Targeting glutamine metabolism sensitizes pancreatic cancer to PARP-driven metabolic catastrophe induced by ß-lapachone

Abstract

BackgroundPancreatic ductal adenocarcinomas (PDA) activate a glutamine-dependent pathway of cytosolic nicotinamide adenine dinucleotide phosphate (NADPH) production to maintain redox homeostasis and support proliferation. Enzymes involved in this pathway (GLS1 (mitochondrial glutaminase 1), GOT1 (cytoplasmic glutamate oxaloacetate transaminase 1), and GOT2 (mitochondrial glutamate oxaloacetate transaminase 2)) are highly upregulated in PDA, and among these, inhibitors of GLS1 were recently deployed in clinical trials to target anabolic glutamine metabolism. However, single-agent inhibition of this pathway is cytostatic and unlikely to provide durable benefit in controlling advanced disease.ResultsHere, we report that reducing NADPH pools by genetically or pharmacologically (bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl)ethyl sulfide (BPTES) or CB-839) inhibiting glutamine metabolism in mutant Kirsten rat sarcoma viral oncogene homolog (KRAS) PDA sensitizes cell lines and tumors to ß-lapachone (ß-lap, clinical form ARQ761). ß-Lap is an NADPH:quinone oxidoreductase (NQO1)-bioactivatable drug that leads to NADPH depletion through high levels of reactive oxygen species (ROS) from the futile redox cycling of the drug and subsequently nicotinamide adenine dinucleotide (NAD)+ depletion through poly(ADP ribose) polymerase (PARP) hyperactivation. NQO1 expression is highly activated by mutant KRAS signaling. As such, ß-lap treatment concurrent with inhibition of glutamine metabolism in mutant KRAS, NQO1 overexpressing PDA leads to massive redox imbalance, extensive DNA damage, rapid PARP-mediated NAD+ consumption, and PDA cell death—features not observed in NQO1-low, wild-type KRAS expressing cells.ConclusionsThis treatment strategy illustrates proof of principle that simultaneously decreasing glutamine metabolism-dependent tumor anti-oxidant defenses and inducing supra-physiological ROS formation are tumoricidal and that this rationally designed combination strategy lowers the required doses of both agents in vitro and in vivo. The non-overlapping specificities of GLS1 inhibitors and ß-lap for PDA tumors afford high tumor selectivity, while sparing normal tissue.Electronic supplementary materialThe online version of this article (doi:10.1186/s40170-015-0137-1) contains supplementary material, which is available to authorized users.

Erratum: From Krebs to clinic: glutamine metabolism to cancer therapy

“…Many candidate preclinical synthetic lethal treatments target pathways or cellular functions that help cancer cells to compensate for the targeting of another pathway or cellular function. The pleiotropic role of glutamine in cellular functions, such as energy production, macromolecular synthesis, mTOR activation, and ROS homeostasis 179 , makes GLS inhibition a potentially ideal candidate for combination therapy, as detailed in Table 3. A few combinations are notable because they reveal novel consequences of glutamine metabolism.…”

Down‑expression of poly(ADP‑ribose) polymerase in p53‑regulated pancreatic cancer cells

“…It comprises three regions: A DNA-binding domain, an automodification domain and a catalytic domain (10). The primary structure of PARP-1 is highly conserved in eukaryotes; distinct catalytic regions exhibit a high degree of homology (10). Increased expression levels of PARP-1 have been identified in multiple types of tumor including breast, prostate and pancreatic cancer, indicating that PARP-1 participates in tumorigenesis and tumor progression (11).…”

“…PARP-1 was the first member of the PARP family to be identified, with a molecular mass of 116Kd (9). It comprises three regions: A DNA-binding domain, an automodification domain and a catalytic domain (10). The primary structure of PARP-1 is highly conserved in eukaryotes; distinct catalytic regions exhibit a high degree of homology (10).…”

Glutamine at focus: versatile roles in cancer

“…As a consequence, combination therapy leads to cell death in oncogenic K-ras-expressing cells but not wild-type K-rasexpressing cells [61]. Together, these finding suggest that Kras-mutant cell line-mediated activation of glutamine catabolism can provide rational targets to be novel anticancer therapies.…”