Hypoxia enhances sensitivity to RAS inhibition in PDAC

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies, in part due to acquired therapy resistance. As ~90% of PDAC tumors harbor activating KRAS mutations, direct inhibition of RAS has emerged as a promising therapeutic strategy. The RAS(ON) multi-selective inhibitor daraxonrasib has demonstrated clinical activity in PDAC and is currently being evaluated in Phase 3 trials; however, monotherapy resistance still emerges underscoring the need to identify biological processes that enable tumor cell survival following RAS inhibition. As RAS signaling regulates cancer metabolism, we hypothesized that metabolic remodeling contributes to RAS inhibitor sensitivity and resistance. To test this, we profiled polar metabolites in PDAC cells treated with RMC-7977, a tool RAS(ON) multi-selective inhibitor. RAS(ON) inhibition led to broad alterations in metabolite levels, including decreased levels of glycolytic and pentose phosphate pathway intermediates. In line with these findings, RMC-7977 treatment reduced glucose uptake and increased lactate secretion, suggesting that RMC-7977 treatment reduces glycolysis and promotes a shift toward increased oxidative metabolism. Given this shift toward oxidative metabolism, which requires mitochondrial respiration, we hypothesized that hypoxia, a hallmark of PDAC, may increase sensitivity to RAS inhibition.  Indeed, PDAC cells exhibited enhanced growth inhibition in response to RMC-7977 in low oxygen conditions. RMC-7977 also suppressed glucose uptake and lactate secretion similarly under normoxic and hypoxic conditions. Pharmacologic inhibition of mitochondrial respiration under normoxia also enhanced RMC-7977 sensitivity. Together, these findings reveal that RMC-7977 reduces glucose uptake and shifts cells toward oxidative metabolism and uncovers a potential metabolic vulnerability involving the PDAC tumor microenvironment that has the potential to enhance the impact of RAS inhibition.