Epigenetic modification of Nrf2 in 5-fluorouracil-resistant colon cancer cells: involvement of TET-dependent DNA demethylation.
Epigenetic modification of Nrf2 in 5-fluorouracil-resistant colon cancer cells: involvement of TET-dependent DNA demethylation.
复制标题
DOI：
10.1038/cddis.2014.149
复制
发表时间：
2014-04-17
影响因子：
9
通讯作者：
中科院分区：
文献类型：
--
作者：
5-氟尿嘧啶（5-FU）是一种广泛用于治疗结直肠癌（CRC）的抗癌药物。然而，对5-FU的耐药性通常会阻碍化疗的成功。核因子-红细胞2相关因子2（Nrf 2）是一种转录调节因子，也是克服5-FU耐药的可能靶点。本研究检查了在对5-FU耐药的人CRC细胞系（SNUC 5）（SNUC 5/5-FUR）中与Nrf 2诱导相关的表观遗传变化。SNUC 5/5-FUR细胞中Nrf 2表达、核转位和与启动子的结合高于SNUC 5细胞。在SNUC 5/5-FUR细胞中激活Nrf 2导致Nrf 2调节基因血红素加氧酶-1（HO-1）的蛋白表达和活性增加。SNUC 5/5-FUR细胞比SNUC 5细胞产生更大量的活性氧（ROS）。siRNA或shRNA介导的Nrf 2或HO-1敲低在体外和体内显著抑制癌细胞活力和肿瘤生长，导致5-FU敏感性增强。甲基化特异性（MS）或实时定量MS-PCR数据显示，与SNUC 5细胞相比，SNUC 5/5-FUR细胞中Nrf 2启动子CpG岛甲基化不足。DNA去甲基化酶10 - 11易位（泰特）在SNUC 5/5-FUR细胞中的表达上调。由5-FU产生的ROS上调TET 1的表达和功能，而抗氧化剂具有相反的作用。这些结果表明，CRC获得5-FU耐药的潜在机制涉及通过DNA去甲基化的表观遗传修饰上调Nrf 2和HO-1表达。
5-Fluorouracil (5-FU) is a widely used anticancer drug for the treatment of colorectal cancer (CRC). However, resistance to 5-FU often prevents the success of chemotherapy. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a transcriptional regulator and a possible target to overcome 5-FU resistance. The present study examined epigenetic changes associated with Nrf2 induction in a human CRC cell line (SNUC5) resistant to 5-FU (SNUC5/5-FUR). Nrf2 expression, nuclear translocation, and binding to promoter were higher in SNUC5/5-FUR cells than in SNUC5 cells. The activated Nrf2 in SNUC5/5-FUR cells led to an increase in the protein expression and activity of heme oxygenase-1 (HO-1), an Nrf2-regulated gene. SNUC5/5-FUR cells produced a larger amount of reactive oxygen species (ROS) than SNUC5 cells. The siRNA- or shRNA-mediated knockdown of Nrf2 or HO-1 significantly suppressed cancer cell viability and tumor growth in vitro and in vivo, resulting in enhanced 5-FU sensitivity. Methylation-specific (MS) or real-time quantitative MS-PCR data showed hypomethylation of the Nrf2 promoter CpG islands in SNUC5/5-FUR cells compared with SNUC5 cells. Expression of the DNA demethylase ten-eleven translocation (TET) was upregulated in SNUC5/5-FUR cells. ROS generated by 5-FU upregulated TET1 expression and function, whereas antioxidant had the opposite effect. These results suggested that the mechanism underlying the acquisition of 5-FU resistance in CRC involves the upregulation of Nrf2 and HO-1 expression via epigenetic modifications of DNA demethylation.