Expression And Significance Of PTEN And P27 In Astrocytic Tumors

ObjectiveBoth PTEN and P27 negatively regulate cell proliferation and closely related to tumor behavior. The purpose of this study was to examine the expression of PTEN and P27 in primary astrocytic tumors and to investigate the relationships between expression of these tumor suppressor and tumor histopathologic grades.MethodsPatient selectionTissue samples of primary astrocytic tumors ( n = 46) and non-tumor brain tissues (n = 10) were obtained from patients who underwent surgery in the Second affiliated hospital of China Medical University between March,2002 and March,2004. All tumors were graded according to Word Heath Organization cri-teria( WHO grade 1 n = 11 ,grade 2 n = 13, grade 3 n = 12, grade 4 n = 10).ImmunohistochemistryA total of 56 formalin-fixed and paraffin-embedded specimens was available for this study. Expression of PTEN and P27 protein was immunohistochemically investigated. Paraffin sections were cut at 5um thickness, deparaffinized with xy-lene and rehydrated. After endogenous peroxidase activity was blocked with 3% H₂O₂ for 10 min at room tempreture,the section were treated with 0. Olmol/liter citrate(PH =6. 0) in a 500-W microwave oven for 15 min for antigen retrieval. After blocking nonspecific reactivity with normal nonimmunone serum for 30 min at room tempreture, the section were incubated with anti-PTEN and anti-P27monoclonal antibody for one night at 4°C thermostat and then with biotin-conju-gated second antibody for an addition 90 min at 37°C. Positive signals were detected by the S-P method with Ultrasensitive? S-P kit. Sections were also coun-terstained with hematoxylin.The labeling indexs of PTEN and P27 were calculated microscopically field at a magnification of 400 x by counting at least 1000 tumor cells form selected fields. Strong reactions in the cytoplasm were considered positive for PTEN. Strong reactions in the nuclei were considered positive for P27.Statistical methodsX* test was used to compare the expression of PTEN and P27 in astrocytictumors and non-tumor brain tissues. Non-parametic Spearman rank correlationcoefficients were used to assess the degree of association among the histopatho-logic grades of tumors,PTEN and P27. Statistical significance was defined as P<0.05.ResultAll of the 56 speciments studied were positive for PTEN and P27. The positive rate of PTEN was 63.4% , the positive rate of P27 was 56.8%. The expression of PTEN and P27 has a significant difference between non- brain tissue, well differentiated astrocytic tumors and poorly differentiated astrocytic tumors ( P <0.05). We also analyzed the relationships between the histopathologic grades of tumors, expression intensity of PTEN and P27. Both PTEN and P27 tended to decrease with tumor grade. There was a strongly negative correlation between PTEN and tumor grade (r = -0.612 ,P <0. 01). There was also a strongly negative correlation between P27 and tumor grade ( r = - 0. 452, P < 0. 01 }. There was a strongly positive correlation between PTEN and P2 7 (r=0.647,P< 0.01).DiscussionBoth PTEN and P27 negatively regulate cell proliferation and closelyrelated to tumor genesis. PTEN is the first tumor suppressor of double specific phosphorylated kinase activity, it suppress cell proliferation and cause apoptosis mainly through PD-k/Akt pathway. P27 is cyclin dependent kinase inhibitor of Cip/Kip that negatively regulates cell procession by binding and inhibiting the Cyclin-CDKs complex.Expression of PTEN and P27 is deregulated in many human tumors. These alteration in PTEN and P27 expression have been associated with the stage and grade of tumors in breast, bladder, cervix and stomach. Here we examined the expression of PTEN and P27 in paraffin sections of primary astrocytic tumors ( n = 46) and non-tumor brain tisssues ( n = 10). All of examined specimens expressed PTEN and P27 protein to various degrees. The expression of PTEN and P27 has a significant difference between non-brain tissue, well differentiated astrocytic tumors and poorly differentiated astrocytic tumors ( P < 0. 05 ). For primary astrocytic tumors, both PTEN and P27 tended to decrease with tumor grade. Nonparametric Spearman rank correlation analysis identified that the tumor grade was negatively correlated with both PTEN expression and P27 expression. We also analyzed the relationship between PTEN expression and P27 expression. There was a strongly positively correlation ( P < 0.01). This result in-dicitied that P27 may be the downstream gene to PTEN.Tian X and Tamiya et al. reported that the high expression of PTEN and P27 were though to reflect cell arrest or a growthinhibited stage in cultured human glioma cells. Taken together, these results suggest the possibility that the status of both PTEN and P27 mirrors the capacity of tumor growth in vivo. Disrupted regulation of PTEN and P27 expression may play an important role in determining the clinical behavior of primary astrocytic tumors. The immunohistochemical reactivity of monoclonal antibody PTEN and P27 may be an useful maker for assessing the histopathologic grades of primary astrocytic tumors. The combined analysis of PTEN and P27 ex-...