TP53 and neoplasm: Interestingly, in addition to an Ink4a/Arf-dependent antitumoural role of IKKβ in skin cancer,7 we observed that overexpression of IKKβ in the absence of either epithelial p53 or both p16 and p19 led to the appearance of maxillary tumours (usually monolateral) that caused facial distortion and swelling in some mice (Fig. 2a, b).