Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy.
Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
Int J Radiat Biol. 2020 Jun;96(6):823-835. doi: 10.1080/09553002.2020.1739774. Epub 2020 Mar 23.
Radiation therapy (RT), by using ionizing radiation (IR), destroys cancer cells inducing DNA damage. Despite several studies are continuously performed to identify the best curative dose of IR, the role of dose-rate, IR delivered per unit of time, on tumor control is still largely unknown. Rhabdomyosarcoma (RMS) and prostate cancer (PCa) cell lines were irradiated with 2 or 10 Gy delivered at dose-rates of 1.5, 2.5, 5.5 and 10.1 Gy/min. Cell-survival rate and cell cycle distribution were evaluated by clonogenic assays and flow cytometry, respectively. The production of reactive oxygen species (ROS) was detected by cytometry. Quantitative polymerase chain reaction assessed the expression of anti-oxidant-related factors including NRF2, SODs, CAT and GPx4 and miRNAs (miR-22, -126, -210, -375, -146a, -34a). Annexin V and caspase-8, -9 and -3 activity were assessed to characterize cell death. Senescence was determined by assessing β-galactosidase (SA-β-gal) activity. Immunoblotting was performed to assess the expression/activation of: i) phosphorylated H2AX (γ-H2AX), markers of DNA double strand breaks (DSBs); ii) p19, p21 and p27, senescence-related-markers; iii) p62, LC3-I and LC3-II, regulators of autophagy; iv) ATM, RAD51, DNA-PKcs, Ku70 and Ku80, mediators of DSBs repair. Low dose-rate (LDR) more efficiently induced apoptosis and senescence in RMS while high dose-rate (HDR) necrosis in PCa. This paralleled with a lower ability of LDR-RMS and HDR-PCa irradiated cells to activate DSBs repair. Modulating the dose rate did not differently affect the anti-oxidant ability of cancer cells. The present results indicate that a stronger cytotoxic effect was induced by modulating the dose-rate in a cancer cell-dependent manner, this suggesting that choose the dose-rate based on the individual patient's tumor characteristics could be strategic for effective RT exposures.
放射治疗（RT）使用电离辐射（IR）破坏癌细胞，诱导 DNA 损伤。尽管不断有研究旨在确定最佳的 IR 治愈剂量，但辐射剂量率（单位时间内给予的 IR 剂量）对肿瘤控制的作用在很大程度上仍不清楚。横纹肌肉瘤（RMS）和前列腺癌（PCa）细胞系分别用 2 或 10 Gy 的剂量率为 1.5、2.5、5.5 和 10.1 Gy/min 的 IR 照射。通过集落形成实验和流式细胞术分别评估细胞存活率和细胞周期分布。通过细胞术检测活性氧物种（ROS）的产生。定量聚合酶链反应评估了抗氧化相关因子（包括 NRF2、SODs、CAT 和 GPx4）和 miRNA（miR-22、-126、-210、-375、-146a、-34a）的表达。通过 Annexin V 和 caspase-8、-9 和 -3 活性评估细胞死亡特征。通过评估β-半乳糖苷酶（SA-β-gal）活性确定衰老。免疫印迹法用于评估：i）磷酸化 H2AX（γ-H2AX），DNA 双链断裂（DSB）的标志物；ii）p19、p21 和 p27，衰老相关标志物；iii）p62、LC3-I 和 LC3-II，自噬调节剂；iv）ATM、RAD51、DNA-PKcs、Ku70 和 Ku80，DSB 修复介质。低剂量率（LDR）在 RMS 中更有效地诱导细胞凋亡和衰老，而在 PCa 中则诱导高剂量率（HDR）坏死。这与 LDR-RMS 和 HDR-PCa 照射细胞激活 DSB 修复的能力较低相一致。调节剂量率不会以不同的方式影响癌细胞的抗氧化能力。本研究结果表明，以依赖于癌细胞的方式调节剂量率可诱导更强的细胞毒性作用，这表明根据个体患者肿瘤特征选择剂量率可能是有效 RT 暴露的策略。
