Quantitative Mass Spectrometry

National Institute Of Environmental Health Sciences

Investigators

Linked publications & trials

Abstract

Quantitative Mass Spectrometry incorporates collaborative projects in which the Mass Spectrometry Group provides quantitative information about, typically, small molecules by GCMS, LCMS and LCMSMS or a combination. An example of the types of projects this includes is the isoprostane analyses undertaken as part of the NIEHS led study of biomarkers of oxidative stress. We currently have several major collaborations underway. [unreadable] 1) with the Zeldin Lab quantitating arachidonic acid metabolites that are relevant to inflammatory, vasodilatory, endothelial protective and post-ischemic cardioprotective effects. [unreadable] 2) a collaboration with James Mohler/Mark Titus on a Program Project (UNC/Roswell Cancer Institute) on Interference with the Androgen Receptor and its Ligands in Recurrent Prostate Cancer. As part of this study, we have: a) successfully developed an LC/MS/MS protocol for the analysis of T, DHT, dihydroepiandrosterone, androsterone, 5-androstenediol, and androstenedione at the low femtomolar level (0.15 to 9 fM except for the saturated diol) based on the use of atmospheric pressure photoionization (APPI). Enhanced sensitivity for non-conjugated ketosteroids, such as DHT, was achieved via the monitoring of an (M+14)+ ion arising from alkylation of the analyte by the methanolic solvent used in APPI. (Patent application pending; b)applied our APPI assay to the quantitation of these analytes in diverse CaP cell lines. In these experiments, either T in combination with inhibitor or 3-androstandediol, was added to the cell lines and DHT levels were measured after 48 hrs incubation.[unreadable] [unreadable] 3) with the Roberts Lab on the affect of a diet high in linoleic acid on cnacer metastasis.[unreadable] Several studies have shown that dietary changes can alter the progression and risk of numerous cancers, including pancreatic, intestinal, and breast cancer. A recent study from the Roberts Lab has reported that linoleic acid (LA), a dietary omega-6 polyunsaturated fatty acid (PUFA), enhances the invasion of peritoneal metastasis of gastric carcinoma cells and stimulates carcinogenesis. The current study expands further on this by studying the fatty acid profile of duodenum and serum in relation to dietary LA levels and the effect on cancer progression in mice receiving OCUM-2MD3 cells, a highly metastatic human gastric carcinoma cell line. The mice were divided into two groups, both of which were fed a high fat diet (23%ww). One group was fed a diet containing a normal proportion of LA (2%w LA) and the other fed a diet high in LA (12%w LA). Fatty acid content of samples was analyzed by gas chromatography/electron impact-mass spectrometry (GC/EIMS). Lipids were isolated, hydrolyzed, and free fatty acids were converted to methyl esters prior to analysis. Fatty acid profiling revealed an increase in LA concentrations in serum and duodenum of mice treated with 12% LA diet when compared to mice treated with 2% LA diet. Lauric (12:0), myristic (14:0), palmitic (16:0), and oleic (18:1n9), however, showed a decrease in concentrations in serum of mice fed the 12% LA diet compared to those fed 2% LA diet. The data show that circulating and tissue fatty acid profiles are affected by dietary intake of linoleic acid and that this dietary change also promotes cancer growth and invasion. The mechanism through which these effects manifest is currently being investigated.