E2F1 and prostate carcinoma: To test the hypothesis that Hes1 is a negative regulator of δ-catenin expression, we co-transfected Hes1 expression vectors (pcDNA-flag-WT-Hes1 or pcDNA-flag-DN-Hes1) and E2F1, together with δ-catenin-luciferase reporter vectors BK1 or BK5, into CWR22-Rv1 or PC3 human prostate carcinoma cell lines.