We previously demonstrated in a mouse embryonic carcinoma cell model that anendogenous dominant negative RARα mutant, lacking part of the E domainharboring the RA-binding domain, induced concerted epigenetic repression of bothRARβ2 and CYP26A1, encoding for aRA hydrolase involved in RA catabolism [8]. Here, CYP26A1 is linked to embryonal carcinoma.