Figure 6. The inhibitory effect of VPA on cell proliferation was not changed by ATG5 rescue in DU145 cells or ATG5 knockdown in LNCaP and PC-3 cells (A) Valproic acid (VPA) dose-dependently inhibited the proliferation of LNCaP, DU145 and PC-3 cells. Logarithmic phase cells were incubated with indicated concentrations of VPA for 48 h. (B) DU145 cells were transfected with a plasmid containing the wild-type ATG5 gene and then treated with indicated concentrations of VPA for 48 h. (C and D) LNCaP and PC-3 cells were transfected with ATG5 siRNA or negative control (NC) siRNA for 48 h, and then treated with indicated concentrations of VPA for another 48 h. Cell proliferation was evaluated using MTS assay (A–D). One representative data of three independent experiments with similar results are shown as mean ± SD. The efficient knockdown of ATG5 protein in LNCaP and PC-3 cells was confirmed by western blotting (C and D, lower panels; VPA = 3.3 mM). The relative levels of ATG5 were normalized to TUBB and the value of NC siRNA-treated control of each group was set as 1.00, respectively.