CDKN1B and pituitary gland adenoma: In addition, a mouse with a mutation (Ser10Ala) of Cdkn1b, which encodes p27, a member of the p21 family of CKIs that abrogated its ability to bind CDKs (Besson et al., 2006), resulted in the development of pituitary adenomas (Besson et al., 2006).