Department of Pathology, Nanfang Hospital, Southern Medical University, Guangzhou, 510515, Guangdong, China.
Department of Pathology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong, China.
Mol Cancer. 2020 Jan 31;19(1):20. doi: 10.1186/s12943-020-1134-8.
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.
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.
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.
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.
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。
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。
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。
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。
