Therefore a possible scheme to explain a role for MDM2 SNP309 G/G in BRCA tumors could be that overexpression of MDM2 in BRCA1/2 tumors results in down-regulation of p53 and allows the development of BRCA1/2 tumors similar to the effect induced by a mutation in p53. This evidence concerns the gene BRCA1 and invasive breast carcinoma.