gms | German Medical Science

Objective: Brain tumors are the most frequent solid neoplasms in pediatric patients. Modern therapy concepts including imaging, surgery, radiation, chemo- and immunotherapy improved the prognosis in the past years, yet a gross total resection is still one of the most important survival factors. On the other hand too radical surgery would cause neurological deficits. Radiation of cells containing higher protoporphyrine IX (PPIX) concentrations after exposure to 5-aminolevulinic acid (5-ALA) with a LASER in the wave length 635nm causes cell death in different pathways including apoptosis and necrosis. This method, called Photodynamic therapy (PDT), would allow direct irradiation of residual tumor cells in eloquent areas of the brain. In the past we demonstrated that the application of 5-ALA to typical pediatric brain tumors in vitro elicit the synthesis of PPIX.

Method: Medulloblastoma (DAOY. UW228), pNET (PFSK-1) and rhabdoid tumor (BT16) cell lines were incubated with 5-ALA in variable concentrations for 4 hours. Afterwards cells were irradiated with a LASER beam in the wave length 635nm. After approximately 12 hours WST-1 viability test was performed. The results were compared to cells not incubated with 5-ALA and irradiated with same LASER beam and to cells incubated with 5-ALA without irradiation.

Results: We demonstrated significant cell death in pediatric tumor cells incubated with 5-ALA and irradiated with LASER in comparison to control groups. In DAOY and PFSK-1 cells the death rate was significant above 5-ALA concentration of 50μg/ml (p<.05), UW228 cell had higher death rate above the concentration of 25 μg/ml (p<0.01) and in BT16 cells it was above a concentration of 75 μl/ml (p<0.01). Neither the incubation with 5-ALA alone, in all concentrations mentioned above, nor the lone irradiation with the LASER beam caused a significant cell death.

Conclusions: We conclude that PDT causes death of cells with higher PPIX concentration after exposure to 5-ALA in vitro. This indicates that PDT could be feasible to eliminate residual brain tumor cells in pediatric patients.