Abstract 3133: Glucose is important for macrophage metabolism and response to immunotherapy in a pancreatic cancer model
Authors: Hue Jonathan J. , Zarei Mehrdad , Graor Hallie J. , Katayama Erryk S. , Hajihassani Omid , Loftus Alexander W. , Rothermel Luke D. , Vaziri-Gohar Ali , Winter Jordan M. 
Published: June 2022

Introduction: Pancreatic cancer (PC) is resistant to systemic therapies. This is at least in part due to the characteristically harsh tumor microenvironment which limits the delivery of systemic therapies and is not conducive to anti-tumor immune cell function. Unfortunately, development of novel therapeutics is arduous. Thus, identification of methods to augment the efficacy of existing therapeutics, such as immunotherapies, represents an attractive option. Herein, we attempt to sensitize PC to a colony stimulating factor 1 receptor (CSF1R) inhibitor by augmenting peripheral glucose levels.

Methods Murine PC cells (KPC) and bone marrow derived macrophages were cultured in hypoglycemic (≤2.5mM) or hyperglycemic (25mM) conditions. Phenotypic (western blot, flow cytometry), metabolic (seahorse, LC-MS metabolomics), and cell survival (clonogenic assay) assays were performed. KPC cells were orthotopically injected into the pancreas of immunocompetent mice for survival studies. Mice were randomized to pexidartinib (a CSF1R inhibitor) or vehicle and received either normal water of 30% dextrose (D30).

Results: In a co-culture experiment, tumor-supporting M2 macrophages increased KPC cell growth by 30%, whereas tumor-fighting M1 macrophages decreased KPC growth by 95%. M1 macrophages were poorly suited to survive in hypoglycemic conditions as compared to hyperglycemic conditions (relative survival: 38% vs 100%, p&lt;0.01). M2 macrophage survival was equivalent (93% vs 100%, p=0.39). When cultured in hypoglycemic conditions, M1 macrophages adopted an M2-like metabolic profile (i.e., increased TCA cycle metabolites and decreased glycolytic metabolites) assessed by both seahorse and LC-MS metabolomics. As glucose concentrations decreased in culture media over time, protein levels of an M1 marker (inducible nitric oxide, iNOS) decreased and an M2 marker (arginase) appeared, suggesting a phenotypic switch. Pexidartinib augmented M1 iNOS protein levels and simultaneously decreased M2 arginase levels. On an in vitro flow cytometric analysis, the percentage of M2 macrophages (CD206+, CD301+, F480+, CD11b+) decreased as glucose concentrations were increased (33.7% vs 38.0%), and decreased further when pexidartinib was combined with hyperglycemia (20.5%). Mice treated with pexidartinib and D30 had improved median survival relative to mice receiving pexidartinib alone (median survival: 42 (IQR: 38, 52) vs 34 (IQR: 32, 38) days, p&lt;0.05) in two independent experiments. Of note, pexidartinib alone did not improve survival as compared to vehicle or D30.

Conclusion: Higher glucose conditions promote M1 macrophage survival and function, while preventing the switch to an M2 phenotype. Also, higher peripheral glucose levels appear to sensitize PC to a CSF1R inhibitor. We plan to validate these findings using other immunotherapeutics (e.g., checkpoint inhibitors).

Citation Format: Jonathan J. Hue, Mehrdad Zarei, Hallie J. Graor, Erryk S. Katayama, Omid Hajihassani, Alexander W. Loftus, Luke D. Rothermel, Ali Vaziri-Gohar, Jordan M. Winter. Glucose is important for macrophage metabolism and response to immunotherapy in a pancreatic cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3133.