环状RNAcirc_001634竞争性结合miR-138-5p促进结直肠癌细胞增殖的机制研究

Circular RNA plays an important role in the development of colorectal cancer (CRC), but its mechanism is unclear. Our previous studies have found that circular RNA circ_001634 is up-regulated in CRC and promoted CRC cell proliferation, while tumor suppressor miR-138-5p inhibited CRC cells proliferation. There was significant negative correlation between the two in CRC tissues. Silencing of circ_001643 could up-regulated miR-138-5p expression obviously. Bioinformatics analysis predicted that circ_001634 possessed three miRNAs response elements that were complementary to miR-138-5p, and two key moleculars of tumor proliferation, KRAS and CD44, were potential targets of miR-138-5p. This project that based on the preliminary work is proposed to demonstrate that circ_001634 regulates the expression of miR-138-5p and downstream target genes KRAS and CD44 due to its competitive combine of miR-138-5p as a ceRNA, and facilitate CRC cell proliferation. Achieveing the goals in this proposal is also expected to provide new targets for the diagnosis and treatment of CRC.

环状RNA在结直肠癌(colorectal cancer, CRC)的发生发展中发挥重要作用，但其作用机制尚不清楚。我们前期研究发现环状RNA circ_001634在CRC中表达上调并促进CRC细胞的增殖，而抑瘤基因miR-138-5p可抑制CRC细胞的增殖；在CRC组织中二者表达水平呈负相关；沉默circ_001634后miR-138-5p的表达水平明显上调。生物信息学分析发现circ_001634存在3个与 miR-138-5p互补配对的miRNA应答元件；同时发现肿瘤增殖关键分子KRAS和CD44是miR-138-5p的潜在靶基因。本项目以前期工作为基础，拟进一步研究circ_001634发挥ceRNA作用竞争性结合miR-138-5p，调控miR-138-5p及其下游靶基因KRAS及CD44的表达，进而影响CRC细胞增殖的分子机制。本项目的完成有望为CRC的诊治提供新的靶点。

结直肠癌（colorectal cancer, CRC）是全球第三大常见的恶性肿瘤。进一步研究CRC的发病机制，寻找新型CRC诊断标志物和药物治疗靶点具有重要的理论和现实意义。大量研究证明非编码RNA在调节多种癌症类型中发挥重要作用，其中包括环状RNA （circular RNA, circRNA）、长链非编码RNA （long non-coding RNAs, lncRNAs)和微小RNA（MicroRNAs，miRNA）等。本课题组系统而持续研究了关键ncRNAs在结肠癌调控机制领域中的作用，我们前期研究发现miR 138-5p能靶向PD-L1从而抑制结肠癌的增殖发展，circ_001634能明显促进CRC细胞的增殖。同时有文献报道，糖尿病与结肠癌的发生相关。我们前期工作及相关文献显示miR-203a在结肠癌等多种肿瘤及糖尿病的发生发展中均发挥关键作用。在本项目中我们进一步通过荧光素酶报告载体实验发现，糖尿病关键调控基因胰岛素受体2（IRS2 ）和癌基因LINC00657均是miR-203a的靶基因。因此，本项目研究miR-203a通过分别靶向IRS2、LINC00657分别参与糖尿病和结肠癌的发生。LINC00657在结直肠癌患者组织中表达上调，富集于CRC干细胞样细胞(CSCs)。LINC00657作为miR-203a的竞争性内源性RNA (ceRNA)，拮抗其抑癌基因的功能，促进CSCs侵袭转移。因此，LINC00657可能成为CRC潜在的预后因素和/或治疗靶点。同时，研究结果提示miR-203a在糖尿病NOD小鼠的胰岛β细胞中表达上调。miR-203a通过IRS2抑制胰岛β细胞的增殖，促进胰岛β细胞凋亡。miR-203a抑制剂的使用可能为今后糖尿病治疗提供新策略，并有希望帮助明确糖尿病与CRC两者之间是否存在直接作用关系，并探讨其内在的生物学机制。