Subcellular colocalization of hypericin with respect to endoplasmic reticulum and Golgi apparatus in glioblastoma cells.

To improve the poor prognosis of patients suffering from malignant glioma, hypericin (HYP)-based photodynamic therapy might be a promising approach. Intracellular localization of HYP was investigated by quantitative colocalization analysis with respect to endoplasmic reticulum (ER) and Golgi apparatus (GA) by double staining experiments with fluorescence microscopy. U373 MG glioblastoma cells were stained with HYP and costainings were applied for specific organelle markers for ER and GA. In cells double-stained with HYP and ER-Tracker, 57% of HYP signals were found within the ER and 52% of the ER compartment showed HYP signals. The colocalization fraction of HYP found in the GA was 36% and 46% of the GA showed HYP signals. In glioblastoma cells, a considerable fraction of HYP is localized in the ER; in addition, a significant amount of the photosensitizer shows colocalization with the GA.