Allelic Loss on Chromosome 8p in BRCA‐1 Mutation Positive Breast/Ovarian Cancers

: Loss of heterozygosity (LOH) on chromosome 8p in 20 BRCA-1 mutation positive familial breast/ovarian cancer patients from nine families was examined. Allelic deletions on chromosome 8p were identified with at least one marker in 11 of 17 (65%) informative cases. Seven of eight (88%) informative cases showed deletion of chromosome 17q consistent with inactivation of the BRCA-1 gene. Our data suggests loss of a tumor suppressor gene on chromosome 8p may be a frequent genetic event in the development of familial breast and ovarian cancer.