Low Frequency Loss of Heterozygosity in the BRCA1 Region in Japanese Sporadic Breast Cancer

To investigate the possible involvement of the BRCA1 gene in Japanese sporadic breast cancer we have analyzed loss of heterozygosity (LOH) at the BRCA1 region (17q12-q22) in 101 sporadic breast cancers using 5 microsatellite markers, such as D17S250, D17S846, D17S855, D17S579, and NME1. The frequency of LOH in each markers was 14.9%(11/74), 11.9 %(8/67),14.3%(12/84),5.3%(4/75), and13.3%(9/68),respectively. The incidence of LOH in at least one of 5 markers was 23.8%(24/101). The LOH at the BRCA1 region did not significantly correlate with clinicopathologic factors. Despite using a microdissection method, the LOH frequency in our series was relatively lower than other reports, especially in Western countries. We suggest that the BRCA1 gene might play only a limited role as a tumor suppressor gene in the majority of Japanese sporadic breast cancers.