title: Effects of hypericin and a chlorin based photosensitizer alone or in combination in squamous cell carcinoma cells in the dark.
abstract: BACKGROUND
  The toxic influence of photosensitizers in the dark is poorly investigated. In our study we used the photosensitizers liposomal meso-tetrahydroxyphenyl chlorin derivative (Foslipos(®)) and hypericin as well as their 1:1 combination on two different head and neck squamous cell carcinoma (HNSCC) cell lines (UMB-SCC 745 and UMB-SCC 969).
  
  
  METHODS
  We examined uptake, efflux and localization of the photosensitizers with confocal microscopy. Fluorescence quantification was measured with a micro-plate spectrometer. Special interest was given to effects on cell proliferation (BrdU proliferation assay), RNA quality (Bioanalyzer measurements) and DNA damage (comet assays) in the dark.
  
  
  RESULTS
  Foslipos(®) uptake was linear over time and its efflux was not achieved even after 24 h while uptake of hypericin reached a plateau after 5 h and was almost eliminated after 24 h. Localization of Foslipos(®) was organelle-unspecific. Hypericin was found mainly at membranes and in trans-golgi network. Foslipos(®) treated cells showed cell toxicity for the highest concentration (10 μg/mL). In contrast, hypericin was toxic for all concentrations (10-0.6 μg/mL). The photosensitizer combination was non-toxic for all concentrations (10-0.6 μg/mL). No changes in RNA quality were monitored. Initial DNA damage was found only in hypericin treated UMB-SCC 745, which recovered after 3h. No significant DNA damage was found for UMB-SCC 969.
  
  
  CONCLUSIONS
  Our data shows that the combinatorial application decrease photosensitizer toxicity, which can be advantageous in PDT treatments.
authors.affiliation: Institute of Anatomy, University of Zürich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland. emina.besicgyenge@uzh.ch
authors.forename: Emina
authors.initials: E
authors.lastname: Besic Gyenge
authors.forename: Patrick
authors.initials: P
authors.lastname: Forny
authors.forename: Daniel
authors.initials: D
authors.lastname: Lüscher
authors.forename: Andrea
authors.initials: A
authors.lastname: Laass
authors.forename: Heinrich
authors.initials: H
authors.lastname: Walt
authors.forename: Caroline
authors.initials: C
authors.lastname: Maake
mesh_terms: D000873:Anthracenes; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000187:drug effects; D003624:Darkness; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D006801:Humans; D008081:Liposomes; D008652:Mesoporphyrins / Q000008:administration & dosage / Q000494:pharmacology*; D018307:Neoplasms, Squamous Cell / Q000188:drug therapy*; D010569:Perylene / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000494:pharmacology*; D012313:RNA / Q000187:drug effects; D021601:trans-Golgi Network / Q000187:drug effects
chemical_list: D000873:Anthracenes; D004338:Drug Combinations; D008081:Liposomes; D008652:Mesoporphyrins; D017319:Photosensitizing Agents; D010569:Perylene; D012313:RNA; C004965:hypericin; C072269:temoporfin