Probing the interaction of macrophages in the pancreatic cancer microenvironment

Co, Ileana Louise (1), McGaha, Tracy (2, 4), McGuigan, Alison P. (1, 3)

(1) Institute of Biomaterials and Biomedical Engineering, University of Toronto

(2) Princess Margaret Cancer Research Centre, University Health Network

(3) Department of Chemical Engineering and Applied Sciences, University of Toronto

(4) Department of Immunology, University of Toronto

Immunotherapies have emerged as promising therapeutics for solid tumours like Pancreatic Ductal Adenocarcinoma (PDAC), but unfortunately still fail due to poor understanding of how immune cells in the tumour microenvironment (TME) are modulated. In particular, tumour associated macrophages (TAMs) are highly plastic immune cells shown to highly infiltrate PDAC and display immunosuppressive and pro- tumorigenic phenotypes depending on their interactions in the TME. While the role of TAMs in tumour progression is known, the intricate mechanisms of how different small molecule gradients like hypoxia drive this pro-tumorigenic phenotype is unknown due largely to the absence of accurate models to study these phenomena.

Using a unique tool called TRACER- an in vitro, paper-based “rollable” 3D tumour - we have been able to recreate layer-specific tumour microenvironments due to hypoxic and metabolic gradients. In this study, primary donor-derived macrophages and pancreatic tumour cells from dissociated patient-derived organoids are resuspended and mixed in a gel blend then seeded onto the TRACER biocomposite paper strips. After 24-48 hours, TRACER is unrolled on-demand for detailed analysis of cell interactions at each layer in correlation to their local microenvironments.

Preliminary results show that primary macrophages can be polarized into specific phenotypes, characterized via qPCR, flow cytometry and immunostaining, can retain plasticity in the TRACER strips and can survive in co-culture with patient-derived organoids. Future experiments involve correlating macrophage phenotype to hypoxic and metabolic graded profiles using metabolomics and scRNA-seq, with the aim of capturing the full landscape of tumour-macrophage reprogramming in the TME to identify a novel class of immunomodulatory drug targets, and subsequently validate these targets in vivo.