Objective:To investigate the effects and possible mechanism of glial fibrillary acidic protein(GFAP)on the proliferation of human astroglioma cell lines U251 by RNA interfering technique. Methods:GFAP si RNA was designed to specifically knockdown endogenous GFAP expression in U251. The m RNA and protein levels of GFAP after si-GFAP transfection were detected to determine the efficiency interference in U251 cells. After knocking down GFAP in U251 cells

the protein levels of GFAP

CREB

cyclin D1

CDK2

CDK4

CDK6

p15

p18

p27

Bax

Bcl-2 and Caspase 3 were assessed by Western blot and the proliferation of cells was measured by MTT assay. Results:(1)Specific inhibition of GFAP expression suppressed cell proliferation

as well as reduced total RNA and protein contents in U251 cells(si-NC group vs. si-GFAP group:t=3.962

P=0.017;t=3.833

P=0.019).(2)In U251 cells

interfering GFAP expression significantly inhibited protein levels of CREB(si-NC group vs. si-GFAP group:t=4.834

P=0.008)

cyclin D1(si-NC group vs. si-GFAP group:t=3.610

P=0.022)

cyclin-depended kinase 2(CDK2)(si-NC group vs. si-GFAP group:t= 6.678

P=0.003)and CDK4(si-NC group vs. si-GFAP group:t=4.530

P=0.011)

and greatly elevated protein levels of p18(si-NC group vs.si-GFAP group:t=-3.339

P=0.029)and p27(si-NC group vs. si-GFAP group:t=13.859

P=0.000)

the cyclin-depended kinase inhibitors(CKIs).(3)Silencing GFAP by si RNA significantly inhibited the proliferation of U251 cells at 24 h and 48 h after the transfection(si-NC group vs. si-GFAP group:t=6.389

P=0.000;t=6.058

P=0.000).(4)Knocking down GFAP exerted no significant effect on the expression levels of apoptotic proteins

including Bax(si-NC group vs. si-GFAP group:t=-0.657

P=0.547)

Bcl-2(si-NC group vs. si-GFAP group:t=-0.991

P=0.378)and caspase 3(si-NC group vs. si-GFAP group:t=-1.848

P=0.138)in U251 cells. Conclusion:GFAP inhibition in U251 cells results in cell cycle arresting

thereby suppresses cell proliferation.