Phosphorylation by Cdk5 on PIKE-A-mediated glioblastoma cell migration and invasion. (A) The effect of blocking Cdk5 on glioblastoma cell migration. After transfection and starvation, U87MG cells (Right) were scored for migration in a blind manner whereas LN-Z308 (Left) cells were first stimulated with IGF-1 before the scoring. (B) The effect of PIKE-A phosphorylation status on U87MG cell migration. Equal numbers of GFP-PIKE WT and RFP-S279A or RFP-S279D positively transfected cells were mixed, plated into transwell chambers, and scored for the migration of GFP and RFP positive cells as described in Materials and Methods. (C) The effect of PIKE-A phosphorylation status on U87MG cell invasion. Experiment was performed as described in B except for that the cells were placed in Matrigel-coated chamber. All of the data above were calculated as means (± SD.) of three independent experiments (*, P < 0.05 and **, P < 0.01, Student's t test).