State Key Laboratory of Molecular Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100021, PR China.
Cell Death Dis. 2021 Nov 11;12(11):1074. doi: 10.1038/s41419-021-04102-y.
Deubiquitinases (DUBs) have important biological functions, but their roles in breast cancer metastasis are not completely clear. In this study, through screening a series of DUBs related to breast cancer distant metastasis-free survival (DMFS) in the Kaplan-Meier Plotter database, we identified ubiquitin-specific protease 12 (USP12) as a key deubiquitinating enzyme for breast cancer metastasis. We confirmed this via an orthotopic mouse lung metastasis model. We revealed that the DMFS of breast cancer patients with high USP12 was worse than that of others. Knockdown of USP12 decreased the lung metastasis ability of 4T1 cells, while USP12 overexpression increased the lung metastasis ability of these cells in vivo. Furthermore, our results showed that the supernatant from USP12-overexpressing breast cancer cells could promote angiogenesis according to human umbilical vein endothelial cell (HUVEC) migration and tube formation assays. Subsequently, we identified midkine (MDK) as one of its substrates. USP12 could directly interact with MDK, decrease its polyubiquitination and increase its protein stability in cells. Overexpression of MDK rescued the loss of angiogenesis ability mediated by knockdown of USP12 in breast cancer cells in vitro and in vivo. There was a strong positive relationship between USP12 and MDK protein expression in clinical breast cancer samples. Consistent with the pattern for USP12, high MDK expression predicted lower DMFS and overall survival (OS) in breast cancer. Collectively, our study identified that USP12 is responsible for deubiquitinating and stabilizing MDK and leads to metastasis by promoting angiogenesis. Therefore, the USP12-MDK axis could serve as a potential target for the therapeutic treatment of breast cancer metastasis.
去泛素化酶（DUBs）具有重要的生物学功能，但它们在乳腺癌转移中的作用尚不完全清楚。在本研究中，我们通过在 Kaplan-Meier Plotter 数据库中筛选一系列与乳腺癌远处无复发生存（DMFS）相关的 DUBs，鉴定出泛素特异性蛋白酶 12（USP12）是乳腺癌转移的关键去泛素化酶。我们通过原位小鼠肺转移模型证实了这一点。我们揭示了高 USP12 水平的乳腺癌患者的 DMFS 比其他患者差。USP12 的敲低降低了 4T1 细胞的肺转移能力，而 USP12 的过表达增加了这些细胞在体内的肺转移能力。此外，我们的结果表明，USP12 过表达的乳腺癌细胞的上清液可以通过人脐静脉内皮细胞（HUVEC）迁移和管形成实验促进血管生成。随后，我们确定中期因子（MDK）是其底物之一。USP12 可以直接与 MDK 相互作用，降低其多泛素化并增加其在细胞中的蛋白质稳定性。MDK 的过表达挽救了 USP12 敲低介导的乳腺癌细胞在体外和体内血管生成能力的丧失。在临床乳腺癌样本中，USP12 和 MDK 蛋白表达之间存在强烈的正相关。与 USP12 的模式一致，MDK 高表达预示着乳腺癌患者 DMFS 和总生存率（OS）较低。总之，我们的研究表明，USP12 负责去泛素化和稳定 MDK，并通过促进血管生成导致转移。因此，USP12-MDK 轴可能成为治疗乳腺癌转移的潜在靶点。
