Isolation of primary cancer-associated fibroblasts from a syngeneic murine model of breast cancer for the study of targeted nanoparticles

Cancer-associated fibroblasts (CAFs) are key actors in the context of the tumor microenvironment. Despite being reduced in number as compared to tumor cells, CAFs regulate tumor progression and provide protection from antitumor immunity. Emerging anticancer strategies aim to remodel the tumor microenvironment through the ablation of pro-tumorigenic CAFs or reprogramming of CAFs functions and their activation status. A promising approach is the development of nanosized delivery agents able to target CAFs, thus allowing the specific delivery of drugs and active molecules. In this context, a cellular model of CAFs may provide a useful tool for in vitro screening and preliminary investigation of such nanoformulations. This study describes the isolation and culture of primary CAFs from the syngeneic 4T1 murine model of triple-negative breast cancer. Magnetic beads were used in a 2-step separation process to extract CAFs from dissociated tumors. Immunophenotyping control was performed using flow cytometry after each passage to verify the process yield. Isolated CAFs can be employed to study the targeting capability of different nanoformulations designed to tackle the tumor microenvironment. Fluorescently labeled H-ferritin nanocages were used as candidate nanoparticles to set up the method. Nanoparticles, either bare or conjugated with a targeting ligand, were analyzed for their binding to CAFs. The results suggest that ex vivo extraction of breast CAFs may be a useful system to test and validate nanoparticles for the specific targeting of tumorigenic CAFs.