Targeting Pancreatic Cancer Metabolic Dependencies through Glutamine Antagonism
Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest types of cancer. A factor that contributes to the poor prognosis of the disease is the complex tumor microenvironment (TME). The PDAC TME is composed of excessive fibrosis and desmoplasia, which creates a harsh environment resulting in hypoxia and altered nutrient availability. To promote survival and proliferation in this environment, PDAC cells can reprogram glutamine (Gln) metabolism. Previous studies have demonstrated that PDAC cells use Gln to support proliferation and redox balance. However, earlier attempts to inhibit Gln metabolism using glutaminase inhibitors resulted in rapid metabolic reprogramming and ultimately therapeutic resistance.  Here, we hypothesized that using a Gln analogue, such as 6-Diazo-5-oxo-L-norleucine (DON), could broadly target Gln metabolism in PDAC and prevent rapid adaptation. Indeed, DON treatment led to a significant decrease in PDAC proliferation in a dose-dependent manner, as well as a profound reduction of various metabolites involved in central carbon and nucleotide metabolism, suggesting that DON creates a metabolic crisis. In addition, we observed a significant decrease in tumor growth in various in vivo models (syngeneic, immunodeficient) using DRP-104 (sirpiglenastat), a novel pro-drug version of DON that was designed to circumvent DON associated GI toxicity and allow the therapeutic exploration of broad Gln antagonism.  Mechanistically, we found that ERK signaling is increased as a compensatory mechanism through the increased activity of receptor tyrosine kinases (RTKs). Combinatorial treatment of DRP-104 and Trametinib (MEK1/2) inhibitor led to a significant increase in survival in a syngeneic model PDAC. Taken together, these pre-clinical results suggest that broadly targeting Gln metabolism could provide a new therapeutic avenue for PDAC and that the combination with an ERK signaling pathway inhibitor could further improve the therapeutic outcome. Overall design: Total  RNA was extracted from tumor and tumor cells using PuTotal RNA from cell cultures and tumors were obtained using TRizol (Thermo, 15596026) and PureLink RNA Midi Kit (Thermo, 12183025) kit according to the manufacturer's instructionsreLink RNA Minit Kit (Thermo Scientific)