The major chemotherapeutic drugs used nowadays to suppress breast cancer cells are developed for targeted delivery of chemo-agents against several molecular and cellular signaling pathway proteins, mainly, for example, ER, PR, HER2, VEGFR1, VEGFR2, and EGFR (Sarkar and Mandal, 2009; Jin and Ye, 2013). The gene discussed is ESR1; the disease is breast cancer.