CDKN1A and neoplasm: As lack of Lkb1 in Ctsk+ cells led to a tumor-like mass in the cortical bone, the expression levels of genes involved in the cell cycle, including Ccnd1, Cdkn1a, Cdkn2a, and Cdkn2b, were determined to characterize the tumor and it was found that they were significantly increased in Ctsk-CKO tibiae at the age of 20 weeks (Figure 1H).