Identification of CXCL5/ENA-78 as a factor involved in the interaction between cholangiocarcinoma cells and cancer-associated fibroblasts

Knowledge of tumor‐stromal interactions is essential for understanding tumor development. We focused on the interaction between cholangiocarcinoma and cancer‐associated fibroblasts (CAFs) in intrahepatic cholangiocarcinoma and reported their positive interaction in vitro and in vivo. The aim of this study is to identify the key protein involved in the interaction between cholangiocarcinoma cells and CAFs and its role on cholangiocarcinoma progression. Using the conditioning medium from cholangiocarcinoma cells, hepatic stellate cells and coculture of them, Protein‐Chip analysis with SELDI–TOF–MS showed that the peak of an 8,360‐Da protein remarkably increased in the coculture medium. This protein was identified as CXCL5/ENA78, epithelial cell‐derived neutrophil‐activating peptide‐78, by q‐TOF/MS/MS analysis. Two cholangiocarcinoma cell lines, HuCCT1 and RBE, produced CXCL5 that promoted their invasion and migration in an autocrine fashion. These effects of CXCL5 significantly decreased by inhibition of CXC‐receptor 2, which is the receptor for CXCL5. In addition, IL‐1β produced by hepatic stellate cells induced the expression of CXCL5 in cholangiocarcinoma cells. In human tissue samples, a significant correlation was observed between CAFs and CXCL5 produced by cholangiocarcinoma cells in intrahepatic cholangiocarcinoma (p = 0.0044). Furthermore, the high‐CXCL5‐expression group exhibited poor overall survival after curative hepatic resection (p = 0.027). The presence of tumor‐infiltrating neutrophils expressing CD66b was associated with CXCL5 expression in tumor cells (p < 0.0001). These data suggest that CXCL5 is important for the interaction between cholangiocarcinoma and CAFs, and inhibition of tumor‐stromal interactions may be a useful therapeutic approach for cholangiocarcinoma.