Photodynamic therapy using talaporfin sodium and semiconductor laser induces dose and time dependent cytocidal effect for human glioma derived stem cells

One of the key factors contributing to the poor prognosis of glioblastoma is the treatment resistance of glioma stem cells (GSCs). In this study, the efficacy of photodynamic therapy (PDT) using talaporfin sodium (NPe6), a second-generation photosensitizer, in combination with a semiconductor laser approved for clinical use in Japan was evaluated. The evaluation was performed in a patient-derived glioma stem cell (GSC) line, MGG8, which was established from human glioblastoma tissue. Under favorable oxygenation conditions, NPe6-PDT induced a dose- and fluence-dependent suppression of mitochondrial metabolic activity in MGG8 cells. Both apoptosis and necrosis occurred in a time-dependent manner. Secondary reactive oxygen species (ROS) levels were also increased following PDT, indicating sustained intracellular oxidative stress. Given that GSC resistance is partly attributed to hypoxic microenvironments that diminish treatment-induced oxidative damage, these findings suggest that strategies to enhance tissue oxygenation could improve the therapeutic efficacy of NPe6-PDT against GSCs. To our knowledge, this is the first study to investigate NPe6-PDT in patient-derived GSCs and provides a foundation for future translational research.