Endocr Relat Cancer 2013 Dec 14;20(6):809-23. Epub 2013 Oct 14.
Departments of Endocrine Neoplasia and Hormonal Disorders Experimental Therapeutics Urology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA Department of Oncology, The University of Naples, Naples, Italy Department of Pathology, Centro Oncologico Fiorentino, Sesto Fiorentino, Florence, Italy Verna and Marrs McLean Department of Biochemistry and Molecular Biology Baylor College of Medicine, Houston, Texas, USA Department of Oncology, Istituto Toscano Tumori, Hospital of Prato, Prato, Italy Department of Gynecologic Oncology, Center for RNA Interference and Non-coding RNAs, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA Department of Endocrinology, University of Messina, Messina, Italy Department of Pathology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA Department of Internal Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA.
MicroRNAs (miRNAs) represent a class of small, non-coding RNAs that control gene expression by targeting mRNA and triggering either translational repression or RNA degradation. The objective of our study was to evaluate the involvement of miRNAs in human medullary thyroid carcinoma (MTC) and to identify the markers of metastatic cells and aggressive tumour behaviour. Using matched primary and metastatic tumour samples, we identified a subset of miRNAs aberrantly regulated in metastatic MTC. Deregulated miRNAs were confirmed by quantitative real-time PCR and validated by in situ hybridisation on a large independent set of primary and metastatic MTC samples. Our results uncovered ten miRNAs that were significantly expressed and deregulated in metastatic tumours: miR-10a, miR-200b/-200c, miR-7 and miR-29c were down-regulated and miR-130a, miR-138, miR-193a-3p, miR-373 and miR-498 were up-regulated. Bioinformatic approaches revealed potential miRNA targets and signals involved in metastatic MTC pathways. Migration, proliferation and invasion assays were performed in cell lines treated with miR-200 antagomirs to ascertain a direct role for this miRNA in MTC tumourigenesis. We show that the members of miR-200 family regulate the expression of E-cadherin by directly targeting ZEB1 and ZEB2 mRNA and through the enhanced expression of tumour growth factor β (TGFβ)-2 and TGFβ-1. Overall, the treated cells shifted to a mesenchymal phenotype, thereby acquiring an aggressive phenotype with increased motility and invasion. Our data identify a robust miRNA signature associated with metastatic MTC and distinct biological processes, e.g., TGFβ signalling pathway, providing new potential insights into the mechanisms of MTC metastasis.