CDKN1A and papilloma: Strikingly, immunohistochemistry of papillomas revealed low levels of p21cip1 in keratinocytes from 19 out of 21 tumors from control animals, but high p21cip1 levels in keratinocytes from 14 out of 15 tumors of Miz1ΔPOZ mice (Figure 4F and G; Figure S8A).