| Summary: | 碩士 === 長庚大學 === 基礎醫學研究所 === 95 === Autophagy is a self-cannibalization process via lysosomes. Initially functions as a cell survival mechanism for energy homeostasis and for removal of damaged organelles, autophagy can also entail cell demise when in excess. Our previous study has shown that inoculation of laser-irradiated B16F10 melanoma cells following 3-hours of Photofrin® treatment results in adaptive anticancer immunity. Dead cells thus prepared serve as a better vaccine than those prepared by freezing and thawing. In this study we used electron microscopy to examine the subcellular events upon Photofrin®-laser treatment. We found that instead of apoptotic morphology, the dying cells exhibited numerous cytoplasmic vacuoles, a feature indicative of autophagic or type II- programmed cell death. Subsequent time course study revealed that Photofrin® alone without irradiation was able to induce autophagy even in the presence of serum. Furthermore, autophagocytosed materials such as mitochondria and melanosomes were seen discharged out of the cells. This process, designated “defecation” by De Duve, appeared to be promoted by the coupling of Photofrin® and irradiation. In addition, we have also found variously-sized microparticles in the supernatant of vaccines that exhibit immuno-potency. We propose the autophagic vacuole-derived defecants (ADD), of which exosomes are also a component, function as a vehicle of tumor antigens, which in concert with antigen presentation cells, account for the efficacy of tumor vaccination.
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