ESR2 and cancer: Although the role of ERβ in TNBC is still unclear, a considerable number of studies have suggested that ERβ expression is beneficial to the treatment and prognosis of triple negative breast cancer, because ERβ can indirectly reduce the activation of androgen receptor (AR) by inhibiting the PI3K/AKT signaling pathway, and plays an anti-cancer role in AR+ TNBC (41).