title: Survival and cell cycle kinetics of human prostate cancer cell lines after single- and multifraction exposures to ionizing radiation.
abstract: OBJECTIVE
  Fractionated radiation therapy is frequently used to treat prostate cancer with an underlying assumption that each daily dose of ionizing radiation (IR) results in equal cell killing. We used three human prostate cancer cell lines to evaluate how survival after a single 2-Gy dose may predict responses after daily repeated 2-Gy exposures.
  
  
  METHODS
  LNCaP, CWR22R, and PC3 cells were used in these studies. Survival after IR exposures was assessed using clonogenic assays and cell cycle responses were determined by flow cytometry.
  
  
  RESULTS
  The experimentally determined multifraction survival differed significantly from that predicted from their single-dose SF2. LNCaP and CWR22R cells showed lower than predicted survivals; PC3 cells exhibited greater than predicted survival. Daily IR exposures resulted in changes in the cell cycle distributions beyond those caused by a single exposure to IR.
  
  
  CONCLUSIONS
  Our results show that in these prostate cancer cells: (1) survival after a clinically relevant dose of IR does not predict survival after multifraction IR, (2) cell cycle responses after a single 2 Gy dose can differ from those that occur when cells receive daily 2 Gy doses, and (3) some cell cycle changes that result from fractionated IR may predict their ultimate survival responses from such treatment.
authors.affiliation: Department of Internal Medicine, Division of Hematology/Oncology, University of California Davis, Cancer Center, Sacramento, CA 95817, USA.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Scott
authors.forename: Paul H
authors.initials: PH
authors.lastname: Gumerlock
authors.forename: Laurel
authors.initials: L
authors.lastname: Beckett
authors.forename: Yueju
authors.initials: Y
authors.lastname: Li
authors.forename: Zelanna
authors.initials: Z
authors.lastname: Goldberg
mesh_terms: D002453:Cell Cycle / Q000502:physiology / Q000528:radiation effects*; D045744:Cell Line, Tumor / Q000528:radiation effects; D002470:Cell Survival / Q000502:physiology / Q000528:radiation effects*; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011836:Radiation Tolerance