miR-155 regulates the ability of circulating cancer cells to colonize and establish metastasis

Abstract: Metastases are established through a complex multistep process by which tumor cells disseminate from the primary tumor and expand at distant sites. Traditionally, studies on metastasis have focused on proteins and protein-coding genes, but recently microRNAs (miRNAs) have achieved increasing interest. miRNAs involved in the metastatic process are poorly defined, and while the use of clinical tissue samples or in vitro assessment for study of the first phases of the metastatic process is not feasible; such processes may be studies using in vivo models created by inoculation of human cell lines into mice. We have used such a model system consisting of three isogenic human cancer cell lines that are equally tumorigenic in mice, but while two of these cell lines give rise to metastasis at different rates, the last one disseminates single cells that remain dormant in distant organs. Using a global LNA- based miRNA microarray platform, 28 miRNAs were found to be significantly altered between the metastatic and non-metastatic cell lines, with mir-155 being the miRNA exhibiting the largest difference in expression level and central in a network analysis. Examining the potential targets of miR-155 identified calumenin, solute carrier family 26 (sulfate transporter) member 2 (SLC26A2), Integrin αV, and CD73, which showed an inverse expression pattern to miR-155 in the metastatic and non-metastatic cell lines as determined by immunocytochemical staining. The miRNAs identified in this study could be markers of the ability of cancer cells to colonize at distant organs. global microRNA profiling of three breast cancer cell lines with different metastatic potential derived from MDA-435

摘要：肿瘤转移是通过复杂的多步骤过程形成的，肿瘤细胞在此过程中从原发肿瘤部位脱落并在远端器官定植扩增。传统上，肿瘤转移研究多聚焦于蛋白质及编码蛋白质的基因，但近年来微小RNA（microRNAs, miRNAs）受到了越来越多的关注。目前，参与转移过程的miRNAs尚未被明确阐明，且利用临床组织样本或体外实验评估转移早期进程的方法并不可行；但可通过将人细胞系接种至小鼠体内构建的体内模型来研究此类转移过程。本研究使用的模型系统包含三株同源人癌细胞系，这三株细胞系在小鼠体内均具有同等的致瘤性；其中两株细胞系可分别以不同速率形成转移灶，而第三株仅能散播单个细胞，并在远端器官中保持休眠状态。本研究采用基于锁核酸（Locked Nucleic Acid, LNA）的全基因组miRNA微阵列平台，在转移性与非转移性细胞系间筛选得到28个差异表达显著的miRNAs，其中miR-155的表达水平差异最为显著，且在网络分析中处于核心地位。通过预测miR-155的潜在靶基因，本研究筛选得到钙联蛋白（calumenin）、溶质载体家族26（硫酸盐转运蛋白）成员2（SLC26A2）、整合素αV（Integrin αV）以及CD73；经免疫细胞化学染色验证，这些靶基因在转移性与非转移性细胞系中的表达模式与miR-155呈负相关。本研究中鉴定得到的miRNAs有望作为癌细胞在远端器官定植能力的分子标志物。本数据集针对从MDA-435细胞系衍生而来的三株具有不同转移潜能的乳腺癌细胞系开展了全基因组miRNA表达谱分析。