gms | German Medical Science

Background: Recurrent disease, multidrug resistance, and delayed diagnosis are major limitations in the therapy of HNSCC. Therefore novel diagnostic/therapeutic options (theragnostics) are desirable. A new innovative approach might be photodynamic therapy (PDT) using hypericin for visualization and treatment of these tumors. The aim of this study was to investigate in vitro effects of hypericin on HNSCC cells and to evaluate PDT as a possible tool for further treatment studies.

Methods: 20000 FaDu cells were incubated with different concentrations (0–50 µM) of hypericin. Hypericin uptake was evaluated by Fluorescence-microscopy. For PDT, cells were irradiated with white light for different time periods (0–25 min). Cytopathologic effects were assessed morphologically. Cells were investigated for cell vitality (MTT) and apoptosis (TUNEL). 100000 DsRed-transfected FaDu cells were xenotransplanted into a quadruple set of nude mice. Tumors were analyzed by OV 100 and fpVCT before and after Hypericin treatment.

Results: A 100% uptake of hypericin was found within HNSCC cells. Hypericin without exposure to white light had no influence on tumor cell biology. After irradiation, PDT resulted in a nearly complete inhibition of cell growth. TUNEL revealed relevant amounts of apoptosis. Mice developed distinct tumors detectable in fpVCT and by OV100. Hypericin-induced PDT had identical effects on FaDu in vitro and in vivo.

Conclusion: Our data suggest hypericin as a novel tool for visualization and PDT of HNSCC. Double imaging using transfected cells and Hypericin offers new possibilities in theragnostics of HNSCC. In future, bioimaging might even allow to track the effective drug compounds (e.g. O₂ ⁺) topologically at the single cell level in vivo.