Expression and role of the immune checkpoint regulator PD-L1 in the tumor-stroma interplay of pancreatic ductal adenocarcinoma

Frontiers in Immunology

Immunology

Sascha Rahn¹  Silje Beckinger²  Tina Daunke²  Susanne Sebens²  Heiner Schäfer²  Anna Maxi Wandmacher³  Daniela Wesch⁴  Markus Eckstein⁵  Arndt Hartmann⁵  Sandra Krüger⁶  Christoph Röcken⁶  Steffen Heckl⁷  Christian Pilarsky⁸ 

[1] Biochemical Institute, Kiel University, Kiel, Germany;Institute for Experimental Cancer Research, Kiel University and University Hospital Schleswig-Holstein, Kiel, Germany;Institute for Experimental Cancer Research, Kiel University and University Hospital Schleswig-Holstein, Kiel, Germany;Department of Internal Medicine II, University Medical Center Schleswig-Holstein, Kiel, Germany;Institute of Immunology, Kiel University and University Medical Center Schleswig-Holstein (UKSH), Kiel, Germany;Institute of Pathology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany;Institute of Pathology, University Medical Center Schleswig-Holstein, Kiel, Germany;Institute of Pathology, University Medical Center Schleswig-Holstein, Kiel, Germany;Department of Internal Medicine II, University Medical Center Schleswig-Holstein, Kiel, Germany;Translational Research Center, University Hospital Erlangen, Erlangen, Germany;

关键词: pancreatic cancer;    immune checkpoint inhibitor;    immune evasion;    tumor microenvironment;    macrophages;    3D co-culture;   

DOI  :  10.3389/fimmu.2023.1157397

 received in 2023-02-02, accepted in 2023-06-09,  发布年份 2023

来源: Frontiers

【 摘 要 】

IntroductionImmune checkpoint inhibitors (ICI), e.g., targeting programmed cell death protein 1-ligand 1 (PD-L1) or its receptor PD-1, have markedly improved the therapy of many cancers but so far failed in pancreatic ductal adenocarcinoma (PDAC). Macrophages represent one of the most abundant immune cell populations within the tumor microenvironment (TME) of PDAC being able to either support or restrain tumor progression depending on their phenotype. To better understand treatment failure of PD-L1/PD-1 inhibitors in PDAC, this study examined PD-L1 expression in the context of a dynamic TME in PDAC with a particular focus on the impact of macrophages.MethodsFormalin-fixed and paraffin embedded tissue samples of primary PDAC tissues and corresponding liver metastases were used for immunohistochemical analyses. Serial sections were stained with antibodies detecting Pan-Cytokeratin, CD68, CD163, CD8, and PD-L1.To investigate whether the PD-1/PD-L1 axis and macrophages contribute to immune escape of PDAC cells, a stroma enriched 3D spheroid coculture model was established in vitro, using different PDAC cell lines and macrophages subtypes as well as CD8+ T cells. Functional and flow cytometry analyses were conducted to characterize cell populations.ResultsImmunohistochemical analyses revealed that PD-L1 is mainly expressed by stroma cells, including macrophages and not PDAC cells in primary PDAC tissues and corresponding liver metastases. Notably, high local abundance of macrophages and strong PD-L1 staining were commonly found at invasion fronts of tumoral lesions between CD8+ T cells and tumor cells. In order to investigate whether PD-L1 expressing macrophages impact the response of PDAC cells to treatment with PD-L1/PD-1 inhibitors, we developed a spheroid model comprising two different PDAC cell lines and different ratios of in vitro differentiated primary M1- or M2-like polarized macrophages. In line with our in situ findings, high PD-L1 expression was observed in macrophages rather than PDAC cells, which was further increased by the presence of PDAC cells. The effector phenotype of co-cultured CD8+ T cells exemplified by expression of activation markers and release of effector molecules was rather enhanced by PDAC macrophage spheroids, particularly with M1-like macrophages compared to mono-culture spheroids. However, this was not associated with enhanced PDAC cell death. ICI treatment with either Durvalumab or Pembrolizumab alone or in combination with Gemcitabine hardly affected the effector phenotype of CD8+ T cells along with PDAC cell death. Thus, despite strong PD-L1 expression in macrophages, ICI treatment did not result in an enhanced activation and cytotoxic phenotype of CD8+ T cells.ConclusionOverall, our study revealed novel insights into the interplay of PDAC cells and macrophages in the presence of ICI.

【 授权许可】

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Copyright © 2023 Daunke, Beckinger, Rahn, Krüger, Heckl, Schäfer, Wesch, Pilarsky, Eckstein, Hartmann, Röcken, Wandmacher and Sebens