摘要目的:研究质子FLASH与常规剂量率(CONV)照射下对人肝细胞WRL68与人肝癌细胞HepG2的差异作用。方法:使用100 MeV强流质子回旋加速器对WRL68与HepG2细胞分别开展常规剂量率(0.8 Gy/min)与超高剂量率(40 Gy/s)的质子4 Gy照射，照射后在不同时间点检测细胞增殖、凋亡与周期阻滞变化，并通过转录组测序对不同细胞的基因表达谱变化进行分析。结果:对于人肝细胞，相较于常规照射，质子FLASH照射提高了细胞增殖活力( t＝10.18~16.67， P<0.05)，降低了细胞凋亡率( t＝3.21~8.30， P<0.05)，同一时间点细胞G 2期阻滞占比有所降低( t＝34.08~65.16， P<0.05)。对于肝癌细胞，相较于常规照射，质子FLASH照射显著抑制了细胞增殖( t＝2.57~9.39， P<0.05)，细胞凋亡水平有所提升( t＝3.25~66.70， P<0.05)，周期变化同样集中于G 2期阻滞( t＝10.87~27.47， P<0.05)。转录组测序结果显示对于WRL68细胞，在FLASH组与CONV组间共发现906个差异表达基因；对于HepG2细胞，在FLASH组与CONV组间共发现1 243个差异表达基因，差异表达基因的基因本体(GO)与京都基因与基因组百科全书(KEGG)分析表明，细胞黏附、氧效应等可能是FLASH-RT的重要微观作用机制。 结论:质子FLASH照射下人肝细胞放射损伤显著降低，而肝癌细胞损伤加重，相关差异表达基因涉及了多类放射生物学功能通路。

abstractsObjective:To investigate the differential effects of proton FLASH irradiation and conventional dose rate (CONV) irradiation on human normal liver cells WRL68 and human hepatocellular carcinoma cells HepG2.Methods:Using a 100 MeV high-current proton cyclotron accelerator, WRL68 and HepG2 cells were subjected to CONV (0.8 Gy/min) and FLASH (40 Gy/s) irradiation with 4 Gy protons. After irradiation, changes in cell proliferation, apoptosis, and cell cycle arrest were detected at different time points. Additionally, transcriptome sequencing was employed to analyze alterations in the gene expression profiles of the two cell lines.Results:For WRL68 cells, compared with CONV irradiation, proton FLASH irradiation enhanced cell proliferative activity ( t=10.18-16.67, P<0.05), reduced the apoptotic rate ( t=3.21-8.30, P<0.05), and decreased the proportion of cells arrested in the G 2 phase at the same time points ( t=34.08-65.16, P<0.05). In contrast, for HepG2 cells, proton FLASH irradiation significantly inhibited cell proliferation ( t=2.57-9.39, P<0.05), increased the apoptotic rate ( t=3.25-66.70, P<0.05), and similarly induced cell cycle arrest predominantly in the G 2 phase ( t=10.87-27.47, P<0.05). Transcriptome sequencing identified 906 differentially expressed genes (DEGs) between the FLASH group and the CONV group in WRL68 cells, and 1 243 DEGs were detected in HepG2 cells. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of these DEGs suggested that cellular adhesion and oxygen effect may serve as crucial microscopic mechanisms underlying FLASH radiotherapy. Conclusions:Under proton FLASH irradiation, the radiation-induced damage to human normal liver cells was significantly alleviated, whereas the damage to hepatocellular carcinoma cells was aggravated. The identified DEGs are involved in multiple radiobiological functional pathways.