Original Articles

Inhibition of STAT3 expression by siRNA suppresses growth and induces apoptosis in laryngeal cancer cells

Authors: Li-fang GAO, De-qi XU, Lian-ji WEN, Xing-yi ZHANG, Yue-ting SHAO, Xue-jian ZHAO

Abstract

Aim: To determine the inhibitory effect of the synthetic STAT3 siRNA on the
expression of STAT3 gene in human laryngeal cancer cell lines Hep2 and to investigate
the effect of STAT3 siRNA on growth and apoptosis in Hep2 cells. Methods:
A pair of DNA templates coding siRNA against STAT3-mRNA was synthesized to
reconstruct plasmid of pSilencer1.0-U6 siRNA-STAT3. Hep2 cells were transfected
with RPMI-1640 media (untreated), plasmid (empty), and STAT3 siRNA,
respectively. Northern blot and Western blot analysis of STAT3 and pTyr-STAT3
expression in Hep2 cells and Western blot analysis of Bcl-2 expression in the Hep2
cell was performed 72 h after transfection. MTT, flow cytometry, and AO/EB
assay were used for determination of cells proliferation and apoptosis in Hep2
cells. Results: pTyr-STAT3 was markedly expressed in untreated Hep2 cells and
the vector-treated Hep2 cells, whereas pTyr-STAT3 expression was significantly
reduced in STAT3 siRNA-transfected Hep2 cells, indicating that STAT3 siRNA
inhibited the activity of STAT3. Transfection of Hep2 cells with STAT3 siRNA
significantly inhibited STAT3 expression at both mRNA and protein level in Hep2
cells and the inhibition was characterized by time-dependent transfection. Treatment
of Hep2 cells with STAT3 siRNA resulted in dose-dependent growth inhibition
of Hep2, this significantly increased apoptotic cell rate, and decreased Bcl-2
expression level in Hep2 cells. STAT3 siRNA had an effect on induction of either
early or late stage apoptosis. Conclusion: This study demonstrates that STAT3
siRNA effectively inhibits STAT3 gene expression in Hep2 cells leading to growth
suppression and induction of apoptosis in Hep2 cells. The use of siRNA technique
may provide a novel therapeutic approach to treat laryngeal cancer and
other malignant tumors expressing constitutively activated STAT3.
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