Vascular endothelial growth factor (VEGF) is well known potent angiogenic

factor [42]. In addition to VEGF, IL-8/CXCL8 and CXCL5 have been identified as important pro-angiogenic proteins in human NSCLC [43, 44]. It has previously been shown that IL-27 has anti-angiogenic activity by down regulating the expression of VEGF, IL-8/CXCL8 and CXCL5 in human multiple myeloma cells [3]. In this study, we examined the production of pro-angiogenic factors, VEGF, IL-8/CXCL8, and CXCL5, to determine the effects of IL-27 on angiogenesis in human lung cancer. STAT1 and STAT3 are known to have opposing roles in VEGF regulation. For example, STAT1 has been shown to be a negative regulator of VEGF and

angiogenesis [16, 45, 46]. In contrast, STAT3 transactivation with other ITF2357 ic50 factors is required for full induction of the VEGF promoter in cancer cells [47]. Similarly, Procaspase activation STAT1 is required for inhibition of IL-8 expression mediated by other cytokines [48]. Constitutive activation or knockdown of STAT3 has been shown to up regulate or suppress IL-8 production in human melanoma cells, respectively [49]. The role of STAT1 and STAT3 pathways in the production of CXCL5 in cancer has not been well studied. On this basis, the expression Selleckchem HDAC inhibitor of angiogenic factors were measured in A549 cells by ELISA after being exposed for 24 hours to IL-27 alone or after being pre-treated with STAT1 siRNA or STAT3 inhibitor, Stattic. Our results demonstrate that the inhibition of STAT1 by siRNA in A549 cells

led to increased production of VEGF, IL-8 and CXCL5 (Figure 6A, 6C, and 6E) while the suppression of STAT3 activation caused reduced secretion of the pro-angiogenic factors diglyceride (Figure 6B, 6D, and 6F). IL-27 treated cells showed statistically significant decrease in expression of VEGF, IL-8/CXCL8, and CXCL5 compared to untreated cells (Figure 6A, 6C, and 6E, respectively). Inhibition of the STAT1 pathway by pretreatment with STAT1 siRNA, but not control siRNA, reversed the IL-27 mediated decreased expression of VEGF, IL-8/CXCL8, and CXCL5, resulting in increased levels of these pro-angiogenic factors to levels significantly higher than untreated controls. Figure 6 Down-regulation of angiogenic factors and up-regulation of angiostatic factors by STAT1-dependent pathway. (A-F) Protein concentrations of VEGF (A, B), IL-8/CXCL8 (C, D), CXCL5 (E, F) secreted by A549 cells were measured by ELISA. A549 cells were either transfected with STAT1 siRNAs (40 nM) or control siRNA for 24 hours and further treated with or without Stattic (7.5 nM) for 1 hour followed by IL-27 (50 ng/mL) treatment for 24 hours. The cell culture supernatants were used for ELISA. * p vs. no treatment, ** p vs. IL-27 by student t- test. The impact of the STAT3 pathway was also studied by the addition of Stattic to the IL-27-treated cells.