title: Aminopeptidase N (APN)/CD13 inhibitor, Ubenimex, enhances radiation sensitivity in human cervical cancer.
abstract: BACKGROUND
  Radiotherapy can be used to treat all stages of cervical cancer. For improving local control via radiotherapy, it is important to use additional antitumor agents. Aminopeptidase N (APN)/CD13, a 150-kDa metalloproteinase, is a multifunctional cell surface aminopeptidase with ubiquitous expression. Recent studies have suggested that APN/CD13 plays an important role in tumor progression in several human malignancies.
  
  
  METHODS
  We investigated whether the suppression of APN/CD13 using Ubenimex, an inhibitor of APN/CD13 activity, may affect tumor radiosensitivity in cervical cancer cells both in vitro and in vivo. Cell surface APN/CD13 activity in HeLa cells was calculated using alanine-p-nitroanilido as a substrate. For colony formation assays, single-dose radiation and/or Ubenimex were administered to each dish of HeLa cells, and these dishes were cultured for 14 days. Molecular changes of apoptosis were determined by Western blot. Apoptosis was evaluated by Annexin-V PI staining (flow cytometry analysis) and the Tunel method. Moreover, we investigated the effect of combining Ubenimex and low-dose radiation on tumor growth using nude mice.
  
  
  RESULTS
  We demonstrated that Ubenimex enhanced the effectiveness of radiotherapy, acting as a radiosensitizer both in vitro and in vivo. In colony formation assays, a significant decline in clonogenic survival was observed in Ubenimex-treated cells. Mice treated with a combination of radiation and Ubenimex showed a significant prolongation of the tumor-doubling time compared with the control, Ubenimex, or radiation-alone groups. We also showed that ubenimex enhanced radiation-induced apoptosis in vitro and in vivo.
  
  
  CONCLUSIONS
  Although further studies are needed, this report suggests that Ubeniemx acts as a radiosensitizer in cervical cancer treatment, and that the inhibition of APN/CD13 activity may represent a new approach for improving the therapeutic efficacy of radiotherapy for uterine cervical cancer.
authors: Department of Obstetrics and Gynecology, Nagoya University Graduate School of Medicine, Nagoya, Japan. shiba@med.nagoya-u.ac.jp. tukamoto@med.nagoya-u.a
authors: Hirohisa
authors: H
authors: Tsukamoto
authors: Kiyosumi
authors: K
authors: Shibata
authors: Hiroaki
authors: H
authors: Kajiyama
authors: Mikio
authors: M
authors: Terauchi
authors: Akihiro
authors: A
authors: Nawa
authors: Fumitaka
authors: F
authors: Kikkawa
mesh_terms: D000818:Animals; D018826:CD13 Antigens / Q000037:antagonists & inhibitors*; D018450:Disease Progression; D005260:Female; D006367:HeLa Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011480:Protease Inhibitors / Q000494:pharmacology*; D011836:Radiation Tolerance; D011878:Radiotherapy / Q000295:instrumentation / Q000379:methods; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*
chemical_list: D011480:Protease Inhibitors; D018826:CD13 Antigens; D007930:Leucine; C012211:ubenimex