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：转移是通过复杂的多步骤过程形成的，肿瘤细胞由此从原发肿瘤播散并在远处器官增殖。长期以来，转移研究多聚焦于蛋白质及编码蛋白质的基因，但近年来微小核糖核酸（microRNAs，miRNAs）受到越来越多的关注。参与转移过程的miRNAs尚不完全明确，且利用临床组织样本或体外评估来研究转移过程的初始阶段并不可行；此类研究可通过将人类细胞系接种到小鼠体内构建的体内模型来开展。本研究使用了由三种同基因人类癌细胞系组成的模型系统，这些细胞系在小鼠体内的致瘤性相当，但其中两种细胞系以不同速率形成转移，而第三种则播散单个细胞，这些细胞会在远处器官中保持休眠状态。通过基于锁核酸（LNA）的全局miRNA微阵列平台，我们发现转移性与非转移性细胞系间有28种miRNAs的表达存在显著差异，其中miR-155的表达水平差异最大，且在网络分析中处于核心位置。通过对miR-155的潜在靶标进行筛选，我们鉴定出了钙联蛋白（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，这些靶标的表达模式与miR-155在转移性与非转移性细胞系中呈负相关，该结果通过免疫细胞化学染色得以验证。本研究中鉴定出的miRNAs可作为癌细胞在远处器官定植能力的标志物。本研究对三种源自MDA-435、具有不同转移潜能的乳腺癌细胞系开展了全局microRNA表达谱分析。