5-Aminolevulinic acid-mediated photodynamic therapy using light-emitting diodes of different wavelengths in a mouse model of peritoneally disseminated gastric cancer

Background5-Aminolevulinic acid (5-ALA) is a precursor of the strong photosensitizer, protoporphyrin IX, in cancer cells. The efficacy of 5-ALA–mediated photodynamic therapy (ALA-PDT) using light-emitting diodes (LEDs) was evaluated in a mouse model of peritoneally disseminated gastric cancer.Materials and methodsThe effects of violet (peak wavelength 410 nm), green (peak wavelength 525 nm), and red (peak wavelength 635 nm) LEDs on reactive oxygen species generation and ALA-PDT cytotoxicity were measured in vitro. 5-ALA was intraperitoneally injected into a mouse xenograft model of peritoneally disseminated enhanced green fluorescent protein-expressing MKN-45 cells, followed by irradiation of micrometastatic nodules on the omentum and evaluation of the necrotic areas of these nodules.ResultsROS generation and the cytotoxic effects of ALA-PDT were highest for the violet and lowest for the red LEDs. The necrotic areas of nodules were significantly larger after irradiation with each LED than in the control mice. The violet and green LEDs had the same anticancer effects, which were significantly greater than those of the red LED.ConclusionsALA-PDT using LEDs was effective in treating peritoneally disseminated gastric cancer. The differences in the anticancer effects among the three light sources indicate the necessity of selecting the light source with the optimal wavelength most effective for in vivo clinical applications.