Introduction: Prostate cancer presents a major health challenge as the second most common cancer in males worldwide. Progression of prostate cancer to androgen-insensitivity has poor prognosis and development of novel therapies is essential to combat this disease. The study of functional expression of ion channels in prostate cancer is an emerging area of research. The aim of the present investigation was to investigate the effect of the Kv channel inhibitor, 4-aminopyridine (4-AP) on human prostate cancer cell lines. Materials and Methods: Human prostate cancer cells lines (PC3, DU145, LNCaP) were used for clonogenic cell survival assays, scratch-wound healing assays and cell proliferation assays. Quantitative data are expressed as mean ± SEM and statistical comparisons were made with ANOVA or unpaired Student’s t-test, with P<0.05 considered to be significant.Results: 4-aminopyridine (4-AP) is a potent inhibitor of several types of voltage-dependent K+ channels and 4-AP sensitive currents have been reported in rat prostate cancer cell lines1. The potential role of 4-AP sensitive channels in cell survival was examined in clonogenic assays. In DU145 cells, 4-AP (N=4) caused a concentration-dependent reduction in cell survival with an IC50 of 1.7mM. Significant reduction occurred with 2.5, 5, 7.5 and 10mM 4-AP (P<0.05; ANOVA with post-Dunnett’s test). Cell proliferation of prostate cancer cell lines was investigated with 4-AP (concentration range 0.1 to 10 mM) in WST-1 proliferation assays. 4-AP decreased proliferation in DU145 cells (N=3) in a concentration-dependent manner with significant reduction over 2.5-10mM (P<0.05); similar effects were observed in LNCaP (N=3) and PC3 cells (N=2). In scratch-wound healing assays which indicate cell migration, 4-AP (5mM) significantly inhibited the % wound closure in DU145 cells (40.7±2.3%, N=3) compared with controls (53.3±4.7%, N=3, P<0.05, unpaired t-test). 4-AP (5mM) also reduced % wound closure in PC3 cells. Conclusions: The Kv channel inhibitor, 4-AP decreased cell proliferation, clonogenic cell survival and cell migration in human prostate cancer cell lines. This data indicates that 4-AP-sensitive channels have important physiological roles in prostate cancer.