Background: There is increasing evidence that adipocytes play an active role in the cancer microenvironment. We have previously reported that adipocytes interact with acute lymphoblastic leukemia (ALL) cells, contributing to chemotherapy resistance and treatment failure. In the present study, we investigated whether part of this resistance is due to adipocyte provision of lipids to ALL cells. Methods: We cultured 3T3-L1 adipocytes, and tested whether ALL cells or ALL-released cytokines induced FFA release. We investigated whether ALL cells took up these FFA, and using fluorescent tagged BODIPY-FFA and lipidomics, evaluated which lipid moieties were being transferred from adipocytes to ALL. We evaluated the effects of adipocyte-derived lipids on ALL cell metabolism using a Seahorse XF analyzer and expression of enzymes important for lipid metabolism, and tested whether these lipids could protect ALL cells from chemotherapy. Finally, we evaluated a panel of lipid synthesis and metabolism inhibitors to determine which were affected by the presence of adipocytes. Results: Adipocytes release free fatty acids (FFA) when in the presence of ALL cells. These FFA are taken up by the ALL cells and incorporated into triglycerides and phospholipids. Some of these lipids are stored in lipid droplets, which can be utilized in states of fuel deprivation. Adipocytes preferentially release monounsaturated FFA, and this can be attenuated by inhibiting the desaturating enzyme steroyl-CoA decarboxylase-1 (SCD1). Adipocyte-derived FFA can relieve ALL cell endogenous lipogenesis and reverse the cytotoxicity of pharmacological acetyl-CoA carboxylase (ACC) inhibition. Further, adipocytes alter ALL cell metabolism, shifting them from glucose to FFA oxidation. Interestingly, the unsaturated fatty acid, oleic acid, protects ALL cells from modest concentrations of chemotherapy, such as those that might be present in the ALL microenvironment. In addition, targeting lipid synthesis and metabolism can potentially reverse adipocyte protection of ALL cells. Conclusion: These findings uncover a previously unidentified interaction between ALL cells and adipocytes, leading to transfer of FFA for use as a metabolic fuel and macromolecule building block. This interaction may contribute to ALL resistance to chemotherapy, and could potentially be targeted to improve ALL treatment outcome.
Bibliographical noteFunding Information:
This work was supported by the National Cancer Institute at the National Institutes of Health (R01 CA201444), The Saban Research Institute, The Children’s Leukemia Research Association, Inc, a Translational Research Program Award from the Leukemia & Lymphoma Society, and a generous gift from the Estate of Helen Dyess. ASD is supported by the National Institutes of Health (R35 GM138003). AJ is supported by the UCLA Tumor Cell Biology Training Program (T32CA009056). None of these funding bodies played a role in the study design, the collection, analysis, or interpretation of data, or the writing of the manuscript.
The authors thank Wesley Dixon for assistance with experimentation, Erik Thomas Jansson for assistance with mass spectrometry experiments and helpful discussions, and the Translational Pathology Core Laboratory in Ronald Reagan UCLA Medical Center for providing anonymized human adipose tissue.
© Copyright © 2021 Tucci, Chen, Margulis, Orgel, Paszkiewicz, Cohen, Oberley, Wahhab, Jones, Divakaruni, Hsu, Noll, Sheng, Zare and Mittelman.
- lipid droplets