[A preliminary study about the interaction between basic fibroblast growth factor and signal transducer and activator of transcription 3 in glioma apoptosis].

OBJECTIVE

To study the relationship of basic fibroblast growth factor (bFGF) and signal transducer and activator of transcription 3(STAT3) in glioma apoptosis and possible mechanisms of its interaction.

METHODS

Two glioblastomamultiforme (GBM) cell lines: U87 (wild-type p53) and U251 (mutant p53) were used in this study and divided into normal control group, mock group and experiment group.Small interfering RNA-carried recombinant lentivirus, LV-bFGFsiRNA and LV-STAT3siRNA, targeting bFGF and STAT3 were constructed respectively. After 48 hours of lentivirus transfection, small molecular inhibitors were used to block specific signaling pathways, AG490 20 µmol/L blocking JAK, LY294002 20 µmol/L blocking PI3K/Akt pathways for 24 hours, 48 hours and 72 hours, respectively. Then, apoptosis, changes in apoptosis-related proteins and mitochondrial membrane potential were detected through the methods of flow cytometry, protein chip and confocal microscopy, respectively.Groups were compared using single factor analysis of variance (One-way ANOVA).

RESULTS

Western blot results revealed the levels of Tyr705 and Ser727 phosphorylationin reduced in a time dependent manner by blocking JAK and PI3K/Akt pathway respectively. The results of flow cytometry showed that the apoptosis rate in normal control group, mock group, experiment group were 17.97% ± 0.24%, 18.26% ± 0.88%, 46.57% ± 1.63% in U87 cells and 15.94% ± 1.18%, 16.88% ± 0.17%, 39.34% ± 0.87% in U251 cells, respectively. There was no statistically significant change between the normal control group and the mock group (P > 0.05) , while when compared with the experiment group, both group showed statistically significant difference (F = 697.41, 729.58, both P < 0.05). The results of protein chip demonstrated that protein expression of Bad, Caspase3, Cytochrome C, p27 were higher and XIAP was lower in the experiment group compared with the normal control group and mock group. Also, confocal microscopy could detect apoptosis and mitochondrial membrane potential reduced significantly in the experimental group compared with the normal control group and the mock group.

CONCLUSIONS

bFGF mainly interacts with STAT3 tyrosine site-pSTAT3(Tyr705) to influence the level of STAT3 phosphorylation;blocking bFGF/STAT3 signaling pathway can induce glioma cell apoptosis through mitochondrial pathway.