Abstract
The past decade has seen a resurgence of interest in photodynamic therapy (PDT), whereby malignant lesions are illuminated by lamps or endoscopically delivered laser beams after administration of malignant tissue-specific photosensitizers. Interest has heightened due to the first report of 5-year disease-free survival of a case of lung cancer treated only by this modality. However controversy has remained as to the exact site of uptake of the photosensitizers and also the effect of PDP at the cellular level.
Movement of mitochondria was reported based on the movement of granules in organella in the 19th century and was demonstrated. in detail by phase microscopy in the year 1954. No report, however, has demonstrated any difference in the mitochondrial movement of normal and tumor cells.
In order to observe possible differences in metabolic activity between normal cells and tumor cells, the mitochondrial movements of normal cells and tumor cells to which those normal cells had been transformed were compared. Photosensitizers which have been reported to have a high affinity for mitochondria induce degeneration and destruction of mitochondria through the production of singlet oxygen. We examined the degree of damage to mitochondria, as indicated by the diminution of mitochondrial movement, and also the exact site of uptake of the photosensitizer, by allowing a photosensitizer to be taken up by tumor cells and applying light.
Our results suggest that there is a significantly greater amount of movement by mitochondria. in malignant cells than in normal cells, that different photosensitizers have different intracellular uptake sites and that this can affect the effects on cells containing such photosensitizers when light is applied.
