SURG-06CALCITRIOL SELECTIVELY ENHANCE QUALITY OF 5-AMINOLEVULINIC ACID METABOLIC IMAGING IN GLIOMAS

Abstract

INTRODUCTION: Gliomas are characterized by their local invasiveness and poor prognosis. It has been demonstrated that the survival benefit is associated with the extent of surgical resection. But it is difficult to distinguish tumor margins due to the infiltrative nature, and gliomas often recur within 2-3 cm from the borders of the resection cavity. Recently, 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. However, insufficient protoporphyrin IX accumulation may limit the benefits of it in low-grade glioma and the marginal area. 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 were assessed. Furthermore, expression of porphyrin synthetic enzymes in pretreated glioma cells was analyzed. RESULTS: Calcitriol can be administered prior to ALA as a non-toxic preconditioning regimen to significantly enhance ALA- induced PpIX levels and fluorescence. This increase in PpIX level was detected preferentially in glioma versus normal cells. Furthermore, mechanistic studies documented that expression of the porphyrin synthesis enzymes coproporphyrinogen oxidase was increased by calcitriol at the mRNA level. CONCLUSION: We demonstrated for the first time a simple, non-toxic and highly effective preconditioning regimen to selectively enhance PpIX fluorescence in glioma cells. This finding suggests that the combined treatment of glioma cells with calcitriol plus ALA may provide an effective and selective therapeutic modality to enhance ALA-induced PpIX fluorescent quality for improving discrimination of tumor tissue.