To determine the mechanisms through which SD-208 induced G2/M arrest in prostate cancer cells, we next assessed the impact of SD-208 on cell cycle machineries at the G2/M transition in DU145 and PC3 prostate cancer cells, which have similar PKD isoform expression patterns [10] As shown in Fig. 5C-D, treatment with increasing concentrations of SD-208 for 24 and 48 h induced the expression of Cip1/p21 in a concentration-dependent manner. Here, PRKD1 is linked to prostate cancer.