Background/Aim: We previously demonstrated that inflammatory cytokine interleukin-6 (IL-6) was produced during cancer progression, worked together with transforming growth factor-beta 1 (TGF-β1), and induced the epithelial–mesenchymal transition (EMT) with chemo-resistance against gemcitabine (GR) at the invasion front of biliary tract cancers (BTCs). However, the significance of cytokine-induced T cell accumulation at the tumor microenvironment in biliary tract cancer (BTC) is not well understood. Because these cytokines (IL-6 and TGF-β1) are able to differentiate naïve T cells into Foxp3-expressing T cells (Tregs) and/or IL-17–producing T helper 17 (Th17) cells, we investigated the relationship between heterogeneous, cancer-producing cytokines and T cell differentiation. Methods: In total, 127 curative resected specimens from patients with BTCs at Osaka University Hospital between 2000 and 2012 were evaluated for IL-6, TGF-β1, Tregs, and Th17 cells by immunohistochemistry. The ability of BTC–GR cells to undergo T cell differentiation was investigated in vitro. Results: Tregs accumulated at the tumor center and Th17 cells accumulated at the invasion front during cancer progression and/or metastasis; each signaled poor prognosis. Treg accumulation was related to TGF-β1 expression by cancer cells, and Th17 cell accumulation was related to IL-6 expression by cancer cells, in resected specimens; this was confirmed in vitro. Compared with parent cells, GR cells produced IL-6 but not TGF-β1 in a time-dependent manner, had EMT features, and induced T cell differentiation to Th17 cells but not Tregs. Conclusion: Cytokines produced by cancer cells (IL-6 and TGF-β1) induced heterogeneity of Tregs and Th17 cells in the tumor microenvironment, supporting progression of BTC.
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