Research on mechanism of exosome derived from EOC on promoting BMSCs and its autocrine effect in micro-environment through activating the VEGF-A/MAPK/ERK pathway

Background: Tumor-derived exosomes mediate intercellular communication in the tumor microenvironment. Epithelial ovarian cancer (EOC) cells secrete exosomes that may regulate bone marrow mesenchymal stem cells (BMSCs), but the underlying mechanisms remain unclear. Objectives: This study aimed to investigate whether EOC-derived exosomes regulate BMSCs through the Vascular Endothelial Growth Factor A(VEGF-A)/Mitogen-Activated Protein Kinase(MAPK)/Extracellular Signal-Regulated Kinase(ERK) signaling pathway and to determine the functional consequences of this interaction. Methods: EOC-derived exosomes (EOC-Exos) were isolated by ultracentrifugation and characterized by transmission electron microscopy, nanoparticle tracking analysis and Western blot. BMSCs were identified by flow cytometry. BMSCs were divided into control, EOC-Exos and EOC-Exos + ERK inhibitor (U0126) groups. Cell cycle distribution was analyzed by flow cytometry. VEGF-A and MAPK/ERK expression were detected by immunofluorescence and Western blot. VEGF secretion was measured by enzyme-linked immunosorbent assay (ELISA) and VEGF mRNA expression was detected by reverse transcription-polymerase chain reaction (RT-PCR). Results: EOC-Exos exhibited a typical cup-shaped morphology, ranged from 30 to 150 nm in size and expressed CD9, CD63 and TSG101. BMSCs highly expressed CD90, CD73 and CD105, with low CD45 and CD34. EOC-Exos treatment significantly decreased the proportion of cells in G0/G1 phase (P=0.007) and increased that in S phase (P<0.001), indicating accelerated cell cycle progression. EOC-Exos time-dependently upregulated VEGF-A protein (P<0.05) and ERK phosphorylation (P<0.001). ERK inhibitor U0126 significantly attenuated EOC-Exos-induced VEGF upregulation (P<0.01), VEGF mRNA expression (P<0.01) and S phase increase (P<0.01). Conclusion: EOC-derived exosomes activate the MAPK/ERK pathway in BMSCs, upregulating VEGF transcription and secretion and accelerating cell cycle progression. ERK inhibition reverses these effects, demonstrating the critical role of this pathway in tumor-stroma interactions.