NHC Key Laboratory of Carcinogenesis, Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, China.
Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, China.
Mol Cancer. 2022 Feb 28;21(1):62. doi: 10.1186/s12943-022-01502-2.
Circular RNAs play an important role in tumor genesis and progression, but they have not been sufficiently studied in patients with nasopharyngeal carcinoma (NPC).
The circular RNA, circCAMSAP1, was screened in NPC cells by RNA sequencing analysis. The expression of circCAMSAP1 in NPC tissues was examined by real-time quantitative polymerase chain reaction (RT-qPCR) and in situ hybridization. Wound-healing, transwell, MTT and flow cytometry assays, and nude mouse tumor models were used to explore the effect of circCAMSAP1 on proliferation and metastasis of NPC in vitro or in vivo. The downstream proteins regulated by circCAMSAP1 were screened using mass spectrometry. The interaction between circCAMSAP1 and the SERPINH1 mRNA was identified using the circular RNA immunoprecipitation method and the luciferase reporter assay. The interaction between SERPINH1 and transcription factor c-Myc was verified through Co-immunoprecipitation (Co-IP) and immunofluorescence. The effect of c-Myc on the generation of circCAMSAP1 was examined through RT-qPCR and chromatin immunoprecipitation. Finally, the splicing factors that promote the production of circCAMSAP1 were explored by RT-qPCR and RNA immunoprecipitation (RIP).
We found that circCAMSAP1 was highly expressed in NPC tissues and promoted NPC proliferation and metastasis. Additionally, circCAMSAP1 promoted SERPINH1 expression through improved SERPINH1 mRNA stability by binding to the 3'-untranslated region (3'UTR) of SERPINH1. Highly expressed SERPINH1 reduced the ubiquitination-degradation rate of c-Myc, causing increased tumorigenesis. Meanwhile, c-Myc, cooperating with splicing factor 10 (SRSF10), could also promote CAMSAP1 pre-mRNA transcription and back-splicing, forming a positive feedback of circCAMSAP1 production, resulting in the proliferation and metastasis of NPC.
Our findings revealed that circCAMSAP1 promotes NPC proliferation and metastasis by binding to the 3'UTR of SERPINH1, suggesting that the positive feedback of circCAMSAP1-SERPINH1-c-Myc may serve as a prognostic biomarker or therapeutic target in patients with NPC.
环状 RNA 在肿瘤发生和发展中发挥重要作用，但在鼻咽癌（NPC）患者中尚未得到充分研究。
通过 RNA 测序分析筛选 NPC 细胞中的环状 RNA circCAMSAP1。通过实时定量聚合酶链反应（RT-qPCR）和原位杂交检测 NPC 组织中 circCAMSAP1 的表达。使用划痕愈合、transwell、MTT 和流式细胞术测定以及裸鼠肿瘤模型，在体外或体内探索 circCAMSAP1 对 NPC 增殖和转移的影响。通过质谱筛选受 circCAMSAP1 调节的下游蛋白。通过环状 RNA 免疫沉淀法和荧光素酶报告基因测定鉴定 circCAMSAP1 与 SERPINH1 mRNA 之间的相互作用。通过 Co-immunoprecipitation (Co-IP) 和免疫荧光验证 SERPINH1 与转录因子 c-Myc 之间的相互作用。通过 RT-qPCR 和染色质免疫沉淀法检测 c-Myc 对 circCAMSAP1 生成的影响。最后，通过 RT-qPCR 和 RNA 免疫沉淀（RIP）探索促进 circCAMSAP1 产生的剪接因子。
我们发现 circCAMSAP1 在 NPC 组织中高表达，并促进 NPC 增殖和转移。此外，circCAMSAP1 通过与 SERPINH1 的 3'UTR 结合，促进 SERPINH1 mRNA 稳定性，从而促进 SERPINH1 表达。高表达的 SERPINH1 降低了 c-Myc 的泛素化降解率，导致肿瘤生成增加。同时，c-Myc 与剪接因子 10（SRSF10）合作，也可以促进 CAMSAP1 前体 mRNA 的转录和反向剪接，形成 circCAMSAP1 产生的正反馈，导致 NPC 的增殖和转移。
我们的研究结果表明，circCAMSAP1 通过与 SERPINH1 的 3'UTR 结合促进 NPC 增殖和转移，提示 circCAMSAP1-SERPINH1-c-Myc 的正反馈可能作为 NPC 患者的预后生物标志物或治疗靶点。
