To study the inhibitory effect of tamoxifen on castration‐resistant PCa in vitro and in vivo, and to examine whether it has an on‐target inhibition on ERα‐mediated cancer growth and survival pathways, we treated castration‐resistant PCa cell lines including VCaP and PC‐3 cells, respectively, with tamoxifen at various doses. Here, ESR1 is linked to posterior cortical atrophy.