Leveraging increased cytoplasmic nucleoside kinase activity to target mtDNA and oxidative phosphorylation in AML

Abstract

Mitochondrial DNA (mtDNA) biosynthesis requires replication factors and adequate nucleotide pools from the mitochondria and cytoplasm. We performed gene expression profiling analysis of 542 human acute myeloid leukemia (AML) samples and identified 55% with upregulated mtDNA biosynthesis pathway expression compared with normal hematopoietic cells. Genes that support mitochondrial nucleotide pools, including mitochondrial nucleotide transporters and a subset of cytoplasmic nucleoside kinases, were also increased in AML compared with normal hematopoietic samples. Knockdown of cytoplasmic nucleoside kinases reduced mtDNA levels in AML cells, demonstrating their contribution in maintaining mtDNA. To assess cytoplasmic nucleoside kinase pathway activity, we used a nucleoside analog 2'3'-dideoxycytidine (ddC), which is phosphorylated to the activated antimetabolite, 2'3'-dideoxycytidine triphosphate by cytoplasmic nucleoside kinases. ddC is a selective inhibitor of the mitochondrial DNA polymerase γ. ddC was preferentially activated in AML cells compared with normal hematopoietic progenitor cells. ddC treatment inhibited mtDNA replication, oxidative phosphorylation, and induced cytotoxicity in a panel of AML cell lines. Furthermore, ddC preferentially inhibited mtDNA replication in a subset of primary human leukemia cells and selectively targeted leukemia cells while sparing normal progenitor cells. In animal models of human AML, treatment with ddC decreased mtDNA, electron transport chain proteins, and induced tumor regression without toxicity. ddC also targeted leukemic stem cells in secondary AML xenotransplantation assays. Thus, AML cells have increased cytidine nucleoside kinase activity that regulates mtDNA biogenesis and can be leveraged to selectively target oxidative phosphorylation in AML.

Genetic Landscape of Electron Transport Chain Complex I Dependency in Acute Myeloid Leukemia

“…This study confirms, in the context of primary AML specimens, the recent observations from others indicating that inhibition of mitochondrial function is a promising therapeutic strategy in AML 21,22,24,26–28 . Importantly, it also identifies and characterizes for the first time AML genetic subtypes most susceptible to respond to mitochondrial targeting.…”

“…HSCs rely primarily on anaerobic glycolysis rather than mitochondrial oxidative phosphorylation (OXPHOS) for energy production and repression of mitochondrial metabolism by autophagy is in fact required for their long-term self-renewing capacity 17–19 . In stark contrast, AML LSC protein expression profiles are enriched for hallmarks of OXPHOS 20 and LSCs rely on mitochondrial function for their survival: they are sensitive to tigecycline, an antibiotic that inhibits mitochondrial protein synthesis 21 and to 2’3’-dideoxycytidine (ddC), a selective inhibitor of mitochondrial DNA replication 22 . Furthermore, AML cells appear to be overall characterized by high OXPHOS activity and high mitochondrial mass, accompanied by low respiratory chain spare reserve capacity as compared to their normal hematopoietic counterparts 23 , and are sensitive to inhibition of the mitochondrial protease ClpP 24 .…”

Global Interactome Mapping of Mitochondrial Intermembrane Space Proteases Identifies a Novel Function for HTRA2

“…We and others have previously shown that acute myeloid leukemia (AML) cells possess unique mitochondrial characteristics, with increased reliance on oxidative phosphorylation . Knockdown of HTRA2 also disrupted cristae structure in the AML cell line OCI‐AML2 (Figure B).…”

Pyrrolo[2,3‐d]pyrimidine (7‐deazapurine) as a privileged scaffold in design of antitumor and antiviral nucleosides

“…AB61 trisphosphate is a substrate for mitochondrial DNA polymerase and therefore AB61 (7a) might interfere with mtDNA replication and mitochondrial functions similarly as described for other nucleoside analogs. 43 The in vivo studies of xenograft models confirmed the promising properties of AB61 (7a) for its further development as an anticancer agent.…”