As shown in Fig. 4, the non-tumorigenic mammary epithelial cell HC11 and prostate cancer cell line PC3 were found to express both receptors (Lanes 1 and 2) as reported by others [14], [36]; in contrast, DU-145 expresses only ERβ [36] (lane 6) and MDA-MB-231 is negative for both ERα and ERβ (lane 5). This evidence concerns the gene ESR1 and prostate cancer.