Th17 cells secrete TWEAK to trigger epithelial-mesenchymal transition and promote colorectal cancer liver metastasis.

Liver metastasis is the leading cause of mortality in patients with colorectal cancer (CRC). Given the significance of both epithelial-mesenchymal transition (EMT) of tumor cells and the immune microenvironment in CRC liver metastasis (CRLM), the interplay between them could hold the key for developing improved treatment options. We employed multi-omics analysis of 130 samples from 18 synchronous CRLM patients integrated with external datasets to comprehensively evaluate the interaction between immune cells and EMT of tumor cells in liver metastasis. Single-cell RNA sequencing analysis revealed distinct distributions of non-malignant cells between primary tumors from patients with metastatic CRC (mCRC) and non-metastatic CRC, showing that Th17 cells were predominantly enriched in the primary lesion of mCRC. TWEAK, a cytokine secreted by Th17 cells, promoted EMT by binding to receptor Fn14 on tumor cells, and the TWEAK-Fn14 interaction enhanced tumor migration and invasion. In mouse models, targeting Fn14 using CRISPR-induced knockout or lipid-nanoparticle-encapsulated siRNA alleviated metastasis and prolonged survival. Mice lacking Il17a or Tnfsf12 (encoding TWEAK) exhibited fewer metastases compared to wild-type mice, while co-transfer of Th17 with tumor cells promoted liver metastasis. Higher TWEAK expression was associated with a worse prognosis in CRC patients. Additionally, CD163L1+ macrophages interacted with Th17 cells, recruiting Th17 via the CCL4-CCR5 axis. Collectively, this study unveils the role of immune cells in the EMT process and identifies TWEAK secreted by Th17 as a driver of CRLM.