Takeshita Akira, Inagaki Keiji, Igarashi-Migitaka Junko, Ozawa Yasunori, Koibuchi Noriyuki
Endocrine Center, Toranomon Hospital and Okinaka Memorial Institute for Medical Research, 2-2-2 Toranomon, Minato, Tokyo 105-8470, Japan.
J Endocrinol. 2006 Sep;190(3):897-902. doi: 10.1677/joe.1.06664.
Resistance to anticancer drugs is often mediated by the overexpression of P-glycoprotein encoded by the multi-drug resistance (MDR1) gene. The nuclear receptor, steroid and xenobiotic receptor (SXR), is one of the key transcriptional regulators of MDR1 gene expression. A variety of xenobiotics bind to SXR, and stimulate transcription on xenobiotic-response elements (XREs), located in the MDR1 gene promoter. Diethylhexyl phthalate (DEHP) is widely used as a plasticizer for polyvinyl chloride (PVC) medical devices. Previous studies have shown that a significant amount of DEHP leaches from PVC infusion bags and lines during interventions, such as total parenteral nutrition, blood transfusion, and cancer chemotherapy. Thus, the leaching of DEHP during parenteral chemotherapy for cancer patients may facilitate MDR1 expression in various tissues, including cancer cells, which may promote drug resistance. To examine such a hypothesis, the effect of DEHP on SXR-mediated transcription of the MDR1 gene was studied in the human colon adenocarcinoma-derived cell line, LS174T cells, which endogenously express SXR. DEHP increased the SXR-mediated transcription of the MDR1 gene in luciferase-reporter assays. The induction by DEHP was abrogated when a reporter plasmid containing mutated DR+4 motif in the XRE was used. In a mammalian two-hybrid assay, DEHP recruited steroid receptor co-activator-1 to the ligand-binding domain of SXR. Finally, using real-time reverse transcriptase-PCR, we showed that DEHP increased MDR1 gene expression in a dose-dependent manner. We conclude that DEHP is an inducer of the MDR1 gene in this cell line. As such, the leaching of DEHP from the PVC medical devices may influence the MDR1 expression, which may induce resistance to drugs in certain populations of cancer cells.
对抗癌药物的耐药性通常由多药耐药（MDR1）基因编码的P-糖蛋白过表达介导。核受体、类固醇和外源性物质受体（SXR）是MDR1基因表达的关键转录调节因子之一。多种外源性物质与SXR结合，并刺激位于MDR1基因启动子中的外源性物质反应元件（XREs）上的转录。邻苯二甲酸二（2-乙基己基）酯（DEHP）被广泛用作聚氯乙烯（PVC）医疗器械的增塑剂。先前的研究表明，在诸如全胃肠外营养、输血和癌症化疗等干预过程中，大量DEHP会从PVC输液袋和输液管中渗出。因此，癌症患者胃肠外化疗期间DEHP的渗出可能会促进包括癌细胞在内的各种组织中MDR1的表达，这可能会导致耐药性。为了验证这一假设，我们在人结肠腺癌来源的内源性表达SXR的LS174T细胞系中研究了DEHP对SXR介导的MDR1基因转录的影响。在荧光素酶报告基因检测中，DEHP增加了MDR1基因的SXR介导的转录。当使用在XRE中含有突变DR + 4基序的报告质粒时，DEHP的诱导作用被消除。在哺乳动物双杂交试验中，DEHP将类固醇受体共激活因子-1募集到SXR的配体结合域。最后，使用实时逆转录-聚合酶链反应，我们表明DEHP以剂量依赖性方式增加MDR1基因表达。我们得出结论，DEHP是该细胞系中MDR1基因的诱导剂。因此，DEHP从PVC医疗器械中的渗出可能会影响MDR1的表达，这可能会在某些癌细胞群体中诱导耐药性。
