title: Topical photodynamic therapy significantly reduces epidermal Langerhans cells during clinical treatment of basal cell carcinoma.
abstract: BACKGROUND
  Topical photodynamic therapy (PDT) is a widely applied treatment for basal cell carcinoma (BCC). PDT-induced immunosuppression leading to reduced antitumour immune responses may be a factor in treatment failure.
  
  
  OBJECTIVE
  To examine the impact of topical PDT on leucocyte trafficking following clinical treatment of BCC.
  
  
  METHODS
  Superficial BCCs in eight white caucasian patients were treated with methyl aminolaevulinate (MAL)-PDT. Biopsies for immunohistochemical assessment were taken from BCCs pre-PDT, 1 h and 24 h post-PDT and from untreated healthy skin.
  
  
  RESULTS
  Treatment of BCC with MAL-PDT produced a rapid neutrophil infiltration, commencing by 1 h and significantly increased at 24 h post-PDT (P < 0·05 compared with baseline). An associated increase in the number of blood vessels expressing E-selectin was observed at 1 h and 24 h post-PDT (both P < 0·05 compared with baseline). In contrast, the number of epidermal Langerhans cells fell sharply by 1 h post-PDT, and remained significantly reduced at 24 h post-PDT (both P < 0·05 compared with baseline).
  
  
  CONCLUSIONS
  Reduction of Langerhans cells during clinical treatment of BCC might potentially impact negatively on antitumour responses through reduced activation of tumour-specific effector cells. Investigation of modified PDT protocols with the aim to minimize immunosuppressive effects while maintaining antitumour efficacy is warranted.
authors.affiliation: University of Manchester, Manchester M6 6HD, UK.
authors.forename: G
authors.initials: G
authors.lastname: Evangelou
authors.forename: M D
authors.initials: MD
authors.lastname: Farrar
authors.forename: L
authors.initials: L
authors.lastname: Cotterell
authors.forename: S
authors.initials: S
authors.lastname: Andrew
authors.forename: A D
authors.initials: AD
authors.lastname: Tosca
authors.forename: R E B
authors.initials: RE
authors.lastname: Watson
authors.forename: L E
authors.initials: LE
authors.lastname: Rhodes
mesh_terms: D000279:Administration, Cutaneous; D000368:Aged; D000622:Aminolevulinic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives*; D002280:Basal Cell Carcinoma / Q000188:drug therapy* / Q000473:pathology; D005260:Female; D006801:Humans; D007801:Langerhans Cells / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D020556:Neutrophil Infiltration; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage*; D012878:Skin Neoplasms / Q000188:drug therapy* / Q000209:etiology
chemical_list: D017319:Photosensitizing Agents; C475457:methyl 5-aminolevulinate; D000622:Aminolevulinic Acid