Inhibition of PMA-induced endogenous PKD1 activation in LNCaP cells. LNCaP cells were pretreated with indicated concentrations of the five analogs for 45 min, then stimulated with 100 nM PMA for 20 min. Cell lysates were immunoblotted for p-S916-PKD1 and p-S742-PKD1. GAPDH was blotted as a loading control. The experiment was repeated at least three times and representative blots are shown.