KillerRed protein basedin vivophotodynamic therapy and corresponding tumor metabolic imaging

Abstract

Photodynamic therapy (PDT) gains wide attention as a useful therapeutic method for cancer. It is mediated by the oxygen and photosensitizer under the speci¯c light irradiation to produce the reactive oxygen species (ROS), which induce cellular toxicity and regulate the redox potential in tumor cells. Nowadays, genetic photosensitizers of low toxicity and easy production are required to be developed. KillerRed, a unique red°uorescent protein exhibiting excellent phototoxic properties, has the potential to act as a photosensitizer in the application of tumor PDT. Meantime, the course of tumor redox metabolism during this treatment was rarely investigated so far. Thus here, we investigated the e®ects of KillerRed-based PDT on tumor growth in vivo and examined the subsequent tumor metabolic states including the changes of nicotinamide adenine dinucleotide hydrogen (NADH) and°avoprotein (Fp), two important metabolic coenzymes of tumor cells. Results showed the tumor growth had been signi¯cantly inhibited by KillerRedbased PDT treatment compared to control groups. A home-made cryo-imaging redox scanner was used to measure intrinsic°uorescence and exogenous KillerRed°uorescence signals in tumors. The Fp signal was elevated by nearly 4.5-fold, while the NADH signal decreased by 66% after light irradiation, indicating that Fp and NADH were oxidized in the course of KillerRedbased PDT. Furthermore, we also observed correlation between the°uorescence distribution of * Corresponding author.† These authors contributed equally to this work. KillerRed and NADH. It suggests that the KillerRed protein based PDT might provide a new approach for tumor therapy accompanied by altering tumor metabolism.

Effects of Photodynamic Therapy on Tumor Metabolism and Oxygenation Revealed by Fluorescence and Phosphorescence Lifetime Imaging

“…Its red-shifted fluorescence emission makes it possible to perform a combined imaging with endogenous fluorescence of metabolic cofactors NAD(P)H and flavins and, therefore, to gain an insight into metabolic mechanisms of cellular-targeted PDT. This opportunity was first demonstrated by Lin et al [41]. The authors assessed autofluorescence intensity of NAD(P)H and flavins in tumors' cryo-sections and showed that NAD(P)H and flavoproteins were oxidized in the course of KillerRed-based PDT.…”

Dynamic visualization of the whole process of cytotoxic T lymphocytes killing B16 tumor cells in vitro

“…[7][8][9][11][12][13] The confocal imaging enables tracking several cellular or molecular events dynamically at high resolution in real time via multichannel parallel detections. [14][15][16][17] In order to visualize the quick changing interactions between tumor cells and CTLs, fluorescent proteins (FPs) and fluorochromes are used to label tumor cells [18][19][20] and CTLs. 8,21,22 Recent studies have studied the kinetics of individual CTL sequentially killing multiple target tumor cells in vitro through microscopy-based methods.…”