Analysis of 12q13-15 genes in parosteal osteosarcoma

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 ampl ified 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 ded ifferentiated) to evaluate if the possible alterations detected of the gene s on chromosome 12 could have a role in the development of this rare bone t umor. Immunohistochemical analysis was performed on formalin fixed, paraffi n embedded tumor sections to evaluate CDK4 and MDM2 protein expression. To measure the degree of SAS and CDK4 gene amplification, quantitative polymer ase chain reaction was done on deoxyribonucleic acid derived from the same samples. The results showed that CDK4 protein was expressed in 92% of the c ases. Strong and uniform CDK4 and MDM2 immunoreactivity was found respectiv ely in three of three and two of three dedifferentiated parosteal osteosarc omas, SAS and CDK4 genes were found to be amplified fourfold in two Grade I I tumors and in one dedifferentiated tumor. These findings, which should be investigated further, might suggest a possible role of the chromosome 12 g enes in the pathogenesis of parosteal osteosarcoma.