Chemotherapeutic Drug-Induced ABCG2 Promoter Demethylation as a Novel Mechanism of Acquired Multidrug Resistance
Chemotherapeutic Drug-Induced ABCG2 Promoter Demethylation as a Novel Mechanism of Acquired Multidrug Resistance
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DOI：
10.1593/neo.91314
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发表时间：
2009-12-01
期刊：
影响因子：
4.8
通讯作者：
Assaraf, Yehuda G.
中科院分区：
文献类型：
--
作者：
Bram, Eran E.;Stark, Michal;Assaraf, Yehuda G.
ABCG2是一种外排转运蛋白，与癌细胞的多药耐药(MDR)有关。然而，导致其在多药耐药肿瘤细胞中上调的最初分子事件却知之甚少。在此，我们探讨了药物治疗对ABCG2启动子甲基化状态的影响，以及由此导致的ABCG2基因在亲本肿瘤细胞系及其MDR亚系中表达的重新激活。我们证明ABCG2启动子甲基化在T细胞急性淋巴细胞白血病(T-ALL)系中很常见，在原发T-ALL淋巴母细胞标本中也存在。此外，柳氮磺胺吡啶和拓扑替康的药物选择分别诱导T-ALL和卵巢癌模型细胞系CCRF-CEM和IGROV1的ABCG2启动子完全去甲基化。这导致ABCG2信使RNA水平的戏剧性诱导(分别是235和743倍)，并随之而来获得依赖ABCG2的MDR表型。定量基因组聚合酶链式反应和ABCG2启动子-荧光素酶报告分析未发现ABCG2基因扩增或差异转录反式激活，这可能是这些MDR细胞ABCG2上调的原因。值得注意的是，通过模拟细胞毒性团注药物治疗，通过12至24小时脉冲暴露于ABCG2沉默的白血病细胞，临床相关浓度的化疗药物柔红霉素和米托蒽醌，导致ABCG2转录显著上调。我们的发现表明，抗肿瘤药物诱导癌细胞ABCG2基因表达的表观遗传重新激活是导致多药耐药的早期分子事件。这些发现对化疗过程中MDR表型的恶性细胞的出现、克隆选择和扩增具有重要意义。
ABCG2 is an efflux transporter conferring multidrug resistance (MDR) on cancer cells. However, the initial molecular events leading to its up-regulation in MDR tumor cells are poorly understood. Herein, we explored the impact of drug treatment on the methylation status of the ABCG2 promoter and consequent reactivation of ABCG2 gene expression in parental tumor cell lines and their MDR sublines. We demonstrate that ABCG2 promoter methylation is common in T-cell acute lymphoblastic leukemia (T-ALL) lines, also present in primary T-ALL lymphoblast specimens. Furthermore, drug selection with sulfasalazine and topotecan induced a complete demethylation of the ABCG2 promoter in the T-ALL and ovarian carcinoma model cell lines CCRF-CEM and IGROV1, respectively. This resulted in a dramatic induction of ABCG2 messenger RNA levels (235- and 743-fold, respectively) and consequent acquisition of an ABCG2-dependent MDR phenotype. Quantitative genomic polymerase chain reaction and ABCG2 promoter-luciferase reporter assay did not reveal ABCG2 gene amplification or differential transcriptional trans-activation, which could account for ABCG2 up-regulation in these MDR cells. Remarkably, mimicking cytotoxic bolus drug treatment through 12- to 24-hour pulse exposure of ABCG2-silenced leukemia cells, to clinically relevant concentrations of the chemotherapeutic agents daunorubicin and mitoxantrone, resulted in a marked transcriptional up-regulation of ABCG2. Our findings establish that antitumor drug-induced epigenetic reactivation of ABCG2 gene expression in cancer cells is an early molecular event leading to MDR. These findings have important implications for the emergence, clonal selection, and expansion of malignant cells with the MDR phenotype during chemotherapy.