Abstract 3155: Metabolic stress induces an intrinsic inflammatory CAF phenotype that regulates stromal architecture in pancreatic cancer

Abstract Macropinocytosis is a critical amino acid supply pathway that fuels the metabolism of tumor cells and cancer-associated fibroblasts (CAFs) in pancreatic ductal adenocarcinoma (PDAC). PDAC tumors are deficient in glutamine, a critical amino acid that tumor cells and CAFs use to sustain their cellular fitness. We have previously shown that both PDAC cells and CAFs stimulate macropinocytosis as an adaptive response to glutamine depletion. How these linked metabolic mechanisms might co-operate to control stromal architecture remains elusive. In this study, we employed glutamine starvation and 5-(N-ethyl-N-isopropyl)-amiloride (EIPA), a selective inhibitor of macropinocytosis, to investigate how metabolic stress impacts the tumor microenvironment. We find that concomitant suppression of glutamine metabolism and macropinocytosis synergizes to drive an intrinsic inflammatory CAF phenotype that requires metabolic stress-induced ERK/MAPK signaling. Utilizing immunocompetent syngeneic mouse models of PDAC, we find that blocking macropinocytosis in these glutamine-depleted tumors diminishes tumor growth and reorganizes the tumor stroma by decreasing collagen deposition, increasing vasculature expansion and enhancing the infiltration of both CD8+ and CD4+ T cells. Alterations in the stromal landscape under these conditions are linked to the enhancement of CAFs that display an inflammatory signature while simultaneously suppressing more myofibroblastic identities within the tumor. Interestingly, we find that these effects on the tumor microenvironment can be harnessed to improve therapeutic responses. We determine that combining macropinocytosis inhibition with immune checkpoint blockade reduces PDAC tumor burden and significantly inhibits metastasis. We also find that macropinocytosis inhibition enhances drug delivery, thereby improving the efficacy of gemcitabine chemotherapy. Our findings demonstrate that intratumoral metabolic stress plays a critical part in preserving and modulating the tumor stroma. Citation Format: Yijuan Zhang, Swetha Maganti, Jennifer Hope, Li Lin, Cheska Marie Galapate, Florent Carrette, Linda Bradley, Cosimo Commisso. Metabolic stress induces an intrinsic inflammatory CAF phenotype that regulates stromal architecture in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3155.