TamoxifenCitrate is used for the treats breast cancer for its selective estrogen receptor modulator action [8].Targeted breast cancer protein like Human epidermal growth factor receptor 2 (HER2), Estrogen receptor alpha (ERα), Progesteronereceptor (PR), Phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), Threonine-protein kinase 1 (AKT), REV-ERB alpha (NR1D1), Breastcancer metastasis suppressor 1 (BRMS1), aromatase, Mammalian or Mechanistic target of rapamycin (mTOR), Cyclin-dependent kinase 4,6(CDK4/6), Tyrosine-protein kinase and Topoisomerase II (TopII) [9]. This evidence concerns the gene NR1D1 and breast cancer.