title: 2-Bromo-5-hydroxyphenylporphyrins for photodynamic therapy: photosensitization efficiency, subcellular localization and in vivo studies.
abstract: BACKGROUND
  Photodynamic therapy (PDT) is a therapeutic modality capable of inducing cell death by oxidative stress through activation of a sensitizer by light. Aryl-porphyrin with hydroxyl groups are good photosensitizers and presence of bromine atoms can enhance the photodynamic activity through heavy atom effect. These facts and our previous work made pertinent to compare the photodynamic capacity of tetraaryl brominated porphyrin (TBr4) with the corresponding diaryl (BBr2) derivative.
  
  
  METHODS
  Cell cultures were incubated with the sensitizers, ranging from 50nM to 10μM and irradiated until 10J. Cell proliferation was analysed by MTT assay. Flow cytometry studies evaluated cell death pathways, mitochondrial membrane potential and ROS. For in vivo studies Balb/c nu/nu mice were injected with 4×10(6)cells. After PDT, monitoring was carried out for 12 days to establish Kaplan-Meier survival curves. Tumours were excised and histological analysis was performed.
  
  
  RESULTS
  Both sensitizers seem to accumulate in the mitochondria. The molecules have no intrinsic cytotoxicity or in non-tumour cells at therapeutic concentrations. Both sensitizers induced a significant decrease of cell proliferation and growth of xenografts of melanoma and colorectal adenocarcinoma. Diaryl BBr2 is more efficient than tetraaryl TBr4, concerning intracellular ROS production, mitochondrial disruption and induction of cell death. The main cell death pathway is necrosis.
  
  
  CONCLUSIONS
  TBr2 and BBr4 are promising sensitizers with good photodynamic properties and have the ability to induce cell death in human melanoma and colorectal adenocarcinoma in vitro and in vivo. We consider that BBr2 is a molecule that should be the subject of extensive studies towards clinical use.
authors: Biophysics Unit - IBILI, Faculty of Medicine, University of Coimbra, Azinhaga de Santa Comba, Celas, 3000-548 Coimbra, Portugal. mafaldalaranjo@fmed.uc.pt
authors: Mafalda
authors: M
authors: Laranjo
authors: Arménio C
authors: AC
authors: Serra
authors: Margarida
authors: M
authors: Abrantes
authors: Marta
authors: M
authors: Piñeiro
authors: Ana C
authors: AC
authors: Gonçalves
authors: João
authors: J
authors: Casalta-Lopes
authors: Lina
authors: L
authors: Carvalho
authors: Ana B
authors: AB
authors: Sarmento-Ribeiro
authors: António
authors: A
authors: Rocha-Gonsalves
authors: Filomena
authors: F
authors: Botelho
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000493:pharmacokinetics; D011166:Porphyrins / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D013347:Subcellular Fractions / Q000378:metabolism*; D016019:Survival Analysis; D015996:Survival Rate; D014018:Tissue Distribution; D016896:Treatment Outcome
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins