Calcitriol enhances 5-aminolevulinic acid-induced fluorescence and the effect of photodynamic therapy in human glioma.

AbstractBackground. Glioma recurrence frequently occurs close to the marginal area of the surgical cavity as a result of residual infiltrating glioma cells. Fluorescence-guided surgery with 5-aminolevulinic acid (ALA) for resection of gliomas has been used as an effective therapeutic approach to discriminate malignant tissue from brain tissue and to facilitate patient prognosis. ALA-based photodynamic therapy is an effective adjuvant treatment modality for gliomas. However, insufficient protoporphyrin IX (PpIX) accumulation may limit the applicability of fluorescence-guided resection and photodynamic therapy in the marginal areas of gliomas. Methods. To be able to understand how to overcome these issues, human glioma cells and normal astrocytes were used as the model system. Glioma cells and astrocytes were preconditioned with calcitriol for 48 hours and then incubated with ALA. Changes in ALA-induced PpIX fluorescence and cell survival after light exposure were assessed. Furthermore, expression of porphy...