In vitro photodynamic therapy of nasopharyngeal carcinoma using 5-aminolevulinic acid

Photochemical & Photobiological Sciences Pub Date: 2002-04-29 DOI: 10.1039/B109817A

Abstract

The purpose of this study was to investigate the potential use of 5-aminolevulinic acid (5-ALA, 5-amino-4-oxovaleric acid) induced protoporphyrin IX (PPIX) for photodynamic therapy (PDT) of nasopharyngeal carcinoma (NPC) and its related mechanisms of inducing cell death. PPIX biosynthesis at 1 to 8 h after incubation of a cultured NPC cell line (HNE1) with 5-ALA (10–5000 μg ml?1) was determined via fluorescence analysis. HNE1 cells were irradiated at 4 h after incubation with 5-ALA (10–200 μg ml?1) by diode laser (λ = 630 nm) at various energy levels (1–50 J cm?2). The survival rates at 6, 12, 24 and 48 h after PDT were determined by MTT assay. Mechanisms of PDT-induced cell death were investigated via Annexin-V/propidium iodide staining and DNA electrophoresis. After incubation with 5-ALA, a time- and dose-dependent increase of cellular PPIX-fluorescence was recorded up to a threshold concentration of 1000 μg ml?1 5-ALA, above which a decline of fluorescence intensities occurred. Similar values of PPIX-fluorescence were found at 100–1000 μg ml?1 of 5-ALA. Unlike sole incubation with 5-ALA or sole laser irradiation, the combination of both factors lead to a significant, concentration-, energy- and time-dependent increase of cell death (p < 0.01). At 100 μg ml?1 ALA and 10 J cm?2 laser irradiation, cellular survival was <5% after 48 h. More than 80% of induced cell deaths thereby occurred via apoptosis within the first 12 h following irradiation; necrosis was accountable for less than 20%. High level induction of apoptosis by 5-ALA-PDT was confirmed by DNA electrophoresis. Our investigations show promising results of 5-ALA based PDT of nasopharyngeal carcinoma in vitro and set the basis for future studies in tumor models or humans, respectively.

Graphical abstract: In vitro photodynamic therapy of nasopharyngeal carcinoma using 5-aminolevulinic acid
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