Multiple regions of chromosome 4 demonstrating allelic losses in breast carcinomas.

Allelotyping studies suggest that allelic losses at one or both arms of chromosome 4 are frequent in several tumor types, but information about breast cancer is scant. A recent comparative genomic hybridization analysis revealed frequent losses of chromosome 4 in breast carcinomas. In an effort to more precisely locate the putative tumor suppressor gene(s) on chromosome 4 involved in the pathogenesis of breast carcinomas, we performed loss of heterozygosity studies using 19 polymorphic microsatellite markers. After precise microdissection of archival surgical cases, we analyzed DNA obtained from 44 breast carcinomas for loss of heterozygosity. In addition, DNA from tumor cell lines derived from 14 of these 44 breast carcinomas were also analyzed. We observed deletions of chromosome 4 at multiple sites in both tumor cell lines and breast carcinomas. The deletions in cell lines and their corresponding tumors were extensive in nature, whereas they were more localized in noncultured breast carcinomas. The localized deletions in the noncultured breast carcinomas clearly defined four nonoverlapping regions of frequent deletions: 4q33-34 (76%); 4q25-26 (63%); 4p15.1-15.3 (57%); and 4p16.3 (50%). Our results suggest that there may be multiple putative tumor suppressor genes, located on both arms of chromosome 4, whose inactivation is important in the pathogenesis of breast cancer.