Breast cancer is the most common type of cancer diagnosed in women in the US and the second most common cause of death in women in the US. Treatment for breast cancer often involves a combination of surgery, chemotherapy, radiotherapy, and hormone therapy. Chemotherapy focuses on inhibiting estrogen binding to receptors, blocking estrogen production, targeting DNA replication, or preventing the division of cancer cells. Though clearly beneficial, the use of these drugs is severely limited due to serious adverse effects.