CDKN2A and neoplasm: Previously, Chen et al. reported an increased expression of genes involved in the Trp53 dependent cellular senescence response in early hyperplasia stages of tumor development in the related Probasin (PB)-Cre targeted Pten knockout mouse model [38] We also observed higher expression of Trp53, Trp53-regulated and Trp53-independent senescence markers Cdkn1a (encoding p21), Dec1 and Cdkn2a (encoding P16) in HP as compared to NP (Fig 5A).