TP53 and squamous cell carcinoma: On the other hand, ΔNp63 is considered to have oncogenic properties based on the following observations: (1) ΔNp63 overexpression is often observed (Parsa et al, 1999; Hibi et al, 2000) and it enhances oncogenic growth in squamous cell carcinomas (Hibi et al, 2000); (2) ΔNp63 could function as dominant negatives against the p53 tumour suppressor activities (Yang et al, 1998); and (3) ΔNp63 overexpression induces nuclear accumulation of β-catenin and activates the β-catenin signalling that promotes cell proliferation (Patturajan et al, 2002).