Homogeneously cross-linked in situ hydrogel enclosing high-density human-cancer cells promotes vascularized in vivo tumor modeling for immune cell therapy

Cancer models in animal studies play a central role in cancer research, particularly in investigating vascularized tumor tissues for the validation of immune cell therapies. However, xenografts relying solely on cancer cells are ineffective for optimal tumor tissue formation. Additionally, tumor modeling using hydrogels with cancer cells to promote vascularization often leaves behind residual biomaterials that inhibit integration with surrounding tissues. To address these issues, we utilized a straightforward in vivo vascularized tumor modeling method with a completely degradable, cross-linker-free carboxymethyl chitosan (CMCTS)/oxidized hyaluronic acid (oHA) hydrogel that encapsulates high-density human cancer cells for in situ injection. The CMCTS/oHA hydrogel was fully degraded within 3 weeks in vitro, enabling three-dimensional (3D) cell condensation. Two weeks after subcutaneous injection in mice, solid tumors formed, with native host vasculature infiltrating the transplanted human cancer cells, confirming spontaneous hydrogel degradation. Following this, human macrophages were administered via tail vein injection, enhancing the accumulation of mouse immune cells in the humanized tumor twofold and showing murine macrophages adjacent to the vasculature. This study thus provides proof-of-concept for a facile and fully vascularized humanized tumor model in mice for validating immune cell therapies.