Fig. 4

Over-activation of STAT3 attenuated the inhibitory effects of CSR on RA-FLS hyperproliferation. RA-FLS were transduced with Ad-STAT3C (RA-FLS^STAT3C) or Ad-Empty (RA-FLS^{Empty vector}) plasmid. (a) Green fluorescent protein (GFP) expression and the protein levels of phospho-STAT3 (Tyr 705), STAT3 and Flag in RA-FLS^{Empty vector} and RA-FLS^STAT3C. Cells expressing GFP displayed green fluorescence. Representative green fluorescent and bright-field microscopy images of RA-FLS^{Empty vector} and RA-FLS^STAT3C are shown in the left panel (Scale bar: 10 μm). Representative immunoblotting results are shown in the right panel. Each membrane was cut based on molecular weights of proteins to be examined before hybridisation with primary antibodies. Original images of all blots are presented in Additional file 5. (b) Over-activation of STAT3 attenuated the inhibitory effect of CSR on RA-FLS hyperproliferation. Transduced RA-FLS were incubated with indicated concentrations of CSR for 1 h and then stimulated with IL-6/sIL-6R (100 ng/ml each) for 48 h. Cell viability was assessed using CCK-8 assays. Data are expressed as mean ± SD of 3 independent experiments. Differences of relative cell viabilities between CSR-treated RA-FLS^{Empty vector} and CSR-treated RA-FLS^STAT3C were calculated. * P < 0.05, ** P < 0.01