Abstract PR-20: Hepcidin-mediated iron sequestration limits CD8+ tumor infiltrating lymphocytes in pancreas adenocarcinoma
Authors: Schoenfeld Joshua D , Ganz Tomas , Vardhana Santosha A 
Published: September 2024

Abstract
Anemia at presentation is a common comorbidity amongst patients with solid tumors and is primarily driven by functional iron deficiency (FID). FID occurs in response to systemic inflammation; IL-6 drives hepatic production of hepcidin, restricting systemic iron availability by both inhibiting gut absorption and driving iron sequestration primarily within macrophages of the reticuloendothelial system. Among patients with solid tumors, pancreas adenocarcinoma (PDAC) carries the highest incidence of ID; FID is present in 35-40% of patients at baseline, however, the role of FID in PDAC biology remains unclear. PDAC is thought to be immunologically ‘cold’ with a tumor microenvironment (TME) relatively devoid of infiltrating CD8+ T cells (TILs). Accordingly, trials of immune checkpoint blockade in genomically unselected PDAC have been disappointing with response rates &lt; 3%. However, PDAC tumors display tremendous immunological heterogeneity, with CD8+ TIL abundance predicting ICB responsiveness in mice and overall survival in patients, suggesting that barriers to intratumoral CD8+ TIL persistence limit immune-mediated control of PDAC. ID is associated with poor vaccine responses in patients and in murine models, FID induced by administration of a hepcidin mimetic (PR73) limits T cell-responses to influenza vaccination and infection. Therefore, we hypothesized that hepcidin-mediated iron sequestration may be a primary driver of immune evasion and limit CD8+ TILs in PDAC. Here we report that analysis of paired pre-treatment peripheral blood samples and biopsies from patients with metastatic PDAC enrolled on the PRINCE trial (NCT03214250) revealed that patients with high serum hepcidin, regardless of the presence of anemia, demonstrated significantly worse overall survival (p = 0.02). Serum hepcidin negatively correlates with CD8+ TIL abundance (p &lt; 0.005) independently of other markers of systemic inflammation suggesting that this is not merely a surrogate for more advanced disease. In a murine model of FID, administration of PR73 (50 nmol/day intraperitoneally) to mice bearing KPC (LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-Cretg/+)-derived tumors selectively limits CD8+ TIL abundance without altering peripheral T cell subsets. Consistent with this, using a novel ratiometric fluorescent reporter to quantify relative local iron availability, PR73 selectively increases reporter activity in intratumoral, but not peripheral, CD8+ T cells. Mechanistically, CD8+ T cells encountering persistent antigen in vitro are uniquely sensitive to iron restriction as compared to acutely stimulated T cells due to antigen-driven mitochondrial dysfunction in a reactive oxygen species (ROS)-dependent mechanism. Our results support that CD8+ T cells experiencing persistent antigen, such as in the TME, are uniquely sensitive to iron deprivation due to disruptions in mitochondrial oxidative metabolism and demonstrate that metabolic constraints within the TME can shape tumoral immunity and may underly the paucity of CD8+ T cells in PDAC.
Citation Format: Joshua D Schoenfeld, Tomas Ganz, Santosha A Vardhana. Hepcidin-mediated iron sequestration limits CD8tumor infiltrating lymphocytes in pancreas adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr PR-20.