CHARACTERIZATION OF RECURRENT HOMOGENEOUSLY STAINING REGIONS IN 72 BREAST CARCINOMAS

Cytogenetic analyses were performed on 223 breast carcinomas, of which 60% contained homogeneously staining regions (hsr), an intrachromosom al cytogenetic feature of gene amplification. The precise hsr localiza tion could be determined for 123 hsr from 72 cases. The juxtacentromer ic region of chromosome 8, band 11q13, and the whole of chromosome 17 were frequently involved. For 28 cases, the origin of the DNA sequence s forming HSR could be investigated by chromosome painting, comparativ e genomic hybridization, and/or Southern blotting. Sequences from chro mosomes II and 17 were mostly found within hsr located on chromosomes I I and 17, respectively. In contrast, sequences from chromosome 8 wer e rarely found within hsr localized on chromosome 8. These observation s suggest that different mechanisms lead to hsr formation in breast ca ncer. Band 11q13 and the 17p chromosome arm may correspond to sites of in situ amplification driven by deletions distal to the amplification target genes. hsr in the region 17q2, which is also a frequent site o f in situ amplification, takes place without the occurrence of a dista l deletion. The short arm of chromosome 8 is often deleted, but freque ntly becomes the site of hsr formed elsewhere in the genome. (C) 1998 Wiley-Liss, Inc.