Abstract B022: A platform to characterize hepatic immunity reveals variation in hepatic infiltration of tumor expanded T cells in “localized” PDAC
Authors: Kanu Elishama N. , Fletcher Ashley A. , Bao Jiayin , Eckhoff Austin M. , Comatas Karrie , Wang Tao , Hwang Bin-Jin , Lidsky Michael E. , Zani Sabino , Blazer Dan G. , Allen Peter J. , Ji Zhicheng , Nussbaum Daniel P. , Crosby Erika J. 
Published: January 2024

Abstract
Even in its earliest stages, pancreatic ductal adenocarcinoma (PDAC) is an essentially incurable disease due to the presence of disseminated, yet radiographically occult cancer cells in the setting of an otherwise “localized” primary tumor. The vast majority (~80%) of patients who undergo curative-intent surgery develop liver metastases, often within six months of surgery, and these hepatic metastases dominate survival outcomes, even in the presence of multisite recurrence. What drives hepatic organotropism remains unknown, in large part due to the exclusion of “normal” liver tissue from PDAC biobanking programs. While recent work in animal models suggests that suppression of the hepatic immune microenvironment may facilitate metastatic progression, confirmatory studies in human patients are lacking, due to a paucity of relevant model systems. To address this deficit, we developed an experimental pipeline to profile hepatic immunity at single-cell resolution vis-à-vis the peripheral and intratumoral immune compartments. We hypothesized that this platform could be leveraged to identify tissue- and patient-specific immunophenotypes associated with hepatic recurrence prior to the development of overt metastases. Patients with localized PDAC at Duke University were enrolled in an IRB-approved (Pro00108288) biobanking program to obtain multisegment liver biopsies, primary tumor specimen, and peripheral blood at the time of curative-intent resection. Immune (CD45+) cells were sorted following enzymatic digestion (tissues) or Ficoll separation (blood) and single-cell gene expression and T cell receptor libraries were created. Data was processed using CellRanger and aligned, filtered, and normalized using R. In total, we identified 32 unique immune cell populations conserved across patients, with both shared and site-specific cell types identified in the T cell, B cell, NK cell, and myeloid compartments. Additionally, we identified expanded T cell clones within the tumor microenvironment and traced a subset of these clonotypes to the premetastatic liver. These tumor-expanded T cells (TTE cells) presumably arise from recognition of a specific tumor antigen, which then instigates activation and proliferation of the clone. Notably, we identified a subset of our patients without known liver metastases who nonetheless demonstrated hepatic infiltration of TTE cells. While the significance of these hepatic TTE cells is still unclear, we hypothesize that this is evidence of a primed immune response to tumor antigens already present in the liver at the time of surgery. This experimental platform has now been implemented within an ongoing window-of-opportunity trial (NCT05634720) testing neoadjuvant hepatic artery chemotherapy in patients undergoing resection of localized PDAC. The correlative scientific objectives will focus on quantifying the variation of hepatic TTE infiltration across patients, determining the function and activation state of hepatic TTE cells, and testing the association between hepatic TTE cell infiltration and clinical outcomes.
Citation Format: Elishama N. Kanu, Ashley A. Fletcher, Jiayin Bao, Austin M. Eckhoff, Karrie Comatas, Tao Wang, Bin-Jin Hwang, Michael E. Lidsky, Sabino Zani, Dan G. Blazer, Peter J. Allen, Zhicheng Ji, Daniel P. Nussbaum, Erika J. Crosby. A platform to characterize hepatic immunity reveals variation in hepatic infiltration of tumor expanded T cells in “localized” PDAC [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B022.