AHR and atrial fibrillation: 2) Reactivation of ERα expression was accompanied by restoration of AhR responsiveness to AF, as indicated by transcriptional induction of CYP1A1, in MDA-MB-231 and Hs578T cells (Figure 3D), whereas the loss of ERα activation in vorinostat-pretreated cells diminished AhR-dependent transcriptional induction of CYP1A1 after AF treatment (Figure 3E).