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Is metabolism an important arbiter of anticancer activity of ether lipids? metabolism of SRI 62-834 and hexadecylphosphocholine by [31P]-NMR spectroscopy and comparison of their cytotoxicities with those of their metabolites


Antineoplastic ether lipids have entered phase I clinical trial and, although their mechanism of action remains unclear, it is widely believed that the plasma membrane is the primary cellular drug target. In the present study the hypothesis was tested that metabolism of ether lipids acts as a detoxification process. [31P]-nuclear magnetic resonance (NMR) spectroscopy was used to study the metabolism of the ether lipid SRI 62-834 (SRI) and the phosphate ester hexadecylphosphocholine (HPC) in the presence of both isolated phospholipases C and D and post-mitochondrial rat liver homogenate. Both SRI and HPC were slowly metabolised by phospholipase D to their alkyl phosphates and choline, and the alkyl phosphates were subsequently metabolised by phosphatase to yield the alcohols and inorganic phosphate. These studies failed to detect any metabolism of either SRI or HPC by phospholipase C, and the metabolism of platelet-activating factor (PAF) by this enzyme was not inhibited by the addition of either compound. The cytotoxicity of SRI, the related compound HPC and their metabolites was determined in vitro using three cell lines. Cytotoxicity was measured by analysis of cell growth kinetics, MTT assay and lactate dehydrogenase release. Closely similar results were obtained in the JB1 rat hepatoma cell line, in the non-transformed BL8 rat hepatocyte cell line, and in A549 human lung adenocarcinoma cells. SRI was the most toxic of the compounds analysed, the concentration required to produce 50% toxicity or growth inhibition (IC50) being 6–9 μm. The putative metabolite of SRI, 2,2′-bis(hydroxymethyl)tetrahydrofuran, and the known metabolites [2′-(octadecyloxymethyl)tetrahydrofuran-2′-yl]methyl phosphate and 2-hydroxymethyl-2-octadecyloxymethyltetrahydrofuran exhibited IC50 values of >200, >100 and 40–70 μm, respectively, consistent with metabolic detoxification. HPC was more cytotoxic (IC50, 37 μm) than its phosphate metabolite (IC50, 140 μm), but its toxicity was similar to that of its metabolite hexadecanol (IC50, 28 μm), suggesting that only the former metabolic route leads to detoxification.

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ET18O CH3 :





lactate dehydrogenase




3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide


nuclear magnetic resonance


platelet-activating factor, 2-acetyl-l-octadecyl-glycero-3-phosphocholine


phosphate-buffered saline

SRI 62-834:

SRI, [2′-(octadecyloxymethyl)tetrahydrofuran-2′-yl]methyl 2-[N,N,N-trimethylammonio]ethylphosphate


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Correspondence to Andreas Gescher.

Additional information

This work was supported by CRC programme grant SP1518 and by an MRC postgraduate fellowship (awarded to F. E. B.). One of the authors (S. E.) is a Lister Institute Fellow and another (C. D.) was supported by the Wolfson Trust

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Bishop, F.E., Dive, C., Freeman, S. et al. Is metabolism an important arbiter of anticancer activity of ether lipids? metabolism of SRI 62-834 and hexadecylphosphocholine by [31P]-NMR spectroscopy and comparison of their cytotoxicities with those of their metabolites. Cancer Chemother. Pharmacol. 31, 85–92 (1992). https://doi.org/10.1007/BF00685092

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  • Lung Adenocarcinoma
  • Ether Lipid
  • Hexadecanol
  • Human Lung Adenocarcinoma Cell
  • A549 Human Lung