title: Experimental investigation of the cytotoxicity of medium-borne signals in human prostate cancer cell line.
abstract: BACKGROUND
  Evidence exists that exposure of non-irradiated cells to Irradiated Cell Conditioned Medium (ICCM) can cause effects similar to those resulting from direct radiation damage. This study attempts to validate the stochastic model, relating absorbed dose to the emission and processing of cell death signals by non-irradiated cells, in vitro in PC3 human prostate cancer cell line.
  
  
  METHODS
  The recipient cell survival was measured after exposure of cells to ICMM derived from donor cells: a) exposed to radiation doses from 2 Gy to 8 Gy and b) of concentrations varying from 2 × 10(2) to 6 × 10(6) irradiated with 2 Gy.
  
  
  RESULTS
  Exposure to ICCM, irradiated with doses between 2-8 Gy, resulted in a significant (p < 0.001) decrease in clonogenic survival of non-irradiated recipient cells compared to the control group. However, dose dependency above 2 Gy was not observed, indicating that any dose threshold was below 2 Gy. A significant (p < 0.001) decrease in survival was found in recipient cells exposed to the ICCM, derived from different concentrations of donor cells exposed to 2 Gy, compared to the control group. The recipient cell survival following exposure to ICCM derived from 2 × 10(2) cells was significantly higher (p < 0.5) compared to the rest of donor cell concentrations, indicating that the toxicity of ICCM depends on the cellular concentration of donor cells. Non-linear regression data fitting provided reasonable agreement with the microdosimetric model for the induction of cell killing through medium-borne signals.
  
  
  CONCLUSIONS
  For the given cell line and given experimental conditions, significant decreases in cell survival were observed in non-irradiated cells exposed to ICCM derived from donor cells of various concentrations and irradiated with different doses.
authors.affiliation: Medical Physics Department, Radiation Oncology, Royal Adelaide Hospital, South Australian Department of Health, South Australia, Australia. svetlana.sjostedt@health.sa.gov.au
authors.forename: Svetlana
authors.initials: S
authors.lastname: Sjostedt
authors.forename: Eva
authors.initials: E
authors.lastname: Bezak
mesh_terms: D000704:Analysis of Variance; D017209:Apoptosis; D024201:Bystander Effect; D002450:Cell Communication / Q000528:radiation effects; D016923:Cell Death / Q000528:radiation effects; D045744:Cell Line, Tumor / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D003470:Culture Media; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy*
chemical_list: D003470:Culture Media