ESR1 and breast cancer: As RASSF1A is a key regulator of the Hippo pathway, and Hippo signaling plays an important role in the control of ERα function and the suppression of luminal breast cancer, we hypothesized that RASSF1A may exert some of its suppressive effects on ERα and FOXM1 through the Hippo pathway, for example, through the Hippo effector YAP1.