缺氧介导肾细胞癌中有机阳离子转运体OCT2表达抑制的机制及逆转耐药研究

In previous studies, we have elucidated the mechanism of DNA methylation mediated inhibition of OCT2 expression in human renal cell carcinoma (RCC), and got a sequentially coadministrated scheme with significant antitumor effect combined with decitabine (DAC) and oxaliplatin (Oxa). The results were published in Sci Transl Med and was evaluated "Opening a door into cancer cells". However, these experiments were carried out under constant oxygen conditions. Recently, we found that there was no significant effect of Oxa on the induction of OCT2 under hypoxic conditions. The results indicated that the above coadministrated scheme may be limited efficacy in the treatment of renal cell carcinoma. Therefore, this project intends to explore the role of hypoxia in the inhibition of OCT2 expression in RCC on the basis of signaling pathways, including HIF, DNMT, MYC, MLL1 and KDM2B/5B and to elucidate the mechanism. And then, to obtain a new three - drug coadministrated scheme of HIF inhibitor - DNMT inhibitor (DAC) - OCT2 substrate anticancer drugs (Oxa), which can be used to reverse the drug resistance of renal cell carcinoma under hypoxia.

前期研究中我们阐明了DNA甲基化介导的肾细胞癌（RCC）中有机阳离子转运体OCT2表达抑制的机制，并获得了抑瘤作用显著的地西他滨（DAC）和奥沙利铂（Oxa）序贯联合用药方案，相关成果发表在Sci Transl Med上，被评价为Opening a door into cancer cells。然而，这些实验都是在常氧条件下进行的。近期我们研究发现，在缺氧条件下地西他滨对OCT2没有显著的诱导作用。该结果预示上述用药方案可能对临床肾癌实体瘤疗效有局限性。因此，本项目拟在已阐明信号通路的基础上围绕缺氧诱导因子HIF、DNA甲基转移酶DNMT、MYC、MLL1和KDM2B/5B等相关因子探究缺氧对RCC中OCT2表达抑制的作用，阐明相关机制，并获得能逆转低氧条件下RCC化疗耐药的“HIF抑制剂—DNMT抑制剂(DAC)—OCT2底物类抗癌药物(Oxa)”的三元联合用药新方案，造福肾癌病人。

肾细胞癌 (RCC)是最致命的泌尿道癌症类型，其对放疗和大多数化疗药物均不敏感。人类有机阳离子转运蛋白2（OCT2，由SLC22A2编码）是介导阳离子药物经肾脏排泄过程中最丰富也最重要的摄取转运蛋白。表观遗传学研究表明，异常高甲基化介导了OCT2表达沉默进而导致肾癌细胞对奥沙利铂产生耐药性。地西他滨(DAC)对OCT2的表观遗传激活可以逆转常氧条件下的这种耐药性。然而，作为实体瘤，RCC表现出低氧微环境。在本研究中，我们发现DAC在低氧条件下不能上调OCT2的表达，OCT2的启动子区域具有高甲基化和低H3K4me3修饰。进一步的机制研究表明，低氧介导了人类平衡核苷转运蛋白1(hENT1)的抑制（其表达在RCC中也异常下调）导致DAC的细胞积累减少。此外，低氧通过诱导组蛋白去乙酰化酶HDAC9的表达，减少OCT2 启动子区H3K27ac修饰的富集，也会导致OCT2的转录抑制。最终，我们开发了一种简单高效的基于血红蛋白的氧纳米载体，用于缓解缺氧条件下RCC细胞中奥沙利铂和DAC的耐药性，具有潜在的临床应用价值。

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