Role of extracellular vesicles as promotors for activation of leukemia‑derived dendritic cell‑mediated antileukemic immune response against AML‑blasts.

The transformation of myeloid leukemia blasts into leukemia‑derived dendritic cells (DC_leu) is a notable phenomenon. Extracellular vesicles (EVs) play a crucial role in modulating physiological and pathological activities, particularly in immune activation. In the present study, EVs were isolated from DC/DC_leu culture supernatants derived from healthy (H) donors (n=9) and patients with acute myeloid leukemia (AML) (n=9) using whole blood (WB) samples, both with and without Kit M (granulocyte‑macrophage colony‑stimulating factor and prostaglandin E₁). This was followed by T‑cell enriched mixed lymphocyte culture (MLC) with Kit M‑treated and untreated WB. To assess the qualitative and quantitative differences in EVs between Kit M‑treated and untreated samples, transmission electron microscopy, fluorescence nanoparticle tracking analysis and multiplex bead‑based flow cytometry were employed. The present findings indicate that DC/MLC supernatant‑derived EVs can be successfully identified, quantified and characterized. Furthermore, these EVs exhibit regulatory properties in both H and AML samples. Results showed that a higher number of CD8⁺ EVs were detected after DC culture compared with before in both H and AML samples. Thrombocyte‑associated EVs (CD41b⁺, CD42a⁺ and CD62P⁺) significantly increased following DC culture in both groups. While low frequencies of progenitor/blast marker (CD133⁺) associated EVs were detected in H samples before and after DC culture, their frequencies increased after DC culture in AML samples. Additionally, a higher number of CD8⁺ and CD2⁺ EVs were observed after MLC culture compared with before in both H and AML samples. Correlation analyses revealed that improved blast lysis in Kit M‑pretreated samples (normalized to control) associated with the presence of EV subtypes associated with T (CD2⁺), B (CD20⁺, 24⁺), and other cell markers (for example, CD31⁺, CD146⁺, CD44⁺ and CD49e⁺). This comprehensive approach provides insights into the impact of Kit M on DC/DC_leu generation and the subsequent activation of immune cells, leading to differences in EV production between H and AML samples.