FL118 induces p53-dependent senescence in colorectal cancer cells by promoting degradation of MdmX.
FL118 induces p53-dependent senescence in colorectal cancer cells by promoting degradation of MdmX.
复制标题
DOI：
10.1158/0008-5472.can-14-0683
复制
发表时间：
2014-12-15
期刊：
影响因子：
11.2
通讯作者：
Wang X
中科院分区：
文献类型：
--
作者：
Ling X;Xu C;Fan C;Zhong K;Li F;Wang X
抗癌剂FL118最近被发现用于筛选人类survivin表达的小分子抑制剂。虽然FL118是喜树碱类似物，但其抗肿瘤效力远优于其他fda批准的喜树碱类似物（伊立替康和拓扑替康）。FL118抗肿瘤作用的作用机制（MOA）尚未完全阐明。在这里，我们报道FL118在p53野生型癌细胞中激活肿瘤抑制因子p53作为一种新的MOA。我们的研究表明，这种MOA涉及诱导MdmX的蛋白酶体降解，MdmX是p53的关键负调节因子，其方式在很大程度上独立于atm依赖的DNA损伤信号通路，但依赖于E3-competent Mdm2。FL118抑制细胞和无细胞系统中Mdm2-MdmX E3复合物的p53多泛素化和单泛素化。相反，FL118刺激mdm2介导的MdmX泛素化。共免疫沉淀显示，FL118轻微降低Mdm2-p53相互作用，适度增加Mdm2-MdmX相互作用，提示Mdm2-MdmX E3复合物的靶向特异性从p53转变为MdmX，导致MdmX降解加速。结果，Mdm2-MdmX E3复合物使p53泛素化减少，进而激活p53信号。FL118激活p53通路可诱导结直肠癌细胞p53依赖性衰老。然而，在p53缺失或MdmX过表达的情况下，FL118促进p53不依赖型细胞凋亡。这两种不同的细胞结果共同促成了FL118抑制结肠癌细胞克隆潜能的有效作用。本研究确定了FL118作为MdmX抑制剂在靶向治疗中的潜在应用。
Anticancer agent FL118 was recently identified in screening of small-molecule inhibitors of human survivin expression. Although FL118 is a camptothecin analogue, its antitumor potency is much superior to other FDA-approved camptothecin analogues (irinotecan and topotecan). The mechanism of action (MOA) underlying the antitumor effects of FL118 remains to be fully elucidated. Here, we report that FL118 activates tumor suppressor p53 as a novel MOA in p53 wild-type cancer cells. Our studies show that this MOA involves an induction of proteasomal degradation of MdmX, a critical negative regulator of p53, in a manner largely independent of ATM-dependent DNA damage signaling pathway but dependent on E3-competent Mdm2. FL118 inhibits p53 polyubiquitination and monoubiquitination by Mdm2–MdmX E3 complex in cells and in cell-free systems. In contrast, FL118 stimulates Mdm2-mediated MdmX ubiquitination. Coimmunoprecipitation revealed that FL118 slightly decreases Mdm2–p53 interactions and moderately increases Mdm2–MdmX interactions, suggesting a change of targeting specificity of Mdm2–MdmX E3 complex from p53 to MdmX, resulting in accelerated MdmX degradation. As a result, p53 ubiquitination by Mdm2–MdmX E3 complex is reduced, which in turn activates p53 signaling. Activation of the p53 pathway by FL118 induces p53-dependent senescence in colorectal cancer cells. However, in the absence of p53 or in the presence of MdmX overexpression, FL118 promotes p53-independent apoptosis. These two distinct cellular consequences collectively contribute to the potent effects of FL118 to inhibit clonogenic potential of colon cancer cells. This study identifies a potential application of FL118 as an MdmX inhibitor for targeted therapies.