Effect of HOXB13 on p21-dependent E2F1-mediated transactivation: A, LNCaP cells were grown under hormone-deprived conditions for 3 days and transfected with pE2F1(3X)-luc, pFLAG-HOXB13, and pCDNA-E2F1. B, Both HCT116 (p21+/+) and HCT116 (p21-/-) cells were transfected with pE2F1-luc and an increased amount of pFLAG-HOXB13. C, HCT116 (p21+/+) cells were transfected with pE2F1-luc, pFLAG-HOXB13, and an increased amount of pFLAG-p21. Corresponding control vectors were used to match each DNA. After 48 hours, the cells were evaluated for luciferase assays. Each bar represents the mean ± S.D. D, S4 cells were treated with Dox to induce HOXB13 followed by Western blot and RT-PCR analyses.