HuR (human antigen R), an mRNA-binding protein responsible for poor prognosis in nearly all kinds of malignancies, is a potential anti-tumor target for drug development. While screening HuR inhibitors with a fluorescence polarization (FP) based high-throughput screening (HTS) system, the clinically used drug eltrombopag was identified. Activity of eltrombopag on molecular level was verified with FP, electrophoretic mobility shift assay (EMSA), simulation docking and surface plasmon resonance (SPR). Further, we showed that eltrombopag inhibited in vitro cell proliferation of multiple cancer cell lines and macrophages, and the in vivo anti-tumor activity was also demonstrated in a 4T1 tumor-bearing mouse model. The in vivo data showed that eltrombopag was efficient in reducing microvessels in tumor tissues. We then confirmed the HuR-dependent anti-angiogenesis effect of eltrombopag in 4T1 cells and RAW264.7 macrophages with qRT-PCR, HuR-overexpression and HuR-silencing assays, RNA stability assays, RNA immunoprecipitation and luciferase assays. Finally, we analyzed the in vitro anti-angiogenesis effect of eltrombopag on human umbilical vein endothelial cells (HUVECs) mediated by macrophages with cell scratch assay and in vitro Matrigel angiogenesis assay. With these data, we revealed the HuR-dependent anti-angiogenesis effect of eltrombopag in breast tumor, suggesting that the existing drug eltrombopag may be used as an anti-cancer drug.

HuR（人类抗原R）是一种负责在几乎所有类型的恶性肿瘤中预后不良的mRNA结合蛋白，是药物开发的潜在抗肿瘤靶标。在使用基于荧光偏振（FP）的高通量筛选（HTS）系统筛选HuR抑制剂时，确定了临床使用的药物Eltrombopag。通过FP，电泳迁移率移动分析（EMSA），模拟对接和表面等离振子共振（SPR）验证了Eltrombopag在分子水平上的活性。此外，我们显示了Eltrombopag抑制了多种癌细胞系和巨噬细胞的体外细胞增殖，并且在具有4T1肿瘤的小鼠模型中也证明了体内抗肿瘤活性。在体内数据显示，Eltrombopag可有效减少肿瘤组织中的微血管。然后，我们通过qRT-PCR，HuR过表达和HuR沉默测定，RNA稳定性测定，RNA免疫沉淀和荧光素酶测定，证实了Eltrombopag在4T1细胞和RAW264.7巨噬细胞中的HuR依赖性抗血管生成作用。最后，我们用细胞划痕法和体外基质胶血管生成法分析了Eltrombopag对巨噬细胞介导的人脐静脉内皮细胞（HUVEC）的体外抗血管生成作用。利用这些数据，我们揭示了Eltrombopag在乳腺肿瘤中的HuR依赖性抗血管生成作用，表明现有药物Eltrombopag可用作抗癌药。