| Cyclin E and p27 are co-regulators of the G1 to S phase transition and closely related to tumor behavior. The purpose of this study was to examine the expression of cyclin E and p27 in primary astrocytic tumors and to investigate the relationships between expression of these cell-cycle regulators and tumor histopathologic grades.MethodsPatient selectionTissue samples of primary astrocytic tumors ( n = 46 ) and non-tumor brain tissues ( n = 8) were obtained from patients who underwent surgery in the second affiliated hospital of China Medical University between April, 1999 and March, 2002. All tumors were graded according to World Health Organization criteria ( WHO grade 1 n = 10, grade 2 n =9, grade 3 n = 15, grade 4 n = 12).ImmunohistochemistryA total of 54 formalin-fixed and paraffin-embedded specimens was available for this study. Expression of cyclin E and p27 protein was immunohistochemically investigated. Paraffin sections were cut ata 5-um thickness, deparaffinized with xylene and rehydrated. After endogenous peroxidase activity was blocked with 3% H2O2 for 10 min at room temperature, the sections were treated with 0.01 mol/liter citrate (pH =6. 0) in a 500-W microwave oven for 15 min for antigen retrieval. After blocking nonspecific reactivity with normal nonimmu-none serum for 40 min at room temperature, the sections were incubated with anti-cyclin E and anti-p27 monoclonal antibody for one night at 4℃ thermostat and then with biotin-conjugated second antibody for an additional 90 min. Positive signals were detected by the S-P method with Ultrasensitive?S-P kit. Sections were also counterstained with hematoxylin.The labeling indexes of cyclin E and p27 were calculated microscopically field at a magnification of 400 x by counting at least 1000 tumor cells from selected fields. Dark brown stains in the nuclei were considered positive for both cyclin E and p27. Positive reactions only in the cytoplasm were omitted.Statistical methodsStudent-t test was used to compare the expression of cyclin E or p27 in primary astrocytic tumors and non-tumor brain tissues. Non-parametric Spearman rank correlation coefficients were used to assess the degree of association among the histopathologic grades of tumors, cyclin E LI and p27 LI . Statistical significance was defined as P < 0.05.ResultsAll of the 54 specimens studied were positive for both cyclin E and p27. The cyclin E LI ranged from 0. 5% to 31. 6% , with themean value of 13. 59% ±9. 66%. The p27 LI ranged from 3.6% to 92.2% , with the mean value of 44. 52% ±25.22%. The expression of cyclin E or p27 has a significant difference among non-tumor brain tissues, low-grade astrocytic rumors and high-grade astrocytic tumors ( P < 0.05 ). We also analyzed the relationships among the histopatho-logic grades of tumors, cyclin E LI and p27 LI . The cyclin E LI tended to increase with tumor grade ( r = 0. 5990, P <0. 01) and the p27 LI decreased significantly with tumor grade (r= -0.7317, P< 0.01). There was a strongly negative correlation between cyclin E LI and p27 LI (r= -0.7538, P<0.01).DiscussionCyclin E and p27 are regulators of the Gl to S phase transition. Cyclin E, one of the cyclins, is a nuclear protein. In cell cycle, expression of cyclin E rises to a maximum level in late Gl phase and it associates with and activates CDK2. The cyclin E-CDK2 complex shows strong kinase activity and leads to further phosphorylation on the pRB protein. p27 is a CDKs inhibitor that negatively regulates cell progression by binding to and inhibiting the cyclin E-CDK2 complex.Expression of cyclin E and p27 protein is deregulated in many human tumors. These alterations in cyclin E and p27 expression have been associated with the stage and grade of tumors in breast, lung, stomach and bladder. Here, we examined the expression of cyclin E and p27 in paraffin sections of primary astrocytic tumors ( n = 46) and non-tumor brain tissues ( n = 8 ). All of examined specimens expressed cyclin E and p27 protein to various degrees. The expres...
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