Genetically encoded BRET-activated photodynamic therapy for the treatment of deep-seated tumors

Photodynamic therapy(PDT)is one of the most appealing photonic modalities for cancer treatment based on anticancer activity of light-induced photosensitizer-mediated reactive oxygen species(ROS),but a limited depth of light penetration into tissues does not make possible the treatment of deep-seated neoplasms and thus complicates its widespread clinical adoption.Here,we introduce the concept of genetically encoded bioluminescence resonance energy transfer(BRET)-activated PDT,which combines an internal light source and a photosensitizer(PS)in a single-genetic construct,which can be delivered to tumors seated at virtually unlimited depth and then triggered by the injection of a substrate to initiate their treatment.To illustrate the concept,we engineered genetic NanoLuc-miniSOG BRET pair,combining NanoLuc luciferase flashlight and phototoxic flavoprotein miniSOG,which generates ROS under luciferase-substrate injection.We prove the concept feasibility in mice bearing NanoLuc-miniSOG expressing tumor,followed by its elimination under the luciferase-substrate administration.Then,we demonstrate a targeted delivery of NanoLuc-miniSOG gene,via tumor-specific lentiviral particles,into a tumor,followed by its successful elimination,with tumor-growth inhibition(TGI)coefficient exceeding 67%,which confirms a great therapeutic potential of the proposed concept.In conclusion,this study provides proof-of-concept for deep-tissue“photodynamic”therapy without external light source that can be considered as an alternative for traditional PDT.