OBJECTIVETo investigate the efficiency of blockage of constitutively activated STAT3 signaling by small interfering RNA (siRNA), and to explore the inhibitory effects on the proliferation of human esophageal squamous carcinoma cells (EC9706 and Eca109).

METHODSEC9706 and Eca109 were transfected with chemical synthesized STAT3 siRNA (100 nmol/L). RT-PCR and Western blot were used to detect STAT3 mRNA and protein expression, including phosphorylated-STAT3 (p-STAT3) before and after the transfection respectively. The changes of DNA-binding activity and cell proliferation were evaluated by electrophoretic mobility gel shift assay and MTT, respectively. Stages of cell cycle were determined by flow cytometry.

RESULTSExpression levels of STAT3 mRNA and STAT3, p-STAT3 proteins were progressively inhibited by STAT3 siRNA at various time points after transfection. STAT3-DNA-binding activity was suppressed after transfection evidenced by electrophoretic mobility gel shift assay. The cell cycle was arrested at G(0)/G(1) phase along with a significant inhibition of cell proliferation after STAT3 siRNA treatment.

CONCLUSIONSTAT3 siRNA specifically and efficiently blocks the constitutively activated STAT3 signaling pathway in human esophageal squamous carcinoma cells, resulting in cell cycle arrest and proliferation inhibition.