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6th ESACP Congress, Heidelberg, April 7-11, 1999 |
A125
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.
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