To investigate the expression of endocannabinoid (EC), arachidonoyl ethanolamide (AEA) and 2-arachidonoylglycerol (2-AG) in biliary tract cancer (BTC) patients’ samples.

Lipids of patients’ plasma and bile (22 BTC patients and 8 benign biliary disease patients) and of paired BTC nest and adjacent normal tissue (15 of the above 22 BTC patients) were extracted by the Bligh and Dyer method (chloroform containing internal standards and methanol were added to above samples) and solid-phase extraction. Derivatisation of the hydroxyl groups of ECs was performed with the silylating agent dimethylisopropylsilyl imidazole. Lipid samples were quantitated by gas chromatography/electron ionization (EI)-mass spectrometry.

Level of 2-AG was upregulated in BTC patients’ plasma [180.01 (140.72-283.84) nmol/L vs 42.33 (25.61-148.93) nmol/L, P<0.05], while level of AEA appeared decreasing trend without significant difference. Level of AEA was lower in BTC patients’ bile [1.80 (0.50-5.00) nmol/Lvs 10.15 (2.68-17.49) nmol/L, P<0.05], while level of 2-AG appeared increasing trend without significant difference. Level of AEA was lower [22.01 (16.55-53.61) pmol/g vs 58.68 (25.36-68.97) pmol/g, P<0.05], while level of 2-AG was upregulated [1.97 (1.44-5.43) nmol/g vs 1.10 (0.36-1.47) nmol/g, P<0.05] in BTC cancer nest than in adjacent normal tissues.

The present study develops a sufficient and reliable method for quantitative determination of AEA and 2-AG in BTC. The dysregulated AEA and 2-AG in body fluids and tumor tissues of patients with BTC can be used as assistant diagnosis of BTC.