To further demonstrate the key role that ERα plays in AhR responsiveness to AF, ERα was transiently knocked down using siRNA in vorinostat-pretreated MDA-MB-231 and Hs578T cells, and the induction of CYP1A1 and SULT1A1 after AFP464 treatment was determined by qRT-PCR. This evidence concerns the gene ESR1 and atrial fibrillation.