miRNA cargo from pleural mesothelioma-derived extracellular vesicles reprograms fibroblasts to a cancer-associated phenotype

This study extensively examines the miRNA cargo of pleural mesothelioma (PM)-derived extracellular vesicles (EVs). Additionally, it highlights their impact on fibroblasts, which are the most abundant cell type in the pleural mesothelioma tumour microenvironment (PM-TME). Our data show that EVs derived from two different PM subtypes, epithelioid and non-epithelioid, have distinct miRNA cargo profiles. These differ from each other and from non-malignant controls. We found that oncogenic miRNAs were upregulated in the PM-derived EVs, while tumour-suppressive miRs were downregulated. Further, we identified miRs that are exclusively present in either epithelioid or non-epithelioid PM subtypes. These miRs could serve as biomarkers to distinguish PM subtypes and aid in treatment decisions. Our omics and molecular analyses show that uptake of PM-derived EVs alters oncogenic signalling, redox homeostasis, inflammatory responses, extracellular matrix remodelling, and proliferation in recipient fibroblasts. We also report that PM-EVs can regulate epigenetic modification by altering EZH2 phosphorylation. Our data demonstrate that EVs from the epithelioid subtype of PM increase phosphorylation of EZH2 at threonine (Thr345) in fibroblasts after EV uptake. This post-translational modification is linked to EZH2 degradation. In contrast, EVs from the non-epithelioid subtype reduce phosphorylation at this site. These findings highlight the ability of PM-derived EVs to mediate subtype-specific epigenetic modulation in recipient fibroblasts. Collectively, this study provides the first comprehensive analysis of miRNA cargo in PM-derived EVs, identifying specific miRNAs involved. Our data demonstrate that PM-derived EVs activate signalling mechanisms that reprogram fibroblasts to acquire a cancer-associated phenotype. The EV-mediated signalling pathway identified in the PM-TME represents a potential therapeutic target for future interventions.