Refinement of the LOH region 1 at 11q23.1 deleted in human breast carcinomas and sublocalization of 11 expressed sequence tags within the refined region

Loss of constitutive heterozygosity at 11q23 has been detected in various h uman solid tumors. Here, we described the analysis of a series of normal an d tumor pairs from 110 breast carcinomas for the presence of loss of hetero zygosity at 11q23 loci. The overall frequency of LOH was 48%, confirming th e importance of deletions at 11q23 in breast tumorigenesis. Previously, we have identified two independent regions of LOH at 11q23, the LOH region 1 a t 11q23.1 and the LOH region 2 at 11q23.3. The most telomeric region was re cently refined between loci D11S1345 and D11S1316, a region of about 1 Mb. However, the LOH region 1, most centromeric, was still not finely refined: the boundaries were defined by loci D11S2000 and D11S897, separated by abou t 8 Mb. Here, me refined its boundaries between loci D11S1347 and D11S927, a region of about 2 Mb. We have mapped 11 expressed sequence tags (ESTs) wi thin this region and excluded another 20. This study represents a further s tep toward the identification of the putative tumor suppressor gene found w ithin the LOH region 1 at 11q23.1.