Osteosarcoma cells‐derived exosomal YES1 promote tumor progression via MAPK pathway

Abstract Osteosarcoma (OS), the most common primary bone tumor in children and young adults, poses significant clinical challenges. In this study, we investigated the role of exosomes—key mediators of intercellular communication—in OS progression and identified potential therapeutic targets. Functional assays in cellular and animal models demonstrated that OS‐derived exosomes markedly enhanced tumor proliferation, migration, and invasion. Data‐independent acquisition‐based mass spectrometry analysis revealed a notable enrichment of the proto‐oncogene tyrosine‐protein kinase YES1 in these exosomes. Bioinformatics and clinical investigations further showed that YES1 is overexpressed in multiple cancers and correlates with poor outcomes; specifically, in OS, elevated YES1 levels were associated with reduced overall survival and adverse prognoses. PCR, Western blotting, and immunohistochemistry (IHC) of clinical samples confirmed its high expression in OS tissues relative to normal counterparts. Mechanistic studies using YES1 knockdown (shYES1) and overexpression (OE YES1) models, coupled with exosome supplementation and pathway modulators, revealed a critical role for ERK phosphorylation in mediating YES1‐driven oncogenic behaviors. In shYES1 cells, tumor proliferation, migration, and invasion were significantly impaired, partially rescued by exosome supplementation, and further suppressed by the inhibitor of MAPK. Conversely, in OE YES1 cells, these malignant phenotypes were markedly enhanced, exacerbated by exosomes, and further promoted by the agonist of MAPK. Western blot analyses supported these observations, showing reduced p‐MEK and p‐ERK but increased p‐p38 and p‐JNK upon YES1 knockdown, with opposite trends in the OE YES1 group; these phosphorylation changes were reversed or attenuated by EGF/IL‐1beta or U0126/SB‐203580 treatment, respectively, without altering total protein levels of MEK, JNK, p38, and ERK. Finally, multiplex IHC validated bioinformatics predictions, demonstrating that YES1 expression is closely linked to immune‐related pathways in OS tissues. Collectively, these findings underscore the pivotal role of exosomal YES1 in OS progression and tumor immunology, highlighting its promise as a biomarker and therapeutic target. By illuminating its function in cancer behavior and immune interactions, this study offers novel insights into improving patient outcomes in OS.