Interaction between non-small-cell lung cancer cells and fibroblasts via enhancement of TGF-β signaling by IL-6

Introduction: Fibroblasts are key components of the tumor microenvironment. We clarified the role of transforming growth factor (TGF)-beta and interleukin (IL)-6 in the interaction between fibroblasts and non-small-cell lung cancer (NSCLC) cells. Methods: We used NSCLC cells (A549, NCI-H358) and normal human lung fibroblast (NHLF) cells to evaluate phenotypic changes in the presence of human IL-6, TGF-beta 1, and conditioned media (CM) from these cells. Possible pathways were evaluated with SB431542, a TGF-beta receptor inhibitor, or an anti-human IL-6 receptor neutralizing antibody (IL-6R-Ab). Results: A549 and NCI-H358 cells incubated with IL-6 (50 ng/mL) and TGF-beta 1 (2 ng/mL) showed significantly increased epithelial-mesenchymal transition (EMT) signaling compared to those treated with TGF-beta 1 alone. Furthermore, NHLF cells were synergistically activated by IL-6 and TGF-beta 1. IL-6 increased the expression of TGF-beta type I receptors on the surface of A549, NCI-H358 and NHLF cells and enhanced TGF-beta signaling. TGF-beta 1 induced phenotypic changes were attenuated by IL-6R-Ab. NHLF cells were activated and A549 cells showed induction of EMT in response to CM from the other cell type. These activities were attenuated by SB431542 or IL-6R-Ab, suggesting that interplay between NSCLC cells and NHLF may lead to increased EMT signaling in NSCLC cells and activation of NHLF cells through TGF-beta and IL-6 signaling. Subcutaneous co-injection of A549 and NHLF cells into mice resulted in a high rate of tumor formation compared with injection of A549 cells without NHLF cells. SB431542 or IL-6R-Ab also attenuated the tumor formation enhanced by co-injection of the two cell types. Conclusion: IL-6 enhanced epithelial cell EMT and stimulated tumor progression by enhancing TGF-beta signaling. IL-6 and TGF-beta may play a contributing role in maintenance of the paracrine loop between these two cytokines in the communication between fibroblasts and NSCLC cells for tumor progression. (C) 2013 Elsevier Ireland Ltd. All rights reserved.