Enhancing radiosensitivity of RNA interference targeting silence STAT3 gene on human laryngeal carcinoma cells

OBJECTIVE To explore the radiosensitivity of human laryngeal carcinoma cell line Hep-2 after inhibition of STAT3(signal transducer and activator transcription 3)gene by transfecting plasmid carrying short hairpin RNA(shRNA). METHODS The vector expressing short hairpin RNA targeting STAT3 gene(pshSTAT3)was constructed. pshSTAT3 and negative control plasmid were transfected into Hep-2 cells by Lipofectamine 2000, and transfection efficiency was observed by fluorescence microscopy and detected by FCM(flow cytometry)at 24h after transfection. Subsequently the cells were radiated by 60Co γ ray at 0, 2, 4, 6, 8,10 Gy. Cell survival after irradiation was evaluated by MTT. FCM was used to detect cell apoptosis rate and STAT3,p-STAT3, bcl-2 protein levels after radiation with 6 Gy. RESULTS The vector expressing short hairpin RNA targeting STAT3 was constructed successfully. MTT assay showed that pshSTAT3 combined with 60Coγ ray significantly inhibited proliferation of Hep-2 cells compared with that in pshNeg and control groups(P 0.05). Flow cytometry showed that apoptosis rate of the pshSTAT3 group was significantly higher than that of pshNeg and untransfected group at the same radiation dosage 0, 2, 4, 6, 8 and 10 Gy(P 0.05). After 6 Gy radiation, STAT3, p-STAT3 and bcl-2 protein levels ofpshSTAT3+radiation group decreased significantly than that of control, radiation, pshNeg, pshNeg+radiation, and pshSTAT3 groups(P 0.05). Meanwhile, FI (fluorescence index)of p-STAT3 showed a positive correlation with levels of bcl-2(r =0.974,P 0.05). CONCLUSION The shRNA targeting STAT3 gene can significantly enhance the sensitivity of human laryngeal carcinoma cells to radiation. The combination of RNA interference targeting STAT3 gene with radiotherapy may be more effective in the treatment of head and neck cancers.