FABP4 controls the transfer of lipids from adipocytes to AML. (A) AML blasts were cultured alone or with adipocytes or BMSC for 48 hours and then the adipocytes and BMSC were assessed for FABP4 mRNA expression using RT-PCR (n = 6). Nonmalignant CD34⁺ cells were cocultured alone or with adipocytes, and FABP4 mRNA expression was measured. Data are represented as mean ± standard deviation. (B) Immunoblot for FABP4 from adipocytes cultured with and without AML blasts. Blots were reprobed for β-actin to show equal sample loading. (C) Enzyme-linked immunosorbent assay to detect FABP4 in media from adipocytes cultured alone or with AML blasts. Data are represented as mean ± standard deviation. (D) AML blasts were cultured alone or with the addition of 2 μg/mL of recombinant FABP4 (his-tagged) for 4 hours. Immunoblots were performed for FABP4 and His. Blots were reprobed for β-actin to show equal sample loading. (E) Adipocytes were infected with FABP4-targeted shRNA or control shRNA lentivirus, and after 72 hours, analyzed for FABP4 protein expression using western blotting. Blots were reprobed for β-actin to show equal sample loading. (F) Adipocytes were infected with FABP4-targeted shRNA or control shRNA lentivirus and after 72 hours preloaded with fluorescent FA DAA and incubated with AML for 24 hours. AML blasts were analyzed for fluorescence using flow cytometry (n = 4). (G) Primary AML blasts or nonmalignant CD34⁺ cells were cultured alone or cocultured with adipocytes or BMSC with and without treatment with FABP4 inhibitor for 72 hours. AML blasts were counted using flow cytometry and Trypan blue exclusion (n = 4). Data are represented as mean ± standard deviation. (H) Adipocytes were infected with FABP4 targeted shRNA or control shRNA lentivirus, and after 72 hours, were incubated with AML for 72 hours. AML blasts and nonmalignant CD34⁺ cells were counted using flow cytometry and Trypan blue exclusion (n = 4). Data are represented as mean ± standard deviation. *P < .05. Ctr, control; FAB, fatty acid binding.