Study On Expression And Correlation Of PTEN And P53 Genes In Osteosarcoma

Objective Osteosarcoma is the most common primary malignant tumor of bone with highest incidence.It often occurs in juvenile and young people.Its pathological characteristics are sarcoma cells producing plenty of osteois tissues,early distant metastasis,and the leading cause of mortality is pulmonary metastases.Traditional therapy includes chemotherapy,prompt diagnosis, and operation performed strictly according to the surgery stage. But the result is unsatisfied .The researches of osteosarcoma are always the emphasis and difficulty in clinical and fundamental studies, therefore the early diagnosis of osteosarcoma and searching a kind of therapy which is specific, high effective and fewer side effects has become an important issue. The genesis of osteosarcom tissue is a progression with many steps and phases and its mechanism is rather complex. Researches have shown that activation of oncogenes and inactivation of tumor suppressor genes are involved in it.PTEN(phosphates and homology deleted on chromosome ten),a recently identified tumor suppress gene (TSG), has complex functions including participating in the embryonic growth, apoptosis and G1 phase cellblock, inhibiting the migration and adherence. Its genetic mutation or deletion and abnormal protein expression are intimately related to occurrence and development of many kinds of tumors. The wide-type p53 gene plays an important role in maintaining normal cell growth and inhibiting the malignant proliferation. P53 gene mutation, which can regulate the expression of many related gene is one of the mechanisms for malignant tumors, P53 gene mutation is an important genetic event related to osteosarcoma. Only mutant type p53 gene can be detected by immunohistochemical method. The expressions and correlation of PTEN and p53 were analyzed by immunchistochemical method to investigate the roles of these genes in development and progression of Osteosarcoma.Methods 40 specimens from osteosarcoma excision were collected. Amongthem male 22, female 18; of them, 16 cases were Osteoblast type osteosarcoma, 11 cases were Chondroblast type osteosarcoma, 9 cases were fibroblasts type osteosarcoma,4 cases were other type osteosarcoma; In addition, of them,15cases were well-differentiated osteosarcoma and 25 were poorly-differentiated osteosarcoma.20 specimens collected during the same period from benign lesion of bone (osteochondroma) operation were taken as the control group.Immunohistochemistry staining(Streptavidin-Peroxidase /S — P method) was performed to detect the expression of PTEN protein and p53 protein, in 40 cases of osteosarcoma. The criteria of positive expression was that brown granule was found in cytoplasm (PTEN)or in nucleus(p53). 5 oncocytes of PTEN or p53 positive expression in high power field were counted randomly in each case. (1) Positive(+): positive oncocytes account <25%;(2) positive (++):positive oncocytes account25~ 50%,(3) positive (+++): positive oncocytes account >50%; negative(-):no positive oncocytes. The data were analyzed by software SPSS 10.0. The difference of PTEN and p53 expression between osteochondroma and osteosarcoma was analyzed with Chi-square Test and exact probability method. The difference of PTEN and p53 expression among different pathological classifications of osteosarcoma was analyzed in the same way. Spearman method was used to analyze the relationship between PTEN and p53 expression among osteosarcoma.Results 1. The positive staining of PTEN mainly located in cytoplasm. The rate of PTEN expression was 90.0% in benign lesion of bone. The positive expression was only 55.0% in osteosarcoma tissues. A significant diference was observed between the two groups (P<0.05). In Osteoblast type osteosarcoma, Chondroblast type osteosarcoma, fibroblasts type osteosarcoma and other type osteosarcoma groups, the positive rates of PTEN were 43.75%,63.64%,66.67%, 50.00% respectively .the diference between them was not significant(p>0.05); In well and poorly-differentiated osteosarcoma groups, the positive rates were 66.67%,48.00% respectively, the diference between them was not significant(p>0.05). In the group with and without pulmonary metastasis, the rates were 18.18% and 68.97% respectively. The diference between them was significant (P<0.05).2. The positive staining of p53 mainly located in the nucleus of osteosarcoma with the positive rate of 57.50%. There were no expressions of p53 in benign lesion of bone tissues and a significant diference was found between them (PO.05). In Osteoblast type osteosarcoma, Chondroblast type osteosarcoma, fibroblasts typeosteosarcoma and other type osteosarcoma groups, the positive rates of P53 were 62.50%,54.55%,55.56%,50.00% respectively .the diference between them was not significant(p>0.05); In well (Grade I-II) and poorly-differentiated osteosarcoma (Grade III) groups, the positive rates were 40.00%,48.00% respectively, the diference between them was not significant(p>0.05). In the group with and without pulmonary metastasis, the rates were 63.64% and 55.17% respectively. The diference between them was not significant (P>0.05).3. Of the 22 specimens of positive PTEN,9cases expressed p53 positively; of the 18 specimens with negative PTEN, 14 cases expressed p53 positively; there was a negative correlation between them (P<0.05).Conclusion 1. The expressions of PTEN were high in benign lesion of bone, but those were low in osteosarcoma; the expressions of PTEN were not related to pathological grades and pathological types. It could be a marker of early diagnosis.2. p53 only expressed in osteosarcoma tissues, not in benign lesion of bone; the expressions of p53 were not related to pathological grades and pathological types. It could be a marker of early diagnosis.3. PTEN and p53 may play an important role in the carcinogenesis of osteosarcoma and are correlated with osteosarcoma.The expressions of PTEN are negatively related to that of p53 in osteosarcoma tissues .The detection of them might be a guide for the early diagnosis and determinant of osteosarcoma.