Doxorubicin-loaded NK exosomes enable cytotoxicity against triple-negative breast cancer spheroids.

Objectives: Natural killer (NK) cells are the most professional innate immune cells that initiate extracellular apoptosis via cytotoxic granules in malignant cells. Antitumoral properties of NK-derived exosomes (Exos) are attributed to their parent cells. Loading drugs into Exos as a carrier can enhance their effect and enable targeted delivery. In the present study, we aim to deliver Doxorubicin (DOX) to the breast cancer spheroids by NK-Exos.

Materials And Methods: Peripheral blood mononuclear cells (PBMC) were used to harvest NK cells, and NK-Exos were isolated from NK cell expansion medium using an Exo-spinTM kit. DOX was loaded via the ultrasonication method. AO/EtBr, Annexin/PI, DAPI, MTT, and spheroids of human breast cancer were used to track the cytotoxic effect of DOX-NK-Exos. The colony formation assay, scratch and transwell assays, Real-Time PCR for p53 and VEGF-A, and WB for protein expression were also performed.

Results: When compared to free DOX, all viability tests validated the inhibitory effects of DOX-NK-Exos. The obtained results indicated that DOX-NK-Exos selectively reduced tumor cell viability and spared fibroblast and MCF-10A as noncancerous cells. Long after spheroid treatment, DOX-NK-Exos' remarkable effect persisted.

Conclusion: Human breast carcinoma mass treated with DOX-NK-Exos underwent apoptosis and showed a strong inhibitory effect on proliferation. Thus, they can reduce the side effects of chemotherapeutics and can be used as drug carriers with selective toxicity. Additionally, the additive action of this combination formula results in a more severe loss in cell viability.