ESR2 and breast cancer: While ERα is recognized as being responsible for breast cancer development, the role of ERβ is controversial [23].The interaction of estrogens with ERs is highly complex, and several other signaling molecules are involved in ER-dependent and ER-independent breast cancer development and complications, including TNBCs [24].Notable signaling molecules and pathways that are involved in the complex interplay of ERs in estrogen-dependent or -independent breast cancer development and progression are growth factors, cytokines, and TGF-β1.