X-Ray Induced Mutation Frequency at the <i>Hypoxanthine Phosphoribosyltransferase</i>Locus in Clinically Relevant Radioresistant Cells  

作　　者：Yoshikazu Kuwahara Mehryar Habibi Roudkenar Yusuke Urushihara Yohei Saito Kazuo Tomita Amaneh Mohammadi Roushandeh Tomoaki Sato Akihiro Kurimasa Manabu Fukumoto 

机构地区：[1]Division of Radiation Biology and Medicine, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, Sendai, Japan [2]Department of Applied Pharmacology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan [3]Medical Biotechnology Research Center, Paramedicine Faculty, Guilan University of Medical Science, Rasht, Iran [4]Fukushima Project Headquarters, National Institute for Quantum and Radiological Science and Technology, Fukushima, Japan [5]Department of Radiopharmacy, Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, Sendai, Japan [6]Department of Anatomical Sciences, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran [7]Department of Molecular Pathology, Tokyo Medical University, Tokyo, Japan

出　　处：《International Journal of Medical Physics, Clinical Engineering and Radiation Oncology》2017年第4期377-391,共15页医学物理学、临床工程、放射肿瘤学（英文）

摘　　要：To elucidate the molecular mechanisms underlying cellular radioresistance, clinically relevant radioresistant cell lines were established via long-term exposure to X-rays with stepwise dose escalation. Established cells continue to proliferate despite exposure to 2 Gy X-rays/day for more than 30 days, a standard protocol in cancer radiotherapy. DNA repair fidelity in radioresistant and the parental cells by evaluating the mutation frequency at the hypoxanthine phosphoribosyltransferase (HPRT) locus after exposure to X-rays was determined. Mutation spectrum at the HPRT locus was examined by multiplex polymerase chain reaction. Rejoining kinetics of X-ray-induced DNA double strand breaks (dsbs) was evaluated by the detection of phosphorylated histone H2AX (γH2AX) after X-irradiation. The fold increase in the HPRT mutation frequency due to acute radiation was similar between radioresistant and the parental cell lines. However, fractionated radiation (FR) consisting of 2 Gy X-rays/day increased the mutation frequency at the HPRT locus in parental but not in radioresistant cells. Analysis of the FR-induced mutations at the HPRT locus revealed a high frequency of deletion mutations (>70%) in parental but not in radioresistant cells. As assessed by γH2AX immunostaining, DNA dsbs induced by acute exposure to 10 Gy of X-rays were repaired to the control level within 7 days in radioresistant but not in the parental cells. Moreover, 2 Gy × 5 FR increased the number of γH2AX-positive cells in parental cultures but not in radioresistant cultures. DNA dsbs induced by 2 Gy/day FR are repaired with fidelity in radioresistant but not in parental cells.To elucidate the molecular mechanisms underlying cellular radioresistance, clinically relevant radioresistant cell lines were established via long-term exposure to X-rays with stepwise dose escalation. Established cells continue to proliferate despite exposure to 2 Gy X-rays/day for more than 30 days, a standard protocol in cancer radiotherapy. DNA repair fidelity in radioresistant and the parental cells by evaluating the mutation frequency at the hypoxanthine phosphoribosyltransferase (HPRT) locus after exposure to X-rays was determined. Mutation spectrum at the HPRT locus was examined by multiplex polymerase chain reaction. Rejoining kinetics of X-ray-induced DNA double strand breaks (dsbs) was evaluated by the detection of phosphorylated histone H2AX (γH2AX) after X-irradiation. The fold increase in the HPRT mutation frequency due to acute radiation was similar between radioresistant and the parental cell lines. However, fractionated radiation (FR) consisting of 2 Gy X-rays/day increased the mutation frequency at the HPRT locus in parental but not in radioresistant cells. Analysis of the FR-induced mutations at the HPRT locus revealed a high frequency of deletion mutations (>70%) in parental but not in radioresistant cells. As assessed by γH2AX immunostaining, DNA dsbs induced by acute exposure to 10 Gy of X-rays were repaired to the control level within 7 days in radioresistant but not in the parental cells. Moreover, 2 Gy × 5 FR increased the number of γH2AX-positive cells in parental cultures but not in radioresistant cultures. DNA dsbs induced by 2 Gy/day FR are repaired with fidelity in radioresistant but not in parental cells.

关 键 词：Clinically RELEVANT Radioresistant (CRR) Cell Hypoxanthine PHOSPHORIBOSYLTRANSFERASE (HPRT) Mutation FREQUENCY Phosphorylated Histone H2AX (γH2AX) X-Rays 

分 类 号：R73[医药卫生—肿瘤]