ESTRO 2025 - Abstract Book

S3900

Radiobiology - Microenvironment

ESTRO 2025

penetration and tumour radiosensitivity. We propose a preclinical micro-physio/pathological system to replicate such microenvironment on-chip and predict chemo-radiation outcomes in pancreatic cancer.

Material/Methods: The microfluidic chip mold was fabricated via 3D printing. The chip was realized by replica molding [3]. Tumour spheroids were obtained with a co-culture of MiaPaCa2 cancer cells and PSCs by liquid overlay technique (LOT). The microvascular network on-chip was obtained by self-assembling, seeding pancreatic endothelial cells and PSCs within a fibrin gel. A custom Fiji macro was implemented to enable high-throughput, observer-independent analysis of tumor spheroid growth rates. Tumour spheroids were further characterized through immunohistochemistry (IHC). Results: The microfluidic chip design successfully incorporates two independent but communicant compartments: a PDAC microenvironment compartment and a vascular microenvironment one (Figure 1a). The PDAC microenvironment consists of tumour spheroids in a desmoplastic-like setting. LOT yielded reproducible spheroids, exhibiting growth up to 14 days, when seeding 500-1 000 cells/well, with a MiaPaCa2 cells to PSCs ratio of 2:1 (Figure 2a). Given its key contribution to PSCs activation, we selected TGF-β as an additive, which significantly enhanced spheroids’ circularity and brought aspect ratio values closer to 1 (Figure 2b). We further generated stratified spheroids to spatially organize a cancer cell core surrounded by an external layer of stromal cells, mimicking the spatial organization typical of PDAC. These spheroids maintained their structural integrity when embedded in fibrin gels (Figure 1b) and presented an external proliferative layer of cells, as revealed by IHC (Figure 2c). For the vascular compartment, we demonstrated the feasibility of obtaining a pancreatic-specific microvascular network in vitro (Figure 1c).