['To observe the suppression of the expression of androgen receptor (AR) gene in PC3 cells after AR-specific siRNAs transfection, and to search for the siRNA (s) with the greatest suppressing efficiency.', 'Five AR-specific siRNAs were selected, RNAi expression vectors were constructed and transfected into PC3 cells, and the AR expression was detected by real time FQ-PCR and Western blot. A nonsense small RNA was set as negative control.', 'Compared with the control group, the AR expression decreased in various degrees in the 5 experimental groups (P < 0.05), and siRNA1, siRNA4 and siRNA5 showed the greatest suppressing efficiency as compared with the other experimental groups, with statistically significant difference (P < 0.05).'] Does [ siRNA knock down the expression of AR gene in PC3 cell lines ]?