Objectives

Chondrosarcomas are malignant bone tumors considered as resistant to radiotherapy. To unravel mechanisms of resistance, we compared biological responses of several chondrosarcomas to X-ray irradiations in normoxia and hypoxia. Since hadrontherapy with Carbon-ions gave interesting clinical outcomes, we also investigated this treatment in vitro.

Methods

Five human chondrosarcoma cell lines were used and cultured in normoxia or hypoxia. Their sensitivities to irradiations were determined by carrying out survival curves. DNA damage was monitored by γH2AX expression. Apoptosis was assessed by cell cycle analysis and Apo2.7 expression, and by evaluating PARP cleavage. Senescence was evaluated using SA β-galactosidase assay. Necrosis, and autophagy, were evaluated by RIP1 and beclin-1 expression, respectively. Mutations in relevant biological pathways were screened by whole-exome sequencing.

Results

X-ray radiations induced death in some chondrosarcomas by both apoptosis and senescence (CH2879), or by either of them (SW1353 and JJ012), whereas no death was observed in other cell lines (FS090 and 105KC). Molecularly, p21 was overexpressed when senescence was elicited. Genetic analysis allowed to identify putative genes (such as TBX3, CDK2A, HMGA2) permitting to predict cell response to irradiations. Unexpectedly, chronic hypoxia did not favor radioresistance in chondrosarcomas, and even increased the radiosensitivity of JJ012 line. Finally, we show that carbon ions triggered more DNA damages and death than X-rays.

Conclusions

Chondrosarcomas have different response to irradiation, possibly due to their strong genetic heterogeneity. p21 expression is suggested as predictive of X-ray-induced senescence. Surprisingly, hypoxia does not increase the radioresistance of chondrosarcomas, but as expected Carbon ion beams are more effective that X-rays in normoxia, whereas their efficiency was also variable depending on cell lines.

中文翻译：

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软骨肉瘤对 X 射线和碳离子照射反应的异质性：五种细胞系的比较研究

目标

软骨肉瘤是被认为对放射治疗有抵抗力的恶性骨肿瘤。为了揭示耐药机制，我们比较了几种软骨肉瘤对常氧和缺氧条件下 X 射线照射的生物学反应。由于碳离子强子疗法产生了有趣的临床结果，我们还在体外研究了这种治疗方法。

方法

使用五种人软骨肉瘤细胞系并在常氧或缺氧条件下培养。它们对辐射的敏感性是通过进行生存曲线来确定的。通过 γH2AX 表达监测 DNA 损伤。通过细胞周期分析和 Apo2.7 表达以及通过评估 PARP 切割来评估细胞凋亡。使用 SA β-半乳糖苷酶测定法评估衰老。坏死和自噬分别通过 RIP1 和 beclin-1 表达进行评估。通过全外显子组测序筛选相关生物学途径中的突变。

结果

X 射线辐射在一些软骨肉瘤中通过细胞凋亡和衰老（CH2879）或它们中的任何一种（SW1353 和 JJ012）诱导死亡，而在其他细胞系（FS090 和 105KC）中未观察到死亡。在分子上，当引起衰老时 p21 过度表达。遗传分析允许识别允许预测细胞对辐射的反应的假定基因（例如 TBX3、CDK2A、HMGA2）。出乎意料的是，慢性缺氧不利于软骨肉瘤的放射抗性，甚至增加了JJ012系的放射敏感性。最后，我们表明碳离子比 X 射线引发更多的 DNA 损伤和死亡。

结论

软骨肉瘤对辐射有不同的反应，可能是由于它们具有很强的遗传异质性。p21 表达被认为可以预测 X 射线诱导的衰老。令人惊讶的是，缺氧不会增加软骨肉瘤的放射抗性，但正如预期的那样，碳离子束在常氧环境中比 X 射线更有效，而它们的效率也因细胞系而异。