Abstract A006: Assessing metabolic requirements for RAS inhibitor resistance in pancreatic cancer

Abstract Mutational activation of the KRAS oncogene in pancreatic ductal adenocarcinoma (PDAC) plays a crucial role in tumor initiation, progression, and alterations of cellular programs that support PDAC growth. Mutant KRAS alters the metabolic state of PDAC and has been linked to upregulation of glycolysis and alterations in the nutrient scavenging pathways autophagy and macropinocytosis. Our lab determined that genetic suppression or inhibition of the RAS pathway unexpectedly resulted in upregulation of autophagy. Additionally, concurrent inhibition of the RAS-MAPK pathway and autophagy synergistically improved anti-tumor efficacy in both PDAC cell lines, organoids, and PDX tumor models. To begin to address the temporal regulation of metabolic signaling following RAS inhibition, we examined the sustainability of upregulated autophagic flux following prolonged (168 h) RAS inhibition. Preliminary data indicates that autophagy upregulation following KRAS inhibition is transient and returns to basal levels following prolonged inhibitor treatment. Given the limited durability of autophagic induction upon RAS inhibition, we sought to determine whether other nutrient scavenging pathways that culminate in the lysosome were altered following prolonged RAS inhibitor treatment. Macropinocytosis is upregulated in PDAC and is RAS-dependent. We monitored macropinocytic uptake following direct inhibition of RAS, and found that following an initial decrease in macropinocytosis, PDAC cells exhibited a compensatory increase in macropinocytotic uptake and utilization at later timepoints. Based on this data, we have begun to interrogate the metabolic phenotypes associated with cells subjected to acute (24-72 h) and prolonged (168 h) RAS inhibitor treatment. Furthermore, we have also derived PDAC cell lines that are resistant to RAS inhibition via prolonged inhibitor dose escalation. We found that RAS inhibitor resistant cell lines have heterogenous capacities for autophagic flux and retain similar sensitivity to autophagy inhibitors. Conversely, resistant cells display persistently increased macropinocytosis, suggesting that that scavenging pathway compensates for metabolic requirements of growth under sustained RAS inhibition. Future studies are aimed at investigating the molecular underpinnings driving upregulated macropinocytosis and more broadly profiling the metabolic landscape of RAS-inhibitor resistant PDAC models. Citation Format: Sarah E. Ackermann, Ryan Robb, Khalilah E. Taylor, Runying Yang, Kirsten L. Bryant. Assessing metabolic requirements for RAS inhibitor resistance in pancreatic cancer abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research—Emerging Science Driving Transformative Solutions; Boston, MA; 2025 Sep 28-Oct 1; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85 (18Suppl₃): Abstract nr A006.