The Acidic Exosomal miR-1246/WASF3 Axis Regulates Hepatic Stellate Cell Activation and Stiff ECM Remodeling to Promote Pancreatic Ductal Adenocarcinoma Liver Metastasis.

Liver metastasis is a major factor contributing to the poor prognosis of pancreatic ductal adenocarcinoma (PDAC). The formation of pre-metastatic niche (PMN) initiates the process of liver metastasis. Exosomes (Exos) act as key mediators of crosstalk between the tumor microenvironment (TME) and the PMN to activate hepatic stellate cells (HSCs) and remodel the stiff extracellular matrix (ECM). In this study, we isolated Exos derived from PDAC cells cultured under acidic conditions and demonstrated that these Exos significantly activate HSCs and promote the remodeling of the stiff ECM, thereby promoting the stemness, migration, and invasion of PDAC cells. High expression of exosomal miR-1246 was screened by miRNA-sequencing, and Wiskott-Aldrich syndrome protein Family Member 3 (WASF3) was identified as the target of miR-1246. Mechanistically, exosomal miR-1246 activates HSCs to remodel the ECM by targeting WASF3 and stimulating the phosphatidylinositol 3-kinase-serine/threonine protein kinase (PI3K/Akt) pathway. Notably, RNA-binding protein immunoprecipitation (RIP) and miRNA pull-down assays were performed to identify that Human Antigen R (HuR) contributes to the enrichment of miR-1246 into Exos. Collectively, exosomal miR-1246 activates HSCs and remodels the stiff ECM to promote liver metastasis, and it may serve as a potential diagnostic and prognostic marker for PDAC liver metastasis.