Collagen-Based Tumor Spheroid Model for Investigating Tumor-Macrophage Interactions through Extracellular Matrix Remodeling

Macrophages in the tumor microenvironment (TME) can constitute up to 50% of tumor mass and play a critical role in cancer cell proliferation, invasion, and metastasis. While their contribution to extracellular matrix (ECM) degradation through matrix metalloproteinases (MMPs) has been explored, the role of other macrophage-derived factors in ECM remodeling and their impacts beyond degradation remain poorly understood. Here, we describe the development of a 3D collagen-based tumor spheroid model to investigate the impact of peripheral blood mononuclear cell (PBMC)-derived macrophages on cancer cell-ECM and cancer cell-macrophage interactions within the TME. We observed that cancer cells stimulated PBMC-derived macrophages into an M2-like phenotype and that tumor spheroid conditioned macrophages (TSCMs) shifted cancer cell populations toward phenotypes with greater invasion distances and reduced circularity, indicative of increased malignancy. Such observations can be explained by macrophage-mediated ECM remodeling. Specifically, we demonstrate that TSCMs secreted a variety of soluble factors that are known to contribute to ECM remodeling, including ECM degradation and fiber realignment. These processes collectively create a tumor-favoring environment by loosening the collagen matrix and aligning fibers that serve as invasion tracks for migrating tumor cells that facilitate cancer cell migration and invasion. This model provides a robust platform to study the interactions between cellular and non-cellular components in the TME and to identify the molecular mechanisms underlying cancer progression. These insights may aid in the development of novel therapeutic strategies targeting macrophage-mediated processes in cancer.