Loss of heterozygosity on chromosome 1q in human breast cancer

Cytogenetic markers involving the long arm of chromosome 1 are the most frequently observed karyotypic changes seen in breast cancer. Based on cytogenetic data, we have used polymorphic DNA markers to search for allelic losses at this chromosome region among 48 breast carcinomas. For SPTA1, allelic losses were seen in 6 of 26 (23%) informative carcinomas, while 3 of 13 (23%) and 5 of 19 (26%) informative patients showed losses at AT3 and D1S53, respectively. The background frequency of allelic loss was obtained from data using 3 other loci on the 1q arm and 2 on the p arm of chromosome 1. With these markers, only 6 of 62 informative patients (8%) showed an allelic loss, with the range being 0-13%. The allelic losses seen on 1q, which were found in 9 carcinomas, comprised an overlapping set; the common region deleted was approximately 26 centimorgans on the q arm of chromosome 1 (bands q23-32 between AT3 and D1S53). These results suggest that inactivation of a gene(s) located on 1q23-32 might contribute to the genesis of breast cancer.