Hsa_circ_001680 通过调节 BMI1 进而调控 miR-340 影响 CRC 的增殖和迁移，并介导其化疗耐药性。

BACKGROUND: Accumulating evidence indicates that circular RNAs (circRNAs) act as microRNA (miRNA) sponges to directly inhibit specific miRNAs and alter their ability to regulate gene expression at the post-transcriptional level; this mechanism is believed to occur in various cancers. However, the expression level, precise function and mechanism of circ_001680 in colorectal carcinoma (CRC) are largely unknown. METHODS: qRT-PCR was used to detect the expression of circ_001680 and miR-340 in human CRC tissues and their matched normal tissues. Bioinformatics analyses and dual-fluorescence reporter assays were used to evaluate whether circ_001680 could bind to miR-340. Circ_001680 overexpression and knockdown cell lines were constructed to investigate the proliferation and migration abilities in vivo and in vitro through function-based experiments, including CCK8, plate clone formation, transwell, and wounding healing assays. The relationships among circ_001680, miR-340 and BMI1 were investigated by bioinformatics analyses, dual-fluorescence reporter system, FISH, RIP and RNA pull down assays. Sphere forming assays and flow cytometry analyses were used to assess the effect of circ_001680 on the stemness characteristics of CRC cells. RESULTS: Circ_001680 was more highly expressed in of CRC tissue than in matched adjacent normal tissues from the same patients. Circ_001680 was observed to enhance the proliferation and migration capacity of CRC cells. Furthermore, dual-fluorescence reporter assays confirmed that circ_001680 affects the expression of BMI1 by targeting miR-340. More importantly, we also found that circ_001680 could promote the cancer stem cell (CSC) population in CRC and induce irinotecan therapeutic resistance by regulating the miR-340 target gene BMI1. CONCLUSIONS: Our results demonstrated that circ_001680 is a part of a novel strategy to induce chemotherapy resistance in CRC through BMI1 upregulation. Moreover, circ_001680 may be a promising diagnostic and prognostic marker to determine the success of irinotecan-based chemotherapy.

背景：越来越多的证据表明，环状 RNA（circRNA）可作为 microRNA（miRNA）海绵，直接抑制特定的 miRNA，并改变它们在后转录水平调控基因表达的能力；这种机制被认为存在于多种癌症中。然而，circ_001680 在结直肠癌（CRC）中的表达水平、精确功能和机制在很大程度上仍是未知的。

方法：采用 qRT-PCR 检测人 CRC 组织及其配对正常组织中 circ_001680 和 miR-340 的表达。采用生物信息学分析和双荧光报告基因检测评估 circ_001680 是否能与 miR-340 结合。构建 circ_001680 过表达和敲低细胞系，通过 CCK8 法、平板克隆形成实验、Transwell 实验和划痕愈合实验等功能实验，在体内和体外研究其增殖和迁移能力。通过生物信息学分析、双荧光报告系统、FISH、RIP 和 RNA 下拉实验研究 circ_001680、miR-340 和 BMI1 之间的关系。采用球体形成实验和流式细胞术分析评估 circ_001680 对 CRC 细胞干性特征的影响。

结果：与同一患者的配对正常组织相比，CRC 组织中 circ_001680 的表达水平更高。circ_001680 可增强 CRC 细胞的增殖和迁移能力。此外，双荧光报告基因检测证实 circ_001680 通过靶向 miR-340 影响 BMI1 的表达。更重要的是，我们还发现 circ_001680 可通过调节 miR-340 靶基因 BMI1 促进 CRC 中的癌症干细胞（CSC）群体，并诱导伊立替康治疗耐药性。

结论：我们的研究结果表明，circ_001680 是通过上调 BMI1 诱导 CRC 化疗耐药的一种新策略的一部分。此外，circ_001680 可能是一种有前途的诊断和预后标志物，可用于确定以伊立替康为基础的化疗的成功。