To determine whether RASSF1A also affects ERα expression and activity in breast cancer cells through activation of FOXO3A transcriptional activity, MCF7 and T47D cells that conditionally express RASSF1A [3] were transiently transfected with the FHRE-Luc reporter plasmid [6] that is transcriptionally activated by the O subgroup of FOX proteins (FOXO proteins). The gene discussed is ESR1; the disease is breast carcinoma.