Mutational analysis of BRCA1 gene in ovarian and breast-ovarian cancer families in Japan.

Abstract

We analyzed the alteration of BRCAI in DNA obtained from 83 individuals of 13 Japanese site‐specific ovarian cancer families and 6 breast‐ovarian cancer families. Six germline mutations were detected in 7 families, which consisted of 4 breast‐ovarian cancer and 3 site‐specific ovarian cancer families, by single‐strand conformation polymorphism analysis, followed by direct sequence determination. The mutations included three framcshifts, two nonsense mutations, and one missense mutation causing loss of a zinc‐binding motif. The frequency of loss of heterozygosity at the microsatellite markers on the BRCAI gene was 57% (8 of 14 cases) in site‐specific ovarian cancer families, and 100% (6 of 6 cases) in breast‐ovarian cancer families. All tumors of the patients carrying a mutation of BRCAI showed deletion of wild‐type alleles, implicating BRCAI as a tumor suppressor gene. Tbese results suggest tbat germline mutations of the BRCAI gene play an important role in the carcinogen‐esis of breast and/or ovarian cancer in a majority of breast‐ovarian cancer families and in some site‐specific ovarian cancer families.