Effects of Bacillus thuringiensis kurstaki on Malpighian Tubule Cells of Thaumetopoea pityocampa (Lepidoptera: Thaumetopoeidae) Larvae

Compared to current treatments including surgery, radiation therapy, and chemotherapy, PDT offers the advantage of an effective and selective method of destroying diseased tissues without damag- ing surrounding healthy tissues. One of the aspects of antitumour effectiveness of PDT is related to the dis- tribution of photosensitizing drugs. The localization of photosensitizers in cytoplasmic organelles during PDT plays a major role in the cell destruction; therefore, intracellular localization of Ph in malignant and nor- mal cells was investigated. The cell lines used throughout the study were: human malignant A549, MCF-7, Me45 and normal endothelial cell line HUV-EC-C. After incubation with Ph cells were examined using fluorescence and confocal microscopy to visualize the photosensitizer accumula- tion. For cytoplasm and mitochondria identification, cells were stained with CellTracker Green and MitoTracker Green, respectively. Distribution of Ph was different in malignant and normal cells and depen- dent on the incubation time. The maximal concentra- tion of Ph in two malignant cell lines (A549 and MCF-7) was observed after 4 hours of incubation, and the most intensive signal was observed around the nuclear envelope. Intracellular distribution of Ph in the Me45 cell line showed that the fluorescence emitted by Ph overlaid that from MitoTracker. This indicates preferential accumulation of the sensitizer in mito- chondria. Our results based on the mitochondrial localization support the idea that PDT can contribute to elimina- tion of malignant cells by inducing apoptosis, which is of physiological significance.