Glutamine mimicry suppresses tumor progression through asparagine metabolism in pancreatic ductal adenocarcinoma

Abstract

In pancreatic ductal adenocarcinoma (PDAC), glutamine is a critical nutrient that drives a wide array of metabolic and biosynthetic processes that support tumor growth. Despite this established dependency, the targeting of specific enzymes involved in glutamine metabolism is yet to yield any clinical benefit. Here, we have examined the therapeutic potential of 6-diazo-5-oxo-L-norleucine (DON), a glutamine antagonist that broadly inhibits glutamine metabolism. We found that DON treatment significantly blocks PDAC tumor growth and attenuates metastasis. Interestingly, we link the effectiveness of DON in PDAC to asparagine (Asn) metabolism. By inhibiting asparagine synthetase (ASNS), DON significantly reduces intracellular Asn production and Asn supplementation rescues the anti-proliferative effects of DON. We discern that PDAC cells upregulate expression of ASNS as a metabolic adaptation and that modulating ASNS levels can impact DON efficacy. Strikingly, in patient-derived organoids, DON responsiveness is inversely correlated with ASNS expression, a feature that is not observed for other metabolic enzymes targeted by DON. We find that treatment with L-asparaginase (ASNase), an enzyme that catabolizes free Asn, synergizes with DON to impact the viability of PDAC cells. Finally, we identify that a combination therapy of DON and ASNase has a significant impact on metastasis. These results shed light on the mechanisms that drive the effects of glutamine mimicry and point to the utility of co-targeting adaptive responses to control PDAC progression.

A Ketogenic Diet Sensitizes Pancreatic Cancer to Inhibition of Glutamine Metabolism

“…Son et al found that genetic targeting of the gln metabolism downstream enzymes GOT1 or GOT2, resulted in a significant decrease in tumor volume in a human PDAC xenograft model, indicating these enzymes could serve as therapeutic targets (28). In accordance, Recouvreux et al reported significant decrease in tumor volume in several PDAC orthotopic models when using the pan-glutamine targeting drug, DON (32). Concerns regarding DON-related toxicity prompted the development of DRP-104, a pro-drug version (32), which showed promising responses in a syngeneic PDAC model (33).…”

“…In accordance, Recouvreux et al reported significant decrease in tumor volume in several PDAC orthotopic models when using the pan-glutamine targeting drug, DON (32). Concerns regarding DON-related toxicity prompted the development of DRP-104, a pro-drug version (32), which showed promising responses in a syngeneic PDAC model (33). Combination therapy with trametinib, a MEK inhibitor, significantly increased survival in the same model, indicating the superior potential of glutamine inhibition when combined with rationally selected complementary therapies (33).…”

“…Glutamine (Gln) plays a multifaceted role in cellular metabolism. The organic backbone contributes to the generation of TCA cycle intermediates through anaplerosis via α-ketoglutarate (14)(15)(16), and the amide nitrogen fuels the biosynthesis of essential metabolites like asparagine and nucleotides (17,18). Previous work by our group revealed that PDAC cells preferentially metabolize Gln when glucose levels are reduced (19).…”

“…Glutaminase (GLS) (which converts glutamine to glutamate prior to entry into the TCA cycle) inhibition, has been explored in pancreatic cancer models as a target of single-agent therapy, and the treatment transiently reduced cellular proliferation in vitro. However, this approach was ineffective across multiple in vivo PDAC models as a monotherapy due to compensatory metabolic reprogramming (17). It was postulated that broadening the inhibition of Gln metabolism to related targets beyond GLS could enhance efficacy and thwart adaptive rewiring changes responsible for resistance.…”