PRL-3 up-regulates exosomal ITGαvβ5 expression to promote liver pre-metastatic niche formation and colon cancer liver metastasis

Liver pre-metastatic niches (PMN) formation is a pivotal process in colorectal cancer liver metastasis (CLM). Phosphatase of regenerating liver-3 (PRL-3) has been demonstrated as a key factor in promoting CRC progression (e.g., therapeutic resistance and metastasis), but its role in liver PMN formation remains unknown. Using mouse models and CRC patient samples, we herein reveal that high PRL-3 expression in CRC cells could enhance the recruitment of myeloid-derived suppressor cells (MDSCs) into the liver and impair the hepatic infiltration of CD8+ T cells, thereby promoting the liver PMN formation and CLM. Mechanistically, high PRL-3 expression could activate the Src/STAT3 signaling pathway in CRC cells and thus up-regulate integrin αvβ5 (ITGαvβ5) expression in their secreted exosomes, which could specifically target F4/80+ macrophages in the liver to activate the P38/STAT1 signaling pathway. With this activation of P38/STAT1 pathway, the secretion of C-X-C motif chemokine ligand 12 (CXCL12) from F4/80+ macrophages is significantly improved, which could enhance the recruitment of MDSCs into the liver and impair the hepatic infiltration of CD8+ T cells, ultimately leading to the liver PMN formation and CLM. Taken together, our findings not only uncover the important role of PRL-3 in CLM via promoting the liver PMN formation, but also provide the evidence for the treatment of CLM by targeting PRL-3.