Susceptibility of Malignant Brain Tumors to 5-aminolaevulinic Acid Mediated Photodynamic Therapy: Direct Phototoxicity and Immunological Effects

Recently we published the article ‘Accumulation of protoporphyrin IX in medulloblastoma cell lines and sensitivity to subsequent photodynamic treatment’ [1]. In this commentary, we review protoporphyrin IX accumulation after application of 5-aminolaevulinic acid and the resulting sensitivity of medulloblastoma cells to photodynamic therapy. We compare the results to glioblastoma cells, including glioblastoma stem-like cells, and address the contribution of the transporter adenosine triphosphate binding cassette subfamily G member 2 (ABCG2) as well as the enzyme ferrochelatase to the process. We discuss possible strategies to improve efficiency of photodynamic therapy, particularly in the clinical setting and highlight the contribution of the antitumoral immune response to the efficacy of this novel treatment modality for brain tumors.