TP53 and neoplasm: In contrast to transgenic mice that either overexpress full length TP53 or the Δ40 p53 isoform, transgenic 'super p53' mice with one (p53-tg) or two (p53-tgb) additional copies of the endogenous TP53 locus have an enhanced DNA-damage response and are tumor resistant, yet age normally and are fertile (García-Cao et al., 2002, 2006; Matheu et al., 2007).