title: Effects of chronic exposure to acidic environment on the response of tumor cells to radiation.
abstract: The influence of short-term exposure to an acidic environment on the radiosensitivity of tumor cells has been extensively explored, but the implication of chronic exposure to an acidic environment for the response of tumor cells to radiation has not been fully elucidated. This study aimed to investigate the effects of chronic pre- and post-irradiation exposure of tumor cells to an acidic environment on the radiation-induced clonogenic death.
  
  
  
  Rat gliosarcoma cells were used throughout the in vitro study. Cells were exposed to pH 6.6 medium for varying durations of up to 4 days before and after X-irradiation. Cell viability, apoptosis, clonogenic cell death and cell cycle distribution were observed.
  
  
  
  Incubation of tumor cells in pH 6.6 medium for 2 or 4 days extended cell cycle, decreased cell viability, and induced apoptotic and clonogenic cell death. The radiation-induced clonogenic death was increased by 2- or 4-day pre-irradiation exposure of tumor cells to pH 6.6 medium, whereas it was reduced by 4-day post-irradiation exposure to an acidic medium.
  
  
  
  Prolonged exposure to an acidic environment enhanced the sensitivity of tumor cells to subsequent X-irradiation. However, the radiosensitization by pre-irradiation exposure was almost completely nullified by prolonged post-irradiation exposure to an acidic environment.
authors.affiliation: a Radiation Bioengineering Laboratory, Department of Nuclear Engineering , Seoul National University , Seoul , Republic of Korea.
authors.forename: So-Ra
authors.initials: SR
authors.lastname: Kim
authors.affiliation: a Radiation Bioengineering Laboratory, Department of Nuclear Engineering , Seoul National University , Seoul , Republic of Korea.
authors.forename: Eun-Hee
authors.initials: EH
authors.lastname: Kim
mesh_terms: D000143:Acids / Q000008:administration & dosage*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D006863:Hydrogen-Ion Concentration; D009374:Neoplasms, Experimental / Q000737:chemistry* / Q000473:pathology / Q000532:radiotherapy*; D011836:Radiation Tolerance / Q000187:drug effects*; D011879:Radiotherapy Dosage; D051381:Rats; D016896:Treatment Outcome
chemical_list: D000143:Acids
keywords: Acidic environment; chronic exposure; radiosensitivity; tumor cells