Expression And Significance Of PTEN,GSK-3β,FAK In Human Astrocytoma

Backgrounds and ObjectivesGliomas are the most common primary brain tumor in adults, and astrocytomas, accounting for 13-26% in intracranial tumors and 21.2%～51.6% in gliomas, are the most frequent neuroepithelial neoplasms. But the prognosis for patients with these tumors remains poor despite advances in diagnosis and standard therapies such as surgery, radiation therapy, and chemotherapy. Progress in the treatment of gliomas now depends to a great extent on an increased understanding of the biology of these tumors. Recent insights into the biology of gliomas include the finding that tyrosine kinase receptors and signal transduction pathways play a role in tumor initiation and maintenance. Phosphorylation and dephosphorylation play an important role in intracellular signaling pathways. As the first identified tumor suppressor gene, PTEN (phosphatase and tensin homology deleted on chromosome 10) negatively regulate cell cycle and multiple signaling pathways, suppressing various physiological functions including cell adhesion, migration, differentiation, senescence, apoptosis and so on. Thus the ralationship between PTEN and tumors has attracted much attention and become a focus in medical research. Deregulation of phosphatidylin-ositol 3-kinase (PI3K) signaling pathways resulting from genetic alterations in the PTEN tumor suppressor gene on 10q23 at the level of LOH, mutation and methylation have been identified in at least 60% of glioblastoma. Loss of PTEN function by mutation or LOH correlates with poor survival in anaplastic astrocytoma and glioblastoma, suggesting that PTEN plays a role in patient outcome. In modern molecular biology, Tumor initiation and maintenance is considered to be a complex alteration process of multiple gene, multiβle factor, multiple procedure, multiple phase. The effect of single gene alteration is limited, therefore investigating the synergetic effect of polygenes may make difference. The studies nowdays has not identified clearly the tumor suppressing mechanism of PTEN, and there is no report about correlation between the expression of GSK-3β,FAK in the brain astrocytoma. In order to further explore the correlation between PTEN and the genesis and progress of astrocytoma, search markers indicating the generation, gradation and prognosis of astrocytoma, and look for usful ways to suppress the genesis and invation of astrocytoma, this research detects the expression of PTEN mRNA,GSK-3βmRNA,FAK gene and protein by immunohistochemisty in 47 cases of astrocytoma tissues and 12 cases of normal brain tisssues, and analyses the correlation between PTEN, GSK-3βand FAK. This article intends to interpret the role of PTEN protein expression in astrocytoma, investigate whether the mechanism of PTEN to suppress astrocytoma is concerned with up-regulation of FAK and down regulation of GSK-3β, and furthermore and provide certain theory basis on further detecting the mechanism of astrocytoma genesis and development and finding out the ways to suppress astrocytoma.Materials and methods47 cases of the fresh human astrocytomas tissues surgically ablated and identified by pathology were collected in the department of neurosurgery of the second affiliated hospital of Zhengzhou University from Jan,2009 to Oct,2009, including 29 cases of male and 18 cases of female,19-73 years old, mean 39.51 years of age. All cases are of intact datas and invaded for the first time. None was treated by radiotherapy, chemotherapy or immunotherapy.According to the WHO (2001) classification of central nervous system tumors, all tumors were histologically classificated and graded as 7 cases of gradeⅠ,21 cases of gradeⅡ,14 cases of gradeⅢ,5 cases of gradeⅣ. The WHO gradeⅠ-Ⅱastrocytomas merged into low-grade malignant group, and the WHO gradeⅢ-Ⅳmerged into high grade. The non-tumor brain tissues serving as control group were obtained from 12 patients requiring surgical decompression due to brain injury or cerebral hemorrhage in the neurosurgery department, in The Second People's Hospital of Zhengzhou and The Second Affiliated Hospital of Zhengzhou University. The