Expression And Clinical Significance Of PTEN Protein In Osteosarcoma

Objective: To investigate the expression and significance of cancer inhibitory gene PTEN protein in osteosarcoma. To analyze the level of its expression in different historical classifacation of osteosarcoma. To determine the possibility of taking PTEN protein as a marker gene for diagnosing osteosarcoma. To observe the clinical value of PTEN expression levels as a reference index for osteosarcoma classification.Methods: 43 specimens collected from osteosarcoma excision were studied. 30 specimens collected during the same period from benign lesion of bone (osteochondroma) operation were taken as the control group. Immunohistochemistry staining ( Elivison TM two steps method) was used to detect the expression of PTEN protein in 43 cases of osteosarcoma [Among them 23 cases were well-differentiated osteosarcoma (Grade I-II) and 20 were poorly-differentiated osteosarcoma (Grade III).]. Phosphate Buffered Saline (PBS) was used instead of anti-PTEN antibody in negative control. The well-differentiated squamous cell carcinoma of lung which had been known was used in positive control group. The criteria of positive expression was that brown granule was found in cytoplasm. 5 oncocytes of PTEN positive expression in high power field were counted randomly in each case. (1) negative(-) : no positive oncocytes or the number of positive oncocytes <10%; (2) Positive (+) : positive oncocytes account for 10% to 40%; (3) positive(++) : >40%. SPSS 10. 0 was used in statistical analysis. The difference of PTEN expression between osteochondroma and osteosarcoma was analyzed with x2 test. The difference of expression among different pathological classifications of osteosarcoma was analyzed in the same way. Spearman method was used to analyze the relationship between historical classification of osteosarcoma and the level of PTEN expression.Results: Immunohistochemistry staining showed that the positive reaction of PTEN protein were all oriented to cytoplasm, which was brown or yellowish-brown granules. The positive expression rate of PTEN protein in 30 cases of benign lesion of bone was 83. 3%. The positive expression rateof PTEN protein in 43 cases of osteosarcoma was 51. 2%. By way of x2 test, the significant difference was observed between bone benign lesion and osteosarcoma (x2 =7.976, P <0. 01). Osteosarcoma with different degrees of histodifferentiation showed different level expression of PTEN protein. The positive expression rate of PTEN protein of well-differentiated osteosarcoma (grade I-II) was 73. 9% (17/23). The positive expression rate of PTEN protein of poorly-differentiated osteosarcoma (grade III) was 25.0% (5/20). There was significant difference between well-differentiated osteosarcoma and poorly-differentiated osteosarcoma statistically (P<0.01). The level of expression of PTEN was negatively correlated to the histological grade of osteosarcoma. There was great significance statistically (rs =-0.4922, P<0. 01). Single factor analysis was used to study the optical density values obtained from all the case groups. The results showed F=47. 9, P>0. 01. There was a great significance statistically. A further intercomparison was made in them and showed q=19. 68, P<0. 05 between Stage I-II of osteochondroma and osteosarcoma, q=24.02, P<0.05 between Stage III of osteochondroma and osteosarcoma and q=43.7, P<0.05 between Stage I-II and Stage III of osteosarcoma. The significant statistical difference was observed in all of them.Conclusion: PTEN protein may be used as candidate gene of cancer inhibitory gene; PTEN protein is a cancer suppressor gene protein which has expression in bone tumors. It might not only be used in the study of pulmonary carcinoma and neurogliocytoma, but also in the study of bone tumor; the expression of PTEN is related to benignancy or malignancy of bone tumor and their degree of differentiation. The expression of PTEN was positively correlated with degree of differentiation.