In vitro and in vivo evaluation of photodynamic techniques for the experimental treatment of human hepatoblastoma and neuroblastoma: preliminary results.

PURPOSE: The purpose of this study was to test the susceptibility of human hepatoblastoma and neuroblastoma cells to photodynamic diagnostics (PDD) and photodynamic therapy (PDT) using 5-aminolevulinic acid (5-ALA) as a photosensitizer.
METHODS: Cell cultures of human hepatoblastoma (HuH6) and neuroblastoma (MHH-NB-11) were incubated with 5-ALA at increasing concentrations to measure the cellular kinetics of photosensitization. After optimizing incubation parameters, the cell cultures were then irradiated with increasing light doses and cell viability was measured by CTB assay. Human fibroblastic cells served as controls. So far, only the hepatoblastoma cell line has been tested in vivo. After injection of HUH6 cells in immunoincompetent rats, the efficacy of PDT was assessed. Photosensitization was achieved by intraperitoneal injection of 5-ALA. The pharmacokinetics of different tissues was studied. In a second study, a PDT of implanted hepatoblastoma, liver and peritoneum was performed. The irradiated areas were excised 48 h after treatment and studied by microscopy.
RESULTS: Cell culture experiments demonstrated a selective fluorescence for both tumor lines compared to controls. The photosensitized tumor cells demonstrated marked reductions in cell viability at significantly lower irradiation doses than the fibroblasts under PDT. The specificity of fluorescence was confirmed in vivo for hepatoblastoma, and all the sensitized and irradiated tumors showed marked phototoxic necrosis.
CONCLUSION: Human hepatoblastoma and neuroblastoma demonstrate marked and specific fluorescence after the application of 5-ALA, making PDD possible. Cell death occurred in both cell lines after PDT in vitro. Additionally, hepatoblastoma was susceptible to PDT in an animal model. Further studies will be necessary to determine the role of PDT and PDD in a clinical setting.