title: Transferrin-conjugated liposome targeting of photosensitizer AlPcS4 to rat bladder carcinoma cells.
abstract: BACKGROUND
  The efficacy and safety of photodynamic therapy for superficial bladder cancer depend on tumor-selective accumulation of the photosensitizer. Bladder transitional-cell carcinoma cells overexpress the transferrin receptor on their surface. We examined whether transferrin-mediated liposomal targeting of the photosensitizer aluminum phthalocyanine tetrasulfonate (AlPcS4) is an effective strategy to attain tumor-selective accumulation of this compound when applied intravesically.
  
  
  METHODS
  AlPcS4 was stably encapsulated in unconjugated liposomes (Lip-AlPcS4) or transferrin-conjugated liposomes (Tf-Lip-AlPcS4). The accumulation of free AlPcS4, Lip-AlPcS4, and Tf-Lip-AlPcS4 in human AY-27 transitional-cell carcinoma cells and in an orthotopic rat bladder tumor model was visualized by fluorescence microscopy. In vitro AlPcS4 accumulation was quantified by fluorescence measurements following drug extraction, and the photodynamic efficacy of AlPcS4 was measured in a clonogenic assay. All statistical tests were two-sided.
  
  
  RESULTS
  AY-27 cells incubated with Tf-Lip-AlPcS4 had much higher intracellular AlPcS4 levels than AY-27 cells incubated with Lip-AlPcS4 (384.1 versus 3.7 microM; difference = 380.4 microM, 95% CI = 219.4 to 541.3; P = .0095). Among rats bearing AY-27 cell-derived bladder tumors, intravesical instillation with Tf-Lip-AlPcS4 resulted in mean AlPcS4 fluorescence in tumoral tissue, normal urothelium, and submucosa/muscle of 77.9 fluorescence units (fu) (95% CI = 69.1 to 86.8 fu), 4.3 fu (95% CI = 4.0 to 4.5 fu), and 1.0 (95% CI = 0.1 to 1.9 fu), respectively, whereas instillation of free AlPcS4 resulted in nonselective accumulation throughout the whole bladder wall, and Lip-AlPcS4 instillation resulted in no tissue accumulation. Photodynamic therapy of AY-27 cells incubated with Lip-AlPcS4 resulted in cell viabilities greater than 90% for all concentrations and incubation times tested; photodynamic therapy of cells incubated with 1 muM Tf-Lip-AlPcS4 or AlPcS4 resulted in cell viabilities of 0.19% (95% CI = 0.02% to 0.36%) and 1.32% (95% CI = 0.46% to 2.19%), respectively. Higher concentrations of either AlPcS4 or Tf-Lip-AlPcS4 resulted in cell kills of more than 3 logs.
  
  
  CONCLUSIONS
  Transferrin-mediated liposomal targeting of photosensitizing drugs is a promising potential tool for photodynamic therapy of superficial bladder tumors.
authors.affiliation: Laboratory for Pharmaceutical Biology and Phytopharmacology, Faculty of Pharmaceutical Sciences, K.U. Leuven, Leuven, Belgium.
authors.forename: Annelies S L
authors.initials: AS
authors.lastname: Derycke
authors.forename: Appolinary
authors.initials: A
authors.lastname: Kamuhabwa
authors.forename: Antoon
authors.initials: A
authors.lastname: Gijsens
authors.forename: Tania
authors.initials: T
authors.lastname: Roskams
authors.forename: Dirk
authors.initials: D
authors.lastname: De Vos
authors.forename: Ahmad
authors.initials: A
authors.lastname: Kasran
authors.forename: Jörg
authors.initials: J
authors.lastname: Huwyler
authors.forename: Ludwig
authors.initials: L
authors.lastname: Missiaen
authors.forename: Peter A M
authors.initials: PA
authors.lastname: de Witte
mesh_terms: D000283:Administration, Intravesical; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002295:Carcinoma, Transitional Cell / Q000188:drug therapy* / Q000378:metabolism; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology*; D008081:Liposomes; D008856:Microscopy, Fluorescence; D009368:Neoplasm Transplantation; D009942:Organometallic Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000494:pharmacology*; D011092:Polyethylene Glycols; D051381:Rats; D011990:Receptors, Transferrin / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy* / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D007211:Indoles; D008081:Liposomes; D009942:Organometallic Compounds; D017319:Photosensitizing Agents; D011990:Receptors, Transferrin; D014168:Transferrin; C048577:aluminum tetrasulfophthalocyanine; D011092:Polyethylene Glycols