Johannessen Charles, Moi Line, Kiselev Yury, Pedersen Mona Irene, Dalen Stig Manfred, Braaten Tonje, Busund Lill-Tove
Department of Medical Biology, UiT-The Arctic University of Norway, Tromsø, Norway.
Department of Clinical Pathology, University Hospital of North Norway, Tromsø, Norway.
PLoS One. 2017 Oct 26;12(10):e0186658. doi: 10.1371/journal.pone.0186658. eCollection 2017.
MicroRNAs (miRNAs) are small non-coding RNAs that function as post-transcriptional regulators of gene expression and are dysregulated in cancer. Studies of miRNAs to explore their potential as diagnostic and prognostic markers are of great scientific interest. Here, we investigate the functional properties and expression of the miR-143/145 cluster in breast cancer (BC) in vitro and in vivo. The ER positive MCF7, the HER2 positive SK-BR-3, and the triple negative cell line MDA-MB-231 were used to assess cell proliferation and cell invasion. Expression of miRNA in 108 breast cancers in the Norwegian Women and Cancer Study and 44 benign tissue controls were analyzed by microarray and validated by RT-PCR. Further, in situ hybridization (ISH) was used to study the cellular and subcellular distribution of the miRNAs. In vitro, miR-143 promoted proliferation of MCF7 and MDA-MB-231 cells, whereas miR-145 and the cotransfection of both miRNAs inhibited proliferation in all three cell lines. The cells' invasive capacity was reduced after transfection and cotransfection of the miRNAs. In line with the tumor suppressive functions in vitro, the expression of miR-143 and miR-145 was lower in malignant compared to benign breast tissue, and lower in the more aggressive tumors with higher tumor grade, loss of ER and the basal-like phenotype. ISH revealed miR-143 to be cytoplasmatic and predominantly expressed in luminal cells in benign tissue, whilst miR-145 was nuclear and with strong staining in myoepithelial cells. Both miRNAs were present in malignant epithelial cells and stromal fibroblasts in BC. This study demonstrates that miR-143 and -145 have functional properties and expression patterns typical for tumor suppressors, but the function is influenced by cellular factors such as cell type and miRNA cotransfection. Further, the nuclear functions of miR-145 should be explored for a more complete understanding of the complexity of miRNA regulation and function in BC.
微小RNA（miRNA）是一类小的非编码RNA，作为基因表达的转录后调节因子发挥作用，且在癌症中表达失调。对miRNA进行研究以探索其作为诊断和预后标志物的潜力具有重大科学意义。在此，我们在体外和体内研究了miR-143/145簇在乳腺癌（BC）中的功能特性和表达情况。使用雌激素受体（ER）阳性的MCF7、人表皮生长因子受体2（HER2）阳性的SK-BR-3以及三阴性细胞系MDA-MB-231来评估细胞增殖和细胞侵袭。通过微阵列分析了挪威妇女与癌症研究中108例乳腺癌及44例良性组织对照中miRNA的表达，并通过逆转录聚合酶链反应（RT-PCR）进行验证。此外，采用原位杂交（ISH）研究miRNA的细胞和亚细胞分布。在体外，miR-143促进MCF7和MDA-MB-231细胞增殖，而miR-145以及两种miRNA共转染均抑制这三种细胞系的增殖。转染和共转染miRNA后，细胞的侵袭能力降低。与体外的肿瘤抑制功能一致，与良性乳腺组织相比，恶性组织中miR-143和miR-145的表达较低，在肿瘤分级较高、ER缺失且具有基底样表型的侵袭性更强的肿瘤中表达更低。ISH显示，miR-143位于细胞质中，主要在良性组织的腔上皮细胞中表达，而miR-145位于细胞核中，在肌上皮细胞中有强染色。两种miRNA均存在于BC的恶性上皮细胞和基质成纤维细胞中。本研究表明，miR-143和-145具有肿瘤抑制因子典型的功能特性和表达模式，但其功能受细胞类型和miRNA共转染等细胞因子的影响。此外，应进一步探索miR-145的核功能，以更全面地了解BC中miRNA调控和功能的复杂性。
