Loss of heterozygosity on chromosome 17q11-21 in cancer of women who have both breast and ovarian cancer

Inherited abnormalities of the BRCA1 gene appear to be involved in some cases where women develop both breast and ovarian cancer independently. The BRCA1 gene is believed to be an important tumor suppressor gene, but at the time of this investigation, its chromosome was known, but not its precise location. Only indirect investigation of abnormalities within regions of its chromosome could be carried out. Its location has since been pinpointed. Cancerous and normal tissue samples were analyzed from 29 women who developed primary cancers of both breast and ovary. DNA analysis revealed abnormalities of the chromosome containing BRCA1 in 46% of breast cancers, 78% of ovarian cancers, and 38% of both cancers. In all cases where the chromosome was abnormal in both cancers, the same strand of the pair was affected. These cases also tended to be among younger women. These women seem more likely to have an inherited genetic defect.