UI-103

Patients with pancreatic ductal adenocarcinoma (PDAC) derive limited benefits from chemotherapy or immunotherapy, with a five-year survival rate still below 10 %. The key therapeutic challenge is the dense fibrosis barrier driven by activated cancer-associated fibroblasts (CAFs) and their secreted collagen, which impedes drug penetration and characterizes PDAC as an immune-desert tumor. To address this challenge, we developed in vivo chimeric antigen receptor macrophages (FAP-CAR-M) targeting fibroblast activation protein-α (FAP), the marker of activated CAFs, to enhance chemo and immunotherapy against PDAC by removing the fibrosis barrier using mannose-modified mRNA-LNP (MLNP). Our results demonstrate that mRNA-MLNP can efficiently reprogram M2 macrophages into FAP-CAR-M. With the FAP-CAR-M treatment, the activated CAF markers (FAP), collagen volume fraction (CVF), and the type I collagen (Col1a1) secretion were decreased by 3-fold, 5-fold, and 4-fold inan orthotopic mouse model of PDAC, respectively. By removing the fibrosis barrier, FAP-CAR-M enhanced the penetration of gemcitabine (GEM) and immune cells, improved PDAC sensitivity to chemo and immunotherapy, and significantly prolonged survival. Therefore, in vivo FAP-CAR-M may represent a potential therapeutic approach to enhance chemo and immunotherapy against PDAC by removing the fibrosis barrier.

Cancer immunotherapy has yielded remarkable results across a variety of tumor types. Nevertheless, the complex and immunosuppressive microenvironment within solid tumors poses significant challenges to established therapies such as immune checkpoint blockade (ICB) and chimeric antigen receptor T-cell (CAR-T) therapy. Within the milieu, tumor-associated macrophages (TAMs) play a significant role by directly suppressing T-cell functionality and fostering an immunosuppressive environment. Effective regulation of TAMs is, therefore, crucial to enhancing the efficacy of immunotherapies. Various therapeutic strategies targeting TAM modulation have emerged, including blocking TAM recruitment, direct elimination, promoting repolarization toward the M1 phenotype, and enhancing phagocytic capacity against tumor cells. The recently introduced CAR macrophage (CAR-M) therapy opens new possibilities for macrophage-based immunotherapy. Compared with CAR-T, CAR-M may demonstrate superior targeting and infiltration capabilities toward solid tumors. This review predominantly delves into the origin and development process of TAMs, their role in promoting tumor growth, and provides a comprehensive overview of immunotherapies targeting TAMs. It underscores the significance of regulating TAMs in bolstering antitumor therapies while discussing the potential and challenges of developing TAMs as targets for immunotherapy.