title: Influence of environmental pH on G2-phase arrest caused by ionizing radiation.
abstract: We investigated the effects of an acidic environment on the G2/M-phase arrest, apoptosis, clonogenic death, and changes in cyclin B1-CDC2 kinase activity caused by a 4-Gy irradiation in RKO.C human colorectal cancer cells in vitro. The time to reach peak G2/M-phase arrest after irradiation was delayed in pH 6.6 medium compared to that in pH 7.5 medium. Furthermore, the radiation-induced G2/M-phase arrest decayed more slowly in pH 6.6 medium than in pH 7.5 medium. Finally, there was less radiation-induced apoptosis and clonogenic cell death in pH 6.6 medium than in pH 7.5 medium. It appeared that the prolongation of G2-phase arrest after irradiation in the acidic environment allowed for greater repair of radiation-induced DNA damage, thereby decreasing the radiation-induced cell death. The prolongation of G2-phase arrest after irradiation in the acidic pH environment appeared to be related at least in part to a prolongation of the phosphorylation of CDC2, which inhibited cyclin B1-CDC2 kinase activity.
authors.affiliation: Department of Microbiology, Inha University, College of Medicine, Inchon, Korea.
authors.forename: Heon Joo
authors.initials: HJ
authors.lastname: Park
authors.forename: Sang Hwa
authors.initials: SH
authors.lastname: Lee
authors.forename: HyunSook
authors.initials: H
authors.lastname: Chung
authors.forename: Yun Hee
authors.initials: YH
authors.lastname: Rhee
authors.forename: Byung Uk
authors.initials: BU
authors.lastname: Lim
authors.forename: Sung Whan
authors.initials: SW
authors.lastname: Ha
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Griffin
authors.forename: Hyung Sik
authors.initials: HS
authors.lastname: Lee
authors.forename: Chang Won
authors.initials: CW
authors.lastname: Song
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Choi
mesh_terms: D016203:CDC2 Protein Kinase / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D015179:Colorectal Neoplasms; D003470:Culture Media; D019926:Cyclin B / Q000528:radiation effects; D056744:Cyclin B1; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D016195:G2 Phase / Q000528:radiation effects*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010766:Phosphorylation; D011839:Radiation, Ionizing; D014407:Tumor Cells, Cultured
chemical_list: C534699:CCNB1 protein, human; D003470:Culture Media; D019926:Cyclin B; D056744:Cyclin B1; D016203:CDC2 Protein Kinase