title: Effects of carbon ion irradiation and X-ray irradiation on the ubiquitylated protein accumulation.
abstract: C-ion radiotherapy is associated with improved local control and survival in several types of tumors. Although C-ion irradiation is widely reported to effectively induce DNA damage in tumor cells, the effects of irradiation on proteins, such as protein stability or degradation in response to radiation stress, remain unknown. We aimed to compare the effects of C-ion and X-ray irradiation focusing on the cellular accumulation of ubiquitylated proteins. Cells from two human colorectal cancer cell lines, SW620 and SW480, were subjected to C-ion or X-ray irradiation and determination of ubiquitylated protein levels. High levels of ubiquitylated protein accumulation were observed in the C-ion-irradiated SW620 with a peak at 3 Gy; the accumulation was significantly lower in the X-ray-irradiated SW620 at all doses. Enhanced levels of ubiquitylated proteins were also detected in C-ion or X-ray-irradiated SW480, however, those levels were significantly lower than the peak detected in the C-ion-irradiated SW620. The levels of irradiation-induced ubiquitylated proteins decreased in a time-dependent manner, suggesting that the proteins were eliminated after irradiation. The treatment of C-ion-irradiated SW620 with a proteasome inhibitor (epoxomicin) enhanced the cell killing activity. The accumulated ubiquitylated proteins were co-localized with γ-H2AX, and with TP53BP1, in C-ion-irradiated SW620, indicating C-ion-induced ubiquitylated proteins may have some functions in the DNA repair system. Overall, we showed C-ion irradiation strongly induces the accumulation of ubiquitylated proteins in SW620. These characteristics may play a role in improving the therapeutic ratio of C-ion beams; blocking the clearance of ubiquitylated proteins may enhance sensitivity to C-ion radiation.
authors.affiliation: Department of Frontier Surgery, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Isozaki
authors.affiliation: Advanced Radiation Biology Research Program, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Fujita
authors.affiliation: Research Center Hospital, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamada
authors.affiliation: Advanced Radiation Biology Research Program, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Imadome
authors.affiliation: Advanced Radiation Biology Research Program, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Shoji
authors.affiliation: Radiation Emergency Medicine Research Program, Research Center for Radiation Emergency Medicine, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Advanced Radiation Biology Research Program, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Nakayama
authors.affiliation: Advanced Radiation Biology Research Program, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Imai
authors.affiliation: Department of Frontier Surgery, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Hisahiro
authors.initials: H
authors.lastname: Matsubara
mesh_terms: D002244:Carbon / Q000737:chemistry / Q000627:therapeutic use; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D004249:DNA Damage / Q000528:radiation effects; D004260:DNA Repair / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D063193:Heavy Ion Radiotherapy; D006801:Humans; D009842:Oligopeptides / Q000008:administration & dosage; D054875:Ubiquitination / Q000528:radiation effects*; D014965:X-Rays
chemical_list: D009842:Oligopeptides; D002244:Carbon; C078846:epoxomicin