ESR1 and breast cancer: The inhibition of the MCF-7 cell viability by enhancing the cell cycle arrest in G2/M phase and regulating the key biomarkers (tumor growth-associated biomarkers, including Erα, 1GPBP2, IGFBP4, GATA3, and apoptosis-associated biomarkers, including ELF5, p53, p21, p18, CDH1, CDH2, and p12) in breast cancer cells was demonstrated.