Cellular and Molecular Radiobiology Laboratory, Lyon-Sud Medical School, UMR CNRS 5822/IP2I, Université de Lyon, Lyon 1 University, Oullins, France; Department of Research and Teaching in Oncology, Hôpital Nord, Saint-Priest en Jarez, France.
Cellular and Molecular Radiobiology Laboratory, Lyon-Sud Medical School, UMR CNRS 5822/IP2I, Université de Lyon, Lyon 1 University, Oullins, France; Department of Biochemistry and Molecular Biology, Lyon-Sud Hospital, Hospices Civils de Lyon, Pierre-Bénite, France.
Int J Radiat Oncol Biol Phys. 2024 Feb 1;118(2):485-497. doi: 10.1016/j.ijrobp.2023.08.045. Epub 2023 Aug 22.
Stress granules (SGs) are cytoplasmic aggregates in which mRNAs and specific proteins are trapped in response to a variety of damaging agents. They participate in the cellular defense mechanisms. Currently, their mechanism of formation in response to ionizing radiation and their role in tumor-cell radiosensitivity remain elusive.
The kinetics of SG formation was investigated after the delivery of photon irradiation at different doses to head and neck squamous cell carcinoma cell lines with different radiosensitivities and the HeLa cervical cancer cell line (used as reference). In parallel, the response to a canonical inducer of SGs, sodium arsenite, was also studied. Immunolabeling of SG-specific proteins and mRNA fluorescence in situ hybridization enabled SG detection and quantification. Furthermore, a ribopuromycylation assay was used to assess the cell translational status. To determine whether reactive oxygen species were involved in SG formation, their scavenging or production was induced by pharmacologic pretreatment in both SCC61 and SQ20B cells.
Photon irradiation at different doses led to the formation of cytoplasmic foci that were positive for different SG markers. The presence of SGs gradually increased from 30 minutes to 2 hours postexposure in HeLa, SCC61, and Cal60 radiosensitive cells. In turn, the SQ20B and FaDu radioresistant cells did not form SGs. These results indicated a correlation between sensitivity to photon irradiation and SG formation. Moreover, SG formation was significantly reduced by reactive oxygen species scavenging using dimethyl sulfoxide in SCC61 cells, which supported their role in SG formation. However, a reciprocal experiment in SQ20B cells that depleted glutathione using buthionine sulfoximide did not restore SG formation in these cells.
SGs are formed in response to irradiation in radiosensitive, but not in radioresistant, head and neck squamous cell carcinoma cells. Interestingly, compared with sodium arsenite-induced SGs, photon-induced SGs exhibited a different morphology and cellular localization. Moreover, photon-induced SGs were not associated with the inhibition of translation; rather, they depended on oxidative stress.
应激颗粒（SGs）是细胞质中的聚集体，其中 mRNAs 和特定蛋白质在响应各种损伤剂时被捕获。它们参与细胞防御机制。目前，它们对电离辐射的形成机制及其在肿瘤细胞放射敏感性中的作用仍不清楚。
用不同剂量的光子照射头颈部鳞状细胞癌细胞系（具有不同放射敏感性）和 HeLa 宫颈癌细胞系（用作参考），研究 SG 形成的动力学。同时，还研究了 SG 的经典诱导剂亚砷酸钠的反应。SG 特异性蛋白的免疫标记和 mRNA 荧光原位杂交使 SG 检测和定量成为可能。此外，还使用核糖体 puromycylation 测定法评估细胞翻译状态。为了确定活性氧是否参与 SG 形成，用药物预处理诱导 SCC61 和 SQ20B 细胞中的活性氧清除或产生。
不同剂量的光子照射导致细胞质焦点的形成，这些焦点对不同的 SG 标记物呈阳性。在 HeLa、SCC61 和 Cal60 敏感细胞中，暴露后 30 分钟至 2 小时，SG 逐渐增加。相反，SQ20B 和 FaDu 耐辐射细胞未形成 SG。这些结果表明，对光子照射的敏感性与 SG 形成之间存在相关性。此外，用二甲基亚砜清除活性氧显著减少了 SCC61 细胞中的 SG 形成，这支持了它们在 SG 形成中的作用。然而，在 SQ20B 细胞中用丁硫氧嘧啶耗竭谷胱甘肽进行的反向实验并未恢复这些细胞中的 SG 形成。
在敏感但不敏感的头颈鳞状细胞癌细胞中，SGs 是在受到照射后形成的。有趣的是，与亚砷酸钠诱导的 SG 相比，光子诱导的 SG 表现出不同的形态和细胞定位。此外，光子诱导的 SGs 与翻译抑制无关，而是依赖于氧化应激。
