Pakniyat Fatemeh, Mozdarani Hossein, Nedaie Hassan Ali, Mahmoudzadeh Aziz, Salimi Mahdieh, Gholami Somayeh
Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran.
Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
J Biomed Phys Eng. 2023 Feb 1;13(1):17-28. doi: 10.31661/jbpe.v0i0.2001-1053. eCollection 2023 Feb.
The paradigm shifts in target theory could be defined as the radiation-triggered bystander response in which the radiation deleterious effects occurred in the adjacent cells.
This study aims to assess bystander response in terms of DNA damage and their possible cell death consequences following high-dose radiotherapy. Temporal characteristics of gH2AX foci as a manifestation of DNA damage were also evaluated.
In this experimental study, bystander response was investigated in human carcinoma cells of HeLa and HN5, neighboring those that received high doses. Medium transfer was performed from 10 Gy-irradiated donors to 1.5 Gy-irradiated recipients. GammaH2AX foci, clonogenic and apoptosis assays were investigated. The gH2AX foci time-point study was implemented 1, 4, and 24 h after the medium exchange.
DNA damage was enhanced in HeLa and HN5 bystander cells with the ratio of 1.27 and 1.72, respectively, which terminated in more than two-fold clonogenic survival decrease, along with gradual apoptosis increase. GammH2AX foci temporal characterization revealed maximum foci scoring at the 1 h time-point in HeLa, and also 4 h in HN5, which remained even 24 h after the medium sharing in higher level than the control group.
The time-dependent nature of bystander-induced gH2AX foci as a DNA damage surrogate marker was highlighted with the persistent foci at 24 h. considering an outcome of bystander-induced DNA damage, predominant role of clonogenic cell death was also elicited compared to apoptosis. Moreover, the role of high-dose bystander response observed in the current work clarified bystander potential implications in radiotherapy.
靶理论中的范式转变可定义为辐射引发的旁观者效应，即辐射的有害效应发生在相邻细胞中。
本研究旨在评估高剂量放疗后旁观者效应在DNA损伤及其可能导致的细胞死亡方面的情况。还评估了作为DNA损伤表现的γH2AX焦点的时间特征。
在本实验研究中，对HeLa和HN5人癌细胞进行旁观者效应研究，这些细胞邻近接受高剂量照射的细胞。将来自接受10 Gy照射的供体细胞的培养基转移至接受1.5 Gy照射的受体细胞。研究了γH2AX焦点、克隆形成和凋亡检测。在培养基交换后1、4和24小时进行γH2AX焦点时间点研究。
HeLa和HN5旁观者细胞中的DNA损伤分别以1.27和1.72的比例增强，这导致克隆形成存活率下降超过两倍，同时凋亡逐渐增加。γH2AX焦点的时间特征显示，HeLa细胞在1小时时间点焦点评分最高，HN5细胞在4小时时间点最高，在培养基共享后24小时，这些焦点仍高于对照组水平。
24小时时持续存在的焦点突出了旁观者诱导的γH2AX焦点作为DNA损伤替代标志物的时间依赖性。考虑到旁观者诱导的DNA损伤的结果，与凋亡相比，克隆形成细胞死亡起主要作用。此外，当前工作中观察到的高剂量旁观者效应的作用阐明了旁观者效应在放疗中的潜在影响。
