ABSTRACT
Chemotherapy is a cornerstone treatment for early and advanced stage breast cancer patients. However, resistance to chemotherapy remains a major obstacle, resulting in disease relapse and progression. Emerging studies demonstrated that miRNAs regulate chemotherapy-induced epithelial-mesenchymal transition (EMT) and drug resistance, but the underlying mechanisms remain unclear. Here we established a doxorubicin-resistant breast cancer cell line MCF-7/Adr, and found these cells exhibited an EMT phenotype featured by a fibroblast-like morphology, increased the capacity of migration and invasion, and underwent the changes of molecular markers of EMT including E-cadherin, N-cadherin, and vimentin. We then compared the miRNA expression profiles between MCF-7/Adr and parental MCF-7 by miRNA microarray, and identified miR-200b as the most dramatically down-regulated miRNA. Overexpression of miR-200b in chemo-resistant cells reversed the EMT phenotype and increased sensitivity to doxorubicin. Inhibition of miR-200b in parental cells induced EMT and resistance to doxorubicin. Furthermore, we characterized the target gene of miR-200b, and showed that overexpression of miR-200b down-regulated FN1 expression and the luciferase activity. Compared with the parental cells, FN1 was significantly elevated in MCF-7/Adr cells. Knockdown of FN1 reversed mesenchymal morphology, inhibited cell migration and invasion, and sensitized cells to doxorubicin. Our data suggest that miR-200b regulates EMT of chemo-resistant breast cancer cells by targeting FN1. miR-200b-based therapy may be an effective strategy in treating advanced breast cancer patients.
Subject(s)
Breast Neoplasms , Cytokines , Down-Regulation , Doxorubicin/pharmacology , Drug Resistance, Neoplasm , Epithelial-Mesenchymal Transition , Gene Expression Regulation, Neoplastic , MicroRNAs , Neoplasm Proteins , RNA, Neoplasm , Breast Neoplasms/drug therapy , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Cytokines/biosynthesis , Cytokines/genetics , Down-Regulation/drug effects , Down-Regulation/genetics , Drug Resistance, Neoplasm/drug effects , Drug Resistance, Neoplasm/genetics , Epithelial-Mesenchymal Transition/drug effects , Epithelial-Mesenchymal Transition/genetics , Female , Fibronectins , Gene Expression Regulation, Neoplastic/drug effects , Gene Expression Regulation, Neoplastic/genetics , Gene Knockdown Techniques , Humans , MCF-7 Cells , MicroRNAs/genetics , MicroRNAs/metabolism , Neoplasm Proteins/biosynthesis , Neoplasm Proteins/genetics , RNA, Neoplasm/genetics , RNA, Neoplasm/metabolismABSTRACT
Recently, chimeric transcripts have been found to be associated with the pathogenesis and poor prognosis of malignant tumors. Through our preliminary experiment, a novel chimeric transcript called chimeric transcript RRM2-c2orf48 was detected in C666-1, a classical cell line of human nasopharyngeal carcinoma (NPC). Therefore, the objective of this study was to demonstrate the existence and expression of novel chimeric transcript RRM2-c2orf48 and to explore the main functions and mechanisms of RRM2-c2orf48 in NPC. In this study, the expression of RRM2-c2orf48 was evaluated in NPC cells and specimens. Effects of RRM2-c2orf48 on migration and invasive capacities were detected in vivo and vitro. Moreover, ways in which RRM2-c2orf48 increases the invasive capacities of NPC were explored. As a result, the presence of novel chimeric transcript RRM2-c2orf48 was confirmed in C666-1 by RT-PCR and sequencing, and it was a read-through between RRM2 and c2orf48 through the transcription of interchromosome. Higher expressions of novel RRM2-c2orf48 were detected in NPC cell lines and NPC tissue specimens relative to the controls and its expression was be statistically relevant to TNM staging. High level of RRM2-c2orf48 could increase the migration and invasive capacities of NPC cells, potentially as a result of NPC cell epithelial-mesenchymal transition. RRM2-c2orf48 could also enhance resistance of chemotherapy. In vivo, RRM2-c2orf48 could enhance lung and lymph node metastasis in nude mice. These results demonstrate that high levels of RRM2-c2orf48 expression may be a useful predictor of NPC patients of metastatic potency, presenting potential implications for NPC diagnosis and therapy.
