ABSTRACT
PURPOSE: To improve therapeutic activity of mitoxantrone (MTO)-based chemotherapy by reducing toxicity through encapsulation in nanoliposomes and enhancing intracellular drug delivery using short-chain sphingolipid (SCS) mediated tumor cell membrane permeabilization. METHODS: Standard (MTOL) and nanoliposomes enriched with the SCS, C8-Glucosylceramide or C8-Galactosylceramide (SCS-MTOL) were loaded by a transmembrane ammonium sulphate gradient and characterized by DLS and cryo-TEM. Intracellular MTO delivery was measured by flow cytometry and imaged by fluorescence microscopy. In vitro cytotoxicity was studied in breast carcinoma cell lines. Additionally, live cell confocal microscopy addressed the drug delivery mechanism by following the intracellular fate of the nanoliposomes, the SCS and MTO. Intratumoral MTO localization in relation to CD31-positive tumor vessels and CD11b positive cells was studied in an orthotopic MCF-7 breast cancer xenograft. RESULTS: Stable SCS-MTOL were developed increasing MTO delivery and cytotoxicity to tumor cells compared to standard MTOL. This effect was much less pronounced in normal cells. The drug delivery mechanism involved a transfer of SCS to the cell membrane, independently of drug transfer and not involving nanoliposome internalization. MTO was detected intratumorally upon MTOL and SCS-MTOL treatment, but not after free MTO, suggesting an important improvement in tumor drug delivery by nanoliposomal formulation. Nanoliposomal MTO delivery and cellular uptake was heterogeneous throughout the tumor and clearly correlated with CD31-positive tumor vessels. Yet, MTO uptake by CD11b positive cells in tumor stroma was minor. CONCLUSIONS: Nanoliposomal encapsulation improves intratumoral MTO delivery over free drug. Liposome bilayer-incorporated SCS preferentially permeabilize tumor cell membranes enhancing intracellular MTO delivery.
Subject(s)
Antineoplastic Agents/administration & dosage , Galactosylceramides/chemistry , Glucosylceramides/chemistry , Mitoxantrone/administration & dosage , Nanoparticles/chemistry , Antineoplastic Agents/pharmacokinetics , Antineoplastic Agents/pharmacology , Cell Survival/drug effects , Drug Stability , Drug Storage , Humans , Liposomes , MCF-7 Cells , Mitoxantrone/pharmacokinetics , Mitoxantrone/pharmacologyABSTRACT
PURPOSE: To improve nanoliposomal-doxorubicin (DoxNL) delivery in tumor cells using liposome membrane-incorporated short-chain sphingolipids (SCS) with selective membrane-permeabilizing properties. DoxNL bilayers contained synthetic short-chain derivatives of known membrane microdomain-forming sphingolipids; C8-glucosylceramide (C8-GluCer), C8-galactosylceramide (C8-GalCer) or C8-lactosylceramide (C8-LacCer). METHODS: DoxNL enriched with C8-GluCer or C8-GalCer were developed, optimized and characterized with regard to size, stability and drug retention. In vitro cytotoxic activity was studied in a panel of human tumor cell lines and normal cells. Intracellular Dox delivery was measured by flow cytometry and visualized by fluorescence microscopy. For a further understanding of the involved drug delivery mechanism confocal microscopy studies addressed the cellular fate of the nanoliposomes, the SCS and Dox in living cells. RESULTS: C8-LacCer-DoxNL aggregated upon Dox loading. In tumor cell lines SCS-DoxNL with C8-GluCer or C8-GalCer demonstrated strongly increased Dox delivery and cytotoxicity compared to standard DoxNL. Surprisingly, this effect was much less pronounced in normal cells. Nanoliposomes were not internalized, SCS however transfered from the nanoliposomal bilayer to the cell membrane and preceded cellular uptake and subsequent nuclear localization of Dox. CONCLUSION: C8-GluCer or C8-GalCer incorporated in DoxNL selectively improved intracellular drug delivery upon transfer to tumor cell membranes by local enhancement of cell membrane permeability.
