Abstract 5: Using stable isotope lipidomics to identify adipocyte-induced alterations in the acute lymphoblastic leukemia lipidome
Authors: Tucci Jonathan , Margulis Katy , Hsu Cheng-Chih , Dixon Wesley , Zare Richard N. , Mittelman Steven D. 
Published: July 2016

Abstract
Obesity is associated with the development and progression of many cancers, including acute lymphoblastic leukemia (ALL). We have shown that ALL cells induce adipocyte lipolysis and take up adipocyte-derived free-fatty acids (FFAs). Here, we use targeted lipidomics with carbon-13 labeling to 1) determine which adipocyte-derived FFAs are taken up by ALL cells, and 2) identify the specific alterations in the ALL cell lipidomic profile caused by co-culture with adipocytes.
Mouse pre-adipocytes (3T3-L1) were differentiated into adipocytes in the presence of U13C-glucose to allow 13C incorporation into adipocyte lipids. ALL cells were then cultured alone or co-cultured over 13C-labeled or non-labeled adipocytes for 72 hours. Following co-culture, ALL cells were harvested and analyzed by nanospray desorption electrospray ionization mass spectrometry (nanoDESI-MS). Lipidomic spectra were analyzed to characterize uptake of adipocyte-derived FFAs identifying 13C-enrichment in ALL lipid moieties. The relative intensities of selected lipid peaks were compared between conditions, after normalization, to evaluate the effects of the presence of adipocytes on ALL lipidome.
Adipocytes differentiated in the presence of U13C-glucose incorporated 13C into numerous triglyceride moieties. In ALL cells co-cultured with labeled adipocytes, 13C enrichment was identified in FFA and phospholipids. Labeling of oleic acid primarily occurred in groups of two, suggesting incorporation of U13C-glucose into adipocyte FFAs through acetyl-CoA-mediated lipogenesis. Similarly, 13C enrichment of ALL cell phospholipids occurred in groups of two and three, mirroring adipocyte incorporation of U13C-glucose into phospholipids through both acetyl-CoA and glycerol. Moreover, ALL cell unsaturated FFAs had a greater 13C enrichment than saturated FFAs (Unsaturated FFAs: 14.1±5.5 vs. Saturated FFAs: 6.6±2.3, p = 0.02; n = 5). When co-cultured over adipocytes, ALL cells contained significantly more FFAs than ALL cells alone (Oleic Acid: 63.0±49.2 vs. 24.1±7.4, p = 0.02; Stearic acid: 20.9±17.5 vs. 8.3±2.2, p = 0.03; Palmitoleic Acid: 11.5±9.8 vs. 3.3±1.0, p = 0.01; Palmitic Acid: 15.1±11.7 vs. 5.5±1.4, p = 0.01; n = 5).
Using stable-isotope lipidomics, we can effectively identify and quantify which ALL cell lipids are derived from nearby adipocytes. This methodology provides comprehensive insight into the cancer cell lipidome and can be extended to understand how genetics, the microenvironment, and treatment affect cancer lipid metabolism.
Citation Format: Jonathan Tucci, Katy Margulis, Cheng-Chih Hsu, Wesley Dixon, Richard N. Zare, Steven D. Mittelman. Using stable isotope lipidomics to identify adipocyte-induced alterations in the acute lymphoblastic leukemia lipidome. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5.