Engineering a soft tumor microenvironment: fibrin-enriched hydrogels promote cancer cell invasion in 3D bioprinted colorectal cancer models

Accurately modeling the tumor microenvironment is crucial for advancing our understanding of colorectal cancer (CRC) progression and therapeutic response. Three-dimensional (3D) hydrogel-based models that mimic the mechanical properties of native tissue serve as a valuable tool for studying tumor–stromal interactions and tumor invasion in vitro. In this work, we developed a 3D bioprinted CRC model by embedding spheroids and human intestinal fibroblasts (HIFs) within the GelMA–PEGDA and GelMA–PEGDA–Fibrin hydrogels to assess the effect of matrix composition and stiffness on spheroid invasiveness. The addition of fibrin resulted in a softer, more viscoelastic hydrogel that promoted fibroblast migration, elongation, and alignment, facilitating more dynamic tumor–stromal interactions. Moreover, both epithelial-like HT29 and mesenchymal-like SW480 spheroids showed more invasive behavior in GelMA-PEGDA-Fibrin hydrogel. This was reflected in distinct phenotypic responses. HT29 spheroids demonstrated greater growth, irregular morphology, and more interaction with elongated fibroblasts, whereas SW480 spheroids exhibited partial dissociation and disruption with a higher number of dispersed cells in GelMA-PEGDA-Fibrin hydrogel. These findings demonstrate the role of matrix softness in promoting the invasiveness of colorectal cancer. Overall, our results highlight the potential of fibrin-enriched soft hydrogel to mimic key features of the tumor microenvironment, offering a powerful tool for studying CRC invasion dynamics and supporting future applications in drug screening and personalized medicine.