POU5F1 and atrial fibrillation: Also consistent with female rats, cells derived from the tumors of AF‐treated male rats showed higher expression of PRL and DPPA4, lower expression of D2R, and increased expression of stem cell regulatory proteins (SOX‐2, OCT‐4, KLF4, SNAIL‐1, and Nestin) when compared with those in AD and PF tumor cells, as determined by western blot (Figure 2A–K) and immunofluorescence (Figure 2I) for proteins and qPCR for genes (Figure 2J–Q).