Effect of HOXB13 on the p21-RB-E2F signaling pathway: A, S4 cells were grown under hormone-deprived conditions for 3 days and induced for HOXB13 with 100nM doxycycline. Extracted lysates were evaluated for Western blot analysis. LNCaP cells were grown under hormone-deprived condition for 3 days. B, Cells were transfected with p21-luc and pFLAG-HOXB13, pCDNA-HOXA13, or pCMV-HOXD13. C, Cells were transfected with pE2F1-luc and pFLAG-HOXB13. D, Cells were transfected with pE2F1-luc, pFLAG-HOXB13, and pCDNA-E2F1. Corresponding control vectors were used to match each DNA. After 48 hours, the cells were evaluated by luciferase assays. Each bar represents the mean ± S.D.