title: The new sensitizing agents for photodynamic therapy: 21-selenaporphyrin and 21-thiaporphyrin.
abstract: BACKGROUND
  Photodynamic therapy may be a promising treatment for patients with tumors. The mechanism of its action is poorly understood and different from the cytotoxic effects induced by antitumor drugs.
  
  
  METHODS
  New sensitizers, termed as 21-selenaporphyrin (SEP) and 21-thiaporphyrin (STSP) were studied for their photocytotoxicity in vitro against selected human cancer cell lines. This study was followed by in vivo screening of the effect of SEP using an animal tumor model. The activity of the new agents was compared with that of a known photosensitizer, namely chlorin e6. In our selection of the cell lines applied for in vitro study, the possible accessibility and effectiveness of photodynamic therapy (PDT) for treatment of colon and urinary bladder cancers, was considered.
  
  
  RESULTS
  New compounds appeared to be not toxic for tested cells in culture, without exposure to light. The STSP exerted in vitro effects comparable with chlorin e6 photocytotoxicity, while SEP appeared to be ineffective. However, in vivo experiments performed in a BFS1 fibrosarcoma tumor model in mice showed that the SEP was at least as much effective as chlorin e6 in the induction of tumor necrosis. In contrast to chlorin e6, SEP-PDT induced no skin sensitization.
  
  
  CONCLUSIONS
  Both new sensitizers can be applied in PDT at no risk of skin damage. The mechanism of the action of these two compounds is probably different, i.e. the 21-thiaporphyrin possibly acts directly on tumor cells and the 21-selenaporphyrin via endothelial cells of newly formed tumor vasculature.
authors.affiliation: Department of Tumor Immunology, Polish Academy of Sciences, Wrocław, Poland.
authors.forename: E
authors.initials: E
authors.lastname: Marcinkowska
authors.forename: P
authors.initials: P
authors.lastname: Ziółkowski
authors.forename: E
authors.initials: E
authors.lastname: Pacholska
authors.forename: L
authors.initials: L
authors.lastname: Latos-Grazyński
authors.forename: P
authors.initials: P
authors.lastname: Chmielewski
authors.forename: C
authors.initials: C
authors.lastname: Radzikowski
mesh_terms: D000818:Animals; D006801:Humans; D051379:Mice; D009336:Necrosis; D016566:Organoselenium Compounds / Q000009:adverse effects; D010778:Photochemotherapy; D017319:Photosensitizing Agents; D011166:Porphyrins / Q000009:adverse effects; D012867:Skin / Q000473:pathology; D013057:Spectrum Analysis; D014407:Tumor Cells, Cultured
chemical_list: C101412:5,20-bis(4-sulfophenyl)-10,15-bis(2-methoxy-4-sulfophenyl)-21-thiaporphyrin; C109728:5,20-bis(4-tolyl)-10,15-(2-sulfophenyl)-21-selenaporphyrin; D016566:Organoselenium Compounds; D017319:Photosensitizing Agents; D011166:Porphyrins