Co-amplification and overexpression of CDK4, SAS and MDM2 occurs frequently in human parosteal osteosarcomas

Abstract

Ampli®cation of genes in the 12q13-15 region occurs frequently in several malignancies including osteosarcoma. The products of these ampli®ed genes are thought to provide cancer cells with a selective growth advantage; however, the speci®c gene(s) driving this amplicon is unknown. We have previously shown that the SAS gene is ampli®ed in most parosteal osteosarcomas. In this study we analysed additional putative growth regulatory genes in this chromosomal region in 24 primary osteosarcoma specimens. CDK4 and SAS were coampli®ed in 6/6 parosteal tumors, and MDM2 was also ampli®ed in 4/5 parosteal cases. In comparison, ampli®cation occurred in only 2/16 classical intramedullary osteosarcomas and involved the SAS gene. Each ampli®ed gene had a correspondingly elevated mRNA level. Four high grade intramedullary tumors had elevated mRNA expression of SAS, but did not exhibit gene ampli®cation. Gene ampli®cation/overexpression was not associated with metastatic disease and did not change markedly with tumor progression, as evidenced by analysis of sequential tumor specimens from eight patients. Three other genes in the 12q13-15 region (CDK2, WNT1 and WNT10b) were not ampli®ed in any of the tumors. The di erent patterns of gene ampli®ca-tion and overexpression of CDK4, SAS and MDM2 in parosteal and intramedullary osteosarcomas may help explain the disparity in the biological behaviour of these two types of 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

“…16,17,21 Ring chromosomes are composed of 12q13-15 clusters containing MDM2 and CDK4 and are due to telomeric deletions. 16,47 Similar cytogenetic abnormalities have previously been described in other low-grade malignancy mesenchymal lesions such as well-differentiated liposarcoma. 48 Overexpression and gene amplification of MDM2 and CDK4 located on chromosome 12q13-15 have been reported to occur in various human sarcomas as the pathway of tumorigenesis or tumor progression.…”

“…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.…”

“…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.…”

Modification of the p53 transgene of a replication-competent adenovirus prevents mdm2- and E1b-55kD-mediated degradation of p53

“…22,23 mdm2 overexpression in fact is a mechanism by which the p53 pathway is inactivated in several cancer types. [24][25][26][27] The adenoviral E1b-55kD protein, similar to mdm2, strongly inhibits p53 function. E1b-55kD reduces p53-mediated transcriptional activation and reduces p53-mediated apoptosis.…”

Regulation of Survivin and CDK4 by Epstein-Barr virus encoded latent membrane protein 1 in nasopharyngeal carcinoma cell lines

“…It is usually thought that CDK4 expressed stably in cells, but recently more and more reports confirmed its over-expression in tumors. Some experiments showed that over-expression of CDK4 was closely associated with the acceleration of tumor cell G 1 -S transition and cell malign-proliferation [18][19][20][21][22][23][24][25][26][27][28][29][30][31]. Only when CDK4 moves from the cytoplasm to the nuclei, it can play its roles in the cell cycle regulation and cell proliferation promotion.…”