Expression of the CEBPB and CEBPD transcription factors is induced by at least three factors:
1) Mitogens such as those present in fetal serum act via the Krox20 transcription factor to activate expression of CEBPB.
2) Glucocorticoids activate expression of CEBPD.
3) Hormones or drugs that increase intracellular cAMP act via pCREB to activate expression of CEBPB.
The detailed mechanisms of activation are not yet known.