DNA copy number amplifications in sarcomas with homogeneously staining regions and double minutes

To identify DNA amplifications in sarcomas, comparative genomic hybridization was performed on 27 cases that were likely to display high-level DNA copy number gains. In all cases, chromosome banding analysis had revealed homogeneously staining regions or double minutes, i.e., cytogenetic signs of gene amplification. In most cases, gains predominated over losses. Low-level amplifications (ratio 1.3:1.5) were seen in 20 cases. High-level amplifications (ratio >1.5) exceeded the frequencies seen in published, unselected sarcomas of similar histotypes and were detected in 16 tumors: 4/4 osteosarcomas, 5/8 malignant fibrous histiocytomas, 3/7 leiomyosarcomas, 1/2 myosarcomas, 0/1 liposarcoma, 0/1 rhabdomyosarcoma, 1/1 pleomorphic sarcoma, 0/1 myxofibrosarcoma, 1/1 malignant mesenchymona, and 1/1 malignant schwannoma, with two to four chromosomal regions involved in nine tumors. Recurrent amplifications involved 1p33-p32, 5p15-p14, 7pter-p12, 7q21-qter, 8q21.3-qter, 11q22-q23, 16p13.2-p12, 19q12-q13.1, 20q11.2-qter, and 22q12-q13. Most of the recurrent gains/amplifications we detected have been reported in sarcomas previously. A novel gain/amplification was seen at 2q14.3-q21 in five cases of four sarcoma types. The disparate pattern of amplified sequences, the poor correspondence between the localization of low- and high-level amplifications, and the chromosomal position of homogeneously staining regions suggest the involvement of many genes in the amplifications and that the genes rarely maintain their native position in these tumors.