Medical Physics Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
Department of Medical Biotechnology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
Mutat Res. 2021 Jul-Dec;823:111760. doi: 10.1016/j.mrfmmm.2021.111760. Epub 2021 Aug 6.
Radiotherapy plays a pivotal role in the treatment of cancer. One of the main challenges in this treatment modality is radiation-induced complications in some patients affected by high radiosensitivity (RS). The differences in RS are determined mainly by genetic factors. Therefore, identifying the genes and mechanisms that affect RS in different cells is essential for evaluating radiotherapy outcomes. In the present study, the ability to repair DNA double-stranded breaks (DSB) is evaluated, followed by examining the expression levels of CDKN1A (p21), cyclinD1, and Mre11 genes in human fibroblasts with different RSs.
MATERIALS & METHODS: Cellular RS was measured by survival fraction at 2 Gy (SF2). The γ-H2AX assay was used for assessing DNA repair capacity. Eventually, gene expression levels from each cell line 4 and 24 h after irradiation (at 2, 4, and 8 Gy) were measured by real-time PCR.
The SF2 values for the cell lines ranged from 0.286 to 0.641, and RS differences of fibroblast cells were identified. Among the studied genes, the expression of Mre11 was the most important. Analysis of the real-time PCR data showed that changes in Mre11 gene expression (4 h after 8 Gy irradiation) were directly correlated with the RS (R = 0.905). The difference in the expression of the p21 gene (4 h after 4 Gy irradiation) was also promising. Finally, the flow cytometry analysis showed that the radioresistant cell lines quickly repaired DBS damages. However, the repair process was slow in the radiosensitive cell line, and the residual damage is significantly higher than other cell lines (P < 0.01).
This study indicates that changes in the expression of p21 and Mre11 genes play an important role in cell response to radiation and thus these genes can be introduced as biomarkers to predict RS in normal cell lines.
放射治疗在癌症治疗中起着关键作用。在这种治疗方式中，主要挑战之一是一些对高放射敏感性（RS）患者发生的放射性并发症。RS 的差异主要由遗传因素决定。因此，确定影响不同细胞 RS 的基因和机制对于评估放射治疗结果至关重要。在本研究中，评估了修复 DNA 双链断裂（DSB）的能力，然后检查了具有不同 RS 的人成纤维细胞中 CDKN1A（p21）、cyclinD1 和 Mre11 基因的表达水平。
通过 2 Gy（SF2）时的存活分数测量细胞 RS。γ-H2AX 测定用于评估 DNA 修复能力。最终，通过实时 PCR 测量照射后每个细胞系 4 和 24 小时的基因表达水平（在 2、4 和 8 Gy 时）。
细胞系的 SF2 值范围为 0.286 至 0.641，确定了成纤维细胞 RS 的差异。在所研究的基因中，Mre11 的表达最重要。实时 PCR 数据分析表明，Mre11 基因表达变化（8 Gy 照射后 4 小时）与 RS 直接相关（R = 0.905）。p21 基因表达（4 Gy 照射后 4 小时）的差异也很有前景。最后，流式细胞术分析表明，耐辐射细胞系快速修复 DBS 损伤。然而，在辐射敏感细胞系中，修复过程较慢，残留损伤明显高于其他细胞系（P < 0.01）。
本研究表明，p21 和 Mre11 基因表达的变化在细胞对辐射的反应中起着重要作用，因此这些基因可以作为预测正常细胞系 RS 的生物标志物。
