724025

MIR655

epithelial-mesenchymal transition (EMT) has recently been recognized as a key element of cell invasion, migration, metastasis, and drug resistance in several types of cancer, including non-small cell lung cancer (NSCLC). Our aim was to clarify microRNA (miRNA)-related mechanisms underlying EMT followed by acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) in NSCLC. miRNA expression profiles were examined before and after transforming growth factor beta1 (TGF-beta1) exposure in four human adenocarcinoma cell lines with or without EMT. Correlation between expressions of EMT-related miRNAs and resistance to EGFR-TKI gefitinib was evaluated. miRNA array and real-time quantitative reverse transcription PCR (qRT-PCR) revealed that TGF-beta1 significantly induced overexpression of miR-134, miR-487b, and miR-655, which belong to the same cluster located on chromosome 14q32, in lung adenocarcinoma cells with EMT. MAGI2 (membrane-associated guanylate kinase, WW, and PDZ domain-containing protein 2), a predicted target of these miRNAs and a scaffold protein required for PTEN, was diminished in A549 cells with EMT after the TGF-beta1 stimulation. Overexpression of miR-134 and miR-487b promoted the EMT phenomenon and affected the drug resistance to gefitinib, whereas knockdown of these miRNAs inhibited the EMT process and reversed TGF-beta1-induced resistance to gefitinib. Our study demonstrated that the miR-134/487b/655 cluster contributed to the TGF-beta1-induced EMT phenomenon and affected the resistance to gefitinib by directly targeting MAGI2, in which suppression subsequently caused loss of PTEN stability in lung cancer cells. The miR-134/miR-487b/miR-655 cluster may be a new therapeutic target in patients with advanced lung adenocarcinoma, depending on the EMT phenomenon.

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype that lacks effective targeted therapies. The epithelial-to-mesenchymal transition (EMT) is a key contributor in the metastatic process. In this study, we found that miR-655 was down-regulated in TNBC, and its expression levels were associated with molecular-based classification and lymph node metastasis in breast cancer. These findings led us to hypothesize that miR-655 overexpression may inhibit EMT and its associated traits of TNBC. Ectopic expression of miR-655 not only induced the up-regulation of cytokeratin and decreased vimentin expression but also suppressed migration and invasion of mesenchymal-like cancer cells accompanied by a morphological shift towards the epithelial phenotype. In addition, we found that miR-655 was negatively correlated with Prrx1 in cell lines and clinical samples. Overexpression of miR-655 significantly suppressed Prrx1, as demonstrated by Prrx1 3'-untranslated region luciferase report assay. Our study demonstrated that miR-655 inhibits the acquisition of the EMT phenotype in TNBC by down-regulating Prrx1, thereby inhibiting cell migration and invasion during cancer progression.CI - (c) 2016 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

We show that Cyclooxygenase-2 over-expression induces an oncogenic microRNA miR655 in human breast cancer cells by activation of EP4. MiR655 expression positively correlated with COX-2 in genetically disparate breast cancer cell lines and increased in all cell lines when grown as spheroids, implicating its link with stem-like cells (SLCs). Ectopic miR655 over-expression in MCF7 and SKBR3 cells resulted in increased proliferation, migration, invasion, spheroid formation and epithelial to Masenchymal transition (EMT). Conversely, knocking down miR655 in aggressive MCF7-COX2 and SKBR3-COX2 cells reverted these phenotypes. MCF7-miR655 cells displayed upregulated NOTCH/WNT genes; both pathway inhibitors abrogated miR655-induced spheroid formation, linking miR655 with SLC-related pathways. MiR655 expression was dependent on EP4 activity and EP4 downstream signaling pathways PI3K/AKT, ERK and NF-kB and led to TGFbeta resistance for Smad3 phosphorylation. Tail vein injection of MCF7-miR655 and SKBR3-miR655 cells in NOD/SCID/GUSB-null mice revealed increased lung colony growth and micrometastases to liver and spleen. MiR655 expression was significantly high in human breast tumors (n = 105) compared to non-tumor tissues (n = 20) and associated with reduced patient survival. Thus miR655 could serve as a prognostic breast cancer biomarker.