ESR1 and Familial prostate cancer: This suggests that downregulating the expression of the ER and/or activating the downstream signaling of the AR can be essential in the fight against breast cancer; however, AR plays a significant role in the development and progression of therapy-resistant prostate cancer [69, 70], indicating that activation of AR to treat breast cancer will have dire effects on the prostate and suggesting that a focus on ER antagonists would be a more efficacious option.