Adriamycin-loaded exosome with anti-CD20 aptamers selectively suppresses human CD20+ melanoma stem cells.

Background: Targeting CD20+ melanoma cancer stem cells (CSCs) subset is essential for treating melanoma. Anti-CD20 aptamer-modified exosomes (ACEXO) loaded with Adriamycin could be a therapeutic strategy for targeting CSCs.

Materials And Methods: Exosomes loaded with Adriamycin were modified with anti-CD20 aptamer and characterized by size and molecular markers using transmission electron microscope and dynamic light scattering. The uptake of ACEXO into CD20+ cells was checked, and its cytotoxicities in CD20+ melanoma cells, HEK 293T, and 3T3 cells were evaluated. At the same time, the in vivo distribution of ACEXO in the tumor-bearing mice model was determined.

Results: The particle size of the exosome is about 80-100 nm. Western blot analysis showed that they expressed the characteristic exosome markers: CD9 and CD63. Quantitative analysis of the mean fluorescence intensity after 4 h incubation showed that ACEXO significantly improved Adriamycin uptake. Notably, the ACEXO killed only CD20+ melanoma cells. In addition, they exhibited good biocompatibility with both 293T and 3T3 cells at all doses. After intravenous injection, exosome distribution data showed that ACEXO's accumulation in the tumor is higher than anti-CD20-modified exosomes (AEXO)'s at all time points, and the accumulation increased as time prolonged. Addition of ACEXO reduces the number of tumorspheres in A375 or WM266-4 cells compared to untreated controls or AEXO-treated group. More important, while treating melanoma tumor-bearing mice, ACEXO-treated group showed the lowest tumor weight without body weight loss.

Conclusion: ACEXO loaded with Adriamycin could suppress tumor cell growth in vitro and in vivo, probably by targeting CD20+ melanoma CSCs.