Abstract 5074: Activation of TGF β-IL6 axis mediates chemoresistance in non-small cell lung cancer by increasing epithelial-mesenchymal transition signaling

Abstract

Abstract The tumor microenvironment is composed of different types of stromal cells that represent a key component of tumor progression, while it has been speculated that stromal components are functionally organized to promote cancer cell survival. A specific subset of stromal cells, termed cancer-associated fibroblasts (CAFs), secretes factors that promote tumorigenesis. We previously reported that CAFs increase the malignant potential of non-small-cell lung cancer (NSCLC) via the TGF β-IL6 axis. The purpose of this study was to clarify the role of the TGF β-IL6 axis in communication between CAFs and NSCLC cells for chemoresistance. Methods We used standard NSCLC cell lines (A549, NCI-H358), NSCLC cells obtained using a cancer tissue-originated spheroid (CTOS) method, lung normal fibroblasts (LNFs), and CAFs obtained from primary cultures of specimens from NSCLC patients to evaluate phenotypic changes in the presence of human IL-6, TGF-β1, and conditioned medium (CM) from the cells. Immunohistochemistry was also utilized to examine the distribution of fibroblasts in 75 tumor specimens obtained from patients with NSCLC after undergoing chemoradiotherapy. Results Expression levels of myofibroblast markers were elevated in CAFs as compared to LNFs, while CM from fibroblasts induced epithelial mesenchymal transition (EMT) in NSCLC cells. CM also enhanced the expression of stem cell markers such as CD44, and increased CD133 mRNA levels in cancer cells and resistance to cisplatin in lung cancer cells as well as CTOS produced cells, indicating that the CM from fibroblasts was biologically active. Furthermore, the concentration of IL-6 was higher in CM from CAFs as compared to that from LNFs, and CM-induced phenotypic changes of cancer cells were inhibited by addition of the IL-6 receptor neutralizing antibody. Cancer cells incubated with IL-6 and TGF-β1 showed significantly increased EMT changes and acquisition of cancer stemness as compared with those treated with TGF-β1 alone, suggesting that IL-6 enhances TGF-β signaling. Cisplatin treatment also increased TGF-β expression in cancer cells, and TGF-β1 activated LNFs and CAFs to increase IL-6 production. Immunohistochemistry was used to examine EMT status, fibroblast distribution, and IL-6 expression in tumor specimens obtained from patients with NSCLC after undergoing chemotherapy. EMT changes of cancer cells were correlated with a diffuse distribution of SMA-stained fibroblasts and stromal IL-6 expression. Conclusion IL-6 from CAFs enhanced epithelial cell EMT and acquisition of cancer stemness by enhancing TGF-β signaling. IL-6 and TGF-β may play contributing roles in maintenance of the paracrine loop between these two cytokines as part of the communication between CAFs and NSCLC cells, resulting in chemoresistance. Citation Format: Yasushi Shintani, Soichiro Funaki, Toru Kimura, Ayako Fujiwara, Tomohiro Kawamura, Toshiya Bessho, Masayoshi Inoue, Masato Minami, Meinoshin Okumura. Activation of TGF β-IL6 axis mediates chemoresistance in non-small cell lung cancer by increasing epithelial-mesenchymal transition signaling. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5074. doi:10.1158/1538-7445.AM2015-5074