Conversely, CRIPTO is directly repressed by the orphan nuclear receptor germ cell nuclear factor (GCNF) which binds to the promoter during retinoic acid-induced differentiation of human embryonic carcinoma cells and by the miR-15a/16 cluster which bind to the 3’UTR of CRIPTO mRNA [47,48]. This evidence concerns the gene NR6A1 and embryonal carcinoma.