Dasatinib-Loaded Erythrocytes Trigger Apoptosis in Untreated Chronic Myelogenous Leukemic Cells: A Cellular Reservoir Participating in Dasatinib Efficiency

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Dasatinib is an ABL1 tyrosine kinase inhibitor (TKI) with a short in vivo plasmatic half-life but with good efficiency, which is not fully understood. We investigated the possibility that circulating erythrocytes store and then provide dasatinib to target cells. In vitro coincubation of dasatinib-treated cells with naïve leukemic cells followed by analysis of kinase inhibition, apoptosis induction, fluorescent molecule exchanges, and dasatinib dosage were performed. Cells incubated with clinically relevant concentrations of dasatinib for a short time retained, after a washout procedure, an intracellular pool of dasatinib which was transferable to naïve BCR-ABL1 expressing cells and induced their apoptosis. This was verified in total blood where the huge cellular volume of erythrocytes constituted a large reservoir of dasatinib able to induce apoptosis in naïve BCR-ABL1 cell lines and primitive chronic myeloid leukemia (CML) CD34+ cells. This dasatinib transfer necessitated a contact between donor and acceptor cells. A component exchange occurred during this contact, carrying dasatinib and other TKIs such as nilotinib or the fluorescent sunitinib. An active pool of dasatinib could be buried inside the circulating erythrocytes, out of reach of detoxifying mechanisms, but still available for target cells and thus extending the acute effect of the plasmatic pool of the drug.