Metastasis formation in colon cancer severely reduces the survival rate in patients. S100A4, a calcium-binding protein, is implicated in promoting metastasis formation in colon cancer. To identify a transcription inhibitor of S100A4, high-throughput screening of 1280 pharmacologically active compounds was performed using a human colon cancer cell line expressing a S100A4 promoter–driven luciferase (LUC) reporter gene construct (HCT116-S1004p-LUC). Niclosamide, an antihelminthic agent, was identified as a potential candidate. Colon cancer cell lines (HCT116, SW620, LS174T, SW480, and DLD-1) were treated with 1 μM niclosamide to analyze the effect on S100A4 mRNA and protein expression by quantitative reverse transcription–polymerase chain reaction and immunoblot assays, and effects on cell migration, invasion, proliferation, and colony formation were also assessed in vitro. The effect of niclosamide on liver metastasis was assessed in a xenograft mouse model of human colon cancer (n = 8 mice) by in vivo imaging. The long-term effect of niclosamide on metastasis formation after discontinued treatment was quantified by scoring, and overall survival (n = 12 mice) was analyzed by Kaplan–Meier method after discontinuation of treatment. All statistical tests were two-sided. Reduced S100A4 mRNA and protein expression, and inhibited cell migration, invasion, proliferation, and colony formation were observed in niclosamide-treated colon cancer cells in vitro. In vivo imaging of niclosamide-treated mice showed reduced liver metastasis compared with solvent-treated control mice (n = 4 mice per group). Compared with the control group, discontinuation of treatment for 26 days showed reduced liver metastasis formation in mice (n = 6 mice per group) (control vs discontinuous treatment, mean metastasis score = 100% vs 34.9%, mean difference = 65.1%; 95% confidence interval [CI] = 18.4% to 111.9%, P < .01) and increased overall survival (n = 6 mice per group; control vs discontinuous treatment, median survival = 24 vs 46.5 days, ratio = 0.52, 95% CI = 0.19 to 0.84, P = .001). Niclosamide inhibits S100A4-induced metastasis formation in a mouse model of colon cancer and has therapeutic potential.

Expression of the Y-box protein YB-1 is increased in proliferating normal and cancer cells, but its role in cell proliferation and cell cycle progression is unclear. We have identified a cell cycle-dependent relocalization of YB-1 from the cytoplasm to the nucleus at the G₁/S phase transition and demonstrate that both the charged zipper and the cold shock domain are involved in regulating this process. Using cell lines that constitutively overexpress YB-1, we show that nuclear accumulation of YB-1 is associated with increased cyclin A and cyclin B1 mRNA and protein expression. We provide evidence that deregulated YB-1 expression is linked to adhesion-independent cell proliferation through the induction of cyclin A. Thus, we have identified YB-1 as a cell cycle stage-specific transcription factor important for cell proliferation.