title: Radiation-induced growth inhibition in transplanted human tongue carcinomas with different p53 gene status.
abstract: OBJECTIVE
  To test p53-dependency in radiation cancer therapy with X-rays (low-linear energy transfer (LET)) or carbon-ion (C-) beams (high-LET heavy ion), we analyzed the radiation-induced growth rate and apoptosis induction in human tongue carcinomas transplanted into nude mice.
  
  
  METHODS
  The SAS cells transfected with mutant p53 gene (SAS/mp53) or a neo control gene (SAS/neo) were transplanted into the thigh of each nude mouse. By measuring the tumor weight (TW), tumor regrowth delay was evaluated when the relative tumor weight (RW) reached 5-fold that of the control group. Apoptosis was analyzed by immunohistochemical and ApopTag stainings.
  
  
  RESULTS
  SAS/mp53 tumors were more resistant to X-ray irradiation than SAS/neo tumors, but not to C-beam irradiation. The relative biological effectiveness (RBE) of C-beams compared to X-rays was 2.1 in SAS/neo tumors and 2.6 in SAS/mp53 tumors. Apoptotic cells were more frequently observed in SAS/neo tumors than in SAS/mp53 tumors in X-ray irradiation but not in C-beam irradiation.
  
  
  CONCLUSIONS
  The radiation-induced growth inhibition of transplanted SAS cells is suggested to be p53-dependent in X-ray irradiation but not in C-beam irradiation. C-beams are proposed as being useful for cancer radiation therapy regardless of p53 gene status.
authors.affiliation: Department of Oncoradiology, Nara Medical University, Kashihara, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Asakawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yoshimura
authors.forename: Akihisa
authors.initials: A
authors.lastname: Takahashi
authors.forename: Ken
authors.initials: K
authors.lastname: Ohnishi
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Nakagawa
authors.forename: Ichiro
authors.initials: I
authors.lastname: Ota
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Furusawa
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Tamamoto
authors.forename: Hajime
authors.initials: H
authors.lastname: Ohishi
authors.forename: Takeo
authors.initials: T
authors.lastname: Ohnishi
mesh_terms: D000818:Animals; D017209:Apoptosis; D002455:Cell Division; D016158:Genes, p53; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009929:Organ Size; D011879:Radiotherapy Dosage; D014062:Tongue Neoplasms / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy; D014162:Transfection; D014183:Transplantation, Heterologous; D014965:X-Rays