Studies On The Correlation Between Foxo3a And Glioma

Objective1. To investigate the expression of FOXO3a in human glioma and the correlation with proliferation marker Ki-67, prognostic indicator p27^kip1 and their clinicopathologic significance. Besides, discuss the effect of abnormal expression of FOXO3a in the occurrence and the development of the glioma.2. To evaluate the specific effect of FOXO3a during glioma cell growth.Methods1. Immunohistochemical technique was used to detect the expression levels of FOXO3a, p27^kip1 and Ki-67 in 70 cases of glioma tissue. The glioma cases characterized in this study included: 34 gradeⅡ(26 fibrillary astrocytoma, 1 protoplasmic astrocytoma, 2 gemistocytic astrocytoma, 3 mixed oligo-astrocytoma and 2 ependymoma); 24 gradeⅢ(22 anaplastic astrocytoma and 2 anaplastic oligodendroglioma); 12 gradeⅣ(8 glioblastoma, 3 malignant ependymoma and 1 medulloblastoma).2. Serum starvation and release were used to synchronize lymphoma cells. Flow cytometer was used to analyze cell cycle. The expression and subcellular localization of FOXO3a and p27^kip1 were detected by western blot and subcellular fractionation. LY294002 was used to treat U87MG cell and T98G cell, the expression and subcellular localization of FOXO3a and p27^kip1 were investigated by western blot, immunoflurescence and subcellular fractionation.Results1. FOXO3a expression directly correlated with malignant grade of glioma. FOXO3a positive expression was significantly associated with pathologic stage of the glioma. On other hand, no significant difference were seen regarding patients'age, gender, KPS score, tumor location, type of surgery, tumor diameter, vessel density, or necrosis. In all cases of glioma analyzed, FOXO3a expression was positively associated with p27^kip1 (Spearman's r=0.845, P<0.001) and was negatively associated with Ki-67 expression (Spearman's r =-0.555, P<0.001).There was also a marked correlation between p27^kip1 and Ki-67 (Spearman's r=-0.647, P<0.001). By using the Kaplan-Meier analysis, patients in the low expression FOXO3a (≤23.5%) group were significantly associated with poor overall survival (P<0.001). Multivariate analysis using the Cox's proportional hazards model showed that FOXO3a protein was an independent prognostic indicator for patients'overall survival (P< 0.001).2. Advances in the cell cycle study have revealed: FOXO3a increased as the cells were treated with serum addition as well as the same kinetics was observed at p27^kip1. Subcellular fractionation showed that FOXO3a was mainly present in the cytoplasm of cells released from G1, leading to the dramatically reduced p27^kip1 nuclear accumulation. Administration of PI3K pharmacologic inhibitor LY294002 abrogated this effect by regulating FOXO3a expression and subcellular localization. Conclusions1. The expression of FOXO3a was closely correlated with the aggressiveness of glioma. It indicates that disregulation of FOXO3a may cause the cell cycle abnormal and promote cell proliferation, thus may play key roles in the occurrence and development of glioma.2. In vitro, FOXO3a modulated the cell cycle by transcriptional regulation of p27^kip1. It suggests that FOXO3a has the potential to as a tumor suppressor gene. Gene therapeutic approaches aimed at PI3K or the pharmacologic inhibitors of PI3K to down-regulate P-FOXO3a expression could be developed for the management of glioma.