TWEAK/Fn14 signalling promotes cholangiocarcinoma niche

Background & Aims: Cholangiocarcinoma (CCA) is a cancer of the hepatic bile ducts that is rarely resectable and is associated with poor prognosis. Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) is known to signal via its receptor fibro-blast growth factor-inducible 14 (Fn14) and induce cholangiocyte and myofibroblast proliferation in liver injury. We aimed to characterise its role in CCA. Methods: The expression of the TWEAK ligand and Fn14 re-ceptor was assessed immunohistochemically and by bulk RNA and single cell transcriptomics of human liver tissue. Spatio-temporal dynamics of pathway regulation were comprehensively analysed in rat and mouse models of thioacetamide (TAA)-mediated CCA. Flow cytometry, qPCR and proteomic analyses of CCA cell lines and conditioned medium experiments with pri-mary macrophages were performed to evaluate the downstream functions of TWEAK/Fn14. In vivo pathway manipulation was assessed via TWEAK overexpression in NICD/AKT-induced CCA or genetic Fn14 knockout during TAA-mediated carcinogenesis. Results: Our data reveal TWEAK and Fn14 overexpression in multiple human CCA cohorts, and Fn14 upregulation in early TAA-induced carcinogenesis. TWEAK regulated the secretion of factors from CC-SW-1 and SNU-1079 CCA cells, inducing polar-isation of proinflammatory CD206+ macrophages. Pharmacolog-ical blocking of the TWEAK downstream target chemokine monocyte chemoattractant protein 1 (MCP-1 or CCL2) signifi- cantly reduced CCA xenograft growth, while TWEAK over-expression drove cancer-associated fibroblast proliferation and collagen deposition in the tumour niche. Genetic Fn14 ablation significantly reduced inflammatory, fibrogenic and ductular re-sponses during carcinogenic TAA-mediated injury. Conclusion: These novel data provide evidence for the action of TWEAK/Fn14 on macrophage recruitment and phenotype, and cancer-associated fibroblast proliferation in CCA. Targeting TWEAK/Fn14 and its downstream signals may provide a means to inhibit CCA niche development and tumour growth. Lay summary: Cholangiocarcinoma is an aggressive, chemotherapy-resistant liver cancer. Interactions between tumour cells and cells that form a supportive environment for the tumour to grow are a source of this aggressiveness and resistance to chemotherapy. Herein, we describe interactions between tumour cells and their supportive environment via a chemical messenger, TWEAK and its receptor Fn14. TWEAK/Fn14 alters the recruitment and type of immune cells in tumours, increases the growth of cancer-associated fibroblasts in the tumour environment, and is a potential target to reduce tumour formation. (C) 2020 European Association for the Study of the Liver. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This study highlights the overexpression of TWEAK/Fn14 in human CCA and the upregulation of Fn14 during TAA-induced carcinogenesis. TWEAK modulates the secretion of factors from CCA cells, influencing the polarization of macrophages and promoting cancer-associated fibroblast proliferation in the tumor microenvironment.