Purpose

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.

Results

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 (R² = 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).

Conclusions

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.

中文翻译：

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不同放射敏感性人成纤维细胞系中辐射诱导的 DNA 损伤和 p21、cyclin D1 和 Mre11 基因表达改变

目的

放射治疗在癌症的治疗中起着举足轻重的作用。这种治疗方式的主要挑战之一是一些受高放射敏感性 (RS) 影响的患者的辐射引起的并发症。RS的差异主要由遗传因素决定。因此，识别影响不同细胞中 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。

材料与方法

通过 2 Gy (SF2) 下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 测量每个细胞系在照射后 4 和 24 小时（2、4 和 8 Gy）的基因表达水平。

结果

细胞系的 SF2 值范围为 0.286 至 0.641，并鉴定了成纤维细胞的 RS 差异。在研究的基因中，Mre11的表达最为重要。实时 PCR 数据分析表明，Mre11 基因表达的变化（8 Gy 照射后 4 小时）与 RS 直接相关（R ² = 0.905）。p21 基因表达的差异（4 Gy 照射后 4 小时）也很有希望。最后，流式细胞仪分析表明，抗辐射细胞系可以快速修复 DBS 损伤。但放射敏感细胞系修复过程较慢，残留损伤明显高于其他细胞系（P < 0.01）。

结论

该研究表明 p21 和 Mre11 基因表达的变化在细胞对辐射的反应中起重要作用，因此这些基因可以作为生物标志物被引入来预测正常细胞系中的 RS。