Laminin γ2‐enriched extracellular vesicles of oral squamous cell carcinoma cells enhance in vitro lymphangiogenesis via intergrin α3‐dependent uptake by lymphatic endothelial cells

Oral squamous cell carcinoma (OSCC) LN1‐l cells previously showed greater capacities for lymphangiogenesis and lymph node metastasis compared to their parental OEC‐M1 cells, in addition to an ability to enhance the migration and tube formation of lymphatic endothelial cells (LECs). Purified by a series of differential centrifugations and characterized using electron microscopy, dynamic light scattering, and western blot, LN1‐1 cell‐derived extracellular vesicles (LN1‐1 EVs) were shown to promote LEC migration, tube formation, and uptake by LECs more effectively than did OEC‐M1 cell‐derived EVs (OEC‐M1 EVs). Using stable isotope labeling with amino acids in cell culture/liquid chromatography‐tandem mass spectrometry based proteomic platform, the laminin‐332 proteins, including laminin α3, β3, and γ2, were validated as highly expressed proteins in LN1‐1 EVs. Clinically, a higher level of laminin‐332 was detected in plasma EVs from OSCC patients with lymph node metastasis than in both healthy controls and OSCC patients without lymphatic metastasis, suggesting EV‐borne laminin‐332 as a novel and non‐invasive biomarker for the detection of lymph node metastasis in OSCC. The knockdown of laminin γ2 and inhibition by anti‐laminin‐332 neutralizing antibodies impaired LN1‐1 EV‐mediated LEC migration, tube formation, and uptake by LECs. Importantly, laminin γ2‐deficient EVs showed a reduced ability to drain into lymph nodes in comparison with the control EVs. Additionally, the laminin 332/γ2‐mediated EV uptake was dependent on integrin α3 but not β1, β4 or α6. Collectively, the uptake of laminin γ2‐enriched EVs by LECs enhanced in vitro lymphangiogenesis and EV‐borne laminin‐332 is thus a viable biomarker for OSCC.

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