OBJECTIVETo investigate the effect of 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT) on MGC-803 human gastric cancer cells in vitro.

METHODSMGC-803 human gastric cancer cells were treated with 5-ALA at various concentrations followed by laser irradiation. The cells were also treated with 5-ALA at the same concentration before laser exposure at various doses. PDT-induced phototoxicity of the cells was determined by MTT assay.

RESULTSAfter laser exposure of the cells at the same dose (25.0 J/cm(2)), the cell survival rates decreased significantly with incubation of the cells with 5-ALA at 0.25, 0.5, 1.0, 2.0 and 4.0 mmol/L, respectively (F=266.39, P<0.001), but 2.0 and 4.0 mmol/L ALA showed no significant difference in lowering the cell survival rates (P>0.05). Following treatment with the same 5-ALA concentration (1 mmol/L), the cell survival rates decreased in response to increased laser doses (at 6.25, 12.5, 25.0, 50.0, and 100 J/cm(2), respectively, F=226.31, P<0.0001). Without laser exposure, the survival rate of the cells did not significantly change for different 5-ALA concentrations (F=0.79, P=0.5383), nor did it undergo obvious variation in response to different laser doses without 5-ALA incubation (F=0.61, P=0.6551).

CONCLUSIONSThe damage of MGC-803 cells by PDT increases with 5-ALA concentration within a relative lower range and is proportional to the laser doses delivered. Without 5-ALA treatment, the laser at the chosen dose cannot produce photodynamic effect and ALA itself is nontoxic. ALA-mediated PDT appears to be a promising therapy for gastric cancer.