BRCA1 and breast cancer: In addition, the close functional relationship between p53 and the breast cancer susceptibility genes BRCA1 and BRCA2 (Jonkers et al, 2001; Ongusaha et al, 2003; Liu et al, 2007) has promoted the investigation of the Arg72Pro SNP as a possible risk modifier in BRCA1/2 mutation carriers (Martin et al, 2003).