RELATION OF EARLY PHOTOFRIN(R) UPTAKE TO PHOTODYNAMICALLY INDUCED PHOTOTOXICITY AND CHANGES OF CELL-VOLUME IN DIFFERENT CELL-LINES

For efficacy of photodynamic therapy, selective uptake and retention o f photoactive substances has been postulated. Therefore, measurements were performed to find out whether the photosensitiser Photofrin(R) is taken up differently in malignant and non-malignant tells in vitro, I n addition, the sensitivity of malignant cells and nonmalignant cells to photodynamic exposure was investigated, by quantifying viability an d volume alterations of the cells. Bovine aortic endothelial cells, mo use fibroblasts and amelanotic hamster melanoma cells were suspended i n a specially designed incubation chamber under controlled conditions (e.g. pH, pO(2), pCO(2) and temperature), After establishing constant baseline conditions, the cellular fluorescence intensity per cell volu me, indicative of the uptake of Photofrin(R), and cell volume were ass essed by how cytometry, and cell viability was quantified by the trypa n blue exclusion test. Photodynamic exposure of cells was performed us ing an argon-pumped dye laser system via a 600 mu m optical fibre at e nergy density of 4 Joules at the cell surface (40 mW/cm(2), 100 s). In comparison to endothelial and fibroblast cells, the melanoma cells ex hibited no increased uptake of Photofrin(R) and no enhanced sensitivit y to photodynamic therapy (PDT). However, the fluorescence intensity/v olume of endothelial cells was two to three times higher at each conce ntration of the photosensitiser. Following PDT, reduction in cell viab ility was dependent on the concentration of Photofrin(R), and directly correlated with fluorescence intensity per cell volume. In addition, the cells of all three lines, treated by PDT, revealed dose-dependent changes in cell volume. Melanoma cells exhibited the most excessive in crease. It is suggested that selective uptake of photosensitiser in vi tro is not characteristic for tumour cells. The high uptake of Photofr in(R) by endothelial cells may indicate that the vascular endothelium is a major target for PDT, leading to cessation of tumour blood how an d subsequent destruction of tumour tissue. In addition, PDT-induced sw elling of tumour cells might represent and effect synergistically impa iring tumour perfusion, and thereby promoting tumour death.