Abstract 4339: Acute lymphoblastic leukemia cells stimulate adipocyte lipolysis and utilize adipocyte-derived free-fatty acids for proliferation
Authors: Tucci Jonathan , Sheng Xia , Mittelman Steven D. 
Published: May 2015

Abstract
Obesity promotes the pathogenesis of many cancers, including acute lymphoblastic leukemia (ALL), the most common childhood malignancy. We have shown that ALL cells interact with adipocytes in vivo and in vitro, and that adipocytes protect ALL cells from chemotherapies. Since cancer cells require free fatty acids (FFA) for energy and as molecular building blocks, we hypothesize that ALL cells gain a survival advantage by stimulating adipocyte lipolysis and using adipocyte-derived FFAs.
To test whether ALL cells stimulate adipocyte lipolysis, 3T3-L1 adipocytes were exposed to ALL-conditioned media for 72 hours, and glycerol release and adipocyte lipid content were measured. To determine whether ALL cells take up adipocyte-derived FFA, adipocytes were pre-labeled with fluorescent FFA (BODIPY), and then co-cultured with murine (8093) and human (BV173, RS4;11, Molt4, Nalm6, SEM, SupB15) ALL cells in a Transwell system. ALL uptake of BODIPY-FFAs was analyzed via flow cytometry. To determine the fate of FFA in ALL cells, ALL cells were incubated with BODIPY-FFA and evaluated by confocal and live cell microscopy, and lipid classes resolved through thin layer chromatography (TLC). Real-time PCR was employed to analyze adipocyte-induced alterations in the transcription of key enzymes in the ALL de novo lipogenesis pathway. Finally, TOFA, an acetyl-CoA carboxylase 1 (ACC1) and steroyl-CoA desaturase 1 (SCD1) inhibitor, was used to block de novo lipogenesis in ALL cells in vitro, and evaluate the ability of ALL cells to use adipocyte-derived FFAs for proliferation.
ALL-conditioned media stimulated 3T3-L1 lipolysis (191.0 vs. 165.5 mg/L glycerol, n=1), reducing adipocyte lipid content as quantified with Oil Red O by 16.8 ± 7.1% (p = 0.047). When murine or human ALL cells were co-cultured with BODIPY-labeled adipocytes, they accumulated the fluorescent label within 48 hours (97-98% of cells labeled positive). TLC, live cell imaging and confocal microscopy demonstrated the majority of this label accumulated within ALL cell phospholipid membranes and triglyceride-laden lipid droplets. Adipocyte co-culture reduced expression of lipogenic enzymes such as fatty acid synthase (FAS), ACC1 and SCD1 in ALL cells. Finally, while TOFA inhibited ALL cell proliferation (6.1 ± 1.1x104 vs. 41.9 ± 4.7x104 cells, p=0.004, n=3), this proliferation was partially rescued by adipocyte conditioned media (ACM, 29.8 ± 9.2 x104, p=0.045 vs. TOFA alone, n=3).
Therefore, we have demonstrated that ALL cells stimulate adipocyte lipolysis and use adipocyte-derived FFAs to supplement de novo lipogenesis and proliferation. This may contribute to the effect of obesity on ALL development and relapse.
Citation Format: Jonathan Tucci, Xia Sheng, Steven D. Mittelman. Acute lymphoblastic leukemia cells stimulate adipocyte lipolysis and utilize adipocyte-derived free-fatty acids for proliferation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4339. doi:10.1158/1538-7445.AM2014-4339