study used RT-PCR and immunohistochemistry SP method to detect the expression of the PTEN gene mRNA, GSK-3B gene mRNA, FAK gene and protein in 47 cases of astrocytoma and 12 cases of non-tumor brain tissue, and analyzed the correlation of PTEN and GSK-3B, FAK. The data was analysed using SPSS software (version 11.0). Chi-square statistics were used for categorical comparisons of rate of sample. The t test was used for measurement data. Spearman rank-sum correlation was used to relate the expression of markers. A value of p<0.05 was considered statistically significant.Results1. Twelve of 12 non-tumor brain tissues were positive for PTEN protein with a positive rate of 100% and twentyfive of 47 astrocytoma tissues were positive for PTEN protein with a positive rate of 53.2%. The difference of PTEN expressions was statistically significant (P<0.01) in astrocytoma and non-tumor brain tissues. The positive rates of PTEN protein expression were respectively 100.0%,67.9% and 31.6% in non-tumor brain tissue, GradeⅠ～Ⅱastrocytoma group, gradeⅢ～Ⅳastrocytoma group. The expression of PTEN protein in GradeⅠ～Ⅱgroup is higher than that of gradeⅢ～Ⅳgroup with significant difference (P<0.05).2. Eight of 12 non-tumor brain tissues were positive for GSK-3Bprotein with a positive rate of 66.7% and fourteen of 47 astrocytoma tissues were positive for GSK-3B protein with a positive rate of 29.8%. The difference of GSK-3βexpressions was statistically significant (P<0.05) in astrocytoma and non-tumor brain tissues. The positive rates of GSK-3B protein expression were respectively 66.7%,42.9% and 10.5% in non-tumor brain tissue, GradeⅠ～Ⅱastrocytoma group, gradeⅢ～Ⅳastrocytoma group. The expression of GSK-3βprotein in GradeⅠ～Ⅱgroup is higher than that of gradeⅢ～Ⅳgroup with significant difference (P<0.05).3. The positive expression rate of FAK protein was 53.2% in astrocytomas and was significantly higher than that in non-tumor brain tissue, which was 16.7%(P <0.01). The positive rates of FAK protein expression were respectively 66.7%,42.9% and 10.5% in non-tumor brain tissue, GradeⅠ～Ⅱastrocytoma group and gradeⅢ～Ⅳastrocytoma group. The differentce of FAK protein expression between GradeⅠ～Ⅱgroup and gradeⅢ～Ⅳgroup was significant (P<0.05).4. The relationship between the expression of PTEN protein and GSK-3βprotein: Of the 25 cases with positive expression of PTEN protein in astrocytomas,14 cases were detected GSK-3βprotein expression; GSK-3βprotein expression was negative in all 22 cases with negative expression of PTEN protein in the astrocytomas, positive correlation between the two protein expression was confirmed via statistical analysis (contingency coefficient r= 0.628, P<0.01).5. The relationship between the expression of PTEN protein and FAK protein: Of the 25 cases with positive expression of PTEN protein in astrocytomas,5 cases were detected FAK protein expression; FAK protein expression was negative in 2 cases out of 22 cases with negative expression of PTEN protein in the astrocytomas. The statistical analysis showed a negative correlation between the expression of the two proteins (contingency coefficient r=-0.696, P<0.01).Conclutions1. PTEN protein is highly expressed in non-tumor brain tissue and it is down regulated in astrocytoma tissues, and reducing as the pathologic grade of astrocytomas increases, suggesting that PTEN gene mutation or deletion is closely related to the occurrence, differentiation, progress of astrocytoma. Detection of PTEN protein expression will help to determine the biological behavior, malignant degree and prognosis of astrocytomas.2. There is a negative correlation between the abnormal expression of PTEN protein and that of FAK protein in astrocytoma, indicatig that the increased expression of FAK protein and the decreased expression of PTEN in astrocytic tumors are not two isolated incidents, there may be some correlation between them, which work together to promote the occurrence and development of astrocytoma.3. There is a positive correlation between PTEN and GSK-3βin the occurrence and development process of human astrocytomas, suggesting that PTEN depend on GSK-3βto promote the development of tumors.