ESR1 and breast cancer: •Preclinical study: ENT increased the expression of ERα and aromatase and restored the sensitization of breast cancer cells to the aromatase inhibitor letrozole. SAHA could enhance the anti-tumor effects of the PARPi olaparib in TNBC cells by regulating the expression of homologous recombination repair (HRR)-related genes and hampering DNA repair.