Abstract 5069: IL-33 secreted by cancer-associated fibroblasts mediates epithelial-stromal interactions and promotes gastric cancer invasion via ERK signaling pathway
Authors: Su Liping , Zhou Quan , Wang Chenchen , Wu Xiongyan , Wang Xiaofeng , Li Jianfang , Zhu Zhenggang , Liu Bingya 
Published: August 2015

Abstract
Background: Cancer-associated fibroblasts (CAFs) are important modifiers of tumor progression, which can actively communicate with cancer cells through soluble factors. Interleukin-33 (IL-33) is a regulator of immune and inflammatory responses and has also been associated with certain epithelial tumors. Although the importance of CAFs in gastric cancer has been documented in experimental studies, the mechanisms by which CAFs and IL-33 promote gastric cancer remain unclear.
Objectives: The aim of this study was to determine the role of IL-33 in the epithelial-stromal interaction in gastric cancer and if CAFs can promote the invasion of gastric cancer cells via ERK pathway through IL-33.
Methods: CAFs and normal fibroblasts (NFs) were isolated from gastric cancer tissues and adjacent non-cancerous tissues respectively. The identification of CAFs was detected by immunofluorescence (IF) and qRT-PCR. IL-33 expression in CAFs and gastric cancer cells was detected by qRT-PCR. CAFs was co-cultured with gastric cancer cells in the presence of exogenous TNF-α, IL-1β and/or their corresponding neutralizing antibodies, the expression of IL-33 in CAFs was detected using qRT-PCR. EMT changes and activation of ERK pathway in gastric cancer cells after co-cultured with CAF-conditioned media were detected by qRT-PCR and western blot, and cell invasion assays were performed by using 8 μm transwell chambers.
Results: Gastric CAFs expressed more α-SMA, a marker of myofibroblasts, and more fibroblast activation protein (FAP) when compared with patient-matched NFs. In comparison to gastric cancer cells and NFs, IL-33 was highly expressed in CAFs. Upregulation of IL-33 in CAFs can be induced by co-culture with gastric cancer cells or in the presence of TNF-α and IL-1β, while deprivation of TNF-α and IL-1β using their neutralizing antibodies inhibited the upregulation of IL-33. CAFs induced EMT changes of gastric cancer cells, which was demonstrated by decreased expression of E-cadherin and increased expression of Twist1, MMP2, ZEB1 and ZEB2. However, deprivation of IL-33 using a neutralizing antibody impaired the EMT changes of gastric cancer cells. Gastric cancer cells co-cultured with CAFs or CAFs conditioned media showed enhanced ability of invasion than gastric cancer cells alone. However, adding neutralizing IL-33 antibody or IL-33-siRNA-CAFs conditioned media or U0126 into the culture system led to significantly decreased invasion (P &lt; 0.05) of gastric cancer cells. Moreover, IL-33 secreted from CAFs activated ERK pathway in gastric cancer cells, however, the invasion of gastric cancer cells was attenuated when IL-33-ERK pathway was blocked.
Conclusions: TNF-α and IL-1β derived from gastric cancer cells can significantly enhance the expression of IL-33 in CAFs, and IL-33 secreted by CAFs promotes gastric cancer invasion via the ERK signaling pathway.
Note: This abstract was not presented at the meeting.
Citation Format: Liping Su, Quan Zhou, Chenchen Wang, Xiongyan Wu, Xiaofeng Wang, Jianfang Li, Zhenggang Zhu, Bingya Liu. IL-33 secreted by cancer-associated fibroblasts mediates epithelial-stromal interactions and promotes gastric cancer invasion via ERK signaling pathway. [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 5069. doi:10.1158/1538-7445.AM2015-5069