Epigenetic transfer of metastatic activity by uptake of highly metastatic B16 melanoma cell-released exosomes

Aim: To investigate potential role of highly metastatic BL6-10 tumor cell-released exosomes (EXO) in transfer of metastatic activity into poorly metastatic tumor cell line F1. Methods: The highly metastatic B16 melanoma cell line (BL6-10) was generated in our laboratory. EXO from this cell line were isolated and amount of exosomal recovered proteins was measured using Bradford assay. For phenotypic analysis BL6-10 and F1 melanoma cells were stained win FITC-conjugated anti-MHC I (H-2K^b), MHC II (Ia^b) and Met 72 antibodies and analyzed by flow cytometry. C57BL/6 mice (8 per group) were injected (i. v.) with 0.5 × 10⁶ F1, BL6-10 and F1_EXO melanoma cells. Lungs were removed 4 weeks after tumor cell injection, fixed in 10% neutral buffered formaldehyde and embedded in paraffin for histological analysis. Results: Data revealed that BL6-10 cells expressed metastasis marker (Met 72 tumor antigen), while F1 cells did not display this cell surface marker. All mice inoculated with BL6-10 melanoma cells had numerous lung tumor colonies, while mice injected with F1 tumor cells were free of lung metastatic colonies. BL6-10 tumor cells-released EXO also expressed Met 72 tumor antigen as BL6-10 tumor cells, but in less amount. Fl tumor cells can uptake EXO from BL6-10 tumor cells and express acquired exosomal Met 72 tumor antigen. Conclusion: The metastatic activity of highly metastatic BL6-10 tumor cells can be transferred to poorly metastatic F1 tumor cells by uptake of highly metastatic BL6-10 tumor-released EXO.