CDK4 and ACTH-producing pituitary gland adenoma: Using a germline transgenic zebrafish model overexpressing PTTG in pituitary corticotrophs to recapitulate human Cushing disease, we tested several small molecule CDK inhibitors on corticotroph adenomas in vivo, including flavopiridol, R-roscovitine (seliciclib; primarily an inhibitor of CDK1 and CDK2 in late G1 but not an inhibitor of CDK4 and CDK6), olomoucine (CDK1, CDK2), PD-0332991 (CDK4/6 in early G1), and CAY10572 (CDK7 in S phase).