Germline mutations of the BRCA1 tumor suppressor gene on chromosome 17
q are involved in a significant fraction of hereditary breast and ovar
ian cancers. Allelic deletions that include the BRCA1 locus are common
in breast and ovarian cancers, implying that somatic mutations of thi
s gene may play an important role in the more common sporadic forms of
these tumors as well. The recent cloning of BRCA1 allows direct testi
ng of this hypothesis. A combination of single strand conformation and
sequencing analyses was used to examine the 22 coding exons and intro
nic splice donor and acceptor regions of BRCA1 for mutations in 115 un
selected Eases of epithelial ovarian carcinoma. Seven mutations were i
dentified, all of which were present in the germlines of patients with
remarkable family or medical histories of breast and/or ovarian cance
r, Eighty-nine of these tumors were examined for loss of heterozygosit
y in the BRCA1 region of chromosome 17q, and 67% of the tumors studied
exhibited allelic deletions that included this region. These data are
consistent with the hypothesis that BRCA1 mutations are involved in t
he etiology of hereditary ovarian carcinomas but occur rarely in spora
dic tumors, and that the frequent allelic loss on chromosome 17q in th
is cancer type reflects the involvement of an additional tumor suppres
sor gene(s).