant increase in activity in cells subjected to hypoxia, and such hypoxia inducibility was lost in truncated constructs lacking the HIF-1 site and in HIF-1 binding site mutants. Extensions of these studies also identified a role for Sp1 in this hypoxia response. Taken together, these data indicate that the MDR1 gene is hypoxia responsive, and such results may identify hypoxia-elicited P-glycoprotein expression as a pathway for resistance of some tumors to chemotherapeutics.