Anticancer Agent Edelfosine Exhibits a High Affinity for Cholesterol and Disorganizes Liquid-Ordered Membrane Structures

Abstract

Edelfosine is an anticancer drug with an asymmetric structure because, being a derivative of glycerol, it possesses two hydrophobic substituents of very different lengths. We showed that edelfosine destabilizes liquid-ordered membranes formed by either 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine, sphingomyelin (SM), and cholesterol (1:1:1 molar ratio) or SM and cholesterol (2:1 molar ratio). This was observed by differential scanning calorimetry in which phase transition arises from either of these membrane systems after the addition of edelfosine. The alteration in the liquid-ordered domains was characterized by using a small-angle X-ray diffraction that revealed the formation of gel phases as a consequence of the addition of edelfosine at low temperatures and by a wide-angle X-ray diffraction that confirmed changes in the membranes, indicating the formation of these gel phases. The increase in phase transition derived by the edelfosine addition was further confirmed by Fourier-transform infrared spectroscopy. The effect of edelfosine was compared with that of structurally analogue lipids: platelet-activating factor and 1-palmitoyl-2-acetyl- sn-glycero-3-phosphocholine, which also have the capacity of destabilizing liquid-ordered domains, although they are less potent than edelfosine for this activity, and lysophosphatidylcholine, which lacks this capacity. It was concluded that edelfosine may be associated with cholesterol favorably competing with sphingomyelin, and that this sets sphingomyelin free to undergo a phase transition. Finally, the experimental observations can be described by molecular dynamics calculations in terms of intermolecular interaction energies in phospholipid-cholesterol membranes. Higher interaction energies between asymmetric phospholipids and cholesterol than between sphingomyelin and cholesterol were obtained. These results are interesting because they biophysically characterize one of the main molecular mechanisms to trigger apoptosis of the cancer cells.

Plasma Membrane Lipid Domains as Platforms for Vesicle Biogenesis and Shedding?

“…As lipid domain modification seems to actively participate to the phenotype of cancerous cells, they could represent interesting targets for anti-cancer treatments. Actually, edelfosine, a synthetic alkyl-lysoPLP with anti-tumor activity, has been shown to destabilize synthetic membranes composed of POPC (palmitoyloleoylphosphatidylcholine)/SM/chol or SM/chol [ 283 ]. It preferentially localizes in rafts in lymphoma cells, where it inhibits the PI3K/Akt proliferation signaling pathway and promotes the recruitment of the death receptor Fas [ 283 , 284 ].…”

Lipid rafts as signaling hubs in cancer cell survival/death and invasion: implications in tumor progression and therapy

“…This suggests that edelfosine put in motion a series of processes that otherwise would remain dormant in the cancer cell, thus offering a new way to promote cell death in tumor cells. Edelfosine accumulated in rafts (96,199,208,211), showed a high affinity for cholesterol (212,213), enhanced membrane thickness (212,213), and induced an increase in membrane fluidity (214,215). Endogenous FasL/CD95L has also been localized in rafts in human natural killer NK92 cell line (which expresses relatively high endogenous amounts of the protein) and in human T cells after activation (217).…”

“…It is interesting to note that the antitumor alkylphospholipid analog edelfosine, which shows a high affinity for cholesterol (212,213,230) and accumulates in lipid rafts (96,154,199,231,232), displays a rather differential mechanism of action to induce apoptosis in hematological and solid tumor cells (98,233). Edelfosine accumulated at the cell surface lipid rafts in different human leukemic cells, leading to raft reorganization, co-clustering of Fas/CD95 and rafts, and apoptosis (96,154,199,200,208).…”

Effect of Erufosine on Membrane Lipid Order in Breast Cancer Cell Models

“…The Lo phase is enriched in saturated lipids and cholesterol and, therefore, provides a simple physical model to study raftlike domains (9,10). In this context, it was shown that APLs partition into lipid bilayers and directly interact with Lo domains (11). The observed effects vary depending on lipid composition and the investigated APL (e.g.…”

“…The observed effects vary depending on lipid composition and the investigated APL (e.g. Edelfosine or Miltefosine) and include: disorganization of Lo domains (11), moderate to significant increase of membrane fluidity (12,13) and stabilization of SM/cholesterol domains (14). More specifically, studies on Erucylphosphocholine (which is more similar to EPC3, due to the shared unsaturated acyl chain) indicate that this APL increases the fluidity of both cellular and model membranes (12), while weakening SM-cholesterol interactions (15).…”