A549 cells were cultured in the presence of JAK inhibitor I (1-100 nM) for 1 hour prior to IL-27 (50 ng/mL) MAPK inhibitor exposure for 24 hours. The activated and total amounts of STAT1 and STAT3 proteins were detected by Western blot. The densitometric measurements of total amounts of STAT1 and STAT3 were taken using Image J1.45o. The values above the figures represent relative density of the bands compared to control DMSO that was set to 1 after normalized to GAPDH. IL-27 regulates and prevents over-expression of STAT3 through activation of the STAT1 pathway The specificity of STAT activation is

determined by the presence of the docking sites on the receptor, and STAT1 and STAT3 have been shown to be activated in response to gp130 receptor activation by various stimuli [29, 30]. STAT1 AZD3965 research buy buy PLX-4720 and STAT3 are known to regulate transcription of target genes playing opposing roles in tumorigenesis [11]. In order to determine if a dominant STAT pathway becomes activated by IL-27, we performed selective inhibition of the STAT1 or STAT3 pathways. A549 cells were transfected with STAT1 siRNAs for 24 hours prior to IL-27 exposure for 15 or 30 minutes, and the activated and total forms of STAT1 and STAT3 were measured by Western blot. The expression of P-STAT1 and T-STAT1 proteins was effectively

abolished after treatment with STAT1 siRNA I or STAT1 siRNA II while transfection with control siRNA did not significantly affect the level of P-STAT1 and T-STAT1 proteins Ribose-5-phosphate isomerase (Figure 3A). It should be noted that lost or reduced p-STAT3 was shown in Figure 3A compared to Figure 1A. This may be due to the procedure of transfection that has been known to induce cellular stress response [31]. Importantly, inhibition of STAT1 resulted in a marked reciprocal increase in P-STAT3 compared to control siRNA-transfected cells. It has been previously shown that STAT3 is constitutively activated

in A549 cells [32]. Our data suggest that STAT1 protein appears to play an important role in suppressing the overexpression of tyrosine phosphorylated STAT3 in human NSCLC cells. Figure 3 Acquisition of a more epithelial phenotype by inhibition of STAT1 expression in IL-27 treated cells. (A) A549 cells were transfected with a non-targeting control or STAT1 siRNAs (40 nM) for 6 hours prior to IL-27 (50 ng/mL) exposure for 15 or 30 minutes. Activated and total amounts of STAT1 and STAT3 proteins were detected by Western blot. GAPDH was used as a loading control. (B) Stattic (7.5 nM) or its diluent (DMSO) was added to A549 cells for 1 hour prior to IL-27 (50 ng/mL) exposure for 15 or 30 minutes. Activated and total amounts of STAT1 and STAT3 proteins were detected by Western blot. (C) After transfection with STAT1 siRNA (40 nM) for 6 hours or Stattic (7.5 nM) pre-treatment for 1 hour, A549 cells were exposed to IL-27 (50 ng/mL) for 24 hours. Morphologic changes were documented and photographed by phase contrast microscopy (50 × magnification).