Intracellular uptake and intracavitary targeting of folate-conjugated liposomes in a mouse lymphoma model with up-regulated folate receptors

Abstract

The folate receptor is overexpressed in a broad spectrum of malignant tumors and represents an attractive target for selective delivery of anticancer agents to folate receptorexpressing tumors. This study examines folate-lipid conjugates as a means of enhancing the tumor selectivity of liposome-encapsulated drugs in a mouse lymphoma model. Folate-derivatized polyethylene glycol (PEG 3350 )-distearoyl-phosphatidylethanolamine was post-loaded at various concentrations into the following preparations: radiolabeled PEGylated liposomes, PEGylated liposomes labeled in the aqueous compartment with dextran fluorescein, and PEGylated liposomal doxorubicin (PLD, Doxil). We incubated folate-targeted radiolabeled or fluorescent liposomes with mouse J6456 lymphoma cells up-regulated for their folate receptors (J6456-FR) to determine the optimal ligand concentration required in the lipid bilayer for liposomal cell association, and to examine whether folate-targeted liposomes are internalized by J6456-FR cells in suspension. Liposomal association with cells was quantified based on radioactivity and fluorescence-activated cell sorting analysis, and internalization was assessed by confocal fluorescence microscopy. We found an optimal ligand molar concentration of f0.5% using our ligand. A substantial lipid dosedependent increase in cell-associated fluorescence was found in folate-targeted liposomes compared with nontargeted liposomes. Confocal depth scanning showed that a substantial amount of the folate-targeted liposomes are internalized by J6456-FR cells. Binding and uptake of folate-targeted PLD by J6456-FR cells were also observed in vivo after i.p. injection of folatetargeted PLD in mice bearing ascitic J6456-FR tumors. The drug levels in ascitic tumor cells were increased by 17-fold, whereas those in plasma were decreased by 14-fold when folate-targeted PLD were compared with nontargeted PLD in the i.p. model. Folate-targeted liposomes represent an attractive approach for the intracellular delivery of drugs to folate receptor -expressing lymphoma cells and seem to be a promising tool for in vivo intracavitary drug targeting. [Mol Cancer Ther 2006;5(4):818 -24]

Design of Folate-Linked Liposomal Doxorubicin to its Antitumor Effect in Mice

“…With regard to folate density, maximal FR-dependent uptake of both NL and SL was obtained previously with a density of 0.2 to 0.5 mol% F-PEG-DSPE (10,17,28,29). Our data on cellular uptake and in vitro cytotoxicity indicated that 0.25 mol% F5-PEG-DSPE in liposomes was optimal for targeting to FR on KB cells.…”

“…In a nonsolid tumor, the high therapeutic efficacy of folate-linked liposomal doxorubicin was reported in mouse ascites leukemia models, in which the treatment route was intraperitoneal injection (14). In addition, the therapeutic efficacy of intravenous treatment with folate-linked liposomal doxorubicin was improved in mice inoculated intraperitoneally with lymphoma cells (32,33). Therefore, further study is needed for FR targeting of solid tumors by intravenous injection of folate-linked liposomes.…”

Folate-Targeted Gadolinium-Lipid-Based Nanoparticles as a Bimodal Contrast Agent for Tumor Fluorescent and Magnetic Resonance Imaging

“…In brief, unmodified nanoparticles (NPs) were prepared from Gd-DTPA-bis-stearylamide/PEG 2000 29,36) Cy7-labeled NPs were prepared via the addition of 0.01 mol% Cy7-PEG 2000 -DSPE to NPs or F-NPs. The lipids were dissolved in chloroform-methanol 4 : 1 (v/v).…”

Nanomedicine for drug targeting: strategies beyond the enhanced permeability and retention effect

“…110,116 In vivo, folate targeting of liposomes has shown the ability to increase the quantity of nanomedicine associated with J6456 lymphoma cells by 17-fold relative to nontargeted liposomes. 117 It must be noted that activated macrophages also express the FR, so it is possible that the therapeutic activity of the liposomes is partially due to targeted elimination of FR-expressing tumor-associated macrophages. 118 High expression of FRs suggests that the folic acid requirements of the cell are high and that appropriate chemotherapeutics may be utilized in order to fully exploit this characteristic.…”