Effects of the antitumoural dequalinium on NB4 and K562 human leukemia cell lines. Mitochondrial implication in cell death.

Dequalinium (DQA) is a delocalized lipophylic cation that selectively targets the mitochondria of carcinoma cells. However, the underlying mechanisms of DQA action are not yet well understood. We have studied the effects of DQA on two different leukemia cell lines: NB4, derived from acute promyelocytic leukemia, and K562, derived from chronic myeloid leukemia. We found that DQA displays differential cytotoxic activity in these cell lines. In NB4 cells, a low DQA concentration (2microM) induces a mixture of apoptosis and necrosis, whereas a high DQA concentration (20microM) induces mainly necrosis. However, K562 cell death was always by necrosis as the cells showed a resistance to apoptosis at all time-periods and DQA concentrations assayed. In both cell lines, the cell death seems to be mediated by alterations of mitochondrial function as evidenced by loss of mitochondrial transmembrane potential, O2*- accumulation and ATP depletion. The current study improves the knowledge on DQA as a novel anticancer agent with a potential application in human acute promyelocytic leukemia chemotherapy.

In vivo biodistribution of erythrocytes and polyethyleneglycol-phosphatidylethanolamine micelles carrying the antitumour agent dequalinium.

Dequalinium (DQA), a lipophilic drug with anti-cancer activity has been incorporated into mouse red blood cells (DQA-RBCs) and polyethylene glycol phosphatidylethanolamine micelles (DQA-PEG-PE-micelles) in order to overcome the drug's solubility problems and to make it suitable for in vivo applications. The incorporation of DQA into erythrocytes, the release of DQA from RBCs in the presence of autologous plasma and the biodistribution of 51Cr-DQA-RBCs and 111In-DQA-PEG-PE micelles in mice has been studied. Under optimal conditions, up to 84.9% of 0.2 mM dequalinium can be incorporated into erythrocytes. The incubation of DQA-RBC with serum leads to the release of DQA over a period of 24 h. Since 51Cr-DQA-RBCs were found to have a long circulation half-life (5-6 days), the use of RBCs as a sustained release system for DQA can be suggested. In contrast to DQA containing erythrocytes, however, DQA loaded 111In-PEG-PE micelles displayed a shorter half-life (4 h) due to their quick uptake by the liver. The further exploration of PEG-PE micelles as a fast acting release system for DQA appears warranted.

In vivo studies on mouse erythrocytes linked to transferrin.

Transferrin (Tf), a plasma protein with numerous, highly specific receptors in proliferating and differentiating cells was already discussed as a targeting ligand for drugs and liposomes in previous studies. In this paper, we deal with erythrocytes linked to Tf as possible physiological targeting carrier systems for delivering anticancer drugs. For that purpose we have used glutaraldehyde (0.1%) as a coupling agent between Tf and erythrocytes. The highest amount of Tf linked to erythrocytes turned out to be 0.76 +/- 0.13 microg Tf/10(6) cells, while reaching 65% of cell recovery. After 13 days, the Tf-erythrocytes hemolysis reached 50%, with transferrin still coupled to erythrocytes. The in vivo kinetic behaviour of intravenously injected 51Cr-Tf-erythrocytes showed a reduced half-life to hours as compared to days of controls. However, a considerable percentage of Tf-erythrocytes (close to 20%) remained circulating for a relatively long period (around 2 days), which made possible the specific targeting by these carrier systems. In vivo biodistribution studies indicated that 51Cr-Tf-erythrocytes rapidly accumulated in the different studied organs (liver, spleen, lungs, kidneys, femur-tibia, and heart), suggesting a selective removal of Tf-erythrocytes by the cells of the mononuclear phagocytic system present mainly in liver and spleen. On the other hand, Tf-erythrocytes showed a poor targeting of heart tissue, therefore a reduced cardiac toxicity should be expected after administration of erythrocyte-encapsulated drugs. The presence of Tf-erythrocytes in femur-tibia and spleen could be related to the Tf-specific binding to the hematopoietic cells containing Tf receptors. The final results of this study encourage additional research on Tf-erythrocyte to investigate the relationship between transferrin-mediated targeting by carrier erythrocytes and uptake of different erythrocyte-encapsulated drugs. Consequently, the current study showed possible use of these carriers as a potential therapeutic tool for drug targeting in animal models with alterations affecting mononuclear phagocytic system or carcinomas of various origins whose cells show elevated number of Tf receptors.