title: Radiation sensitizing effect of estramustine is not dependent on apoptosis.
abstract: BACKGROUND
  Estramustine is an anti-mitotic cytostatic drug that also enhances the effect of radiotherapy. The mechanism of radiosensitization is not thoroughly known. Since both radiotherapy and estramustine induce apoptosis in prostate cancer cells, we conducted an experiment to show whether radiosensitization is mediated by apoptosis.
  
  
  METHODS
  DU-145 human prostate cancer cells were xenografted to nude mice and treated with estramustine for 2 weeks and external radiation for 3 to 6 days (18 to 36 Gy). Tumor regression was measured mechanically and the rate of apoptosis defined by the amount of low molecular weight DNA fragmentation. Follow-up time was 1 to 18 days.
  
  
  RESULTS
  The tumor size regressed in the group of mice receiving both radiotherapy and estramustine. Four weeks after the treatment, apoptosis was accentuated in the tumors treated with estramustine or radiation but not with their combination.
  
  
  CONCLUSIONS
  Estramustine potentiates radiotherapy, but not by enhancing radiation-induced apoptosis.
authors.affiliation: Department of Urology, Helsinki University Central Hospital, Helsinki, Finland. kaarlo.stahlberg@hus.fi
authors.forename: Kaarlo
authors.initials: K
authors.lastname: Ståhlberg
authors.forename: Kalevi
authors.initials: K
authors.lastname: Kairemo
authors.forename: Krista
authors.initials: K
authors.lastname: Erkkilä
authors.forename: Virve
authors.initials: V
authors.lastname: Pentikäinen
authors.forename: Pekka
authors.initials: P
authors.lastname: Sorvari
authors.forename: Kimmo
authors.initials: K
authors.lastname: Taari
authors.forename: Leo
authors.initials: L
authors.lastname: Dunkel
authors.forename: Sakari
authors.initials: S
authors.lastname: Rannikko
mesh_terms: D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000009:adverse effects / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D053938:DNA Fragmentation / Q000187:drug effects / Q000528:radiation effects; D004961:Estramustine / Q000009:adverse effects / Q000494:pharmacology*; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D011838:Radiation-Sensitizing Agents / Q000009:adverse effects / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D018931:Antineoplastic Agents, Hormonal; D011838:Radiation-Sensitizing Agents; D004961:Estramustine