To assess the role of CK1α in SDF1 proliferation blockade, CK1α was knocked down by siRNA and its effect on CSPC proliferation assessed. A) CK1α siRNA, 20 nM, decreased levels to 9.0±2.8% of scrambled. B) CK1α siRNA knockdown decreased CK1α protein expression and S45 β-catenin phosphorylation. C) CK1α siRNA blocked CSPC proliferation similar to that of 25 nM SDF1 treatment for 24 hours. Values are the mean ± SE, n=2-4. * p<0.05, ** p<0.01 vs Veh or Scr siR, †† p<0.01 vs treated control.