Acquired resistance in AML cell lines to the bifunctional electrophile busulfan is associated with changes in mitochondrial copy numbers and lipid and cholesterol metabolism

Purpose: Alterations in mitochondrial copy number (mtDNA-CNs) may affect the sensitivity of cells to reactive oxygen species (ROS)-generating compounds, such as busulfan (BU). In this work, we investigated whether the resistance of AML cell lines to ROS-generating compounds, Busulfan (BU), or and the DNA synthesis inhibitor cytarabine (ara-C) was associated with an increase of mtDNA-CNs. Methods: Myeloid cells (MOLM13) were exposed to five consecutive BU treatments to acquire BU resistance (5TBU). The 5TBU and control cell lines, treated with DMSO, were further exposed to five consecutive ara-C treatments to obtain cells resistant to both BU and ara-C. We estimated the 50% inhibitory concentration (IC50) of BU and ara-C in these cells and quantified mtDNA-CNs by RT-qPCR of MTND1. We also performed gene expression profiling to assess how resistance to BU and treatement with DMSO affect the transcriptional activity of cells. Results: mtDNA-CNs were associated with cellular sensitivity to BU, but not to ara-C. Cholesterol and fatty acid synthesis pathways appear to be important in cellular adaptation to BU.