RESUMO
BACKGROUND: Parosteal osteosarcoma (POS) is a unique low grade osteosarcoma. Two separate oncogenes, MDM2 and CDK4, are specifically amplified in POS. Its clinical behavior is usually indolent. In some occasions, it may progress to high grade and become fatal. Malignant transformation with high grade differentiation is the most reliable indicator to predict its aggressiveness and metastatic potential. This study is to discover the relationship between gene amplification and grading. METHODS: Retrospective analysis of MDM2/CDK4 expression/amplification using immunostaining, multiplex quantitative polymerase chain reaction (MQPCR) and fluorescence in situ hybridization (FISH) were studied on 14 patients with recurrent POS. RESULTS: Forty tumor specimens in formalin-fixed paraffin-embedded blocks from 14 patients of POS were included in this study. Twenty-seven tumors are low-grade, 13 are high-grade. All POS showed increased expression of both MDM2 and CDK4 proteins, but not those from conventional osteosarcoma. Except some tumors were non-informative (poor DNA quality), the rest of POS had a marked increase of MDM2 and CDK4 genes copies by MQPCR, and confirmed by MDM2 FISH. Moreover, the folds of amplification increase as tumors progress. And, the amplification folds in high-grade POS are consistently higher than those of conventional ones. CONCLUSION: FISH and MQPCR are both useful assays for estimating oncogene amplification status in bone tumors. Amplification levels of MDM2 and CDK4 are related to tumor grading and progression. Molecular determination of gene amplification status can be a reliable alternative for predicting clinical behavior of POS at small biopsies.
Assuntos
Neoplasias Ósseas/genética , Quinase 4 Dependente de Ciclina/genética , Amplificação de Genes , Osteossarcoma Justacortical/genética , Proteínas Proto-Oncogênicas c-mdm2/genética , Adolescente , Adulto , Neoplasias Ósseas/patologia , Criança , Feminino , Humanos , Hibridização in Situ Fluorescente , Masculino , Reação em Cadeia da Polimerase Multiplex , Gradação de Tumores , Osteossarcoma Justacortical/patologia , Estudos Retrospectivos , Adulto JovemRESUMO
The region q13-15 of chromosome 12 frequently is altered in human sarcomas, and several genes, such as SAS, CDK4, and MDM2, have been found to be amplified in bone and soft tissue sarcomas. These genes and their products were studied by quantitative polymerase chain reaction and immunohistochemical analysis in 25 parosteal osteosarcoma samples (22 Grades I or II, three dedifferentiated) to evaluate if the possible alterations detected of the genes on chromosome 12 could have a role in the development of this rare bone tumor. Immunohistochemical analysis was performed on formalin fixed, paraffin embedded tumor sections to evaluate CDK4 and MDM2 protein expression. To measure the degree of SAS and CDK4 gene amplification, quantitative polymerase chain reaction was done on deoxyribonucleic acid derived from the same samples. The results showed that CDK4 protein was expressed in 92% of the cases. Strong and uniform CDK4 and MDM2 immunoreactivity was found respectively in three of three and two of three dedifferentiated parosteal osteosarcomas. SAS and CDK4 genes were found to be amplified fourfold in two Grade II tumors and in one dedifferentiated tumor. These findings, which should be investigated further, might suggest a possible role of the chromosome 12 genes in the pathogenesis of parosteal osteosarcoma.
Assuntos
Neoplasias Ósseas/genética , Cromossomos Humanos Par 12/genética , Quinases Ciclina-Dependentes/genética , Proteínas de Membrana/genética , Proteínas de Neoplasias/genética , Proteínas Nucleares , Osteossarcoma Justacortical/genética , Proteínas Proto-Oncogênicas/genética , Quinase 4 Dependente de Ciclina , Humanos , Imuno-Histoquímica , Reação em Cadeia da Polimerase , Proteínas Proto-Oncogênicas c-mdm2 , TetraspaninasRESUMO
A parosteal osteosarcoma of the distal femur with a typical radiographic and macroscopic appearance is reported. On histology the tumour was dominated by large numbers of osteoclast-like giant cells in a fibro-osseous background and islands of immature bone. Most of the neoplastic bone lacked osteoblastic rimming. There was no spatial relationship between the giant cells and areas of haemorrhage. Signs of 'dedifferentiation' were lacking. Cytogenetic a analysis revealed telomeric associations which are frequently found in giant cell tumours of bone. Parosteal osteosarcoma may, on histological appearances, hardly be recognizable as malignant. In addition, unusual changes such as abundant giant cells may be misleading in the absence of clinico-pathological correlation.