Abstract
BackgroundBTC is an aggressive disease exacerbated by inflammation and immune suppression. Expansion of immunosuppressive cells occurs in biliary tract cancer (BTC), yet the role of BTC-derived cytokines in this process is unclear.MethodsActivated signalling pathways and cytokine production were evaluated in a panel of human BTC cell lines. Human peripheral blood mononuclear cells (PBMCs) were cultured with BTC supernatants, with and without cytokine neutralising antibodies, and analysed by flow cytometry or immunoblot. A human BTC tissue microarray (TMA, n = 69) was stained for IL-6, GM-CSF, and CD33+S100a9+ cells and correlated with clinical outcomes.ResultsImmunomodulatory factors (IL-6, GM-CSF, MCP-1) were present in BTC supernatants. BTC supernatants expanded CD33dimCD11b+HLA-DRlow/− myeloid-derived suppressor cells (MDSCs) from human PBMCs. Neutralisation of IL-6 and GM-CSF in BTC supernatants inhibited activation of STAT3/5, respectively, in PBMCs, with heterogeneous effects on MDSC expansion in vitro. Staining of a BTC TMA revealed a positive correlation between IL-6 and GM-CSF, with each cytokine and more CD33+S100a9+ cells. Increased CD33+S100a9+ staining positively correlated with higher tumour grade, differentiation and the presence of satellite lesions.ConclusionBTC-derived factors promote suppressive myeloid cell expansion, and higher numbers of CD33+S100a9+ cells in resectable BTC tumours correlates with more aggressive disease.
Highlights
biliary tract cancer (BTC) is an aggressive disease exacerbated by inflammation and immune suppression
The presence of IL-6, granulocyte macrophage colonystimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), and monocyte chemoattractant protein-1 (MCP-1) in BTC supernatants was further validated with enzyme-linked immunosorbent assay (ELISA) kits (Supplementary Fig. 1)
IL-6 and GM-CSF are predominant cytokines that induce myeloid-derived suppressor cells (MDSCs) expansion and activation of Jak/STAT signalling by BTC supernatants We evaluated the BTC cell lines that made abundant IL-6 and GM-CSF to determine the roles of these cytokines in mediating MDSC expansion
Summary
Expansion of immunosuppressive cells occurs in biliary tract cancer (BTC), yet the role of BTC-derived cytokines in this process is unclear. BTC supernatants expanded CD33dimCD11b+HLA-DRlow/− myeloid-derived suppressor cells (MDSCs) from human PBMCs. Neutralisation of IL-6 and GM-CSF in BTC supernatants inhibited activation of STAT3/5, respectively, in PBMCs, with heterogeneous effects on MDSC expansion in vitro. Staining of a BTC TMA revealed a positive correlation between IL-6 and GM-CSF, with each cytokine and more CD33+S100a9+ cells. CONCLUSION: BTC-derived factors promote suppressive myeloid cell expansion, and higher numbers of CD33+S100a9+ cells in resectable BTC tumours correlates with more aggressive disease. We hypothesised that the inflammatory nature of this disease may promote suppressive myeloid cell expansion that acts to limit lymphocyte responses to BTC. Immunotherapy has limited impact on BTC,[9] a report by Tran et al demonstrated that adoptive transfer of tumour-infiltrating lymphocytes can mediate BTC regression.[10,11]
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