BRCA1 and breast cancer: While BRCA1 mutations are rare in sporadic breast cancers, BRCA1 dysfunction has also been reported in 24–63% of these cases and is associated with reduced or complete loss of BRCA1 mRNA and protein abundance [5,6,7], BRCA1 protein mis-localisation [2,8], as well as BRCA1 gene promoter methylation [9].