6th ESACP Congress, Heidelberg, April 7-11, 1999

A125
PHOTOSENSITIZER ACCUMULATION, INTRACELLULAR LOCALISATION AND PHOTODYNAMIC TREATMENT OF UROTHELIAL CELL LINES FOLLOWING INCUBATION WITH 5-AMINOLEVULINIC ACID
Seidl J, Krieg R, Fickweiler S, Knüchel R

Institute of Pathology, University of Regensburg, Regensburg, Germany

Aim: Photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA) is of rapidly growing interest in treatment of bladder cancer. However, only little information is available about intracellular ALA-induced protoporphyrin IX (PPIX) accumulation and subsequent pathways to cell death. The aim of our study was to investigate PPIX accumulation and intracellular localisation, both relevant for the effectiveness of PDT. Methods: Two bladder carcinoma cell lines (RT4, J82) and a normal urothelial cell line (UROtsa) were incubated with ALA (100Ág/ml) for 30-180 minutes. Accumulation of the photosensitizer PPIX was quantified using flow cytometry. PDT was performed using incoherent light at different wavelength ranges (<450nm, >460nm, >590nm, 400-700nm) and light doses (0Jcm-2-20Jcm-2). Cellular PPIX distribution was analysed using fluorescence microscopy and co-staining for mitochondria. Results: RT4 cells, derived from a well differentiated carcinoma, showed higher PPIX accumulation than J82 and UROtsa (RT4>J82>UROtsa). The response to PDT was higher for RT4 than for J82 and UROtsa for all wavelength ranges used (RT4>J82=UROtsa). In RT4 cells the photosensitizer is located in cytoplasmic and/or membrane regions for each incubation time. The same PPIX distribution is seen in J82 and UROtsa after long incubation times (180 minutes), whereas short incubation intervals (30 minutes) lead to a distinct but not mitochondrial localisation. Conclusions: Higher PDT effectiveness may partly be due to higher PPIX accumulation (RT4). Similar responses of J82 and UROtsa, although having different PPIX content, can not be explained by sensitizer localisation. Future experiments have to investigate cell damaging and repair mechanisms to clarify this effect.