Involvement of lipid rafts in the localization and dysfunction effect of the antitumor ether phospholipid edelfosine in mitochondria

Abstract

Lipid rafts and mitochondria are promising targets in cancer therapy. The synthetic antitumor alkyl-lysophospholipid analog edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine) has been reported to target lipid rafts. Here, we have found that edelfosine induced loss of mitochondrial membrane potential and apoptosis in human cervical carcinoma HeLa cells, both responses being abrogated by Bcl-xL overexpression. We synthesized a number of new fluorescent edelfosine analogs, which preserved the proapoptotic activity of the parent drug, and colocalized with mitochondria in HeLa cells. Edelfosine induced swelling in isolated mitochondria, indicating an increase in mitochondrial membrane permeability. This mitochondrial swelling was independent of reactive oxygen species generation. A structurally related inactive analog was unable to promote mitochondrial swelling, highlighting the importance of edelfosine molecular structure in its effect on mitochondria. Raft disruption inhibited mitochondrial localization of the drug in cells and edelfosine-induced swelling in isolated mitochondria. Edelfosine promoted a redistribution of lipid rafts from the plasma membrane to mitochondria, suggesting a raft-mediated link between plasma membrane and mitochondria. Our data suggest that direct interaction of edelfosine with mitochondria eventually leads to mitochondrial dysfunction and apoptosis. These observations unveil a new framework in cancer chemotherapy that involves a link between lipid rafts and mitochondria in the mechanism of action of an antitumor drug, thus opening new avenues for cancer treatment.

Antitumor alkyl-lysophospholipid analog edelfosine induces apoptosis in pancreatic cancer by targeting endoplasmic reticulum

“…First, we found that all pancreatic cancer cell lines used in this study incorporated high amounts of drug ( Figure 1c). Next, we found that the new fluorescent edelfosine analog 1-O-[11 0 -(6 00 -ethyl-1 00 ,3 00 ,5 00 ,7 00 -tetramethyl-4 00 ,4 00 -difluoro-4 00 -bora-3a 00 ,4a 00 -diaza-s-indacen-2 00 -yl)undecyl]-2-O-methylrac-glycero-3-phosphocholine (Mollinedo et al, 2011) accumulated in the ER of HuP-T4 and Capan-2 cells (Figure 2a), as assessed using a version of red fluorescence protein targeted to the ER lumen (ER-targeted red fluorescence protein), which completely co-localized with the ER marker calreticulin (Klee and PimentelMuinos, 2005). Incorporation of fluorescent 1-O-[11 0 -(6 00 -ethyl-1 00 ,3 00 ,5 00 ,7 00 -tetramethyl-4 00 ,4 00 -difluoro-4 00 -bora-3a 00 , 4a 00 -diaza-s-indacen-2 00 -yl)undecyl]-2-O-methyl-rac-glycero-3-phosphocholine into the cells was blocked by adding the parent drug edelfosine (data not shown), thus behaving as a reliable edelfosine fluorescent analog to visualize the subcellular location of the drug 'in situ'.…”

“…The subcellular localization of edelfosine in pancreatic cancer cells was examined with the newly synthesized edelfosine fluorescent analog 1-O-[11 0 -(6 00 -ethyl-1 00 ,3 00 ,5 00 ,7 00 -tetramethyl-4 00 ,4 00 -difluoro-4 00 -bora-3a 00 ,4a 00 -diaza-s-indacen-2 00 -yl)undecyl]-2-O-methyl-rac-glycero-3-phosphocholine (Mollinedo et al, 2011), a kind gift from F. Amat-Guerri and A. U. Acun˜a (Consejo Superior de Investigaciones Cientı´ficas, Madrid, Spain). ER was visualized by transfecting cells with 4 mg of a plasmid encoding ER-targeted red fluorescence protein (Klee and Pimentel-Muinos, 2005), kindly provided by FX Pimentel-Muinos (Instituto de Biologı´a Molecular y Celular del Ca´ncer, Centro de Investigacio´n del Ca´ncer, Salamanca, Spain).…”

Alteration of Plasma Membrane Organization by an Anticancer Lysophosphatidylcholine Analogue Induces Intracellular Acidification and Internalization of Plasma Membrane Transporters in Yeast

“…The plasma membrane (PM) 4 of eukaryotes represents one of the most complex biomembranes, featuring an asymmetric lipid distribution between the two leaflets of the bilayer as well as lateral domain organization within leaflets. Lipid rafts are dynamic areas of the membrane rich in sterols and sphingolipids that serve as platforms for the association of membrane proteins.…”

Edelfosine Induced Suicidal Death of Human Erythrocytes

“…Mechanisms involved in edelfosine-induced apoptosis include formation of plasma membrane lipid rafts recruiting death receptor and downstream apoptotic signaling molecules [14,16,19,20,24,25,27], endoplasmic reticulum (ER) stress response [13,17,20,29,30], mitochondrial depolarisation [20,25,35], cytochrome c release [13], caspase activation [3,13,16,23] and generation of reactive oxygen species [13,31,35].…”