Differentially amplified chromosome 12 sequences in low‐ and high‐grade osteosarcoma

Abstract

Most osteosarcomas are highly aggressive malignancies characterized by a complex pattern of chromosome abnormalities. However, a subgroup of low-grade, parosteal tumors exhibits a relatively simple aberration pattern dominated by ring chromosomes carrying amplified material from chromosome 12. To assess whether sequences from this chromosome were differentially amplified in low- and high-grade osteosarcomas, copy numbers of the CCND2, ETV6, KRAS2, and D12S85 regions in 12p and the MDM2 region in 12q were evaluated by interphase or metaphase fluorescence in situ hybridization (FISH) in 24 osteosarcomas. Amplification of MDM2 was detected in all five low-grade and four high-grade osteosarcomas, all of which showed ring chromosomes. An overrepresentation of 12p sequences was found in 1/5 low-grade and in 9/19 high-grade tumors. Multicolor single-copy FISH analysis of metaphase cells from six high-grade tumors showed that extra 12p material either occurred together with MDM2 in ring chromosomes or was scattered over the genome as a result of complex structural rearrangements. Most tumors (8/10) not containing amplification of the assessed chromosome 12 loci exhibited a nondiploid pattern at evaluation with probes for centromeric alpha satellite sequences. These findings indicate that gain of sequences from the short arm of chromosome 12 could be a possible genetic pathway in the development of aggressive osteosarcoma.

MDM2 and CDK4 immunohistochemistry is a valuable tool in the differential diagnosis of low-grade osteosarcomas and other primary fibro-osseous lesions of the bone

“…The biomolecular study of MDM2 amplification in low-grade osteosarcomas, including aCGH, FISH and PCR, has revealed a frequency range of 19-100 and 12-80% for CDK4. 19,47,52,59,60 The highest amplification frequencies were obtained with Q-PCR 52 on frozen samples and with FISH and Southern blotting 19,47 on unspecified material. DNA extraction from paraffin blocks can explain the disappointing results with Q-PCR in two studies.…”

“…In contrast to the complex karyotypes previously reported in conventional osteosarcoma, 43 low-grade osteosarcoma is characterized by a simple karyotype with supernumerary ring chromosomes 19,[44][45][46] and over-representation of 12q sequences on CGH. 16,17,21 Ring chromosomes are composed of 12q13-15 clusters containing MDM2 and CDK4 and are due to telomeric deletions.…”

“…Although some studies have reported 12q amplification in conventional high-grade osteosarcomas, with a frequency ranging from 0 to 27%, 19,50,52-59 the majority have indicated that amplification of MDM2 and CDK4 is a typical feature of parosteal osteosarcoma and lowgrade central osteosarcoma. 16,17,19,21,47,52,60,61 One study showed a high level of CDK4 and MDM2 amplification in a series of nine osteosarcomas of the jaw, including five intermediate and high-grade osteosarcomas. 51 However, gnathic osteosarcomas have particular clinical and biological profiles that differ from conventional high-grade osteosarcomas of long bones and that require further specific investigation.…”

“…These tumors seem to share similarities in changes in cytogenetics and molecular genetics involving ring or giant marker chromosomes, which contain amplification of the 12q13-15 region, including murine doubleminute type 2 (MDM2) and cyclin-dependent kinase 4 (CDK4). [16][17][18][19][20][21] The purpose of this study was to determine the value of MDM2 and CDK4 immunostaining for the differential diagnosis of low-grade osteosarcomas and benign fibrous or fibro-osseous lesions. We then investigated the immunohistochemical status of 72 low-grade osteosarcomas and 107 fibrous or fibro-osseous lesions of the bone or paraosseous soft tissue.…”

Immunohistochemical analysis of MDM2 and CDK4 distinguishes low-grade osteosarcoma from benign mimics

“…Parosteal osteosarcoma was repeatedly shown to harbor one or more supernumerary ring chromosomes, often as the sole abnormality. [9][10][11][12] This low number of chromosomal imbalances is in contrast with the complex numerical and structural aberrations observed in conventional osteosarcoma. 3 The ring chromosomes of parosteal osteosarcoma were found, by comparative genomic hybridization, to carry amplified 12q13-15 genetic material.…”