Phototoxicity of flavoprotein miniSOG induced by bioluminescence resonance energy transfer in genetically encoded system NanoLuc-miniSOG is comparable with its LED-excited phototoxicity.

Photodynamic therapy (PDT) is a clinical, minimally invasive method for destroying cancer cells in the presence of a photosensitizer, oxygen, and a light source. The main obstacle for the PDT treatment of deep tumors is a strong reduction of the excitation light intensity as a result of its refraction, reflection, and absorption by biological tissues. Internal light sources based on bioluminescence resonance energy transfer can be a solution of this problem. Here we show that luciferase NanoLuc being expressed as a fusion protein with phototoxic flavoprotein miniSOG in cancer cells in the presence of furimazine (highly specific NanoLuc substrate) induces a photodynamic effect of miniSOG comparable with its LED-excited (Light Emitting Diode) phototoxicity. Luminescence systems based on furimazine and hybrid protein NanoLuc-miniSOG targeted to mitochondria or cellular membranes possess the similar energy transfer efficiencies and similar BRET-induced cytotoxic effects on cancer cells, though the mechanisms of BRET-induced cell death are different. As the main components of the proposed system for BRET-mediated PDT are genetically encoded (luciferase and phototoxic protein), this system can potentially be delivered to any site in the organism and thus may be considered as a promising approach for simultaneous delivery of light source and photosensitizer in deep-lying tumors and metastasis anywhere in the body.