Abstract 2750: Short-chain lipids catalyse intracellular drug accumulation by a transient molecular gateway that allows plasma membrane traversal

Abstract

Abstract BACKGROUND: The lipid composition of the plasma membrane provides an effective barrier towards exogenous, potentially cytotoxic molecules. As a consequence, membrane traversal of most therapeutic drugs is sub-optimal and remains a major limitation for clinical efficacy. We previously identified a class of short-chain sphingolipids that facilitate the accumulation of amphiphilic compounds, including the cytostatic drug doxorubicin, within tumor cells, leading to improved therapy response. AIM: In order to elucidate the mechanism of action of short-chain lipids, both in vitro and model membrane studies and in silico molecular dynamics simulation experiments were designed. RESULTS: We demonstrate that short-chain sphingolipids act at the level of the plasma membrane, however, independently of lipid microdomain (raft) formation or membrane proteins. In artificial lipid membranes of well-defined compositions short-chain sphingolipids enhanced doxorubicin-membrane traversal similar to cell membranes; N-octanoyl-glucosylceramide decreased the translocation half-time of doxorubicin over liquid ordered lipid membranes by a factor 1.93 (p < 0.05). In case of liquid disordered membranes, a comparable effect was observed (factor 1.91; p < 0.05); lipid phase separation (raft formation) did not affect enhanced doxorubicin translocation. Molecular dynamics simulations revealed that the short-chain lipids act by assembling a transient molecular gateway for doxorubicin. Accordingly, the free energy barrier for the hydrophilic head group of the drug to dehydrate and translocate to the opposite side of the membrane is reduced by two-fold (p < 0.05). CONCLUSION: Short-chain lipids catalyse the transbilayer movement of amphiphilic cytostatic drugs to achieve higher intratumoral drug accumulation, and their action is explained by the formation of a transient lipid gateway in the plasma membrane of the tumor cell, thus facilitating drug translocation and subsequent intracellular accumulation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2750. doi:1538-7445.AM2012-2750