A Novel Combined Approach of Short-Chain Sphingolipids and Thermosensitive Liposomes for Improved Drug Delivery to Tumor Cells.

Despite the advantages of liposomal drug delivery, the bioavailability of the chemotherapeutic drugs to tumor cells is limited by their slow release from nanocarriers and low drug permeability across cell membranes. Drug encapsulation into stealth thermosensitive liposomes can improve drug delivery to tumors by combining efficient accumulation at tumors and the active release of the payload following remote heat triggering. Short-chain sphingolipids are known to enhance cellular uptake of amphiphilic drugs. We hypothesized that short-chain sphingolipids could be utilized to further improve intracellular drug delivery from a thermoresponsive formulation by enhancing the cell membrane passage of released drug. The following two strategies were investigated: (1) co-delivery of C8-glucosylceramide and doxorubicin within the thermosensitive liposomes and (2) pretreatment with glucosylceramide-enriched drug-free liposomes and subsequent treatment with doxorubicin loaded thermosensitive liposomes. Liposomes were prepared and extensively characterized. Drug uptake, cell cytotoxicity and live cell imaging were performed under normothermic and hyperthermic conditions in melanoma cells. In these studies, hyperthermia improved drug delivery from doxorubicin loaded thermosensitive formulations. However, the results from cell experiments indicated that there was no additional benefit in the co-delivery strategy using doxorubicin loaded glucosylceramide-enriched thermosensitive liposomes. In contrast, cellular studies showed significantly higher doxorubicin internalization in the pretreatment strategy. One-hour exposure of the cells to C8-glucosylceramide before applying hyperthermia caused improved doxorubicin uptake and cytotoxicity as well as an almost instantaneous cellular entry of the doxorubicin released from thermosensitive liposomes. This novel, two-step drug delivery approach can be potentially beneficial for the intracellular delivery of cell impermeable chemotherapeutics.

Defined lipid analogues induce transient channels to facilitate drug-membrane traversal and circumvent cancer therapy resistance.

Design and efficacy of bioactive drugs is restricted by their (in)ability to traverse cellular membranes. Therapy resistance, a major cause of ineffective cancer treatment, is frequently due to suboptimal intracellular accumulation of the drug. We report a molecular mechanism that promotes trans-membrane movement of a stereotypical, widely used anti-cancer agent to counteract resistance. Well-defined lipid analogues adapt to the amphiphilic drug doxorubicin, when co-inserted into the cell membrane, and assemble a transient channel that rapidly facilitates the translocation of the drug onto the intracellular membrane leaflet. Molecular dynamic simulations unveiled the structure and dynamics of membrane channel assembly. We demonstrate that this principle successfully addresses multi-drug resistance of genetically engineered mouse breast cancer models. Our results illuminate the role of the plasma membrane in restricting the efficacy of established therapies and drug resistance - and provide a mechanism to overcome ineffectiveness of existing and candidate drugs.