Liu Wensheng, Yue Fei, Zheng Minhua, Merlot Angelica, Bae Dong-Hun, Huang Michael, Lane Darius, Jansson Patric, Lui Goldie Yuan Lam, Richardson Vera, Sahni Sumit, Kalinowski Danuta, Kovacevic Zaklina, Richardson Des R
Department of General Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, P.R.China.
Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, New South Wales 2006, Australia.
Oncotarget. 2015 Apr 20;6(11):8851-74. doi: 10.18632/oncotarget.3316.
N-myc downstream regulated gene-1 (NDRG1) is a potent metastasis suppressor that plays a key role in regulating signaling pathways involved in mediating cancer cell invasion and migration, including those derived from prostate, colon, etc. However, the mechanisms and molecular targets through which NDRG1 reduces cancer cell invasion and migration, leading to inhibition of cancer metastasis, are not fully elucidated. In this investigation, using NDRG1 over-expression models in three tumor cell-types (namely, DU145, PC3MM and HT29) and also NDRG1 silencing in DU145 and HT29 cells, we reveal that NDRG1 decreases phosphorylation of a key proto-oncogene, cellular Src (c-Src), at a well-characterized activating site (Tyr416). NDRG1-mediated down-regulation of EGFR expression and activation were responsible for the decreased phosphorylation of c-Src (Tyr416). Indeed, NDRG1 prevented recruitment of c-Src to EGFR and c-Src activation. Moreover, NDRG1 suppressed Rac1 activity by modulating phosphorylation of a c-Src downstream effector, p130Cas, and its association with CrkII, which acts as a "molecular switch" to activate Rac1. NDRG1 also affected another signaling molecule involved in modulating Rac1 signaling, c-Abl, which then inhibited CrkII phosphorylation. Silencing NDRG1 increased cell migration relative to the control and inhibition of c-Src signaling using siRNA, or a pharmacological inhibitor (SU6656), prevented this increase. Hence, the role of NDRG1 in decreasing cell migration is, in part, due to its inhibition of c-Src activation. In addition, novel pharmacological agents, which induce NDRG1 expression and are currently under development as anti-metastatic agents, markedly increase NDRG1 and decrease c-Src activation. This study leads to important insights into the mechanism involved in inhibiting metastasis by NDRG1 and how to target these pathways with novel therapeutics.
N-myc下游调控基因1（NDRG1）是一种有效的转移抑制因子，在调节参与介导癌细胞侵袭和迁移的信号通路中起关键作用，这些信号通路包括源自前列腺、结肠等的信号通路。然而，NDRG1降低癌细胞侵袭和迁移从而抑制癌症转移的机制和分子靶点尚未完全阐明。在本研究中，我们使用三种肿瘤细胞类型（即DU145、PC3MM和HT29）中的NDRG1过表达模型，以及在DU145和HT29细胞中沉默NDRG1，发现NDRG1在一个特征明确的激活位点（Tyr416）降低了关键原癌基因细胞Src（c-Src）的磷酸化。NDRG1介导的表皮生长因子受体（EGFR）表达和激活的下调导致了c-Src（Tyr416）磷酸化的降低。事实上，NDRG1阻止了c-Src与EGFR的结合以及c-Src的激活。此外，NDRG1通过调节c-Src下游效应器p130Cas的磷酸化及其与CrkII的结合来抑制Rac1活性，CrkII作为激活Rac1的“分子开关”。NDRG1还影响了另一个参与调节Rac1信号传导的信号分子c-Abl，进而抑制了CrkII的磷酸化。相对于对照，沉默NDRG1增加了细胞迁移，而使用小干扰RNA（siRNA）或药理学抑制剂（SU6656）抑制c-Src信号传导可阻止这种增加。因此，NDRG1在降低细胞迁移中的作用部分归因于其对c-Src激活的抑制。此外，目前正在开发作为抗转移药物的新型药理学试剂，可诱导NDRG1表达，并显著增加NDRG1并降低c-Src激活。这项研究为NDRG1抑制转移的机制以及如何用新型疗法靶向这些通路提供了重要见解。
