The roles of the breast cancer susceptibility genes BRCA1 and BRCA2 in sporadic breast
carcinomas are unclear. Only a small percentage of sporadic breast tumours appear to carry
somatic mutations in the BRCA2 gene, despite the fact that 30-40% of sporadic breast
cancers show LOH at this locus. The idea that there is another critical gene at 13q12-q13
remains plausible, and BRCA2 may be inactivated by a mechanism other than somatic mutation. The data presented here indicate a role for BRCA2 in the pathogenesis of sporadic breast tumours associated with overexpression, although the mechanisms by which this tumour suppressor gene exerts a positive effect on cell proliferation remain to be determined.
The thought that up-regulation of BRCA2 may be a protective response, and BRCA2
expression status may have prognostic significance, is deserving of further investigation.