Retinoic acid has previously been shown to inhibit tumor cell proliferation in a mouse model of Cushing’s disease, a finding that was accompanied by decreased levels of ACTH and cortisol.62 Retinoic acid pharmacologically inhibits cell proliferation and ACTH secretion in the AtT-20 pituitary corticotroph cell line via induction of BMP-4 expression,63 however this mechanism still appears to be mediated by epidrugs and augmented by retinoic acid.16 The gene discussed is POMC; the disease is neoplasm.