Lentiviral-shRNA-Mediated STAT3 Silencing Enhangces Chemosensitivity To 5-Fluorouracil In Human Gastric Cancer Cells

Objective:Gastric cancer, one of the most common cancers in the world, has been considered as the second leading mortality related to cancer diseases worldwide^. As medical technology development, the survival rate in early gastric cancers significantly improved compared with the previous, but only 5-20% patients could live for 5 years with advanced or metastatic gastric cancer [2]. For such patients, chemotherapy is the main clinical strategy by inducing apoptosis in tumor cells in order to exert anti-tumor effects. However, the tumor cells acquire tolerance during chemotherapy, leading to gastric cancer responds poorly to chemotherapy. Clinically, the function is limited by changing the combination of chemotherapy drugs. Owing to the high mortality ratio, exploration of new therapeutic targets of GC is challenging and urgent.Signal transducers and activators of transcription 3 (STAT3) involved in the regulation of several signal transduction pathways, plays important role in cell growth, proliferation, differentiation, apoptosis and other physiological processes. Recent studies show, STAT3 is related to induce tolerance to chemotherapy in a variety of tumor cells, and it is not clear in gastric cancer cells.Therefore,our reseach is to investigate the effect and the mechanisms of lentiviral-shRNA-mediated STAT3 silencing on the chemosensitivity to 5-Fu of human gastric cancer cells.Methods:The shRNA sequences targeting STAT3 was constructed and transfected human gastric cancer cells SGC-7901 by lentiviral vectors. The interference effect of STAT3-shRNA was detected by real-time PCR and western blot. The chemosensitivity to 5-Fu was analyzed by MTT assay and the flow cytometry was used to examine cell apoptotic rate. Western blot was used to compare the expressions of anti-apoptotic proteins Bcl-2、 Mcl-1、survivin.Results:Lentiviral vectors containing shRNA targeting STAT3 gene were successfully established and transfected into SGC-7901 cells. Real-time PCR and western blot analysis showed that the STAT3-shRNA significantly inhibited the mRNA expression by 54% and protein expression by 40%(P<0.05). The inhibitory rate of cell proliferation and the apoptotic rate were obviously higher in the cells treated by STA3-shRNA (P<0.05). STAT3-shRNA also induced downregulation of the anti-apoptotic proteins Bcl-2、Mcl-1 and survivin (P <0.05).Conclusion:In summary, STAT3-shRNA could effectively inhibit the proliferation and accelerate the apoptosis of SGC-7901 cells, leading to enhance their sensitivity to 5-Fu. The mechanism may be related to block STAT3 signaling pathway though inhibiting STAT3 activation, thus decreasing expressions of its downstream anti-apoptotic proteins Bcl-2、 Mcl-1 and survivin.