In vitro Proof of Concept of Photodynamic Therapy Efficiency in the Treatment of Glioblastoma

5-ALA photodynamic therapy (5-ALA-PDT) could be a novel approach to treat glioblastoma. However, we observed an in vitro resistance of human glioblastoma cells to 5-ALA-PDT. ABCG2, a transporter responsible of the efflux of the photosensitizer protoporphyrine IX (PpIX) could be implied in this resistance. We aimed here to correlate PpIX accumulation and ABCG2 transporter expression with the efficacy of in vitro PDT on glioblastoma. For each of 6 cell lines (4 glioblastomas, 2 controls), assessment of: cell death after PDT (Cell viability); PpIX metabolization and efflux (fluorometry); ABCG2 transporter transcriptomic expression (RTqPCR) and proteinic expression (Western-blot; flow cytometry); PpIX and ABCG2 transporter localization (Confocal microscopy). We have observed different time and dose dependent PDT efficacy and PpIX metabolization regarding the different cell lines studied. There is a correlation between intracellular PpIX, its efflux, and PDT efficacy. Our preliminary results need to be correlated with ABCG2 expression.