Consistent with the effects of PAD4 inhibition in ER+ breast cancer cells, endogenous PAD4 inhibited breast cancer progression by limiting the size of the CSC population in a variety of breast cancer models in vitro and in vivo, and this effect was associated with the epigenetic repression of the stemness master transcription factors NANOG and OCT4 [251]. This evidence concerns the gene POU5F1 and breast cancer.