Komplexes 3-D-in-vitro Modell für die Analyse von Immunsuppressionsmechanismen bei T-Zellen im Pankreaskarzinom

Abstract

Pancreatic cancer has emerged as one of the most fatal malignancies displaying various immunosuppressive mechanisms. Inactivation of cytotoxic T cells as well as their trapping within the peritumoral fibrous tissues contribute to local immunosuppression. In order to analyze these phenomena we have developed a three-dimensional in vitro model mimicking the in vivo situation of pancreatic cancer. Human pancreatic cancer cell line spheroids are co-cultured with activated human T cells as well as human fibroblasts in a three-dimensional collagen gel. Potentially activating or suppressive factors can be added and their impact on T cell activation and migration can be assessed by cryosections of the three-dimensional co-cultures followed by immunohistochemistry. In this model the phenotype of T cells is identical to that of pancreatic cancer T cells in vivo: Some T cells infiltrate tumor spheroids but mostly display a loss of the CD3-ζ chain, which is essential for T cell activation. The vast majority of T cells are trapped within the peritumoral fibrous tissue and also show a loss of CD3-ζ. Neutralization of TGF-ß or Fas ligand could not reverse these phenomenons. We conclude that this three-dimensional in vitro system mimics the in vivo situation of pancreatic cancer including infiltrating T cells, their loss of activation and T cell trapping. Fas ligand and TGF-ß, likely contributors of immunosuppression, do not seem to play a role in this context. Furthermore, the impact of other potentially immunosuppressive or stimulating factors can be analyzed and may be the first step towards developing effective immunotherapies against pancreatic cancer.