ABSTRACT
PURPOSE: To characterize PTEN gene alterations and their expressions during the development of osteosarcoma. MATERIALS AND METHODS: We studied the pattern of deletion, mutation and expression of PTEN in normal bone tissues, tumor samples of 22 patients of osteosarcoma, and 4 osteosarcoma cell lines (HOS, U2-OS, MG-63 and Saos-2). The tissue was analyzed for deletion and mutational inactivation of PTEN by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and direct sequence analysis, and examined for abnormalities in expression by immunohistochemistry. RESULTS: In this study, neither mutation nor deletion of PTEN was found. Expression of PTEN protein was increased, without deletion or mutation of the PTEN gene, in 22 patients of osteosarcoma and in 4 osteosarcoma cell lines. Nuclear staining was more intense than the cytoplasmic staining in normal bone tissues and osteosarcoma cell lines, but in osteosarcoma tissues PTEN was expressed mainly in the cyto-plasm. CONCLUSION: These results suggest that abnormal expressions of PTEN by differential compartmentalization may play a role in the development and progression of osteosarcoma, instead of genetic alterations of PTEN.