Approximately 70% of breast cancers are ER-positive and/or PR-positive, hence the focus of the present study is on Luminal A, a type of breast cancer where the proliferating cells are hormone-receptor positive (estrogen-receptor and/or progesterone-receptor positive), HER2 negative, and has low levels of the protein Ki-67, which subsequently facilitates in controlling the growth of cells5. The gene discussed is ESR1; the disease is breast cancer.