Expression of p27kip1 Protein in Astrocytic Tumors

Kim, Dae Yong; Son, Hyun Jin; Chung, Myoung Ja; Kang, Myoung Jae

Abstract

OBJECTIVE
The cyclin-dependent kinase inhibitor p27kip1 protein is a negative regulator of the cell cycle, and its degradation is required for entry into the S phase. Loss of p27kip1 expression has been reported to be associated with aggressive behavior in a variety of tumors of epithelial and lymphoid origin. However, its association with various astrocytic tumors has not been clearly demonstrated. We studied to investigate the relationship of p27kip1 expression with the biological behavior of astrocytic tumors in addition to study on the role of p27kip1 in the tumorigenesis of these tumors.
PATIENTS AND METHODS
From 1990 to 1998, a total of 29 astrocytic tumor of all grades obtained by operative resection were included for evaluation. We studied the expression of p27kip1 protein immunohistochemical assay in astrocytic tumors and compared the findings with the clinicopathologic parameters. Immunohistochemical staining was performed on formalin-fixed paraffin-embedded sections by the avidin-biotin-peroxidase complex method. According to WHO classification, all cases were divided into astrocytomas(4 cases), anaplastic astrocytomas(9 cases), and glioblastomas(16 cases) by 3 pathologists. Clinical information was obtained from medical records, and others such as location and size of tumors from imaging studies.
RESULTS
Mean p27kip1 protein labeling indexes(LI, mean+/-standard deviation) of astrocytomas, anaplastic astrocytomas, and glioblastomas were 80.6+/-9.1, 63.6+/-21.0, and 28.9+/-18.7, respectively, and were inversely correlated with grade of glial tumors(p<0.0001). Mean p27kip1 protein LI in the recurrent group was lower than that in the non-recurrent group, but there was no significant difference statistically(p=0.464). Additionally, p27kip1 protein expression did not show any significant relationship to other prognostic factors such as age(p=0.1643), tumor size(p=0.8), or location(p=0.8).
CONCLUSION
These results suggested that reduced expression of p27kip1 protein may play a important role in the malignant transformation process of astrocytic tumor cells.