Rashed Faisal Bin, Kate Wisdom Deebeke, Fanta Mesfin, Wiebe Leonard Irving, Kumar Piyush, Weinfeld Michael
Department of Oncology, University of Alberta, Edmonton, AB T6G 2R3, Canada.
Antioxidants (Basel). 2023 Feb 6;12(2):389. doi: 10.3390/antiox12020389.
Cellular adaptations to hypoxia promote resistance to ionizing radiation (IR). This presents a challenge for treatment of head and neck cancer (HNC) that relies heavily on radiotherapy. Standard radiosensitizers often fail to reach diffusion-restricted hypoxic cells, whereas nitroimidazoles (NIs) [such as iodoazomycin arabinofuranoside (IAZA) and fluoroazomycin arabinofuranoside (FAZA)] can preferentially accumulate in hypoxic tumours. Here, we explored if the hypoxia-selective uptake of IAZA and FAZA could be harnessed to make HNC cells (FaDu) susceptible to radiation therapy. Cellular response to treatment was assessed through clonogenic survival assays and by monitoring DNA damage (immunofluorescence staining of DNA damage markers, γ-H2AX and p-53BP1, and by alkaline comet assay). The effects of reoxygenation were studied using the following assays: estimation of nucleoside incorporation to assess DNA synthesis rates, immunofluorescent imaging of chromatin-associated replication protein A as a marker of replication stress, and quantification of reactive oxygen species (ROS). Both IAZA and FAZA sensitized hypoxic HNC cells to IR, albeit the former is a better radiosensitizer. Radiosensitization by these compounds was restricted only to hypoxic cells, with no visible effects under normoxia. IAZA and FAZA impaired cellular adaptation to reoxygenation; high levels of ROS, reduced DNA synthesis capacity, and signs of replication stress were observed in reoxygenated cells. Overall, our data highlight the therapeutic potentials of IAZA and FAZA for targeting hypoxic HNC cells and provide rationale for future preclinical studies.
细胞对缺氧的适应性会促进对电离辐射（IR）的抗性。这给严重依赖放射治疗的头颈癌（HNC）治疗带来了挑战。标准的放射增敏剂往往无法到达扩散受限的缺氧细胞，而硝基咪唑类化合物（NIs）[如阿拉伯呋喃糖碘氮霉素（IAZA）和阿拉伯呋喃糖氟氮霉素（FAZA）]可以优先在缺氧肿瘤中积累。在这里，我们探讨了是否可以利用IAZA和FAZA对缺氧的选择性摄取使HNC细胞（FaDu）对放射治疗敏感。通过克隆形成存活试验以及监测DNA损伤（DNA损伤标志物γ-H2AX和p-53BP1的免疫荧光染色以及碱性彗星试验）来评估细胞对治疗的反应。使用以下试验研究复氧的影响：估计核苷掺入以评估DNA合成速率、对与染色质相关的复制蛋白A进行免疫荧光成像作为复制应激的标志物以及定量活性氧（ROS）。IAZA和FAZA都使缺氧的HNC细胞对IR敏感，尽管前者是更好的放射增敏剂。这些化合物的放射增敏作用仅局限于缺氧细胞，在常氧条件下没有可见效果。IAZA和FAZA损害了细胞对复氧的适应性；在复氧细胞中观察到高水平的ROS、DNA合成能力降低以及复制应激的迹象。总体而言，我们的数据突出了IAZA和FAZA针对缺氧HNC细胞的治疗潜力，并为未来的临床前研究提供了理论依据。
