Peptidylarginine deiminases 4 (PAD4), a kind of enzyme capable of converting protein arginine or mono-methylarginine into citrulline, has been identified to display a key role in diverse diseases. Radiotherapy is frequently used in nasopharyngeal carcinoma (NPC) treatment and induces DNA double strand breaks. In this study, whether PAD4 inhibitor YW3-56 affects the radiosensitivity of NPC cells was explored. RT-qPCR, immunofluorescence, western blot, clonogenic survival, and flow cytometry assays were used to assess the function of PAD4 and YW3-56 in NPC. We found the upregulation of PAD4 expression in NPC cells. PAD4 overexpression suppressed NPC cell apoptosis and promoted cell cycle, while PAD4 depletion had an opposite result. Moreover, the survival of NPC cells after irradiation was increased by overexpression of PAD4. PAD4 overexpression inhibited DNA damage and sensitivity of NPC cells to irradiation. Functional assays showed that YW3-56 treatment promoted DNA damage, apoptosis, and radiosensitivity of NPC cells. Importantly, YW3-56 treatment inhibited tumor growth in vivo. Overall, this study revealed the efficacy of PAD4 inhibitor YW3-56 in promoting sensitivity of NPC cells to irradiation.

中文翻译：

---

PAD4抑制剂促进鼻咽癌细胞的DNA损伤和放射敏感性

肽基精氨酸脱亚胺酶 4 (PAD4) 是一种能够将蛋白质精氨酸或单甲基精氨酸转化为瓜氨酸的酶，已被鉴定为在多种疾病中发挥关键作用。放射疗法常用于鼻咽癌 (NPC) 治疗并诱导 DNA 双链断裂。在这项研究中，探讨了 PAD4 抑制剂 YW3-56 是否影响 NPC 细胞的放射敏感性。RT-qPCR、免疫荧光、蛋白质印迹、克隆存活率和流式细胞术测定用于评估 PAD4 和 YW3-56 在 NPC 中的功能。我们发现 NPC 细胞中 PAD4 表达的上调。PAD4 过表达抑制 NPC 细胞凋亡并促进细胞周期，而 PAD4 耗竭具有相反的结果。此外，PAD4 的过度表达增加了辐射后 NPC 细胞的存活率。PAD4 过表达抑制 DNA 损伤和 NPC 细胞对辐射的敏感性。功能分析表明，YW3-56 处理促进了 NPC 细胞的 DNA 损伤、细胞凋亡和放射敏感性。重要的是，YW3-56 治疗抑制了体内肿瘤的生长。总的来说，这项研究揭示了 PAD4 抑制剂 YW3-56 在促进 NPC 细胞对辐射的敏感性方面的功效。