CircRNA SFMBT2作为ceRNA调控miR-491促进结肠癌肝转移的作用机制研究

Colorectal cancer liver metastases (CRLM) is the leading cause of death in patients, and the mechanism is very complicated. Circular RNA (circRNA) is a novel non-coding RNA (ncRNA) and plays an important role in carcinogenesis and cancer development. However, the role of circRNA in CRLM is unknown. We have been working on ncRNA and we found that a relatively new circular RNA-circSFMBT2 was upregulated in colon cancer tissues that developed CRLM in our chip assay. Further research proved that circSFMBT2 could promote the proliferation and invasion of colon cancer cells. However, the detailed mechanism is unclear. Further studies showed that circSFMBT2 could bind with miR-491, a tumor suppressing miRNA, and thus regulate the expression of MMP25 which is a target of miR-491. Based on these results and existed theory, we speculate that circSFMBT2 may function as a competing endogenous RNA (ceRNA) to inhibit miR-491, therefore contributing to the upregulation of its targets. It then results in development of colon cancer and CRLM. This may be a new mechanism of CRLM. We will perform in vivo, in vitro and clinical studies to verify the hypothesis. Our study will provide a new therapeutic target and theoretical basis for the treatment of colon cancer liver metastasis.

结肠癌肝转移是导致患者死亡的首要原因，其机制十分复杂。环状RNA（circRNA）是一种新的非编码RNA，在结肠癌肝转移中的作用尚不明确。我们一直致力于非编码RNA研究，前期应用芯片分析发现circSFMBT2（一个新的环状RNA）在肝转移的结肠癌组织中表达增加，并促进结肠癌细胞的增殖和侵袭能力；进一步研究发现circSFMBT2可与miR-491结合，促进其靶基因MMP25的表达。由此我们推测circSFMBT2可能作为竞争性内源RNA（ceRNA）来抑制miR-491对其靶基因的调节，促进结肠癌肝转移的发生发展，这可能是结肠癌肝转移的一个新机制。为验证这一假说，拟从体内、体外以及临床水平全面研究circSFMBT2作为ceRNA吸附miR-491，形成调控网络来调节相关靶基因进而促进结肠癌肝转移的作用。本课题将为结肠癌肝转移提供新的治疗靶点，为结肠癌的精准治疗提供新的理论基础。

结直肠癌是世界范围内的高发疾病，死亡率和发病率都很高。目前结直肠癌主要治疗手段为手术，化疗，放疗及综合治疗，仍然需要更为有效的早期诊断方式和更为精准的治疗靶点。环状RNA（ circRNA）是一种新的非编码RNA，在结肠癌中的作用尚不明确。现有研究发现circRNA可以作为微小RNA（miRNA）的内源性竞争性RNA（competing endogenous RNA, ceRNA）来发挥作用。我们分析TCGA数据库中的数据发现miR-491 和FOXP4（forkhead box P4）在结直肠癌组织中表达分别下调和上调。生物信息学分发现has-circ-0000212（circSFMBT2）可以和miR-491结合。芯片分析结果发现circ_0000212在肝转移的结肠癌组织中表达增加。荧光素酶报告实验和RNA免疫沉淀（RIP）实验发现miR-491 可以和FOXP4或circ-0000212结合。对circ-0000212的表达进行分析，发现其在大肠癌组织中表达高于正常组织，并且主要在细胞质中表达。CCK-8和克隆形成实验发现miR-491可以抑制结肠癌细胞增殖而circ-0000212可以促进结肠癌细胞增殖。进一步分析发现miR-491 和 FOXP4与临床病理特征相关。功能研究发现，miR-491 可以通过靶向FOXP4抑制细胞增殖，而circ-0000212 可以作为miR-491 的ceRNA调节FOXP4的表达来促进结肠癌细胞的恶性行为。上述结果表明circ-0000212是一个新的促瘤分子和潜在的药物靶标。