The classical functions of p53 protein are those related to its role on DNA 
damage, cell growth arrest, senescence and apoptosis. For this reason it is 
called 'the guardian of the genome' and is considered one of the most important 
players in the development of cancer. However, more recently it has been show 
that p53 is not only involved in cancer, but also in ageing. p53 is stimulated 
by stress, which in turn results in the activation of a wide range of 
transcriptional targets. Low-intensity stress will activate p53 in a manner 
which results in antioxidant response, thus protecting against ageing because of 
its antioxidant function. On the contrary, high-intensity activation of p53 will 
result in an increase of oxidative stress by activation of p53-mediated 
pro-oxidant targets, thus increasing the rate of ageing, but protecting against 
cancer.