Mutant p53: the loaded gun.

Alterations in the p53 gene are the most common genetic defects found in tumors so far. Taking into account that p53 is a powerful inducer of cell death it is not surprising that the abolition of its function occurs almost universally during tumor development. There are several features of p53 inactivation in tumors which are quite unique. Firstly, mutations occur at high frequency in the p53 gene, ie, around 50% of human tumors carry p53 mutations. Secondly, mutations are largely of the same type, ie, 87% of them are point missense mutations resulting in a substitution of one amino acid residue. Thirdly, the majority of mutations occur in the DNA binding domain of p53. Finally, mutant p53 proteins accumulate at high levels in tumor cells. Can we take advantage of p53 mutations in tumor cells to selectively kill them? Is this the Achilles heel of tumors that can be exploited for novel non-toxic anticancer therapy? In this review the possible approaches toward reactivation of mutant p53 in tumors will be discussed.