Fabio Hecht, Laura Valerio, Carlos Frederico Lima Gonçalves, Marylin Harinquet, Rabii Ameziane El Hassani, Denise P Carvalho, Stephane Koundrioukoff, Jean-Charles Cadoret, Corinne Dupuy
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引用次数: 0
Abstract
Objective: Ionizing radiation generates genomic instability by promoting the accumulation of chromosomal rearrangements. The oncogenic translocation RET/PTC1 is present in more than 70% of radiation-induced thyroid cancers. Both RET and CCDC6, the genes implicated in RET/PTC1, are found within common fragile sites - chromosomal regions prone to DNA breakage during slight replication stress. Given that irradiated cells become more susceptible to genomic destabilization due to the accumulation of replication-stress-related double-strand breaks (DSBs), we explored whether RET and CCDC6 exhibit DNA breakage under replicative stress several days post-irradiation of thyroid cells.
Methods: We analyzed the dynamic of DNA replication in human thyroid epithelial cells (HThy-ori-3.1) 4 days post a 5-Gy exposure using molecular DNA combing. The DNA replication schedule was evaluated through replication-timing experiments. We implemented a ChIP-qPCR assay to determine whether the RET and CCDC6 genes break following irradiation.
Results: Our study indicates that replicative stress, occurring several days post-irradiation in thyroid cells, primarily causes DSBs in the RET gene. We discovered that both the RET and CCDC6 genes undergo late replication in thyroid cells. However, only RET's replication rate is notably delayed after irradiation.
Conclusion: The findings suggest that post-irradiation in the RET gene causes a breakage in the replication fork, which could potentially invade another genomic area, including CCDC6. As a result, this could greatly contribute to the high prevalence of chromosomal RET/PTC rearrangements seen in patients exposed to external radiation.
目的：电离辐射通过促进染色体重排的积累而产生基因组不稳定性。70%以上由辐射诱发的甲状腺癌存在致癌易位 RET/PTC1。与 RET/PTC1 有关的基因 RET 和 CCDC6 都位于常见的脆性位点内，即在轻微的复制压力下容易发生 DNA 断裂的染色体区域。鉴于辐照细胞因复制应激相关双链断裂（DSB）的积累而更易发生基因组不稳定，我们探讨了甲状腺细胞辐照几天后，RET和CCDC6是否会在复制应激下发生DNA断裂：我们利用分子 DNA 梳理技术分析了人类甲状腺上皮细胞（HThy-ori-3.1）在 5-Gy 照射 4 天后的 DNA 复制动态。通过复制时间实验评估了 DNA 复制时间表。我们采用了 ChIP-qPCR 分析法来确定辐照后 RET 和 CCDC6 基因是否断裂：结果：我们的研究表明，甲状腺细胞在辐照后数天出现的复制应激主要导致 RET 基因中的 DSB。我们发现，甲状腺细胞中的 RET 基因和 CCDC6 基因都会发生晚期复制。然而，只有RET的复制速度在辐照后明显延迟：结论：研究结果表明，RET基因在辐照后会导致复制叉断裂，从而有可能侵入另一个基因组区域，包括CCDC6。结论：研究结果表明，辐照后 RET 基因会导致复制叉断裂，从而有可能侵入另一个基因组区域，包括 CCDC6，因此，这在很大程度上导致了外照射患者染色体 RET/PTC 重排的高发病率。
期刊介绍：
The ''European Thyroid Journal'' publishes papers reporting original research in basic, translational and clinical thyroidology. Original contributions cover all aspects of the field, from molecular and cellular biology to immunology and biochemistry, from physiology to pathology, and from pediatric to adult thyroid diseases with a special focus on thyroid cancer. Readers also benefit from reviews by noted experts, which highlight especially active areas of current research. The journal will further publish formal guidelines in the field, produced and endorsed by the European Thyroid Association.
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