SLC25A1 Reprograms Mitochondrial and Fatty Acid Metabolism to Promote the Progression of Acute Myeloid Leukemia

Metabolic reprogramming is a hallmark of tumors, contributing to tumor initiation, progression and drug resistance. In acute myeloid leukemia, cells usually depend on both enhanced glycolysis and oxidative phosphorylation for their energy needs. The persistence of therapy resistance in some AML patients underscores the urgency of identifying novel metabolic targets. Here, we revealed the vital role of citrate transporter SLC25A1 in maintaining AML cell survival and regulating its drug sensitivity, establishing it as a promising metabolic target for AML therapy.

We first showed that the SLC25A1 expressions were elevated in AML patients both on mRNA and protein level, which were associated with poorer outcomes. Genetic and pharmacological inhibition of SLC25A1 significantly suppressed the proliferation and clonogenicity, promoted apoptosis of leukemic cell lines, as well as the primary AML cells from patients. The specific inhibitor of SLC25A1 had no effect on the proliferation of mononuclear cells (MNCs) from healthy bone marrow at the same concentrations. Our data indicated that SLC25A1 was a potential target for AML therapy, which was further confirmed in AML mice carrying with AE9a or MLL-AF9.

Functionally, inhibition of SLC25A1 revealed the mitochondrial damage and ROS increasing in AML cells by transmission electron microscopy (TEM), mitochondrial membrane potential and extracellular flux analysis, as well as flow cytometry and fluorescence microscopy. The restoration of cell viability by ROS scavenger N-acetyl-L-cysteine (NAC) in the context of SLC25A1 inhibition suggested that SLC25A1 deficiency inhibited cell survival through the upregulation of ROS. Given this, we found that targeting SLC25A1 could enhance the sensitivities of AML cells to two clinically available anti-leukemic drugs, BCL-2 inhibitor venetoclax and chemotherapy drug daunorubicin (DNR).

Mechanically, we found that SLC25A1 was closely correlated with ROS metabolic process, extrinsic apoptotic signaling pathway and oxidative phosphorylation, as well as nicotinate metabolism and fatty acid metabolism, analyzed by gene expression data and metabolic data. We next verified that a series of key enzymes involved in fatty acid metabolism were down-regulated following SLC25A1 KD, accompanied by metabolites in fatty acid synthesized pathway. We also revealed that a self-protection mechanism after stress by up-regulating phosphoglycerides (PGs) and triglycerides (TAGs) in SLC25A1 KD cells, and the effect could be reversed by inhibiting DGAT1, a key enzyme catalyzing the conversion of fatty acids to TAGs.

In conclusion, targeting mitochondrial metabolism and fatty acid metabolism using the SLC25A1 inhibitor might be a potential novel strategy for enhancing AML therapy and overcoming drug resistance.