Bone Marrow Adipocytes Drive Transcriptional Changes In Leukemic Blasts To Enhance Their Capacity To Derive Energy From Free Fatty Acid Metabolism

Introduction: Most patients diagnosed with acute myeloid leukaemia [AML] die of their disease and the average age of patients at diagnosis is 72 years. For this reason, new therapeutic strategies with tolerability in the fragile, less fit population is necessary for reducing the mortality rate associated with this disease. The tumor microenvironment is an emerging target in the search for less cytotoxic therapies. We have previously shown that the adipocyte component of the bone marrow (BM) is a key player in blast survival, proliferation and chemotherapy evasion. In this study, we draw focus onto the status of an adipocyte rich environment in the context of leukemia and highlight the key players in regulating leukemic cell metabolism through transport and metabolism of fatty acids. Objective: We hypothesize that the presence of adipocytes within the proximity of AML blasts creates a FA rich environment for increased β - oxidation within the blasts. Methods: We used primary AML blasts and normal CD34+ hematopoietic stem cells (HSC) following informed consent (LRCEref07/H0310/146). Adipocytes were derived from bone marrow stromal cells (BMSC). Differential expression analysis of RNA sequencing data (GEO ID: GSE49642, GSE48846) was used to compare respiratory gene signatures of BM AML blasts, peripheral blood obtained AML and normal CD34+ HSC. Fatty acid binding protein 4 (FABP4) and carnitine palmitoyltransferase 1A (CPT1A) were identified as one of the key genes involved in the lipolysis and oxidation signature differential expression. Oxygen consumption rate (OCR) of adipocyte co-cultured blasts and normal CD34+ were analyzed using Seahorse technology. Lentiviral-knockdown of FABP4 and CPT1A were performed on blasts prior to in vivo xenograft mouse model injection. Results: Leukemic blasts showed increased adipocyte lipolysis stimulation compared with normal CD34+ cells. Moreover, adipocytes increased transcriptional activation of FABP4 and CPT1A in malignant blasts compared to CD34+ HSC. FABP4 inhibitor reduced AML blast survival when cells were cultured with adipocytes which is in contrast to normal CD34+ HSC. Moreover, AML had increased oxygen consumption rate when grown on adipocytes which was inhibited by etomoxir (β - oxidation inhibitor). Finally in-vivo lentiviral mediated knockdown of FABP4 and CPT1A reveled an increased survival of AML xenografts. Conclusion: Our results show that the stimulation of lipolysis and fatty acid oxidative genes that contribute to the genetic signatures of these processes are a malignant blast exclusive profile. Interventions at a molecular level reveal survival favorable outcomes in xenograft models suggesting the need for enhancing strategies which include targeting the FABP4 and CPT1A axis. Our data provide a biologic rationale for exploring future therapies that target the adipocyte/AML interactions. Citation Format: Manar Shafat, Thomas Oellerich, Sebastian Mohr, Stephen Robinson, Dylan Edwards, Rachel Piddock, Amina Abdul-Aziz, Christopher Marlein, Matthew Fenech, Jeremy Turner, Matthew Lawes, Lyubov Zaitseva, Johnathan Watkins, Kristian Bowles, Stuart Rushworth. Bone marrow adipocytes drive transcriptional changes in leukemic blasts to enhance their capacity to derive energy from free fatty acid metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4327. doi:10.1158/1538-7445.AM2017-4327