TP53 and cervical squamous intraepithelial neoplasia: We observed that Hipk2−/− Tp53−/− MEFs, despite the presence of CIN, proliferate and spontaneously immortalize, as well as Hipk2+/+ p53−/− MEFs, suggesting that p53 inactivation leads to the acquisition of tolerance to the CIN induced by hipk2 absence (Figures 4B-D).