CRISPR-Cas9-Loaded Theranostic Liposomes for Enhancing Radiosensitization of Prostate Cancer through POLD4 Gene Editing under Real-Time MRI Monitoring.

Radiotherapy is a fundamental treatment for prostate cancer; however, its therapeutic efficacy is frequently limited by radioresistance mediated through DNA repair mechanisms and other biological factors. Although gene therapy holds promise for overcoming such resistance, identifying effective radiosensitization targets and developing efficient gene delivery systems remain practically challenging. In this study, transcriptomic analysis of radiotherapy-treated prostate cancer cells revealed a marked upregulation of DNA polymerase delta subunit 4 (POLD4), a target that has not been systematically studied. To evaluate the potential of POLD4 for overcoming radioresistance, CRISPR-Cas9-based plasmids along with ultrasmall superparamagnetic iron oxide nanoparticles (USPIONs) were encapsulated within cationic liposomes for achieving an MRI-trackable gene delivery platform (plasmid and iron oxide co-loaded liposomes, termed PIO@Lipo). Comprehensive in vitro and in vivo studies demonstrated that PIO@Lipo enabled efficient POLD4 knockdown. Furthermore, PIO@Lipo synergized with radiotherapy to induce extensive DNA damage, promote tumor cell apoptosis, and remodel the immunosuppressive microenvironment. Notably, PIO@Lipo displayed superior MRI contrast enhancement capability and passive tumor targeting ability. In conclusion, this study has identified POLD4 as a potent target for radiosensitization, capable of disrupting DNA damage-repair homeostasis through MRI-monitored gene editing, thereby offering a promising strategy to enhance the efficacy of radiotherapy in prostate cancer.