Although these frequent p53 mutations serve primarily to abrogate the tumour-suppressor function of wild-type p53, there is growing evidence that the resultant mutant p53 proteins may also contribute actively to tumourigenesis through either a dominant-negative or a gain-of-function mechanism (Sigal and Rotter, 2000; Cadwell and Zambetti, 2001; Zalcenstein et al, 2003; Kim and Deppert, 2004). This evidence concerns the gene TP53 and neoplasm.