Circular RNAs (circRNAs) are widely expressed in human cells and are closely associated with cancer development. However, they have rarely been investigated in the context of nasopharyngeal carcinoma (NPC). We screened a new circRNA, circRNF13, in NPC cells using next-generation sequencing of mRNA. Reverse transcription polymerase chain reaction and RNA fluorescence in situ hybridization were used to detect circRNF13 expression in 12 non-tumor nasopharyngeal epithelial (NPE) tissues and 36 NPC samples. Cell proliferation was detected using MTT and flow cytometry assays, and colony formation capability was detected using colony formation assays. Cell migration and invasion were analyzed using wound-healing and Transwell assays, respectively. Cell glycolysis was analyzed using the Seahorse glycolytic stress test. Glucose transporter type 1 (GLUT1) ubiquitination and SUMOylation modifications were analyzed using co-immunoprecipitation and western blotting. CircRNF13 and Small Ubiquitin-like Modifier 2 (SUMO2) interactions were analyzed using RNA pull-down and luciferase reporter assays. Finally, to test whether circRNF13 inhibited NPC proliferation and metastasis in vivo, we used a xenograft nude mouse model generated by means of subcutaneous or tail vein injection. We found that circRNF13 was stably expressed at low levels in NPC clinical tissues and NPC cells. In vitro and in vivo experiments showed that circRNF13 inhibited NPC proliferation and metastasis. Moreover, circRNF13 activated the SUMO2 protein by binding to the 3′- Untranslated Region (3′-UTR) of the SUMO2 gene and prolonging the half-life of SUMO2 mRNA. Upregulation of SUMO2 promotes GLUT1 degradation through SUMOylation and ubiquitination of GLUT1, which regulates the AMPK-mTOR pathway by inhibiting glycolysis, ultimately resulting in the proliferation and metastasis of NPC. Our results revealed that a novel circRNF13 plays an important role in the development of NPC through the circRNF13-SUMO2-GLUT1 axis. This study implies that circRNF13 mediates glycolysis in NPC by binding to SUMO2 and provides an important theoretical basis for further elucidating the pathogenesis of NPC and targeted therapy.

中文翻译：

---

环状RNA circRNF13通过SUMO2抑制鼻咽癌增殖和转移


环状RNA（circRNA）在人类细胞中广泛表达，与癌症的发生密切相关。然而，它们很少在鼻咽癌（NPC）的背景下进行研究。我们使用下一代 mRNA 测序在 NPC 细胞中筛选了一种新的 circRNA，circRNF13。采用逆转录聚合酶链反应和RNA荧光原位杂交检测12例非肿瘤鼻咽上皮（NPE）组织和36例鼻咽癌样本中circRNF13的表达。使用MTT和流式细胞术检测细胞增殖，并使用集落形成分析检测集落形成能力。分别使用伤口愈合和Transwell实验分析细胞迁移和侵袭。使用 Seahorse 糖酵解应激测试分析细胞糖酵解。使用免疫共沉淀和蛋白质印迹分析 1 型葡萄糖转运蛋白 (GLUT1) 泛素化和 SUMO 化修饰。使用 RNA Pull-down 和荧光素酶报告基因检测分析 CircRNF13 和小泛素样修饰符 2 (SUMO2) 相互作用。最后，为了测试circRNF13是否抑制体内NPC增殖和转移，我们使用皮下或尾静脉注射产生的异种移植裸鼠模型。我们发现circRNF13在鼻咽癌临床组织和鼻咽癌细胞中稳定低水平表达。体外和体内实验表明circRNF13抑制NPC增殖和转移。此外，circRNF13通过与SUMO2基因的3'-非翻译区（3'-UTR）结合并延长SUMO2 mRNA的半衰期来激活SUMO2蛋白。 SUMO2的上调通过GLUT1的SUMO化和泛素化促进GLUT1降解，从而通过抑制糖酵解来调节AMPK-mTOR通路，最终导致NPC的增殖和转移。我们的结果表明，一种新型的 circRNF13 通过 circRNF13-SUMO2-GLUT1 轴在 NPC 的发育中发挥重要作用。该研究提示circRNF13通过与SUMO2结合介导鼻咽癌糖酵解，为进一步阐明鼻咽癌发病机制及靶向治疗提供重要理论依据。