BMSC donate their mitochondria to leukemic blasts. (A) Mitochondrial DNA copy number was assessed in primary nonmalignant CD34⁺ cells (n = 7) and primary AML blasts (n = 9; P = .0164). (B) Mitochondrial DNA copy number was assessed in primary AML blasts (n = 6) in monoculture vs coculture with BMSC for 72 hours and 1 week (P = .0022). (C) BMSC were transduced with a rLV.EF1. mCherry-Mito-9 Lentivirus. AML blasts were cultured on mCherry-Mito-9 positive BMSC and were analyzed by live cell imaging after a 1-week culture. Bright field, mCherry-Mito9, and merged channels are shown for BMSC only and 3 primary AML patient samples. (Scale bar = 10 µm.) (D) Live cell imaging was repeated with 5 primary AML patient samples; the percentage of mCherry positive AML blasts is presented. (E-F) Primary AML blasts (n = 11) or nonmalignant CD34⁺ cells (n = 7) were prestained with 200 nM MitoTracker Green FM for 24 hours on BMSC stained with MitoTracker Green FM. MitoTracker fluorescence was analyzed in the AML blasts and nonmalignant CD34⁺ cells by flow cytometry. A Wilcoxon matched pairs signed rank test was used to determine significance; P ≤ .001 for the AML blasts and P > .05 for the nonmalignant CD34⁺ cells.