X‐ray‐Guided In Situ Genetic Engineering of Macrophages for Sustained Cancer Immunotherapy

Abstract Effective repolarization of macrophages has emerged as a promising approach for anticancer therapy. However, there are very few studies on the effect of reprogramming macrophages from M2 phenotype to M1 phenotype without reconversion while maintaining an activated M1 phenotype. Moreover, these immunomodulatory methods have serious drawbacks due to the activation of normal monocytic cells. Therefore, it remains a challenge to selectively reprogram tumor‐associated macrophages (TAMs) without systemic toxicities. Here, X‐ray‐guided and triggered remote control of a CRISPR/Cas9 genome editing system (X‐CC9) that exclusively activates therapeutic agents at tumor sites is established. Under X‐ray irradiation, X‐CC9 selectively enhances M2‐to‐M1 repolarization within the tumor microenvironment, and significantly improves antitumor efficacy with robust immune responses in two animal models. This strategy provides an ideal method for improving the safety of macrophage polarization and may constitute a promising immunotherapy strategy.