Exhaustion of Tumor-Reactive CD8+ T-Cells in a Murine Model of Pancreatic Cancer
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Date
2023-05
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The Ohio State University
Abstract
Pancreatic cancer has a five-year survival rate of 11.5% and is ranked third in the United States for cancer-related deaths. Despite promising advances in other cancers, current treatments (chemotherapy and immunotherapy) are not as effective for pancreatic cancer. Improved outcomes, potentially mediated by immunotherapy, are associated with increased T-cell presence within the tumor microenvironment. We aim to assess the therapeutic impact via the phenotype and exhaustion status of these cells. To accomplish this, our study evaluates a KPC murine model of pancreatic cancer, genetically designed to mimic the key characteristics of pancreatic cancer in humans. This model also includes a tumor-associated antigen luciferase-SIYRYYGL for the detection and evaluation of antigen-specific T-cells.
To develop this model, C57BL/6 male mice were injected subcutaneously with KPC-PK5L1932 pancreatic cancer cells, which include a tumor-associated antigen and luciferase for bioluminescent imaging of cells in vivo (PDX1-Cre/LSL-KRasG12D/p53R172H/wt/Luciferase-SIYRYYGL). Tumor growth was monitored over two months, and immune cells in the tumors, spleens, and lymph nodes were characterized using high-dimensional flow cytometry with an H-2Kb-SIYRYYGL dextramer reagent to detect antigen-specific T-cells. Consistent tumoral growth was observed over the course of the 51-day study. Analysis via flow cytometry of the infiltrating murine immune cell populations revealed a distinct antigen-specific (H-2Kb-SIYRYYGL) CD8+ T-cell population in the tumor which was minimally present in the spleen and lymph node. This subset of tumoral cells also showed a high expression of the exhaustion markers PD-1 and TOX compared to the other CD8+ T-cells in the spleen and lymph node, suggesting the localized exhaustion of T-cells in the tumor.
The successful tumor growth and detection of antigen-specific T-cells and other immune cells via flow cytometry demonstrates that our KPC murine model of pancreatic cancer can effectively be used for further exploratory experiments and analysis of immune infiltration. The antigen-specific T-cells were identified as having phenotypes consistent with T-cell exhaustion, which was not prominently seen with the cells of the spleen or lymph nodes. With this model developed, future studies will further evaluate these immune cell populations and reveal the impact of chemotherapy and/or immunotherapy.
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Keywords
Pancreatic cancer, Tumor-reactive T-cells, Murine model, Immune exhaustion, High-dimensional flow cytometry, Chemotherapy & immunotherapy