SOX2 and embryonal carcinoma: In keeping with a restricted expression of RARγ within primitive cells, the binding sites for RAR/RXR dimers within undifferentiated F9 embryonal carcinoma cells coincided with loci that are targeted by transcription factors that are important to pluripotency (SOX2, NANOG, and POU5f1) (Chatagnon et al., 2015).