miR-29b/c-ID1参与急性髓系白血病地西他滨耐药的研究

DAC is inhibitor of DNA methyltransferase, which has a good effect in the treatment of leukemia. However, the primary or secondary resistance to DAC may occur during therapy. The mechanisms related to DAC resistance remain poor understood. In our previous study, we found miR-29b/c were decreased expressed in various kinds of leukemia cells and in AML patients, which associated with poor prognosis; Using DAC treatment, decreased methylation and up-regulated expression level of miR-29b and miR-29c was detected in DAC sensitive cells. And inhibitor of DNA binding 1 (ID1) was down-regulated. While decreased methylation and no significant change in expression of miR-29b and miR-29c was detected in DAC-resistant cells; but ID1 expression was significantly up-regulated. It is suggested that miR-29b/c-ID1 might be involved in DAC resistance. This study will analyze mechanism of miR-29b/c-ID1 involved resistance to DAC, to enhance decitabine effect by miR-29b/c-ID1 ways and supply theoretical foundation for increasing the anti-leukemic effect of DAC.

去甲基化药物地西他滨（DAC）是DNA甲基化转移酶抑制剂，在白血病治疗上已取得较好疗效，但患者在治疗过程中可出现原发或继发耐药，其机制尚不明确。前期研究发现miR-29b/c在AML患者和多种白血病细胞中均表达下调，其低表达与AML预后不良相关；DAC敏感细胞经过DAC处理后miR-29b和miR-29c启动子区域甲基化水平降低、表达上调，同时DNA结合抑制因子ID1表达下调。而在DAC耐药细胞中miR-29b和miR-29c启动子区域甲基化水平降低，但其表达水平无明显改变，ID1表达却明显上调。因此，我们推测miR-29b/c诱导的ID1非甲基化依赖的表达异常可能参与DAC耐药过程。本课题将从表观遗传学角度分析miR-29b/c-ID1参与DAC耐药作用机制，为增加DAC的抗白血病的疗效提供理论依据。

地西他滨是一种用于治疗白血病的DNA甲基转移酶抑制剂，但在治疗过程中可能会出现对DAC的原发性或继发性耐药。其耐药机制目前知之甚少。在这项研究中，我们发现miR-29b和miR-29c在各种白血病细胞系和AML患者中表达下调，并与AML患者不良预后相关。在DAC敏感细胞中，miR-29b和miR-29c能够抑制细胞生长，促进细胞凋亡，并增加对DAC的敏感性。同样，它在DAC耐药细胞中发挥抗白血病作用。当DAC耐药细胞中的miR-29b和miR-29c启动子发生去甲基化改变，但其表达未上调。此外，miR-29b的靶基因之一ID1的表达在miR-29b转染的白血病细胞中下调。体外实验和小鼠体内实验结果显示，ID1能够促进细胞生长，抑制细胞凋亡，并降低DAC敏感性。ID1在用DAC处理的DAC敏感细胞中下调，而在DAC抗性细胞中上调。ID1启动子区在DAC耐药细胞和敏感细胞中呈完全未甲基化状态。miR-29b诱导的生长抑制、增加的DAC敏感性和凋亡可以通过增加ID1表达来消除。这些结果表明DAC通过作用于miR-29b来调节ID1的表达。非甲基化依赖性的由miR-29b诱导的ID1异常表达可能参与了白血病细胞获得DAC耐药性的过程。circ_0059707是ID1剪切过程中形成的环状RNA，荧光素酶报告基因实验的结果显示circ_0059707和miR-29b存在靶向结合。在过表达circ_0059707的K562细胞中miR-29b表达下调，ID1表达增高，提示circ_0059707可能通过与ID1竞争结合miR-29b参与DAC耐药。