title: Targeting the metastasis suppressor, NDRG1, using novel iron chelators: regulation of stress fiber-mediated tumor cell migration via modulation of the ROCK1/pMLC2 signaling pathway.
abstract: The iron-regulated metastasis suppressor, N-myc downstream-regulated gene 1 (NDRG1), is up-regulated by cellular iron depletion mediated by iron chelators and can inhibit cancer cell migration. However, the mechanism of how NDRG1 achieves this effect remains unclear. In this study, we implemented established and newly constructed NDRG1 overexpression and knockdown models using the DU145, HT29, and HCT116 cancer cell lines to investigate the molecular basis by which NDRG1 exerts its inhibitory effect on cell migration. Using these models, we demonstrated that NDRG1 overexpression inhibits cell migration by preventing actin-filament polymerization, stress fiber assembly and formation. In contrast, NDRG1 knockdown had the opposite effect. Moreover, we identified that NDRG1 inhibited an important regulatory pathway mediated by the Rho-associated, coiled-coil containing protein kinase 1 (ROCK1)/phosphorylated myosin light chain 2 (pMLC2) pathway that modulates stress fiber assembly. The phosphorylation of MLC2 is a key process in inducing stress fiber contraction, and this was shown to be markedly decreased or increased by NDRG1 overexpression or knockdown, respectively. The mechanism involved in the inhibition of MLC2 phosphorylation by NDRG1 was mediated by a significant (P < 0.001) decrease in ROCK1 expression that is a key kinase involved in MLC2 phosphorylation. Considering that NDRG1 is up-regulated after cellular iron depletion, novel thiosemicarbazone iron chelators (e.g., di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone) were demonstrated to inhibit ROCK1/pMLC2-modulated actin-filament polymerization, stress fiber assembly, and formation via a mechanism involving NDRG1. These results highlight the role of the ROCK1/pMLC2 pathway in the NDRG1-mediated antimetastatic signaling network and the therapeutic potential of iron chelators at inhibiting metastasis.
authors.affiliation: Department of General Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Sun
authors.forename: Daohai
authors.initials: D
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Zheng
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhao
authors.forename: Minhua
authors.initials: M
authors.lastname: Zheng
authors.forename: Zaklina
authors.initials: Z
authors.lastname: Kovacevic
authors.forename: Des R
authors.initials: DR
authors.lastname: Richardson
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D024722:Cardiac Myosins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects* / Q000235:genetics; D055785:Gene Knockdown Techniques; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology*; D058990:Molecular Targeted Therapy; D018994:Myosin Light Chains / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009362:Neoplasm Metastasis; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D022502:Stress Fibers / Q000378:metabolism*; D013882:Thiosemicarbazones / Q000494:pharmacology; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000099259:N-myc Downstream-Regulated Gene 1 Protein
chemical_list: D000199:Actins; D024722:Cardiac Myosins; D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D007502:Iron Chelating Agents; D018994:Myosin Light Chains; D013882:Thiosemicarbazones; D054460:rho-Associated Kinases; D000099259:N-myc Downstream-Regulated Gene 1 Protein; C107184:myosin light chain 2; C515851:ROCK1 protein, human