BACKGROUND AND PURPOSE: As an important oncogenic miRNA, miR-21 has been 
reported to play crucial roles in glioblastoma (GBM) carcinogenesis. However, 
the precise biological function and molecular mechanism of miR-21 in GBM remain 
elusive. This study is designed to explore the mechanism of miR-21 involved in 
the control of GBM cell growth.
METHODS AND RESULTS: MTT assay, cell cycle analysis, and apoptosis analysis 
showed that reduction of miR-21 inhibited cell growth in U87 and LN229 GBM 
cells. Further, reduction of miR-21 decreased the expression of human telomerase 
reverse transcriptase (hTERT) and repressed STAT3 expression and STAT3 
phosphorylation. STAT3 inhibition led to a remarkable depletion of hTERT at both 
mRNA and protein levels by binding to the hTERT gene promoter by performing 
luciferase reporter assay and chromatin Immunoprecipitation PCR. Finally, 
knockdown of miR-21 considerably inhibited tumor growth and diminished the 
expression of STAT3 and hTERT in xenograft model.
CONCLUSION: Our findings indicate that miR-21 regulates hTERT expression 
mediated by STAT3, therefore controlling GBM cell growth.