Potential antitumor activity of novel DODAC/PHO-S liposomes

Abstract

In recent studies, we showed that synthetic phosphoethanolamine (PHO-S) has a great potential for inducing cell death in several tumor cell lines without damage to normal cells. However, its cytotoxic effect and selectivity against tumor cells could increase with encapsulation in cationic liposomes, such as dioctadecyldimethylammonium chloride (DODAC), due to electrostatic interactions between these liposomes and tumor cell membranes. Our aim was to use cationic liposomes to deliver PHO-S and to furthermore maximize the therapeutic effect of this compound. DODAC liposomes containing PHO-S (DODAC/PHO-S), at concentrations of 0.3–2.0 mM, prepared by ultrasonication, were analyzed by scanning electron microscopy (SEM) and dynamic light scattering. The cytotoxic effect of DODAC/PHO-S on B16F10 cells, Hepa1c1c7 cells, and human umbilical vein endothelial cells (HUVECs) was assessed by MTT assay. Cell cycle phases of B16F10 cells were analyzed by flow cytometry and the morphological changes by SEM, after treatment. The liposomes were spherical and polydisperse in solution. The liposomes were stable, presenting an average of ∼50% of PHO-S encapsulation, with a small reduction after 40 days. DODAC demonstrated efficient PHO-S delivery, with the lowest values of IC 50% (concentration that inhibits 50% of the growth of cells) for tumor cells, compared with PHO-S alone, with an IC 50% value of 0.8 mM for B16F10 cells and 0.2 mM for Hepa1c1c7 cells, and without significant effects on endothelial cells. The Hepa1c1c7 cells showed greater sensitivity to the DODAC/PHO-S formulation when compared to B16F10 cells and HUVECs. The use of DODAC/PHO-S on B16F10 cells induced G 2 /M-phase cell cycle arrest, with the proportion significantly greater than that treated with PHO-S alone. The morphological analysis of B16F10 cells by SEM showed changes such as “bleb” formation, cell detachment, cytoplasmic retraction, and apoptotic bodies after DODAC/PHO-S treatment. Cationic liposomal formulation for PHO-S delivery promoted cytotoxicity more selectively and effectively against B16F10 and Hepa1c1c7 cells. Thus, the DODAC/PHO-S liposomal formulation presents great potential for preclinical studies.

Modulation of pro-apoptotic effects and mitochondrial potential on B16F10 cells by DODAC/PHO-S liposomes

“…Recently, the PHO-S was encapsulated in DODAC liposomes by our research group, aiming to maximize the antitumor effect and providing a greater availability of PHO-S in the tumour microenvironment [ 4 ].…”

“…This result demonstrates the efficacy of liposomal formulation DODAC/PHO-S to promote B16F10 cell death. Recently, these liposomes were evaluated on normal and did not promote significant cell death [ 4 ]. Studies have shown that the use of nanocarriers are promising drug delivery systems, presenting several advantages such as low skin irritation and increased protection of the encapsulated drug.…”

“…Our results demonstrated that PHO-S was cytotoxic on melanoma tumor cells associated with apoptotic effect, without any effect on normal cells, as such human normal endothelial, fibroblasts and lymphocytes cells [ 1 – 3 ]. However, its cytotoxic effect and selectivity against tumor cells could increase with encapsulation in cationic liposomes, such as dioctadecyldimethylammonium chloride (DODAC), due to electrostatic interactions between these liposomes and tumor cell membranes [ 4 ].…”

“…Recently our group encapsulated PHO-S in DODAC liposomes (DODAC/PHO-S), because this cationic liposomes can interact with the PHO-S due to electrostatic attraction, in aqueous solution after being subjected to phase transition temperature and subsequent sonication. Physical–chemical analysis showed that these liposomes were stable [ 4 ].…”

“…The treatment of B16F10 and Hepa1c1c7 cells with DODAC/PHO-S liposomes demonstrated the lowest values of IC 50% for tumour cells, compared with PHO-S alone, with an IC 50% of 0.8 mM for B16F10 cells and 0.2 mM for Hepa1c1c7 cells, and without significant effects on endothelial cells [ 4 ]. Thus, we aimed to evaluate the potential of DODAC/PHO-S liposomes on modulates the expression of pro-apoptotic proteins and the mitochondrial electrical potential.…”